How much boost and hp can a 98 3100 handle

[joshua52mcclain]

Ok it is a 92 firebird witch has a 3.1 ill be doin a good amount of homework before I decide what route im going to take Im take a sc off a gtp and make a custom plenum and notch the fire wall for the rear facing intake or turbo set up but I know alittle more about sc I've only ever had one turbo car factory turbo never got into that motor 96gsx awd

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Ok well literally just got her in the driveway now ill truly know what im working with cuz I might be wrong on the year

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Yes.

[joshua52mcclain]

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[joshua52mcclain]

Ok well literally just got her in the driveway now ill truly know what im working with cuz I might be wrong on the year

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[fasteddi]

Im assuming that 2.8 3.1L 3.4L rwd gen 1 cranks are all cast?

[robertisaar]

GM says gen4 cranks are forged steel.
GM says the gen3.5 3500 cranks are cast iron or forged steel.

The 85.5+ cranks are not as weak as people would have you believe. I think I've seen a total of 2 broken allegedly from too much power, but I think it was mor abuse than power because other people have made more power than the two broken crank owners claimed to have made.

Also 660s have forged rods.

The 3500 (LX9) has a steel crank, I want to say forged, but I think it was more likely cast steel. Earlier cranks were cast iron. I'm not entirely sure what the LZ engines (3500 and 3900 with VVT) have but I believe they are a similar material to the LX9.

[fasteddi]

Well a 3.1L is a stroked 2.8L. A 3.4L is a bored out 3.1L. So the stroke on a 3.1L and 3.4L should be the same. As for the 3500 im not sure as i never really messed with them. I have a 3.1L and last weekend I ran 4 passes all in the 11.60s at 119Mph on a stock crank and rods. Now it may be a freak car but if the tune is dead on you can obvously handle a ton of HP and Tq. For some reason i think that the 3900s had forged rods or a forged crank? On the non vvt ones? But the raven will know best over me.

[joshua52mcclain]

Ok I got you I was told the 2.8s stoke is 3" and the 3.1/4/5 are like 3.3" or something like that and for a turbo build the shorter stoke would be more reliable (for stock cranks) and handle more boost is this true? And would I be able to run 3.5 crank and rods in a 3.4 block because my understanding is the 3.5s are stronger

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[fasteddi]

Do yourself a favour and grab a 3.4 bottom end (from an F-body) and use the entire 3500 top end. This gets you the best flowing conventional pushrod top end, along with OEM provisions for the crank trigger that will be needed for the DIS system.

The 2.8 block can be used, but it's more work, due to needing an external crank trigger, and you're limiting the over displacement and narrows down your head choices. I used a 2.8 block for one of my hybrids years ago, simply because I couldn't find an affordable 3.4 block at the time. We're talking back in 2002 or 2003, so they were still relatively new at the time.

Definilty what he said. If i wouldnt of had 2 3.1L engines already at the time i would have used a 3.4L and did a 3500 top end on my build.

Do yourself a favour and grab a 3.4 bottom end (from an F-body) and use the entire 3500 top end. This gets you the best flowing conventional pushrod top end, along with OEM provisions for the crank trigger that will be needed for the DIS system.

The 2.8 block can be used, but it's more work, due to needing an external crank trigger, and you're limiting the over displacement and narrows down your head choices. I used a 2.8 block for one of my hybrids years ago, simply because I couldn't find an affordable 3.4 block at the time. We're talking back in 2002 or 2003, so they were still relatively new at the time.

[joshua52mcclain]

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[joshua52mcclain]

Hi fasteddi thanks for all the help but I've put the brakes on my 3.1 grand prix im finish it as is no turbo just the p&p and acouple little things because I was recently given this 89 2.8l 5 speed firebird wich is going to be my go-fast car im planning to use the 2.8 bottom end maybe upgrade the bearings have it balanced maybe larger bore .20 over larger pistons the ported 3400heads with 3.5 upper plenum and a nice shiny turbo how do you think I should go about the bottom end

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[fasteddi]

Thanks man, its taken alot of work to get my car where it is.

Yea building up a 3400, 3500, or 3900 is fun and believe me you can hit some big hp goals. Toss on a turbo someday and its all over. Its a power house with boost. i just have a little 3.1L and even with that little amount of CI i still make as much power as many cars in my sportsman class at the race track. And i get good mpgs and have a full interior minus a/c.

[joshua52mcclain]

Nice i love your car its alot more respectable to me to build a so called low power engine than to build easy power aka the 3800 sc yea its easy but weres the fun in that I've been contemplating going for the 300hp na I've been finding more and more 60degree parts sites im thinking if I can get 300hp na in a decent budget id rather go na we'll see it'll be a long road ahead