3400/3500 top end swap on a 2.8

[Tonglebeak]

Hi. I've heard that the 2.8 (mpfi) can make a decent high-revving top-end motor, however it's highly restricted with air flow. It was suggested to me that I do a top end swap on it with 3400 and/or 3500 parts. My 2.8 is a gem off the line, but then starts losing it towards the redline, so I wouldn't mind giving this swap a try...

A couple questions: will this require removing the engine? How hard will this be for someone who has never done any work directly to an engine before (but has done other work to the car, and isn't a dumbass >_>)?

Also, what kind of gains could be expected with this as far as horsepower, 1/4 mile, etc, and would the new 2.8 be able to support forced induction after the swap?

[ForcedFirebird]

What car, and is it a gen 1 or 2 660?

2000+ 3400/3100 top end could be done, 3500 heads have too big of chambers for the bore.

Do you have a distributor now? If so, you have to convert to DIS.

[Tonglebeak]

Gen 2 I believe. 1988, DIS, MPFI, blah blah.

[El_Diablo]

you could always do 3100/3400 heads and a 3500 LIM and UIM

[Superdave]

you could always do 3100/3400 heads and a 3500 LIM and UIM

the 3500 LIM won't match up to the 3400 heads.. Not even close.


do a '2000+ 3400 top end with a 3500 plenum, also do yourself a favor and add in a decent cam to take advantage of the extra flow.

The H272-2 from Crane would open up that 2.8 and make it sing.

[El_Diablo]

true, idk why i said that... lol, im out of it, sorry for the bad information

[ForcedFirebird]

the 3500 LIM won't match up to the 3400 heads.. Not even close.


do a '2000+ 3400 top end with a 3500 plenum, also do yourself a favor and add in a decent cam to take advantage of the extra flow.

The H272-2 from Crane would open up that 2.8 and make it sing.

The stock ECM will handle a top end swap, but not a cam that big. Should be tuned anyways for best results - but just thought I'd add that to Dave's comment in case you were going to be running with no tune.

[Tonglebeak]

I'll get a tune if need be.

So, do I need to swap out any pistons or connecting rods? I need 3400 upper and lower manifolds then, and not 3500? How difficult would this be for me to do, I've never done any work on an engine before but I have done other work on the car? Also, how big will the gains be?

[El_Diablo]

you'll need a 3100 or 3400 top end (the 2000+ are the same between both engines) but you can use a 3500 UIM on the large port 3400/3100 LIM



so basically the shopping list for the major parts is this-
3100/3400 heads
3100/3400 LIM
3100/3400/3500 UIM

any combination of those parts will work as long as you use 2000+ parts...

[3100 MPFI]

There are several different heads you can use, but you need to look into what your goal is. If you remove the engine to do this swap, you might want to take advantage of that fact and stroke the 2.8 up into a 3.1. Then again, if you are pulling the engine, you might want to just do a 3100/3400 swap. I swapped a 1999 3100 into my 1988 Cutlass Supreme. It pretty much dropped right in, but there is a lot of work to be done.

Keep in mind that when using the 3100/3400 heads, you will need the 3100/3400 EXHAUST MANIFOLDS, and CROSSOVER, which means dealing with the downpipe.

You WILL have tuning issues. I tried to get a 3100 to run on a 3.1 MPFI programming. Didn't work. There are also a lot of little things you will need to address.

Knowing which engine you are working on does not really help us. We need to know the YEAR, MAKE, and MODEL of the car that this is going to be in so that we can offer advice into more specific things that have to be done.

[Tonglebeak]

It's an 88 cutlass ciera...I'm not interested in swapping the whole thing out. That'll defeat the purpose of what I'm trying to do.

[3100 MPFI]

Okay. I understand about what you are trying to do. Been there done that.

You will need to address certain minor things when you do the swap.

The main parts (heads, upper and lower intake), those are not going to be a problem. The main issues you are going to have is the exhaust system (you might have to get the exhaust downpipe from a newer 3100 Cutlass Ciera) and you will need to get coolant hoses (heater core, radiator), so you will need to be sure you get the right ones.

All in all, it is not going to be too bad too do. The hardest part will be getting it to run right. No matter what, you WILL need tuning. Not impossible, but that will be the biggest issue to overcome.

Also, are you keeping the stock tranny? I know you are trying to keep it simple, but keep in mind that if you have to do all this work, be sure you have a good tranny. Don't know what you have planned for that, but if you swap out the tranny, you might need a different computer. Example would be replacing a 3 speed tranny with a 4T60-E will require the newer ECM to run the tranny.

You will have to do some wiring as well for the hybrid. You can use the main part of your 2.8 harness, but you will need to lengthen the TPS, and IAC wires, as well as rewire the coolant temp sensor (you will probably have to go from the 2 seperate sensors to the single 3 wire sensor, which is NOT a difficult swap).

There are also some things to you will not know about until you get to that bridge, but we are all here to help.

[Tonglebeak]

I would like to keep the current tranny as of right now. the th125c has a very good reputation, and it can take some punishment. I'm only at 119k on it and it still has a long life ahead of it.

Can you provide input on what gains I can expect out of this, and is this something someone who has never directly worked on an engine can do?

[3100 MPFI]

It is something you can do, BUT, you have to give yourself more time and patience with it. If there is even one small detail you don't understand, you HAVE to ask about it to make sure you don't mess anything up.

I recommend getting a service manual for your car (your year), and then get one for a newer version of your car that will cover the 3100 aspects (seeing that is what will be closest to your car).

You can never tell what gains you will get, and how it will effect your engine. A perfect example of this is when I built my 3100, a friend of mine (gpse3400 on this site), but up a 3400 in the EXACT SAME WAY. We had pretty much identical engines.

The main difference was his was all GRUNT, and my was a SCREAMER. He had a lot of power off the line, but like all these engines went flat by 6000 RPM. I, on the other hand, had no power before 4000 RPM, but I pulled HARD from 4000 RPM to 7000 RPM. That is the perfect example of never knowing what will happen.

No matter what, it will be interesting, to say the least.

[Tonglebeak]

Yeah, I already have a service manual for 88. Never thought about getting one for a later year...

I talked about this with my cousin, and he wants me to ask this: what happens with timing? He thinks putting new heads on will screw my timing.