Head change Al to Iron?

[NAP1947]

I have searched this site and a few others trying to determine if iron 2.8 heads can be fitted to a 3.1 that originally had aluminum heads. I have been trying to find a good 3.1 iron head motor without success but see lots of aluminum head engines. My application will be in a rear wheel drive car and requires a carb not FI. Cost is an issue. If someone can point me to help I would really appreciate it.

Thanks

[IsaacHayes]

You'd need RWD iron head 3.1 pistons (2.8 pistons I don't think works cause it's different stroke), and also the starter will be on the wrong side.

Have you looked for camaro 3.4 iron v6s too? Might find one of those easier than a 3.1 rwd

[NAP1947]

Here is what I have learned so far, no guarantee of accuracy, 2.8 and 3.1 blocks are the same, the crank and pistons are different but they use the same con rods. In GM's Chevrolet Power book it says iron heads have siamese intake runners and aluminum are separate, other than that it says the differences are in the valves and combustion chamber. As I have a 2.8 carb intake and rebuilt 2.8 heads and need a new or rebuilt block (my block is the early 2.8 with small bearings) I feel the move to 3.1 makes sense. I have looked at 3.4 Camaro/Firebird but they are pretty scarce here in Canada. I can get good low mileage FWD 3.1's, I need to confirm that I can use the 2.8 heads and intake.

Thanks

[Superdave]

Like previously stated, the FWD blocks are different than the RWD blocks, the mounting bosses are in different spots and the starter is on the opposite side.

your best bet is to find a 3.4 from a 93-95 Camaro and put your carb setup on it, it's a bolt-in and you'll gain a few HP.

[mongo]

Someone will have to verify this for the 3.1 but usually the Alum head engines have dished pistons for valve clearance and the Iron head engines use flat top pistons. So, your valves may hit the pistons and any money you would have saved may be eaten up when you try and locate the correct length pushrods if you don't still have them from the 2.8...

[WrathOfSocrus]

If you are determined to get a 3.1 RWD you will either need one that came stock in a vehicle like the camaro or pick up a junkyard RWD 2.8 and use a 3.1 crank with RWD 3.1 pistons. It will probably be easier to find the 2.8 and use the 3.1 parts to stroke it to 3.1. Of course if u find a RWD 3.1 it would be less work.

The 3.4 although not as easy to find would give more power.

[NAP1947]

I guess the consensus is 2.8 stroked to 3.1 or 3.4. While I do have the whole 2.8, including good rods I would need the iron head 3.1 pistons as well. I will keep looking but I still do not know for sure if I can put the iron heads on a FWD block with iron head pistons, can someone answer that?

Thanks

[Canyonero]

You can find a RWD 3.1L in a 1991-1992 Isuzu Rodeo. Those should be around Canada. Starter will be on the wrong side though.

[TiredGXP]

You can put the 2.8 iron heads on a Gen II FWD 3.1 that came with aluminum heads. I have one in the works now for the Fiero. Donor car was 1990 Lumina.

You will need the iron head pistons (smaller dish than the aluminum head pistons because of the larger combustion chamber in the iron heads).

You're better off with the '85 and up heads that came with fuel injection because they have larger valves than the heads used in carburator applications.

[geoffinbc]

Your answer is YES you can do it and its not that hard. You just need different pistons. But if your going in for a rebuild it will be a snap to make the change. You said your block was an early engine with small mains. This block cannot be modified to work with the 3.1L crank. Assuming you get the mains bored to bolt the crank in there is still no main seal available for the one piece seal crank that will work in that block. So your only hope is to find at least a 2.8L with a one piece rear main seal then it will allow the 3.1L crank to drop right in.

If this engine is destin for a Camaro or S-10 just remember than a FWD 3.1L will not bolt in. However if this is a custom application like a sand rail or something then its all up to you. There is no difference between a FWD and RWD block other than the drivers side mounting boss and the starter location. But keep in mind that even if the chassis does not care where the starter goes a RWD transmission will not accommodate a drivers side starter unless you find that rare Camaro bellhousing with 2 starter pockets.

[NAP1947]

Thanks to everyone for their input, I have what I need to know. I am putting the engine into an MGB so the basic block configuration is not an issue and I have one of the dual pocket bell housings with my T5.

Again, thanks to everyone.

[geoffinbc]

Sounds like your all set then.

[NAP1947]

Thank you all for this information. The engine is destined for an MGB and I have a Camaro bell housing on a T5 that has the double starter ears. If I cannot find a good 3.4 I will modify FWD to RWD configuration.

Thanks again