I know you boys thought… Scoob gave up, the guy has no stick-to-itiveness’, what a poser or worse, but this is not the case. My father (80) was diagnosed with cancer a few months back and I have been busy helping out and taking care of my mom (76) while he has been sick. Everything is getting back to normal now and the doctor said he got all of the tumor and my dad will be OK in short the surgery was a success, so it seems that I will get some time to play with the Fiero soon and I thought I’d update you sports fans on where I’m at…
Since my last post I have made several trips to the bone yard in an attempt to locate a suitable engine, and have found a few with high miles that were all whored out and not worth taking a chance on. A month or two ago I was perusing Craigslist searching the Tri-State area using the key word search “Z24” and having some luck finding 95 and earlier cars, but no 96 or 97 models with the better heads and intakes. My brother suggested using TGP as the search word with low miles and a blown auto transmission for the advertised price of 250$ for the whole car. Excited I responded to the add but, got no response from the seller and figured some other lucky slob got my car. Then to my surprise I received an E-mail from the seller stating that he still had the car but had lost the title, no problem I messaged back I don’t need a title just a parts car, but the seller insisted that he would not sell the car with out the title. A few more weeks went by with no more contact with the seller even though I sent several messages in reference to the car. Then yesterday out of the blue I received another E-mail from the seller telling me he had received the title and was ready to do business. I hope to get the car next week, it should provide a wiring harness, ECM, all the accessories and what ever else I can scavenge off of it. I look forward to checking the clearance of the aluminum rods in the block. Wish me luck, thanks for looking.
------------------ Scoobysruvenge
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10:32 AM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
Good to hear from you. Thanks for the parts offer, but I think I have got everything I’m going to need accept a dummy block for set up. Do you have one ??? The Z34s seem to have the 3.4 DOHC engine in more abundance than most other models from my bone yard sorties. I did a lot of searching and found a lot of Z34s w/3.4 DOHC but they were either too expensive or polishing brass on the Titanic. I feel lucky to have scammed up the TGP I found, it has less than 100k, still runs and drives with a mildly slipping transmission according to the Owner.
Good to hear from you. Thanks for the parts offer, but I think I have got everything I’m going to need accept a dummy block for set up. Do you have one ??? The Z34s seem to have the 3.4 DOHC engine in more abundance than most other models from my bone yard sorties. I did a lot of searching and found a lot of Z34s w/3.4 DOHC but they were either too expensive or polishing brass on the Titanic. I feel lucky to have scammed up the TGP I found, it has less than 100k, still runs and drives with a mildly slipping transmission according to the Owner.
Let me know…
Uh... I don't think that you can get a Z34 of that vintage without a 3.4TDC... that would be why so many Lumina Z34s have that engine.
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02:04 PM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
Z34 was in fact the option code for the package that included the 3.4 TDC engine, so the two are synonymous. Also, the Olds Cutlass International and Pontiac Grand Prix GTP (not entirely sure on the exact models, but they were the W-chassis from Olds and Pontiac) also had the TDC from '91-'93. All three were available with the Getrag 284 stick.
Z24 is a Cavalier option. I sure hope you're actually searching for Z34. Check out www.car-parts.com
I have '96 cylinder heads, LIM and fuel rail. I'm missing one of the cam carriers, however.
Would it be possible to make a quick measurement of the valves in those heads? maybe even the lifter diameter? That part number listing for the 96 heads indicate the valves are larger than the earlier heads, as well as smaller lifters. I was under the impression that only the 97 heads had smaller lifters.
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03:40 PM
Oct 2nd, 2009
gt40racer Member
Posts: 75 From: Abu Dhabi, UAE Registered: Mar 2002
Is it true ??? Did GM mass produce a forged steel crank for the 3x00 engine ??? I stumbled into this doing some research on the 3900 engine. It seems that some people out there are claiming that the LX9 sports a forged steel crank with a casting number of 7484. Below is one of the web pages I found some of this information on along with the claim of forging.
3500 LX9 is listed as having…. Forged steel crank 7484 casting Stock forged steel rods 9.8:1 SCR stock pistons (Nice ratio for a turbo engine and are probably turbo friendly hypereutectic material)
If this is true these cranks could support the high horsepower that so many of us desire. I see Joe Upson has a couple of these engines and seems to know something about these cranks.
I have a 3900 thread going where he has posted before, I will ask what he knows. If any one has info on this let me know.
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10:29 AM
PFF
System Bot
Oct 14th, 2009
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
The 7484 crank is indeed a real factory forged crank with 2.25” journals this means that this crank will bolt directly into a 3x00 engine. Using aftermarket forged small block rods (which by the way can be had ridiculously cheap) in a 3.4 requires only minor machining on the Big end of the rod (100$ or less at your local machine shop) I doubt you will need to remove any other material as the aluminum small Chevy rods I have will fit my 3.1 Mclaren block with very minor material removal. When I had my aluminum test rod machined I asked about having the small end hole bushed and was told that the bushing would be so thin that it would be easier and cheaper bore out what ever pistons I was going to use. So here’s the skinny
1. Acquire a LX9 3500 crank – I plan to go to the local kidney foundation junk yard to get mine (129.99) cheaper if I simply remove the crank. 2. Buy some forged rods (400 $) or less for a 600 HP set of Eagle or Scat rods. 3. Machine the rods and pistons (200 $) 4. That’s it.
129.99 + 400 + 200 = 729.99
That’s a seriously potent bottom end good to 600 HP for under a grand, if any of you have read the “Head gaskets for a turbocharged 2,8 v6” thread the guy is making almost 500 HP with a 2.8. Crazy right, it just goes to show with the right parts and level of boost massive power can be extracted from these little engines. After reading his thread I was truly inspired other than that Norwegian forged crank he was using, but with the confirmation of the 7484 factory forged crank I look forward to stretching the 3.4 DOHCs legs with this information. By the way if you haven’t looked at that Head gaskets for a turbocharged 2,8 v6 thread you really should.
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07:53 AM
Oct 15th, 2009
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
I had almost given up on acquiring the 96 GTP car I found a few months ago on craigslist due to the lack of communication from the seller and was considering a 3900 swap, but then I read this email today.
I'm sorry for the delay. As I mentioned I am currently studying abroad in Italy. I wont be able to make it home till late december however if you are still interested in the car then I will be sure to contact you.
Subject: RE: 1996 Pontiac Grand Prix GTP Needs Trans - $250 To: dmellinger@XXXX.com From: louis.a.barnette@XXXX.com Date: Wed, 14 Oct 2009 09:25:12 -0400
The 96 has the preferred heads and intake and I will gladly wait for December to acquire it, it has less than 100,000 miles with maintenance records.
I have also found a forged crank that will work in the block and will be looking for a car at the junkyard to swipe it from (3500 LX9 with 7484 casting) according to Joe Upson it is the standard crank for this engine. I am stoked and rejuvenated with this new information. I will post further when I have all the details.
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09:51 AM
joshh44 Member
Posts: 2166 From: Nanaimo, B.C, Canada Registered: Aug 2007
As I stated above after a lot of research and discussion here on PFF about 3900 and 3500 engine swaps I was ready to bail on my 3.4 DOHC project in favor of a 3900 6 speed swap.
Then two things happened… Dawn came early and I was perusing the PFF Tech page when I stumbled into Borretti’s article about head gaskets for a turbo 2.8, the title tweaked my interest and caught my interest.
After reading his thread I felt inspired and compelled to march on with 3.4 DOHC project.
Later that morning I received the above E-mail about the 96 GTP for 250$ from the studious Dylan schooling in Italy.
So now it’s a waiting game for the 3.4, but while I wait I will be trying to locate a LX9 3500 equipped car cannibalize for the forged crank.
I found a short block engine in Greenville NC that was not running when it came in for 150$
This is a small price for a forged crank much less a short block, my problem is that Greenville is a 3 hour ride for a trashed crank.
My question is this is the 3500 LX9 an interference motor??? If it is, its possible that some valves were bent when a timing belt cut loose and the bottom end is just fine.
Any help would be appreciated.
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02:02 PM
Nov 12th, 2009
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
I am patiently waiting to pick up the 96 TGP and its DOHC engine in December, while I have been waiting I have decided to use a 3500 7484 crank and have the journals turned down to the standard 60 D 2’’ size to take advantage of the forging. Since I will be machining the crank down I might as well have it stroked for maximum displacement, this means that a custom piston will be needed. The CD on the stock piston is 1.464, piston manufacturers can reduce this to as little as 1’’ on a NA motor but for a blown motor more than 1’’ CD will be needed. In order to figure out how small I can go on the piston CD I need the CC of the combustion chamber for the DOHC heads and is the CC different on the 96 and later heads???
Can anyone help with this???
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02:52 PM
Nov 23rd, 2009
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
I contemplated abandoning the aluminum rods and going with a longer one for a little more dwell time, through some investigation this is what I found.
Increase the stoke of the engine to improve low end torque, since I plan to regrind the 3500 LX9 crank from 2.25 down to 2.1 or stock 2.0 journal size, just offset grind it for more stroke. Add 6mm 84mm increased to 90mm (84mm stroke increased to 90mm)
Increase the bore TO 40 over. (Bore 92mm at 40 over = 93.020mm)
Number three increase the dwell time of the piston with a longer rod. (5.7 rod to the popular SBC size of 5.85)
Doing the math this comes out to be 3.7 just shy of 3800 engine displacement. (224 CU or 3669.8 = 3.7 liter)
Stock piston height is 1.464 and can be shrunk to as little as 1.200 for a turbo application. I’d hoped to use a 5.85 rod for some more dwell time
These are preliminary numbers I should have details on the exact math soon.
Here is some of the preliminary math I’ve come up with for stroking the 3.4… The formula is as follows: Deck Height – (Stroke/2 + Rod Length + Piston Deck Clearance) = Compression Height
6 Inch rod used Deck Height – 8.818 Stroke/2 – 1.771609095 Rod Length – 6.0 Piston Deck Clearance – .010 Compression Height = 7.781609095 Compression Height subtracted from Deck Height = 1.036390905 With .000 Piston Deck Clearance = 1.046390905 Minimum Deck Height – 1.200 Verdict – Unusable
5.85 Inch rod used Deck Height – 8.818 Stroke/2 – 1.771609095 Rod Length – 5.85 Piston Deck Clearance – .010 Compression Height = 7.631609095 Compression Height subtracted from Deck Height = 1.186390905 With .000 Piston Deck Clearance = 1.196390905 Minimum Deck Height – 1.200 Verdict – Acceptable with .000 PDC
5.7 Inch rod used Deck Height – 8.818 Stroke/2 – 1.771609095 Rod Length – 5.7 Piston Deck Clearance – .010 Compression Height = 7.481609095 Compression Height subtracted from Deck Height = 1.336390905 With .000 Piston Deck Clearance = 1.346390905 Minimum Deck Height – 1.200 Verdict – Usable with .000 PDC and .010 PDC
It looks like I will be using those aluminum rods I have after all, the small ring package that the 5.85 (slightly less than the 1.200 minimum needed for a turbo piston) rod requires in combination with .000 PDC I have decided to stay away from the longer rod.
I will still use the stroke and bore increase as previously planned for 3.7 displacement and use my 5.7 aluminum rods as originally planned.
Until I actually have the block in hand these numbers are only conjecture based on posted clearances for the 3.4 DOHC.
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08:16 AM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
Intake 205.1 duration, Exhaust 210 duration IVO -7.5 IVC 32.5 EVO 35 EVC -5
IVO - Inlet valve opens
IVC - Inlet valve closes
EVO - Exhaust Valve Opens
EVC - Exhaust valve Closes
I have I have looked at some V6 turbo grind cam specs for mild street performance, engines this is what I have so far. WIW below (What I Want) of course I have a lot more work to do before I settle on a hard set of numbers as the camshaft specs I have been looking at are single cam 2 valve pushrod specs.
I am assuming that the – negative IVO / EVC numbers on the factory cams are referenced to TDC therefore they are at BTDC and the IVC / EVO are referenced to BDC as the specs given for the stock 3.4 DOHC cams do not include this information.
IVO difference between the two is - 14.5 Degrees TDC IVC difference between the two is + 25.5 Degrees BDC EVO difference between the two is - 31 Degrees TDC EVC difference between the two is - 19 Degrees TDC
Remember I am planning on using the stock cam shafts, most likely the 94/95 units as they boast slightly larger numbers, however bigger is not always better. I quote Corky Bell on several counts…
“The characteristics of long duration and high overlap of performance oriented cams in N/A engines is unwelcome in the turbo engine”
“Rule: it’s hard to find a turbo cam that works better than the stock item below 15 PSI”
This does not mean there is not some performance to be gained from a minor regrind of the stock units to be a friendlier to the addition of the turbo.
Simply finding a taller 35mm lifter would allow for some extra manipulation of the camshaft numbers.
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08:50 AM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
I left work Friday from MD at noon and set off to get back home to Virginia, any one who travels 95 knows Friday is the worst day for traffic and DC/MD/VA boasts some of the worst traffic in the nation.
I jockeyed for position around the 495 raceway, uh I mean beltway hoping to get out of Dodge before the insanity of Friday traffic could impose its dark will on me, you see my local junkyard called. While I was out of town Mark at Action called and informed me the 3500 LX9 engine I had been waiting to be removed at one of their sister junk yards had been pulled and they needed a deposit to have it delivered to my junk yards location… I needed to be there by 5:00 I rolled in behind a SUV with government tags an engaged the warp drive
Mapquest lists this my trip at just under 2 hours 30 minutes, but it regularly takes me 4-5 hours to make this commute so it was going to be close to get there before they closed.
Following the 2 ton traffic wedge for an hour got me close to getting off the belt way and on to 95 S, but then my lucky charm SUV headed off the beltway and I was left alone to fend for myself against the ever growing hoard of vehicles choking the path home.
With a lead foot, some luck and a few middle fingers I managed to get of the beltway and on to 95S, this made me feel no better because I still hade to make it past miles of HOV lanes, Quantico Marine base and Fredericksburg.
Coming up on the HOV lane entrance I could see it was flowing well, I contemplated running the HOV gauntlet patrolled and enforced by VA State Police, but remembering they were having a crack down that week on HOV offenders AT A 125$ a pop. I decided not to gamble the HOV lanes as a single occupant and stayed on my course of 95S.
As I approached Woodbridge I saw a sea of brake lights and a column of smoke in the distance. F%@K what manner of misfortune had the gods plagued me with now! I could hear the Fire and Police sirens closing in behind, I desparately maneuvered to the far left lane as traffic was slowing to a crawl, the suddenly caught site of it… a early 80s caprice with the whole front end in flames, the tires billowing putrid black smoke.
I snuck by on the far left shoulder just as the emergency services rolled up and closed the road just two cars behind me made before the road was closed. I thought about getting a pick for you guys, but I wanted no part of the IED waiting to go off on the side of 95.
Blowing through Quantico with little fanfare and getting past Fredericksburg with minor delays left me with an easy ride the rest of the way to Action Auto Parts in the neighboring city of Hopewell.
Arriving in the environmentally friendly city of Hopewell
I headed strait for Action Auto Parts and made it just before they closed.
I hurried inside to find Mark suffering from the Swine flu, so I kept my distance and pushed the cash his way with a broom handle. “I will have them pull the balancer and look for your 7484 casting numbers on Monday and give you a call” Mark responded…
So it’s Monday and I am waiting for my call. I will post more on this crank swap as I go, should be soon.
Thanks for the interest.
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10:26 AM
Nov 24th, 2009
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
I am still waiting to hear from Action on those crank numbers, if Joe Upson is cruising this thread can you tell me more about where to find the 7484 casting number on the snout of the crank???
I am still waiting to hear from Action on those crank numbers, if Joe Upson is cruising this thread can you tell me more about where to find the 7484 casting number on the snout of the crank???
All cranks were not tagged with the part number behind the the balancer bolt. All 3900 engines have a steel crank. The cast crank is rare and the most consistent way of determining steel vs. cast is to look at the parting line on the first throw, it is characteristically wide. The crank also looks unusual compared to the cast crank, that was the first thing I noticed before discovering my crank was forged. The cast crank will have a pencil lead thin parting line on the first throw just like the older cranks.
Here I have 3 different cams, I am only looking at the valves opening and closing for this exercise. The 3 cams listed are for Buick 231 v6 engines… NA represents the stock non-turbo cam, the GN represents a stock Grand National cam and the G+ represents a big street/strip cam for the Grand National. I plan on using my car for more than drag racing so the G+ numbers do not apply to my engine, I posted them as a comparison.
NA IVO 12 BTDC = The valve opens 12 degrees BTDC GN IVO 22 BTDC = The valve opens before the NA cam by 10 degrees (sooner) G+ IVO -4 BTDC = The valve opens after (ATDC) the NA cam by 16 degrees (later)
Here we see that the GN cam gets the intake valve open a little sooner than the NA cam. The race G+ cam specs are in the opposite direction when looking for all out top end performance rather than the good drivability of the stock GN turbo cam.
NA EVO 52 BBDC = The valve opens 52 degrees BBDC GN EVO 66 BBDC = The valve opens before the NA cam by 14 degrees (sooner) G+ EVO 36 BBDC = The valve opens after the NA cam by 16 degrees (later)
Here we see that the GN cam gets the exhaust valve open a little sooner than the NA cam. The race G+ cam specs are in the opposite direction when looking for all out top end performance rather than the good drivability of the stock GN turbo cam.
Getting the valves open earlier for a street turbo engine vs a NA engine seems to be a trend looking at these numbers. It also seems that this is the opposite for a drag race turbo application.
NA IVC 60 ABDC = The valve closes 60 degrees ABDC GN IVC 58 ABDC = The valve closes before the NA cam by 2 degrees (sooner) G+ IVC 36 ABDC = The valve closes before the NA cam by 24 degrees (sooner)
Here we see that the GN cam gets the intake valve closed a little sooner than the NA cam, but not by much.
This trend of closing the intake valve sooner seems to be a trend that continues with the G+ cam.
NA EVC 20 ATDC = The valve closes 20 degrees ATDC GN EVC 14 ATDC = The valve closes before the NA cam by 6 degrees (sooner) G+ EVC -4 ATDC = The valve closes before (BTDC) the NA cam by 24 degrees (sooner)
Here we see that the GN cam gets the exhaust valve closed a little sooner than the NA cam, but not by much.
This trend of closing the exhaust valve sooner seems to be a trend that continues with the G+ cam as it actually starts at BTDC.
What have I learned from this exercise is that getting the valves both exhaust and intake open sooner seem to be a good thing when comparing NA engines vs mild street turbo engine specs. This also seems to hold true for closing the valves when comparing NA vs turbo cam specs.
In short mild street turbo engines open the valves sooner than on a naturally aspirated engine, the street turbo engine also closes the exhaust and intake valves sooner than on NA engine.
Now I know DOHC engines are going to be different compared to 2 valve push rod motor. I am simply looking for trends between NA vs Turbo camshafts for the same engines. I plan on doing a few other engines to see if the trends above hold true, if they do then I can use the numbers as percentages and see if my stock cams can benefit from a little manipulation like getting the valves open a little soone and getting them closed a little sooner… nothing extreem .
Lots to come on this subject, any thoughts, observations or criticism is welcome.
Thanks for looking
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11:57 AM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
Here are some numbers for a 3.8 V6 NA stock cam and a mild SC cam.
NA IVO -8 BTDC = The valve opens -8 (ATDC) degrees BTDC SC IVO -6 BTDC = The valve opens before the NA cam by 2 degrees (sooner)
NA EVO 40 BTDC = The valve opens 40 degrees BTDC SC EVO 52 BTDC = The valve opens before the NA cam by 12 degrees (sooner)
NA IVC 28 BTDC = The valve opens 28 degrees BTDC SC IVC 36 BTDC = The valve opens before the NA cam by 8 degrees (sooner)
NA EVC -12 BTDC = The valve opens -12 (ATDC) degrees BTDC SC EVC -6 BTDC = The valve opens before the NA cam by 6 degrees (sooner)
We can see that the trend is again getting the valves open sooner and closed sooner like the last two examples.
Its going to take some more math and time to figure out but what I gather from this little bit of math is that if I alter the NA cams in my engine I should be looking at shortening the exhaust and intake opening and closing times to bring them more in line with a turbo configuration.
These numbers are purely speculative for now, but I think I am on the right track.
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01:41 PM
Will Member
Posts: 14249 From: Where you least expect me Registered: Jun 2000
Comparing cams between 3.4 TDC and 3.8 won't necessarily be illuminating. The 3.4 has MUCH better head flow/displacement than the 3.8 or 3800. The 3.4 is also limited to stock or reground cams as blanks were never made. You'll probably just have to take what you can get.
You really should be looking at four valve engines turbo and non turbo even if they are four cylinder engines because the flow dynamics between an iron head early casting vs. aluminum head four valve casting are apples and oranges. The greatly increased flow in the four valve head may result in too much cam going by iron head specs. Remember the DOHC motor is already sluggish on the bottom end, too much more cam than stock will make it even worse before boost onset. Timing advance for example is much higher in the iron head motor than it is in the aluminum head motor, different principles at play but still a result of the difference in design and material.
Look at the stock engine specs and maybe add a little to them while at the same time reducing the overlap some. I know it seems like I always have something to say regarding certain subject areas, but much of what I hash out comes from the books I have actually read through like the one on camshafts in front of me now. The problem is that the information has not kept up with the technology as far as do it yourself books are concerned.
Do the flow math on your engine and go from their with your cam choice. You're looking at cams for two engines that are both larger than yours yet produce equal to or less horsepower than yours in naturally aspirated form so that can't be a good start.
Will you beat me to the punch
[This message has been edited by Joseph Upson (edited 11-24-2009).]
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02:09 PM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
Comparing these 3 sets of engine cam specs for Lobe Center Angle, Intake Center Line and intake/exhaust Duration
GM 231 NA vs Turbo Lobe Center angle NA 112 GN 110 We see LCA has a small reduction of 2 (Less) Intake Center Line NA 108 GN 110 We see the ICL has a small increase of 2 (More) Duration Intake NA 212 GN212 We see no increase in duration on the intake side for the turbo application. (Same) Duration Exhaust NA 212 GN212 We see no increase in duration on the exhaust side for the turbo application. (Same)
GM 3.8 NA vs SC Lobe Center angle NA 110 SC 115 We see LCA has a large increase of 5 (More) Intake Center Line NA 106 SC 113 We see the ICL has a large increase of 7 (More) Duration Intake NA 191 SC 210 We see a large increase in intake duration of 19 on for the SC application. (More) Duration Exhaust NA 201 SC 220 We see a large increase in exhaust duration of 19 for the SC application. (More)
Ford 3.8 NA vs SC Lobe Center angle NA 112 SC 115 We see LCA has an increase of 3 (More) Intake Center Line NA 108 SC 108 We see the ICL has a large increase of 10 (More) Duration Intake NA 200 SC 210 We see a large increase in intake duration of 10 on for the SC application. (More) Duration Exhaust NA 208 SC 226 We see a large increase in exhaust duration of 18 for the SC application. (More)
We can see that the LCA for 2 out of these 3 engines gets an increase, the exception is the GM 231
We can see all three engines increase for the ICL, a substantial increase in some cases.
We see the as far as duration goes 2 out of three engines get a substantial increase, the Grand National being the exception with the duration staying the same between the Turbo and NA cams.
Could the difference in these 3 be that 2 are SC engines and the oddball GN is a turbo car???
It seems looking at the info so far that while a turbo engine are supposed to suffer from long duration street turbo cams can stand a little more duration both on the exhaust as well as the intake.
It also seems evident that the ICL could use some increase when running a turbo application.
2 out of the three engines also had an increase in the LCA, the GN being the oddball again… could this be the turbo vs SC application???
More number crunching to come…
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02:22 PM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
Comments from you are always welcome, I have learned a lot from both you Joe and Will here at PFF. Besides with my volatile nature and soap box drama (according to some other members) you guys are some of the few members with skin thick enough to put up with me.
As always thanks for your input.
You are right the flow will be much different, between DOHC, SOHC and Push rod engines.
What I am looking for are the turbo cam spec trends with these engines, right now these are the engine specs I have readily available.
I plan on some sampling some DOHC engines as well to see if these observations will hold true, but full cam specs can be hard to find. I have been using comp cams as a resource for the numbers I have posted, their selection of turbo cams is limited so my search for DOHC specs will need another resource.
Wish me luck.
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02:36 PM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
My Idea for the cams is this, if I can source a 35mm lifter from another engine that is taller than the stock one it should give me a lot more room to change the specs. A taller lifter would mean that I would have to grind the entire cam down to get it back to spec. This would give me more material on the stock cam allowing for an increase if I need it. If I can not find a taller lifter I could machine the bore to accept a different diameter size lifter that is taller. At least that’s my idea.
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02:46 PM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
Supercharger cams are different still than turbo cams. Look into some updated books on cam dynamics. The basics are too much to put in a posting but not that overwhelming especially with illustrations. Early exhaust openning is contra indicated in turbo engines, for example, the turbo has greater exhaust back pressure compared to a supercharger which has no direct effect on the exhaust back pressure.
[This message has been edited by Joseph Upson (edited 11-24-2009).]
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03:35 PM
Nov 25th, 2009
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
I was suspicious about SC vs Turbo grinds, I have some Turbo/NA Eclipse DOHC specs I’m crunching now and should post them soon.
Any other cars that come with the same engine in both Turbo and NA trim that you guys know of that I can research let me know. I am most interested in DOHC engines but will look at almost anything.
Can't help on the turbo/na. Have you looked at the Z06 cam specs? 122.5* LSA on that s/c engine. I've always read that a wider LSA is better for boosted apps. Never heard of one so wide before now.
Can't help on the turbo/na. Have you looked at the Z06 cam specs? 122.5* LSA on that s/c engine. I've always read that a wider LSA is better for boosted apps. Never heard of one so wide before now.
If I'm not mistaken that excessive LSA is actually a result of VVT which I recall reading some of the LS engines have including the Vette unless I'm getting it mixed up. Not much was said about it in the past but some small blocks were sporting the same VVT function now found in the 3900 which also has a very wide LSA. I had it narrowed down to about 114 but no longer believe it is necessary since most traditional cam grinders don't think much of the GM V6 and are probably going by old standards. The wide LSA combined with the factory lobe specs is complimentary as demonstrated by the completely different results when both cams are advanced and retarded in Desktop Dyno. The 114 LSA does not like being retarded beyond 0 degrees at all. Otherwise the increased LSA is much better for reducing intake charge contamination with combustion gases.
It is, the extra wide LSA also helps in eliminating the EGR valve.
In the process of trying to gather more info on the effects of VVT regarding whether the maximum retarded position produces the greatest performance or actually results in EGR function and reduced power, I found a free cam selection software on the comps site:
Here are some numbers for Mitsubishi eclipse 2.0 DOHC NA stock cam and a mild Turbo cam.
NA IVO -14 ATDC = The valve opens -14 ATDC TC IVO -8 ATDC = The Turbo cam opens later by 6 degrees (Later)
Reference -14 means ATDC actually means 14 BTDC and -8 ATDC is actually 8 BTDC This means that the turbo cam opens the valve later.
NA EVO 26 BBDC = The valve opens 26 degrees BBDC TC EVO 40 BBDC = The valve opens before the NA cam by 14 degrees (sooner)
NA IVC 18 ABDC = The valve closes 18 degrees ABDC TC IVC 32 ABDC = The valve closes later the NA cam by 14 degrees (Later)
NA EVC -22 BTDC = The valve opens -22 degrees BTDC TC EVC -16 BTDC = The valve opens before the NA cam by 7 degrees (sooner)
Reference -22 means BTDC actually means 22 ATDC and -8 BTDC is actually 8 ATDC This means that the turbo cam opens the valve sooner.
We see in this example that the turbo intake valves open later and close later than the NA cam.
We also see that the turbo exhaust valve opens sooner and closes sooner than a NA cam
NA TC LCA 110 114 ICL 106 110
We can see that the LCA for the NA cam is 110 and the turbo cam gets an increase of 4 to make it 114.
We can see the ICL for the NA cam is 106 and the turbo cam gets an increase of 4 to make it 110.
What I have learned from this example:
Intake valves open and close later than NA cam. Exhaust valves open and close sooner than a NA cam. The turbo cam sees an increase in LCA vs the NA cam The turbo cam sees an increase in ICL vs the NA cam.
I will now have to search out other DOHC engines an apply the same math to see if it holds true for other DOHC engine examples.
Thanks for the interest. Numbers sourced from Crower.com
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01:47 PM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
It looks like this is going to take some room here on the PFF forum to work out, rather than clogging up my Turbo DOHC thread with this discussion I am Going to move it to its own thread “turbo camshaft grinds explored” any more speculative discussion on this subject will be posted here on PFF at https://www.fiero.nl/forum/Forum2/HTML/104913.html
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02:20 PM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
The meat heads at Action are giving me a little run around, they said they pulled the balancer nut and the numbers were no where close to the 7484. Not satisfied with this answer I called their sister yard to see WTF was going on, well they haven’t pulled any parts or balancer of the engine yet, so he is taking care of it now I should know something by 3:30 pm today (I hope) The engine is out of a 2005 Uplander, it should be the forged unit (I hope) I will let you guys know, when I know
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02:49 PM
Scoobysruvenge Member
Posts: 550 From: Richmond Virginia Registered: Apr 2009
I was just on the phone with GM and they told me that they only list one crankshaft number for the 2005/2006 Uplander #12577484. So it should be a forged crank.
