i was reading deans post on the 60*v6 performance manual(sticky) and it was talking about how all rwd and fwd drive v6's from 82-86 got cast iron, and how 87 and up fwd got aluminum. i'm guessing they didn't mention rwd because they don't exist. but since i'm building up a new 2.8 anyways i figure its worth a shot to try and find some btter heads

i'm pretty sure its a no, but hopefully one of you can prove me wrong

 

you can run the aluminum heads on a RWD motor but your will have to run the FWD pistons to get you the right compression ratio and you'll need a custom intake manifold.

 

yeah i knew about that, kinda figured it was only fwd that got aluminum heads

 

So the FWD heads have less compession then ours? Could they be milled to regain it? Sorry have not researched this at all!

 

no....the have very small combustion chambers. they will make the CR about 12:1 (i think) if you try to run stock RWD 3.1 pistons with those heads. the FWD pistons have a bigger dish.

 

Thanks! Ok I got ya, did not know which way GM took them! That would be some serious compression though! Funny how they got the aluminum heads. We have the performance cars! Honestly you would have thought GM would ahve done more to the heads when they went to the 3.4.

 

GM used those aluminum heads for the high output Celebritys.

 

Yes, the rwd engines generally had more power i believe.

 

i'm not sure which had more hp but the FWD motors weren't really tuned to be hi-performance. they probably didn't have very good cams. there is no question that the aluminum heads are better and it would have been nice if GM had put them on the RWD motors.

 

i still don't understand it. a camaro should have power, even a v6 one. so we should of gotten aluminum heads

 

What's to understand? We are talking about GM here. From the research I have done on it, GM didn't use them on the F-bodys because of CAFE (Consumer Average Fuel Efficiency). Apparently, the heads worked better on the RWD cars but it also raised levels of gas consumption and pollution.

 

Of course, sacrafice the f-body so they can have the gas guzzing emissions polluting SUVs, but still keep the average pollution down of the GM line!

 

3.1 pistons are cut for the valves? They'll actually work with the splayed valve arrangement of the Gen II aluminum heads?? Did someone prove this, or are we just guessing? I mean I could see this working if the aluminum heads had valves that were perpendicular to the deck, but they're not, they're at angles...!

 

no, 3.1 pistons do not have valve pockets cut or anything but neither did the FWD motors. they have deeper dishes in the pistons. i have 2 or maybe 3 of these motors at the shop so i have looked at the heads and pistons a few times before. i would guess that you could have problems with clearance between the valves and pistons if you tried to run RWD pistons with the FWD heads, along with the compression issue. but, FWD pistons with those heads then all you have to worry about is and intake manifold...

 

Hi,

I've a "high output Celebrity" with flat top pistons and stock aluminum heads. I use felpro head gaskets and 0 lash + 1/2 turn in valve adjustment, but I need burn my EPROM in order to run good ( I have 19lbs Denso injectors too).

Emmisions are legal (HC: 95 ppm, CO: 0.2% - max: 100ppm, 0.5%).

Denis V.

 

flat top pistons and aluminum heads? what kind of compression does that give you? i'd guess that its fairly high.

 

HA, Exactly!

My first compression gauge did: POF!... and died.

Today is 238 PSI per cylinder (at first, was 248 PSI).


Denis V.

 

my fwd 2.8 liter on my chevy corsica has aluminum heads.

 

So for RWD, the 3.1 is a flat top just like the 2.8 RWD piston? But 3.1 & 2.8 FWD pistons are dished a little?

I've been meaning to go to a junkyard and pull the top off a FWD Gen II motor, just never got that far. (Actually I only went to a yard once all summer... and it wasn't even for my Firebird- go figure.)

 

2.8 FWD pistons are dished A LOT. 3.1 I think is the same (only strokes bigger than 2.8, i think).

Newer 3100 SFI FWD pistons (Chevy Lumina/Montecarlo 1997 & around) are dished too.

The "dish" is a big chamber (in c.c.) .

 

no, the RWD 2.8 i think is flat top. the 3.1 RWD has dished pistons stock. i would guess that the FWD 3.1s have a bigger dish than the FWD 2.8s because of the longer stroke. either that or the FWD 3.1s have a higher compression ratio than the FWD 2.8s.

Denis.V do you know your compression ratio? not just the PSI per cylinder...

 

No, sorry, I don't have idea about compression ratio. Only PSIs.

(Stock CR was 8.9:1. I think if the dished space is reduced to zero, the new combustion chamber will be around 1/3 than the stock).

 

O.K. guys:

I did a long, long search and I found one of my old dished stock pistons. I did some measurements and I got some specifications from Chilton's and www.60degreeV6.com.

Then, I put all data in the "juice machine" (liquateur) = the compression ratio calculator from www.camaroz28.com and,

My new compression ratio is:............

14.1

And my new max HP: 151


Denis V.

 

14.1?? do you run that thing on Av Gas? or just run the timing about 10 degrees retarded?? how do you manage 14.1:1?

 

HA!, Yes, near to Jet A-1(101 octane):

I use 97 octane gas and I'm testing timing retard without knock around 13º (I just buy a new battery for my laptop in ebay).

One main thing for manage this CR without knocks as a "carpenter bird" (or "woody woodpecker") is to put the coolant temperature into a min. variation range. For this reason, my cool. fan starts @ 92ºC and stop @ 89ºC (88ºC is 190ºF).


Denis V.

 

you must have better gas in Chile or something. I'm running 93 octane pump gas with my 10.75:1 CR, about 12 degrees of base timing and I get *some* spark knock. And, my motor almost never gets above 160 degrees F.

 

Local gas stations only have unleaded gas 97 , 95 and 93. The law use the "California emissions" parameters for cars test since 1993. All the companies uses additives in its gas for marketing purposes. Shell uses "anti-friction treatment" for "better mileage" and other local company sells the ridiculous "ultra-green gas" for no-contamination.

Note that my 13º retard were by retarding the complete "main spark table". You speak about "base timing". It's the same?.

 

OK, let's toss some info out.

1) 2.8s and 3.1s RWD have flattop pistons. The difference is the compression height.

2) '87+ FWD = aluminum heads

3) Al heads = 26.5cc

4) Fe heads = 49.5cc (both are IIRC)

5) AM91, he's taken 13º TOTAL timing out of the spark tables... that means he's running like 23-26º total, vs your what... 36º?

6) The difference in chamber size, in the FWD vs RWD heads/pistons, is taken up in the dish of the FWD pistons.

 

When I tested the gas 93 v/s 97, knocks remains the same. Based upon my experiencie, the key for manage the high compression was the coolant temp and the spark adv. Since 160ºF sound as an appropiate temp for detonation control I assume that AM91... must test others degree retards in order to eliminate knocks. Otherwise problem could be a vacuum leak or bad EGR valve if equiped, because the 0 knock IS POSSIBLE with high C.R. under any loads and accelerations.

(Or a bad injector.....?)

 

so if he is at 14.1:1 whats so bad about 12:1?

what about using the aluminum heads from tese fwd 2.8's and 3.1's on a 3.4? or are 3.4 heads better?

!!!!!!!!!!!!!!we should make a sticky about what pistons and what heads come from what fwd and rwd motors.

 

In my opinion the aluminum heads are better but i am biased since I own one (88 Z24 Cavalier was a 2.8 now has a 00 3100) and am still modifying it along with the Z28.

The RWD heads and the 87-94ish FWD aluminum heads are similar in size IIRC. The big difference is in the chamber size. The older 3100 have better flowing heads than the 3.1 and the current(00+) 3100 and all years of the 3400 have the freest flowing heads of them all. (3500 shares the same heads too.)

I will try to remember to post the valve sizes later.

The 2.8/3.1s had flat tappet cams. While the 3X00 engines recieved rollers.

The 3X00 engines also have a structural oil pan which helps strenthen the engine. It also has a windage tray.

Just some info off the top of my head about the FWD cars:

2.8 - 130 HP / 155 lb-ft of torque
3.1 - 140 HP / 165 lb-ft of torque
95-99 3100(3.1) - 155 HP / 180 lb-ft of torque
00+ 3100 - 175 HP / 195 lb-ft of torque
3400(3.4) - 185 HP / 205 lb-ft of torque
3.4 DOHC - 205 HP / 220 lb-ft of torque(I think it increased a little in later years.)

Compression FWD:

2.8 / 3.1 - 8.9:1
3100 / 3400 - 9.6:1
3.4 DOHC - ????

You can put the aluminum heads on a RWD but if you wanna use pump gas you have to change the pistons. You also have to use the intake that came with those heads also. Also the exhaust manifolds will need to be changed. If you have headers you should be alright. They bolt right up.

IIRC you have to change the timing chain cover over if you use the 3X00 heads. Along with the P/S pump.

That is all I can think of for now. If you have questions post em up and I will try and anser them.

 

Yeah, thanks. However there are a couple of guys here (me included) who have some of the aluminum heads and some of the iron heads laying around that we can compare. I don't see why you'd have you change the timing cover to run the aluminum headsor the p/s pump. Two things that McKinney Racing has planned for this summer is to build a base manifold to go with the aluminum heads and BRACKETS to bolt your accessories back on the front of the motor just like they come factory. By the way, its not just your opinion that the aluminum heads are better, there is no question that they are.

 

So with the new base manifold in the works for the aluminum heads can you use the RWD runners?

 

That's the plan. Our goal is to setup it up the same way as the stock RWD setup but match up to the FWD heads. RWD runners could be a little small though becuase the FWD heads have bigger ports.

 

Hmmm...

Well in that case, perhaps the intake I'm getting that replaces the factory intake & runners (which has bigger ports then stock) would work?

That could be interesting...Conceivabley I could use your base and the FWD aluminum heads if my combo is not spot on when I'm done. Could go with high compression for a N/A combo, or the FWD pistons for a turbo down the road application!

Hmmm...

 

.
1910 FruitGum Company

 

To me the FWD heads was more of a engine compartment packaging need than true performance need for FWD vehicles.
Plus GM was making & selling anything back then, including lots of base V6 Fbody, so no true need to improve upon that 60* V6 mill of that era. Considering GM was going to use the 3800V6 as the standard FBody engine in future (Gen4 rides).
PS I consider it lucky for us 3rd Gen folks that GM decided to increase displacment (to 3.4!) as this engine ended it's production line life in the F Body.