Yeah, the stock crank is a piece with only two counterweights. The Mercruiser crank is fully counterweighted.

The AMC 258 had a similar pairing... early engines used a fully counterweighted crankshaft that weighed 66# or so. Later engines used a lighter crank with fewer counterweights that only weighed 40ish #. For racing use, the 66# crankshaft is a MUST HAVE, despite the extra weight because the lighter crank can only take limited abuse, especially at high RPM.

Ok, well I travelled far and wide to Rancho Cordova today and managed to find TWO S-10's with a 2.5L installed, and I pulled one from a 91 or 92 S-10 that had been totaled in a crash - always a better bet. Long story short, I worked my way in the hot sun beyond complete dehydration/shutdown and was too weak to pull it apart after 3 hours of fighting with it, cursing, and being displeased with it in general. Though I did manage to pick it up and shove it in the passenger seat of my car, somehow.

Pics:


91-93 S-10 2.5L shortblock.


You can see that the water pump is indeed front mount... I'll need to route the belts and such to work, but it doesn't seem like it'd be difficult to do at all. I opened the lid on my current 2.5 car, and by eye it looks like it shouldn't collide with the frame, though I'll need to use a piece of flexi-hose type rad hose to connect it up to the coolant pipe - on the opposite direction the fitting comes out.



It is indeed true that the S-10 blocks have provisions on BOTH sides of the block for a starter... Wouldn't it be nice if all GM blocks did? The holes are tapped on the FWD side, even.



Hang on a sec... This block looks no different than most other iron duke blocks on the inside! Thicker castings, eh?


10044311, this part number comes up on Google under the following link: http://www.northeastmachine.../20030519catalog.pdf It seems to be listed as "2.5L OHV 4 vin A (trk) S10 chassis, Grumman body - postal vehicle" So I guess this block IS the very same block that's used in the Grumman LLV mail truck. It doesn't get much heavier duty than mail service... Which furthers my suspicions that a thicker block, much less Super Duty like block exists - except for the marine or SD block.


It is gear drive, like earlier dukes, as opposed to chain driven on the 91-93 car engines. I believe both VIN R and U went to chain drive in 91?

So long story short, aside from the water pump needing some work, it seems to have all the provisions required for the Super Dookie project, including distributor drive and provisions for the gear drive that the marine engines used also. I guess I'll take it and hope that the lack of complaints about blocks failing, and the possible mention of early blocks being used at 200HP power levels in early Fiero pace car development aren't far from the truth.

You forgot to point out one major difference between the car and truck blocks. If that is truly a 90's engine, it'd be missing the counter balance shafts, as used in the car engines. But that is what I have been looking for, pics of the inside of a S-Dime block.

Oh yeah, I forgot about that... The crankshaft is clearly from after when they went to DIS and had the balancer, but they don't use it. It seems to confirm what I've heard as well.

Put in some time after work again... The 1990 vin R duke's combustion chambers came out to 51cc's, measured twice with a digital burette and purpose made plexiglas chamber cover. I didn't have the proper spark plug on hand, so I installed some Bosch plug they use on the LS6 engines just as an approximation. It's likely the real plug will take up less space (this one seemed to be relatively long reach), so the chambers may measure closer to 55cc's or whatnot. If anything, I'll err to the safe side, compression wise.

Using Desktop Dyno 2000's Compression Math tool:

Bore 4.000"
Stroke 3.000"

Cyl Vol: 617.78cc
Combustion Vol: 83.27cc
Total Vol: 150.8ci
Compression Ratio: 8.42

Head Chamber Volume: 51cc
Head Gasket Bore 4.045" (measured old gasket)
Head Gasket Thickness 0.038 (measured old gasket)
Head Gasket Volume 8.0cc

Piston Down From TDC: -0.045"
Volume above piston: 15.00cc
Deck Volume @ TDC: 24.27cc

GM says 9:1 compression ratio, though it's not far off. It looks like if I zero deck the block, we're looking at 9.35:1, or almost an entire point increase. This does not account for going .030" over though. With .030" overbore, it looks like it comes out to 9.47:1 CR, just about perfect. So either achieving zero deck, or milling the block down to zero deck should work out pretty well in terms of compression and quench, though one may require different pushrods or rocker arm spacers though.

Here's some more brain picking since I have purchased a mercruiser 3.0 late model crank. The mercruiser puts out 140 hp, is that because of the extra cubes, cam ,heads ,compression or what? Does anybody have the cam specs of both the 2.5 (110hp) and 3.0(140hp) mercruiser. Do all the 2.5 heads have the same shape and size combustion chambers? A small chamber head would be more efficient in all aspect, mpg and torque or at least that's what I think, plus having a longer stroke and hopefully long rods (6"). Also what is the best CR to run on 87 octane. I'm also going to have to find an 86-87 duke block and add a crank trigger since this is going into an 88. Will I need a cam positioner sensor? One more question, Some say they're getting 40+ mpg with a 5 speed and a duke. What is the gear ratio in 5th gear? I was thinking if I could get more low end torque I could go one gear ratio higher ( lower number) and increase mpg. Using a 4T60. Good thinking or not?

------------------

85 GT 3.4
14.9 @ 90 1.9 60' Old TH125/3.06
Unknown New 4T60/3.42

quote Originally posted by Blue Shift: GM says 9:1 compression ratio, though it's not far off. It looks like if I zero deck the block, we're looking at 9.35:1, or almost an entire point increase. This does not account for going .030" over though. With .030" overbore, it looks like it comes out to 9.47:1 CR, just about perfect. So either achieving zero deck, or milling the block down to zero deck should work out pretty well in terms of compression and quench, though one may require different pushrods or rocker arm spacers though.

If you want gas mileage (commuter car, right?) go all the way to 10:1. You should be able to run that on 91 if you get the quench right.

quote Originally posted by Lilchief: Well I talked to my engine builder today and he said we could use a crank trigger and cam position sensor on a 86-7 block with a mercruiser crank and make it compatible with the 88 ecm.

86 and 87 car blocks are not similar. 3.0 cranks don't have a crank trigger. Are you talking about using an 88 truck ECM with distributor?

KurtAKX : I'm not sure on what year they changed the block, was it 87 when they change to the DIS and internal oil filter? I need some inlightenment on the issue. I'm Wanting to use my 88 Fiero ECM. I went out to look at the engine and the key doesn't work. So I'm at everybodies mercy right now till I get it open. I was talking about an external crank trigger and adding a cam position sensor to the cam gear cover with the gear modified by adding a magnet or something similiar. So what block do I need? An 85-86?

quote Originally posted by Lilchief: KurtAKX : I'm not sure on what year they changed the block, was it 87 when they change to the DIS and internal oil filter? I need some inlightenment on the issue. I'm Wanting to use my 88 Fiero ECM. I went out to look at the engine and the key doesn't work. So I'm at everybodies mercy right now till I get it open. I was talking about an external crank trigger and adding a cam position sensor to the cam gear cover with the gear modified by adding a magnet or something similiar. So what block do I need? An 85-86?

84 is distributor, flat lifter
85-86 are distributor, roller lifter.
The changeover happened over two years. 87 was the first year of crank trigger. "regular" oil filter, no balance shafts.
88 was the first year of balance shafts and internal oil filter
You don't need a cam position sensor at all to run the 7748 ECM which is the stock ECM for both 87 AND 88.
If you're doing an external trigger like those TCE guys do, then you could really use any year block.

KurtAKX: Thanks for the engine info. I got my mercruiser crank today, $60 off ebay. Now I need to find a 85-86 2.5 block and a 90s model head and intake. Managed to get the trunk open too.
Blue Shift: Didn't mean to high jack your thread (is that the right word) but this is something I'm interested in too. And I won't know if I don't ask. So what is the balance shafts?

Hmm. So I was browsing around when I found the Gilbert Chevrolet website, which mentions a part number 00347056. Described as: "Pontiac - Performance cast-iron, designed to be used on 151ci or 153ci engines. (Single Head)special order only" 358 bucks... Is that the super duty head? On the CG forum, somebody replied to a question about it:

Jerry,
This head has been in GMPP's catalog for years, but they have never said more then this about it. I copied all the information directly from their catalog. They no longer show it in thier catalog, but it is still available. This part we don't stock because it's a 4 cylinder head and you are the first person that I know of that has even asked about it. Since we don't have one in stock, I can't take a look at one. Actually I don't see any dealers having one of these in stock, but there are 68 of them at one of GM's plants. You may have to contact GM directly about this head through their GM Goodwrench site which now incorporates the GMPP products.
http://www.gmgoodwrench.com...p/perfparts/home.jsp

Hey Blue, I think that head is non-crossflow. Also since you work at a machine shop, maybe you could tell me how much the .060" difference in CH between the 3.0l merc pistons and stock 2.5 pistons will affect my comp ratio?

quote Originally posted by patch: Hey Blue, I think that head is non-crossflow. Also since you work at a machine shop, maybe you could tell me how much the .060" difference in CH between the 3.0l merc pistons and stock 2.5 pistons will affect my comp ratio?

I tried posting once but the forum ate it. Take 2:

So you have the stock piston (and SBC pistons) at 1.560"CH, and the Mercruiser pistons are supposedly 1.625" CH, which gives you a .065" increase in compression height. It could vary, depending on the source you read the specs from. Assuming the stockers sit .045" below the deck (and this assumption is based off of one piston I measured on one bore with a beater caliper), the Mercruiser pistons will sit .020" ABOVE the deck if this is the case, leaving a mere .019 of head gasket left for quench - about half of the .040" that's advised here. Entering it into Desktop Dyno 2K, the compression goes from 8.5:1 stock (with .030 overbore) to 9.98:1 with the pistons .020 out of the hole.

Now that I think of it, one crazy idea would be to use one of those "head saver" shims to bring it all up to the right height with mercruiser pistons...There is also a remote possibility that the Merc pistons could end up somewhere near zero deck for this engine as is; I've read that the stock compression distance is supposed to be 9.06" for the duke parts, while the deck height is supposed to be 9.150" - If and only if this is true, the stock pistons sit .090" below the deck, and you could fill .065 of that with Merc piston, then mill .025 off the block to make for good quench!

See, what I need to know is the factory specs for the 2.5 crank centerline to deck height. It's easy to find the lengths of the rod and piston compression distance, but without knowing what the block deck height is supposed to be, we're all guessing here. I could possibly try to mic my block at work and see what I can find, but it'll be hard to measure accurately. Still I suppose it's better than trying to measure from the top of the piston to the deck.

Artificial displacement enhancement:








Its been hard trying to build a Super Duty, a SC motor, and set up a P4 ECM swap for stock engines all at the same time, but here's what I was plugging away starting to mock up last night.

I think those vice-grips will play hell with your hood, . . . ;^)

Norm

Where will the fuel come from?

quote Originally posted by Will: Where will the fuel come from?

Gas tank

quote Originally posted by Will: Where will the fuel come from?

'7749 Turbo Sunbird ECM (compatible with 2.5 distributor)
Port fuel setup with injectors pointed up from under the runners like "Turbo Super Duty" thread (not ideal, but still better than TBI)
3800 SC series 1 injectors.
Haven't found a convenient fuel rail to parts-bin yet.

The real question is "what will you do to the passenger side strut tower to clear that SC nose?"

[This message has been edited by KurtAKX (edited 08-20-2008).]

quote Originally posted by KurtAKX: '7749 Turbo Sunbird ECM (compatible with 2.5 distributor) Port fuel setup with injectors pointed up from under the runners like "Turbo Super Duty" thread (not ideal, but still better than TBI) 3800 SC series 1 injectors. Haven't found a convenient fuel rail to parts-bin yet. The real question is "what will you do to the passenger side strut tower to clear that SC nose?"

It would probably be a lot easier to go with a centrifugal supercharger such as a Paxton or Vortec supercharger. They are smaller, lighter, easier to mount, and easier to integrate an intercooler on.

quote Originally posted by Doug85GT: It would probably be a lot easier to go with a centrifugal supercharger such as a Paxton or Vortec supercharger. They are smaller, lighter, easier to mount, and easier to integrate an intercooler on.

While I don't disagree that CSCs are much easier from a vehicle integration standpoint, the ultimate goal of this exercise is to have something that anyone can duplicate in their backyard with cheap off-the-shelf parts (like the 94-95 Series 1 blower and injectors).

The other driver behind this is that since we run out of useable revs so quick, this application is much better suited to a positive displacement forced induction solution. CSCs are like turbos in that they don't make full boost at low RPM.

That clears a lot up. I can see where you are coming from.

What if you rotated the engine 45 deg towards the firewall, then built a transmission adaptor plate 45 deg offset and treated it just like 1/2 of a SBC. The supercharger should clear the strut tower easily but the exhaust and engine mount would have to be redone.

[This message has been edited by Doug85GT (edited 08-20-2008).]

Flip the intake and mount the supercharger on the bottom side. This might get you the needed clearance (or atleast make it less of an issue). The alternator would need a new home, but hey if it was easy everyone would do it. Then for grins you could put a stock 2.5 air filter housing on it.

I like the supercharged 2.5 concept!

[This message has been edited by fieroguru (edited 08-20-2008).]

quote Originally posted by fieroguru: Flip the intake and mount the supercharger on the bottom side. This might get you the needed clearance (or atleast make it less of an issue). Then for grins you could put a stock 2.5 air filter housing on it. I like the supercharged 2.5 concept!

I was going to suggest that... gear drive it off the cam!

Why an M62 instead of M90? The M90 should be at LEAST as easy to get as the M62.

Less mass to spin? . . . . It's a 4 banger after all, sometime one CAN get too much of a good thing.

Norm

quote Originally posted by Will: I was going to suggest that... gear drive it off the cam! Why an M62 instead of M90? The M90 should be at LEAST as easy to get as the M62.

The pulley ratio I'd need for a blower with that much displacement per revolution would be pretty comical looking. M90 is just too damned big. I'd have to turn it too damn slow.

I have yet to secure the crank, rods, or pistons from the Mercruiser 3.0L yet - I'm currently bogged down finishing off (another) 383 for my boat, but it's almost done. If anybody has the aforementioned parts for sale, or knows of any for sale, let me know!

quote Originally posted by KurtAKX: The pulley ratio I'd need for a blower with that much displacement per revolution would be pretty comical looking. M90 is just too damned big. I'd have to turn it too damn slow.

Haha, who cares how it looks? I saw a guy with a 6-71 on top of a 355. You know what pulley ratio he had on it? He UNDERdrove the blower. The blower pulley was bigger than the crank pulley. You're not using the 3800 guys as guidelines for how fast to turn the thing, are you? They overspeed it so much it's not even funny.

quote Originally posted by Will: Haha, who cares how it looks? I saw a guy with a 6-71 on top of a 355. You know what pulley ratio he had on it? He UNDERdrove the blower. The blower pulley was bigger than the crank pulley. You're not using the 3800 guys as guidelines for how fast to turn the thing, are you? They overspeed it so much it's not even funny.

No, I have to underdrive so much its not even funny. I'd have to run it at just about 1:1, at which point its going so slow air slips back past the rotors.

Here are some specs on Eaton superchargers. The M62 should be more than enough for the 2.5 Duke.

http://www.capa.com.au/eaton_m62data.htm

[This message has been edited by Doug85GT (edited 08-21-2008).]

quote Originally posted by Doug85GT: The M62 should be more than enough for the 2.5 Duke. http://www.capa.com.au/eaton_m62data.htm

Correct.
The engine this unit came off of was a 3.8 liter, and it moves enough air to make 225 hp, so its plenty large enough for my application. Its actually just about ideal.

I'd have another problem with the M90, which is trying to fit its wider case in between the 2.5's valve cover and the trunk.


Oh yeah, edit to add that M62 is what lives on the LSJ 2.0 SC Ecotecs making 205 hp, which is all the more I'm expecting in this build.

[This message has been edited by KurtAKX (edited 08-21-2008).]

KurtAKX: Did you come up with a solution to the tensioner proplem. I'm wanting to use a 85-86 block in a 88. Could I just use the stuff off the 85-86 as far as belts go?

Some more questions. Did 85-86 2.5s have serpentine belts or v belts? I looked at a 86 citation 2.5, it had vbelts. Would this be a problem going into a 88 ?

quote Originally posted by Lilchief: Some more questions. Did 85-86 2.5s have serpentine belts or v belts? I looked at a 86 citation 2.5, it had vbelts. Would this be a problem going into a 88 ?

Yeah the dukes up to 86' had V-Belts in them. I believe they changed in 87 to Serpentine. And DIS. And no provision for a distributor or conventional oil pump. So yeah, unless you're hellbent on using the mercruiser crank like I'm going to try, I would advise against using a pre 88 duke in your 88. In fact, if you want to stay 2.5, go find yourself a 1990+ Vin R duke from a Cutlass Ciera - 110HP stock, and much improved. It'll drop right into an 88. Otherwise, find yourself a crank and welcome to the experiment.

Also, progress is quite slow right now - Between work, 3 hours on the road a day in commute time, and finishing off my boat engine (timer is ticking to get it broken in before the cam lube drips off!). I'll be investigating sources of more parts this weekend.

More interesting info I found after finding a late/recent 3.0 crank that said to be .955" rod journal width. I found this info: http://www.standardcranksha...atalog.html?sid=4740

181 3.0 4 74-93 Marine application used in Mercruiser and OMC engines with a two piece rear oil seal. N393775, N398776, N9341352 44 12430
3.0 4 94-99 Marine application used in Mercruiser and OMC engines with a one piece rear oil seal. Rod thrust width is 1.035". N14094623, 14096624 54 12870
3.0 4 00-04 Marine and industrial application. The crankshaft is not machined for a pilot bearing or bushing. Rod thrust width is 1.035". 14096624 54 10470
3.0 4 00-05 Marine and industrial application. The crankshaft is not machined for a pilot bearing or bushing. Rod thrust width is .955". 93436083 54 10480
3.0 4 00-05 Marine and Industrial application. The crankshaft is machined for a pilot bearing or bushing. Rod thrust width is .955". 14096624 54 10500

So I think it's clear we need to avoid the early 3.0 crank. One could go with the normal Marine crank and use the Chevy I-6 style rods, but what's with the crank with .955" rod journal widths? I think its small block width. I-6 rods are supposed to be 1.029" wide, and the actual bearing surface on the crank measures 1.035". A small block has a .940" wide rod, so .955" seems reasonable. The only thing that's unclear is the diameter of the journals. If it uses SBC rods, then it opens up a HUGE door to performance rods - one could get them in any length or style desired. Now if only we had a good block...

Well I guess I'll have to check to see which crank I got, it's a 99 one piece. But i did some engine shopping at the junk yards, for a good block to start with. I was looking for a 87 2.5. Found one in a 87 Ciera ( door said mfg date 10/86 ). Want one with external oil filter, serpentine belt and no distributor. Will I have any problems using this in a 88 with a 4T60 ( interference with oil filter )? And where is a good place to find a roller cam ?

quote Originally posted by Lilchief: Well I guess I'll have to check to see which crank I got, it's a 99 one piece. But i did some engine shopping at the junk yards, for a good block to start with. I was looking for a 87 2.5. Found one in a 87 Ciera ( door said mfg date 10/86 ). Want one with external oil filter, serpentine belt and no distributor. Will I have any problems using this in a 88 with a 4T60 ( interference with oil filter )? And where is a good place to find a roller cam ?

Hold on a sec, anything that's DIS (which I was sure 87+ is, though trucks were distributor all the way to 93) will not work with the 3.0 crank - it doesn't have the big gear needed to drive the balancer/oil pump setup. You'll probably need to use an 86 and down block to make it happen, which is the route I'm taking.

quote Originally posted by Lilchief: And where is a good place to find a roller cam ?

Iron dukes 1985 and later of all flavors. Just be aware that you can't put a roller in a 84-earlier block because you've got to use the "figure 8" lifter alignment guides that fit the 85+ blocks.

The Fiero store sells an aftermarket roller which is still very streetable but is significantly bigger than stock.