I've been reading a bunch on the hybrids lately, but I was left with a couple questions that I didn't get answered through searches/reading.

How much is being left on the table with a 3400 top end compared to the 3500 top end when you factor in a cam and headers? Are we talking 5-10 HP or 20-30?

Second, for a street car, is the 11.xx:1 compression streetable on 87 octane pump gas with the 3.4 pistons, or do you need to go with the 3400 pistons? I know people have talked about running the 3.4s, but I wasn't sure how well the knock could be tuned out for a daily driver.

Thanks,
Douglas

 

11:1 compression and 87 octane probably would not be a good combination. I had about 10.75:1 in my built 3.1 (iron heads) and ran 93 all the time. Still got some spark knock under certain conditions.

 

What type of bump in compression can the alum heads take over the iron? I know that alum heads resist detonation better then iron, but I don't know how much better.

 

It really depends on what cam you choose, Use the specs figure out the dynamic compression and you'll have your answer.


If it's going to be mildly cammed then it would probably be a good idea to go with 3400 pistons.


3500 top end is much better than the 3400 stuff out of the box, You are looking at around a 20 HP difference stock for stock. Factor in the cam and headers and depending on the specs there could be up to a 30-40 HP difference. (assuming un-ported)

 

The 3500 heads can only be used on 3.4 or 3400 blocks. So if you are starting with a 2.8L or 3.1L block, then you can only use the 3400 heads of the two choices.

 

I have a 3.4 block that I pulled this weekend.

I will return the 3400 stuff I picked up today since it is that big of a difference. Lucky for me to was easy to pull. The 3400 short block was gone, so I couldn't get the pistons anyway. On to search for the 3500 stuff.

 

i have a few questions so instead of creating a new thread i thought i would ask them here.
1. will the 3400 SFI UIM work with the 3500 LIM and heads? the reason i ask is because the 3500 UIM is one of the ugliest intakes i have ever seen, and at my local yard i find 3400s all the time.
2. what will it take to make the DIS work? i plan on getting a 3.4l rwd out of a friends 96 camaro.
3. my desired setup would be 3.4L RWD, 3400 UIM 3500 LIM and heads, 3400 or 3500 pistons and a cam that leans more towards mpg but still gives a little kick. what tuning would have to be done to make this car run and what HP and ftlbs can i expect out of this setup?

 

It will work, but you will have to do some blending between the ports of the UIM and the LIM. I would consider a different way to dress up the 3500 UIM though, with it's larger plenum it's great for transitional changes in RPM due to throttle changes, and has shown to improve low RPM power on engines that had previously been equipped with a 3400 UIM (and LIM).

Using the 3.4 block, it won't take much more than plugging the CPK into the ICM, as far as the external engine connections go. The ECM will need the proper offsets for the ignition in order to fire at the correct time relative to the piston position. Starting with a 1227730 (or similar replacement) ECM and FWD code from a Cavalier or similar will get you the proper ignition base. Some consideration might need to be made for the VSS side of things depending on exactly which bin (oe MEMCAL) you start with and what you car currently has. Your car being a 1992 should already have this ECM, but the igintion parameters will still require a different bin or MEMCAL.

With the 3.4 block you won't be using 3500 pistons.

Tuning will depending on a bunch of variables, but even a stock cavalier bin will start most any 660 hybrid, extreme cammed, compression, etc examples would be the exception. Tuning for power and driveability is an engine by engine basis.