2.8 cheap race motor upgrades?

[Superdave]

Ben (SappySE107) pointed out a few flaws I had in the above setup, mainly the crappy quench, and that a 272 grind is on the low end of what is needed for that CR. So, I started playing around with some other configurations and came up with something I think you will like. Start with a 3400 block (a 3.4 block out of a Camaro would work as well), and install a 2.8 crank along with 3.4DOHC pistons. Then slap on some 3500 heads and topend. This will result in a displacement of 3028cc (your limit is 3088cc, correct?) and a CR of 11.89, with a quench of 0.05" (0.35-0.45" is optimum). Get a 272 or higher type grind, and you should definitely make some good power (once its tuned, of course).

I said something similar in the other thread however i forgot about the DOHC pistons.

This would be the best idea and in the end you would have a serious engine. The 3500 stuff is like the holy grail of Gen3 parts.


For the cam, I don't know that i'd trust a flat tappet for this kind of abuse. You could convert to a roller or just start off with a 3400 FWD block since you have to make mounts anyways. The 3400 block has improved oiling and strength, it's also got crossbolted mains and all the provisions to run DIS.

[sureshot007]

If I use a FWD block, won't I have an issue with my tranny bolting up?

[bszopi]

Both Dave and I are bolting FWD 3500s up to RWD trannys. If there is a bellhousing that will allow your existing tranny (AXx? something) to a 60V6, then there is probably a bellhousing that will also work with the FWD blocks. There are a few bellhousings out there for manual trannies (T5 comes to find) that have starter pockets on both sides, therefore allowing the FWD block to bolt up without any issues. But, as I stated in my post above, you could use a 3.4 iron head, which will be set up for a RWD tranny, and just put a 3500 top end on it.

[95Grand-Am]

Ben (SappySE107) pointed out a few flaws I had in the above setup, mainly the crappy quench, and that a 272 grind is on the low end of what is needed for that CR. So, I started playing around with some other configurations and came up with something I think you will like. Start with a 3400 block (a 3.4 block out of a Camaro would work as well), and install a 2.8 crank along with 3.4DOHC pistons. Then slap on some 3500 heads and topend. This will result in a displacement of 3028cc (your limit is 3088cc, correct?) and a CR of 11.89, with a quench of 0.05" (0.35-0.45" is optimum). Get a 272 or higher type grind, and you should definitely make some good power (once its tuned, of course).




Some good Ideas, but what would you suggest for connecting rods? You would have to have some custom rods made.

[Guest]

I'm not sure I'd go the short stroke 3.1 route in this application, only because it would be dangerously close to the limit. The displacement checkers are known for not being too accurate, especially on a higher SCR engine. I would just hate to see all this work put into an engine that is either deemed "illegal" because of an inaccurate tool, or because the overbore to rebuild puts it there.
I think I'd stick with the 2.8 or 3.1 block, using a 2.8 crank. Overbored .30 (.75mm), that nets a 2.9L which should be plenty, and is getting close to the limits.
I'd definatly use the 3400 (2000+ 3100) top end though. I do agree the 3500 top end would be ideal, though, in which case the larger bore 3.4/3400 block would be needed. I suppose a welded and offset gorund crank to reduce stroke even more, would help keep tabs on the displacement, might help it rev more too, though torque would be lacking, and that's the reason I haven't persued building a short stroke 3.1, did lots of planning at one time, lots of modeling with Desk Top Dyno (Yeah I know, but the accuracy is decent enough), and just couldn't get the same torque with the short stroke as I could with a long stroke, and the small boost in high RPM HP wasn't enough to sway me. I wasn't limited to displacment though. If I was, I might have persued it.

[Superdave]

If I use a FWD block, won't I have an issue with my tranny bolting up?

What side of the engine is your starter currently on?

[sureshot007]

Passenger side

[francis_t]

Go with a carb or trueleo intake. Yeah I'm bias we make em. But the stock intake is the biggest power limiting thing on the engine. Makes you shift at say 4.5K RPM which stinks, especially for a race car. Other mods will help but you'll hit that wall at too low an RPM. The stock headers stink too.

[SappySE107]

Really, carb or trueleo over gen 3 top end?