2.8?

[Mr_Efficiency]

I am planing on building a hybrid motor and boosting it, but i want minimal down time on my car and instead of rebuilding the motor in the car I was looking at getting another motor and building it then taking the car off the road for a weekend to swap in the new motor.

I was planing on using a 3.1 but i came acrossed a complete 2.8 for free.

What would be the downsides to using a 2.8? its the exact same as a 3.1 isnt it, except for the stroke obviously. I would get better gas mileage, lol

there is only a five hp and 5tq diffrence in the two motors, so its not a huge deal to me, im not looking for all out race motor, just something boosted to have fun with.

is the 2.8 and 3.1 cam the same?

anyone ever hybrid or boost a 2.8?

atleast i'd be diffrent

[3100 MPFI]

The 2.8 hybrid will be the same as the 3.1 hybrid.

In fact, I threatened Ben that if he kept pissing me off about using a 3100 instead of a 3400, or 3500, I would stick a 2.8 crank and rods in there and have a 2800.

All the 2.8 is is a destroked 3.1 MPFI. I think that the 2.8 revs up faster and higher (due to the shorter stroke). I know my 3100 revs higher than a 3400, but that is a built-up engine.

[Mr_Efficiency]

I've been reading up on this more and i have a few more questions:

what will my compression come out like? are the 3.1 and 2.8 heads the same? if yes then the compression will be ok.

and what about injectors, I need less fuel now that i have less displacement, so I might be ok with stock TGP 22lbs injectors then with 9psi, correct?

[3100 MPFI]

can't help with the turbo, but to the best of my knowledge, the ONLY changes were the stroke.

The heads ARE the same (I have 2.8 heads on my 3.1 right now). As for the fuel injectors, I am pretty sure those were the same as well.

[bszopi]

What year 2.8?

[3100 MPFI]

My 2.8 heads are 1988 and 1989 (from 2 different cars).

I am not sure about all the years, but I know for a fact the 2.8 was used 1987-1989 in the gen 2 form.

[bszopi]

The question I have is for the original poster. If the free engine he is getting is a pre-85 (??), then it has the smaller journal crank which is crap.

[ForcedFirebird]

The 2.8 hybrid will be the same as the 3.1 hybrid.

In fact, I threatened Ben that if he kept pissing me off about using a 3100 instead of a 3400, or 3500, I would stick a 2.8 crank and rods in there and have a 2800.

All the 2.8 is is a destroked 3.1 MPFI. I think that the 2.8 revs up faster and higher (due to the shorter stroke). I know my 3100 revs higher than a 3400, but that is a built-up engine.

Don't you mean use 2.8 pistons and crank in a 3100? The rods are the same, the pin height is different on the pistons.

I am planing on building a hybrid motor and boosting it, but i want minimal down time on my car and instead of rebuilding the motor in the car I was looking at getting another motor and building it then taking the car off the road for a weekend to swap in the new motor.

I was planing on using a 3.1 but i came acrossed a complete 2.8 for free.

What would be the downsides to using a 2.8? its the exact same as a 3.1 isnt it, except for the stroke obviously. I would get better gas mileage, lol

there is only a five hp and 5tq diffrence in the two motors, so its not a huge deal to me, im not looking for all out race motor, just something boosted to have fun with.

is the 2.8 and 3.1 cam the same?

anyone ever hybrid or boost a 2.8?

atleast i'd be diffrent

Yes hybrids and boosted gen1's have been done.

Since you are doing a rebuild anyways, you can use 3.1 pistons and crank and it will be a 3.1. You need some 3100 (or Gen2 3.1) pistons with those heads if boosting. OR you can use the 3.1 pistons and have a high compression torque monster.

*But* as Brad said, make sure it's an '86 or later or you may be wasting your time.

[Mr_Efficiency]

yeah its an 88 2.8, so its the good one. I'm thinking of leaving it a 2.8, and since the 3.1 and 2.8 heads are the same that means if i use the 3100 heads, I'll get the same compression ratio as if i was using a 3.1, correct?

what does the compresion of a hybrid come out to anyways?

[bszopi]

To test for CRs for various combos, use the site calculator:

http://wiki.60degreev6.com/index.php?title=Compression_Ratio_Calculator

To get values for the different engines, just do a stock engine calc and copy the numbers down.

[Mr_Efficiency]

thanks a lot, i have some good calculators for that but just didnt have the specs, I'll give that a try now.

... it says the 3100 and aluminum head 2.8 and 3.1 have the same combustion chamber cc's so my compression wont change.

[3100 MPFI]

I think the only thing that might change with the compression will have to do with which headgasket you use. I think if you use the 3100 head gasket, you will lose some compression, but the 2.8/3.1 headgasket will keep it the same.

Something like that.

Once again, I am trying to think on an empty stomach. No food = no brain.

[Mr_Efficiency]

yeah i was going to ask about that, so the 3100 head gaskets are thicker?

[ForcedFirebird]

yeah i was going to ask about that, so the 3100 head gaskets are thicker?

Gen3 pistons protrude .020" out of the block, hence the reason for .060" compressed height gaskets (gives you exactly .040" quench).

The RWD gaskets are .040" compressed height, and you may have valve slapping the pistons with high RPM's with only .020" clearance.

[Mr_Efficiency]

ok thanks

what about the cam? i know i dont have the $$ for a new one but i was doing some research and found that the fiero 2.8 HO (L44) uses the same cam from the 3.4 in the firebirds and camaros. how much better is this cam over the stock 2.8/3.1 cam?