Considering a head swap, suggestions?

[ForcedFirebird]

I went to the JY to find a manifold and came across a lot of 3.1's. Quite a few were FWD with aluminum and saw one (93?) Camaro.
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Just a couple of questions...
1. Would the 3.4 Camaro heads flow better than the 3.1(LHO)?
2. If I do go with the FWD aluminum heads, what years had the largest combustion chambers (in hopes of not changing my pistons yet)?
3. Is the SFI better/worse than MPFI (could take the whole top end)?

I really want to use the Keith Black .30 over forged pistons I am looking at (getting them for $100) in my next engine and would like to work a set of heads that can be transferred over to the .30 over block.
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Any suggestions would be appreciated!

[discostu]

1. I think the 3.4L Camaro heads flow a little better then the 3.1L aluminum heads, but I can't find any specific data right now... Can anyone confirm this?
The newer 3100 and 3400 aluminum heads flow way better then the old 3.1L and the 3500 heads outflow everything.

2. The aluminum head cc's are all nearly the same. You're looking at approximately 12:1 compression with Camaro pistons and aluminum heads.

3. SFI is a form of MPFI that gives you better mileage, and is only a function of computer programming. Without an OBD2 computer, your car will be MPFI.

You could look at getting an entire top end from a 2000+ 3100, or a 3400, or best of all a 3500. With any of those top ends you'll be doing way better then with your current top end, but you'll have to change your pistons.

[SappySE107]

I haven't flowed an iron head to compare its flow vs a gen 2 3.1. I have the 2.8/3.1 heads flowed and on the site. I wouldn't use the 3.1 heads when you can use 3400 heads. 3500 heads won't fit a 3100 bore.

The iron heads have a lot bigger CC than the aluminum heads. I can modify a 3400 head to have a large combustion chamber but you would still be running high compression. With proper tuning and a good cam, thats not a problem.

SFI requires the ECM, not the top end. The SFI manifolds flow better than the MPFI manifolds. Again, not sure on iron head stuff, so im commenting on aluminum head.

[ForcedFirebird]

1. I think the 3.4L Camaro heads flow a little better then the 3.1L aluminum heads, but I can't find any specific data right now... Can anyone confirm this?
The newer 3100 and 3400 aluminum heads flow way better then the old 3.1L and the 3500 heads outflow everything.

The Camaro heads I looked at are iron.

2. The aluminum head cc's are all nearly the same. You're looking at approximately 12:1 compression with Camaro pistons and aluminum heads.

12:1, isn't that conservative? I've heard it was closer to +13:1 (unconfirmed). With this question, I was asking what are the largest chambers for the AL heads, and what did they come out of (year)?

3. SFI is a form of MPFI that gives you better mileage, and is only a function of computer programming. Without an OBD2 computer, your car will be MPFI.

The reason would simply be that the port pattern looked different on the SFI from the MPFI. It looked to me that I would need to use the SFI IM to go with the heads.

You could look at getting an entire top end from a 2000+ 3100, or a 3400, or best of all a 3500. With any of those top ends you'll be doing way better then with your current top end, but you'll have to change your pistons.

I'm getting such a good deal on the pistons, I want to use them in the next engine. If this means I MUST stay with iron, I will. However if I can mod the AL heads to work with these pistons, would be even better. Either way the heads would go on the current engine that has the pistons that mate with the iron heads.
Does anybody know if there is enough material in the chambers of the aluminum's to lower the CR enough to run on pump gas?
Also thicker head gaskets could be used (would help a little).

[ForcedFirebird]

I haven't flowed an iron head to compare its flow vs a gen 2 3.1. I have the 2.8/3.1 heads flowed and on the site. I wouldn't use the 3.1 heads when you can use 3400 heads. 3500 heads won't fit a 3100 bore.

The iron heads have a lot bigger CC than the aluminum heads. I can modify a 3400 head to have a large combustion chamber but you would still be running high compression. With proper tuning and a good cam, thats not a problem.

SFI requires the ECM, not the top end. The SFI manifolds flow better than the MPFI manifolds. Again, not sure on iron head stuff, so im commenting on aluminum head.

How high of compression? I have a CNC machinist in my pocket (good friend plus I'm remodeling his house) I just don't know how much material is there that can be removed without trying it, and the cheapest JY AL's I can find local are $75 each.
When I get the pistons, I'll see if they can be dished slightly also.

[SappySE107]

Watch ebay for cylinder heads. I never pay more than 50 plus shipping for a set, unless i have to have them asap.

[Superdave]

your best bet is to have the pistons modified (if you're worried about the compression). Use a complete 3400 top end, switch that 3.1 over to DIS and run it on a Jbody/Lbody ECM and harness. you'll pick up a ton of power.

[ForcedFirebird]

Watch ebay for cylinder heads. I never pay more than 50 plus shipping for a set, unless i have to have them asap.

Thanx for the tip, seems like there are a lot of bent valves on there!!! Do you think many people re-install the pushrods wrong, lol?!

[ForcedFirebird]

I haven't flowed an iron head to compare its flow vs a gen 2 3.1. I have the 2.8/3.1 heads flowed and on the site. I wouldn't use the 3.1 heads when you can use 3400 heads. 3500 heads won't fit a 3100 bore.

The iron heads have a lot bigger CC than the aluminum heads. I can modify a 3400 head to have a large combustion chamber but you would still be running high compression. With proper tuning and a good cam, thats not a problem.

SFI requires the ECM, not the top end. The SFI manifolds flow better than the MPFI manifolds. Again, not sure on iron head stuff, so im commenting on aluminum head.

How much could you reduce the SCR, and how much would you charge? Also would be interested in some higher lift springs as the 1.7RR's broke one of my stockers.
EDIT: Are the 3400 heads compatable with my IM?

[sharkey]

if you swap heads, you will need to swap upper and lower intakes aswell.

your best bet would be to go with a 3500 top end. the 3500 heads have a 32cc combustion chamber. on my motor (currently 9.2:1 with ironheads forged pistons and .060" gaskets) i figured around 11.35:1, wich is still streetable with good fuel, but with boost its to high. another thing ot keep in mind is the headers are gonna need to be custom built aswell.

now you run into the issue of the distributor. it may clear the upper intake, but i cant confirm that. if you want to swap to dis, you will need a crank trigger, as your block doesnt have the provisons. the 60 degree store has one listed that will work with any gm dis. as for computer, i think with your current setup you would be better off to go with a stand alone such as a megasquirt and get rid of the rising rate regulator.

[ForcedFirebird]

MS is comming, all in good time. No the dizzy won't clear the manifold but there is a way around this by simply making the dizzy longer. this will cause clearance problems with my stock hood - that I want to keep.

[Superdave]

if you swap heads, you will need to swap upper and lower intakes aswell.

your best bet would be to go with a 3500 top end. the 3500 heads have a 32cc combustion chamber. on my motor (currently 9.2:1 with ironheads forged pistons and .060" gaskets) i figured around 11.35:1, wich is still streetable with good fuel, but with boost its to high. another thing ot keep in mind is the headers are gonna need to be custom built aswell.

now you run into the issue of the distributor. it may clear the upper intake, but i cant confirm that. if you want to swap to dis, you will need a crank trigger, as your block doesnt have the provisons. the 60 degree store has one listed that will work with any gm dis. as for computer, i think with your current setup you would be better off to go with a stand alone such as a megasquirt and get rid of the rising rate regulator.

But remember, he can't use the 3500 top end. the combustion chambers are too wide for the 3.1 bore.

[ForcedFirebird]

But remember, he can't use the 3500 top end. the combustion chambers are too wide for the 3.1 bore.

By how much? I'm getting ready for a .030 over 3.1 build with forged internals (just picked up some Keith Black pistons). Guess I might just work over the iron heads.

[Guest]

The 3.4 iron heads are EXACTLY the same as the 3.1 iron heads, whihch are EXACTLY the same as the 2.8 HO Iron heads, so the 3.4 Iron heads flow a LOT less than any aluminum head.

I would forget getting the deal on teh iron head pistons and build something that will have more power using the available aluminium heads.

You'll get it all together with the "deal pistons", spending MORE money on the heads trying to get them to flow, as good as a stock 3400 head, and end up with less power and more p[rone to detonation, than using the aluminium head as well. Aluminium heads are less prone to pre-det, due to the fact that the aluminium pulls more heat away from the cylinders faster than iron heads do. The accepted running compression ratio is accepted to be a full point lower using aluminium heads, effectivly, than using iron heads with the same SCR, due to the heat loss, hence why most companies can run higher SCRs with less problems with pre-det, along with other variables like chamber and piston shape, but the material has a huge effect.
Speaking of chamber shape, the aluminium head has a MUCH superior heart shaped design that promotes swirl and fuel suspension to get a better overall burn over the iron head.

So in short those "deal pistons" that you are about to buy, will not be so much of a deal, when you are limiting yourself.

[Superdave]

By how much? I'm getting ready for a .030 over 3.1 build with forged internals (just picked up some Keith Black pistons). Guess I might just work over the iron heads.

more than you could safely bore a 3.1.

use 3400 heads and lower intake manifold with a 3500 plenum, port match everything and you'll be in damn good shape.