Well, I broke down and decided to start porting out my spare set of heads for my 3.4 DOHC. I saw firsthand some great improvements that can be made to these heads with minimal knowledge (no not a rip on anyones inteliegnce) and minimal work. So I figured that since this can be done with such ease, I would show the rest of the fiero community things to look for and hopefully some real good looking (and performing) results. For those of us that are not aware the stock 3.4 DOHC heads are lacking flow on the exhaust side, as shown from this chart...

Here's the data. (Taken at 67*F using a PMI9000 flow bench, 28" of water. We used a short molded entry to the itake and no pipe on the exhaust):

[Sorry if the columns don't line up perfectly.]

Lift intake Exhaust
.050 49.0 28.6
.100 96.3 74.2
.150 139.6 98.6
.200 177.3 125.7
.250 206.9 139.7
.300 232.5 148.7
.350 252.5 154.8
.400 263.5 155.95
.450 267.5 157.1
.500 268.7 157.2

as seen in this thread: http://www.60degreev6.com/index.php?name=PNphpBB2&file=viewtopic&t=7190

So as you can see the stock ports on the exhaust are far less than the "perfect" 80% flow, which is probalbly why they re-designed the 96-97 heads. So basically the goal that I'm having in my head porting is to fine tune the intake side and do as much as i can with the exhaust side to open it up, which should hopefully get me closer to that perfect flow ratio. So here are some before pictures:

Just a basic shot of the heads dissassembled and cleaned up a little.

A pic of the difference in valve size between the exhaust and intake valves.

Bottom/exhaust side

Top/intake side

Exhaust side bowl area

intake side bowl area (the arrows point to an area where the mill left a flaw, this is also present on the exhaust side but because of the carbon build-up it is hard to see but definatly can be felt.)

Exhaust side inner bowl/transition area, the arrow points to the divider that takes up some flow area.

Simular shot of the intake side... ahhh much better

the port view of the large divider

a simular view of the intake side

i have a ton of gaskets including all the stem seals. I know I dont have head gaskets, but anything else you need, lemme know I'll see if I have it.

Excellent thread! I'm sure that there will be a number of people who will be interested in seeing your results. A + fpr you!

Nolan

Still waiting on the porting kit, i think it'll be here tomorrow.

86GT3.4DOHC... I will probalbly end up ordering a gasket kit because its usually cheaper to get the whole kit than a few odds and ends, but if i need anything ill let ya know.

sourmug, thanks for the feedback, i'll try to keep it as detailed as possible!

Hey madman thanks for the write-up. It's always good to have some knowledge of differant heads and runner designs. Please change the macro setting on your camera , that will help to clear the pics up.

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HARDCORE SBC CRONIE AND PROUD OF IT ! GOT TQ ?

Just to add to the knowledge base for those (like me) who have never done any porting:
http://www.chevyhiperformance.com/techarticles/95518/
http://www.sa-motorsports.com/diyport.shtm

Nolan

fierofreak, the first like 3 posts in the thread were all my camera too (and they look pretty good imho). they seemed to work fine close up. I hadnt had the camera long enough to learn about the macro mode when i took the pictures of the friends port work, so before i shot pics of my own heads i figured it out. so when i start porting my own set i should have some good pictures to show. sorry about the ones that describe what i would like to accomplish, they do truely suck. Good reading sourmug, i'd give you another plus but it wont help me. and i know i allready said this but it was confirmed when i tracked the port kit, it will be here tomorrow :-D

quote Originally posted by fieromadman: As of now I am waiting on a porting kit that should be here tomorrow or thursday at the latest. To see the port kit that I ordered, go here: http://store.summitracing.com/ and enter part number SUM-G1060.

+

I love it when people post part #'s , it doesn't happen too often

I'm looking forward to seeing your results....especially since the DOHC presentation you and Dave put on has me VERY interrested in this engine.

good luck

Well i recieved the porting kit and started to port today. Whew! its going to be alot of work! I have 3 hours into it so far and have gotten a little over half of one of the exhaust ports done. I plan on doing more tonight but I need a rest from doing this. I got some more pictures to share though!

I setup the workbench so that I have a dropcloth under it so all of the metal shavings fly on to that instead of the floor and also when the workbench gets covered i dont feel bad about brushing it on the floor. I elected to use a standard die grinder to do the porting, the only thing with using that is that its easy to get too high of an RPM and chew up the bits, especially the smaller ones. The summit kit that i ordered looks like it should work out ok but I wish it had more 60 grit large rolls because with the gasket matching and the grinding of that hump below the divider it takes up alot of the bit, im half way through the first bit and still have not completely finished that port.

to start i marked off the area around the ports with first a scribe to put a little edge on it i could feel then i used a sharpie to trace the area outside of the scribed mark so that if i start taking off pieces of the blue i know that i have gone too far. other than that i just went to town on the thing, grinded out that hump and increased the inner port size because flow is only as good as its smallest part. i also did the bowl area where their bit left imperfections. I also tried to take out anycasting flaws and blend the bottom part of the port from the bowl area through the dived area. this was hard because you are limited with what angles you can get the bit in there.

as you can see grinding that hump off is quite a challenge, but i think that it will increase flow alot when it is all blended together.

here it is finished up on the one side and pretty well stock on the other except for the hump being ground away and the gasket matching. if you look closely you can see a difference in the port size.

continued on the next post...

Looking good so far. Yes I imagine that it's going to be a lot of work.

Nolan

i got that whole port finished tonight, so i have one to go from, now its just systematically going through each of the other exhaust ports to make it looks like that one. i started gasket matching and removing the hump on the other 2 ports on that head, i will be starting to do that to the other head tomorrow as well. I think that its looking pretty good so far. i havent polished it yet, but i plan on doing all of that last.

Ok, well I spent about 2.5 hours on the heads today, and got quite a bit accomplished. Like I said in my previous post, I was planning on going through all of the exhaust ports in a systematic way so that I'm doing everything simular and in order to keep my porting equal in every way possible. Besides that it makes it easier because you dont have to turn the head constantly in order to see what you are doing. Things are going quite well so far.

Heres a picture of the one exhaust port that was allready done today.

And heres the work that i started to do today, removing that ledge in the exhaust port and also gasket matching it.

A simular angle to the first picture that I posted today. Notice how you can see alot more of the valve area on the ported one than on this picture. It's quite noticeable in real life.

and this is where i ended today with all of the exhaust ports gasket matched and with the hump/ledge removed. Next will be the bowl work and just opening up the inner port size to match the bowl and gasket matching.

just a close-up of the gasket matching and hump removal. Grinding down that hump takes quite a bit of time especially to make it flow well, but i think that the gains will be worth it.

The majority of the time spent on the exhaust side will now be spent grinding away at this area on all of the ports that are left. Its really hard to get the tool in there properly to make it flow, but I have been having ok luck, and i think that the increased size will make it far worth it. Besides that, if you look at the areas that i have ported in allready you can see the grit on the bit is fairly low, like 80 grit i believe, so i still need to spend time polishing the ports with a higher grit bit.

More sometime soon! Any comments are appreciated, even if you think that I am doing something wrong, or you would do it differently.

I pulled a spare set of heads out and looked at them. Be careful with that hump that runs across the exaust port, I was probing the coolant passage and best I can tell, the hump is very thin. I dont know what idiot designed this head, while the intake it great, the exaust port has 2 coolant passages runging through it, WTF....

it has TWO passages running through it? Wheres the other one, i saw the one running through the divider, and i havent really done any grinding on the divider, just a little bit. The part that i was most concerned with was the grinding away of that hump in the exhaust port, but thats done on all of the ports and theres no holes yet. judging by the visual inspection that I gave, i dont think that theres a coolent passage that runs right by that hump anyhow. Ahh hell, if these heads blow, i can always put my other set back on lol!

I thought I read someone people were getting over 300cfm through these heads when ported? Sounds well worth it.

i was refering to the hump at the bottom of the port, it too is a coolant passage

you mean the hump that i allready ground down completely on all of the ports (in most of the pictures the heads are upside down...)? I guess I remeber a coolent passage going there but it seems a little more towards the block than where I'm grinding, I'll take another look at it.

I spent some time doing some research today, and came across this again: http://60degreev6.com/modules.php?set_albumName=DOHC&op=modload&name=gallery&file=index&include=view_album.php&page=1

Theres a bunch of cut-away views of the earlier heads, and it does indeed show that you have to be really careful int he exhaust ports. The bottom part of the area on the exhaust port right past where the valve is has a coolent passage in it as well, so I'm going to have to be really careful about not grinding away too much material there. On the one port that I allready finished i fear that I may have made it too thin. I guess time will tell! (fingers crossed)

On another note, I made a little more progress today, cleaned up 4 of the exhaust bowls so far, will probalbly go back to it later today. I'm working on getting some pictures of what some of the "professional" 3.4 DOHC head porters have done and I hope to compare notes before i go much farther.

.

[This message has been edited by Dave Gunsul (edited 03-29-2006).]

Well I finally got around to working onthe heads again. I started out tonight with ahving all fo the exhaust ports gasket matched and 6 of the 12 exhaust bowls ported out and one of the exhaust ports completly done.

I first started by finishing up the bowls....

one head down....

even though all of the ports on that head had the bowls done and the ports gasket matched there is still the matter of porting out all of the insides...

yep.. looks like the insides need to be cleaned out

but the bowls look good except for that line that is visible in some parts of most of them. id decided to leave it because i didnt want to create and indent in the bowl to direct air in the wrong direction. It is pretty smooth with anyhow and i feel that the shape will have decent flow to it.

both heads bowl areas are done:

continued on next post....

Looks good.

i liked the other guys' better.

..

[This message has been edited by Dave Gunsul (edited 03-29-2006).]

Nice work, but one question.

I've come to understand you need to polish your exhaust ports to prevent carbon buildup and to promote clean air movement. Similarly, I understand one polishes the intake bowls. I see you've left them rough so far. Is polishing still coming?

Arn

Edit - sorry, I missed our comment about polishing Nice work. Please show us the pics when you're done.

[This message has been edited by Arns85GT (edited 12-15-2005).]

I intend upon keeping this thread updated and even giving driving impressions when they get put on. So trust me, you will see pictures of them done!

As for the polishing, i do need to polish the exhaust ports still but i think that im going to hold off on polishing the intake ports because i have heard that the rough surface helps to promote better fuel mixture. Like I have said, I intend to keep it pretty simple on the intake ports, just knife edging cleaning up any casting flaws and cleaning out the bowls.

Josh,
Gee.. I wonder why you like the other guys heads better!!

probably because that guy is an artist. your mount is done.

My Grandmother could port heads faster than you.

Make any progress lately?

James, what do you think I am, some sort of a machine!? No, I didnt make any progress, now lay off me!

I was hoping that I would find some time lately, but just havent. Its not like Im stopping the project though, I just need to find some time, prolly after the holidays.

As a side note, I've been driving my car lately and have the itch to get more power, especially in the higher RPMs so I'm very happy that I decided to do the ehad porting, its just that now I might need light weight lifters and another chip with a higher rev limiter if all goes well.

Slightly off topic: If/when I'm looking for a 3.4, what year/model is the best and what should be avoided?

quote Originally posted by Gokart Mozart: Slightly off topic: If/when I'm looking for a 3.4, what year/model is the best and what should be avoided?

All of the models are the same. As far as years, there are 3 "gens," 91-93, 94-95, and 96-97. None are really best or worse, they are all pretty much the same. The 96-97 had better intake manifolds, better exhaust side on the ehads, but the cams aren't as good and havn't been adjusted yet by anyone with good gains. The 91-93 wiring harness/ECU is the most popular and simple (OBDI), but has its drawbacks. It is not nearly as accurate, cannot be tuned as well, and is batch fire, where it fires each bank together, thus "pooling" the fuel charge on the closed valves. The 94-95 uses a 4-wire O2 sensor, camshaft position sensor, an extra crank sensor, and fires the injectors sequentially for more low and torque. It is also more complicated. It is known as OBD1.5. OBDII, 96-97, is the most complicated and the most accurate. It also makes for a harder swap as far as wiring is concerned. You can run any year engine on OBDI, and you can run a 94-97 engine on OBD1.5. I chose 94-95 becuase it is, IMHO, the best compromise between air/fuel accuracy and complexity.

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"all pushrod motor are better than the dohc because it has less rotational mass"
-rick17, MyMonte member, owner of a 3100 Monte Carlo LS

Lots of pics, few numbers.

Flow numbers tell the story. How about some before & after polishing?
Or now?

I dont have a flowbench availible to get get flow numbers. im doing this on my own at home just because i feel that i can make some decent horsepower for really cheap after looking at all of the flaws that these heads have. If i do get a chance to get them flow tested im sure that i will, but i just dont see it happening. i do have stock flow number to compare to if i ever do get them tested though.

well i finally got around to the heads again tonight. I remebered that i havent had a chance to post the picture of all of my spare head parts. Ahh yes... 24 valves and springs and keepers and etc... Yes i know that my valves are in desperate need of cleaning...

Well heres what i started working on today, finishing up all of the exhaust ports. notice how the right side is smaller than the left... that was the only one left that i needed to gut the insides out on yet.

heres an overview of the exhaust side of that head at that point. notice all of the marks. i used those to tell me what had been done allready so i didnt forget to port anything and also didnt do anything twice.

the non ported side.. (from the bowl angle)

VS the ported side..

heres a few views of the finished bowls..

the other side of that bowl...

continued on next post...

I bought a port and polish video from summit. It said to leave them unpolished to give better fuel atomization and to avoid fuel puddles.

Justin