3.1 crank for 2.8?

[Blastin06]

This is my first post and i did look around and found similar post but i just wanted to make sure it would work before spending tons of money on faliure.

Im looking to put a turbo on my 85 2.8 fiero v6 im looking for about 300hp

The question begins with..I had read that the 3.1 crank was stronger then the 2.8, and that the 3.1 would fit in the 2.8....i was wondering if this was true and how much work would have to be done..


I really just want a stronger crank for the 2.8 by what ever means, i already have to have custom forged rods and pistons made for low compression because the fiero store only sells higher compression forged stuff

and any ideas for how much i should bore the block out, i was gonna bore it out quite a bit then realized that with a turbo set up the internals might not hold up...

any help would be awsome...
Thanks

[sharkey]

the strength issue with the 2.8l crank is the 80-mid 85. they had smaller main journals and were known for breaking. at the same time they went to the large journal crank they also changed to a 1 peice rear main seal. so if you have a 1pc rear seal, you have a large journal crank. the 2.8l large journal crank is the same as a 3.1l crank, except for the 3.1l crank having a longer stroke (by 8mm).

if you want to build an ironhead 3.1l, your pistons are very limited. basicly, there are no forged pistons, anything you would want to use with boost would be custom, wich realy isnt so bad.

[Blastin06]

so if i do have the larger main journal would the 3.1 crank still be a good idea for a turbo setup or just keep the 2.8?
Thanks sharkey

[torq455]

longer stroke=more cubes=more torque which in turn makes more power. i'd put the 3.1 crank in. either crank is strong enough to handle 300 hp without issues.

[Blastin06]

ok cool,
so in either case weather i go with the 2.8 or 3.1 crank i could stick with the stock conecting rods and they should b able to handle 300hp right?

Then im down to only ordering custom pistons....any good places?

[megafreakindeth]

the 3.4 block is stronger and has more bore than the 2.8 might wanna think about that. it uses a 3.1 crank and a much larger bore to make 3.4ltrs. theyre cheap too, but keep in mind that a longer stroke will rev slower because the crank is wider. on the other hand a larger engine will spool a turbo faster so its all trade offs. also if the design1 setup makes 220 with an ihi turbo then a 3.4 with the ever popular t3/t4 will easily hit your mark.

As for pistons if your taking it to a machine shop theyll know where to get em otherwise youll have know the measurements to give to a piston company to lower compression.

[Arns85GT]

bubble bursting

300hp? I doubt it. The hottest 2.8 turbo I've seen to date barely breaks 200hp.

There is a guy in Scandinavia who allegedly did one to 300hp but that was an extremely tricked out engine which he spent a pot full of money to build. I think you are talking over $10,000 USD.

If you want 300 hp, you are definitely talking an engine swap unless you have really deep pockets and some pretty impressive knowledge in engine building.

Just my .02 and I hope it helps.

[SappySE107]

Are you talking wheels or crank? 200 chp is stock turbo 3.1 range and 200 whp is modded 5 speed 3.4 DOHC NA range. 300 chp isn't hard with boost and 300 whp doesn't take 10k.

The problem with power in a 2.8 with iron heads are the iron heads.

[Blastin06]

ok my real problem is that i already have a 2.8 tore apart and i really dont want to do an engine swap becase i dont want to hassle with building customparts to make it fit in and then rework the electrial ie the compuer and all that stuff...im not a complete noob on the machenical stuff but i dont know much on swapping parts out and the tunning invloved....my goal is to put a turbo on the 2.8 block i guess run about 8 psi so that hopefuly i wont have to rework the computer.....i know this wont be 300 hp (i was just putting that out there) i was reading on a form and is said that putting in the 3.1 crank would be a good idea for strenth...........


My goal for the project is to put a turbo on an 85 2.8 fiero engine....with as little minpulation the the ecm as possible....

[megafreakindeth]

the hottest 2.8 made 200hp? 3200 dollars from design one will get you 200 hp on a 2.8, at least they claim. as for 300 hp tho i wont say i know for sure but a t3/t4 on a 3.4 camero engine should get damn close even if all you do for tuning is keeping the o2 voltage over .85.

as for trying to keep cpu tuning out of the picture, while possible its not reccomended. it may run for a while but (at least for me) the goal is to keep it running forever. in which case a proper tune is essencial.

[Blastin06]

ok so i guess going through all the work for a turbo just for ~40 hp isnt the trade off i had hoped for....if i bore it out a little and but the 3.1 crank for the longer stoke...will that make much of a difference and will i still have to have tuning done???
Thanks to all

[megafreakindeth]

40 hp from a turbo is a low expectation. the motor makes 140 to the crank so minus mabye 30 something and thats to the wheels. design1 claims 200 to the wheels. so thats more than 40. the only reason i keep mentioning them is that i dont think anyone else makes a kit anymore so thats my only example.

if you got really into the output of the engine you need to retune some cars if you add a cold air intake. your car will live if you dont but there will be lean spots and whatnot. going ahead and boring out the cylinders will affect head flow and increasing the displacement will affect fuel requirements and curves. you might be able to get away with running real rich but its not gonna be ideal. plus it seems you want to race an rx7 while ur gas milage will always be better than his, the hp output of a rotary is where your going to need all you can get

[AVIANVEE6]

Non Boost 3.4

I like the $1700 price or the new 3.4 but I would like to know how much weight could be saved by switching to alumanim heads(GM PART # 10048649). If anyone has a picture of the flywheel end of this engine 2.8-3.4 pushrod without the flywheel on I would apreciate a haveing a copy.

Considering a ultralight http://www.stalkerv6.com without the cost of the alumanim block which would save 47lbs.

Matt

the 3.4 block is stronger and has more bore than the 2.8 might wanna think about that. it uses a 3.1 crank and a much larger bore to make 3.4ltrs. theyre cheap too, but keep in mind that a longer stroke will rev slower because the crank is wider. on the other hand a larger engine will spool a turbo faster so its all trade offs. also if the design1 setup makes 220 with an ihi turbo then a 3.4 with the ever popular t3/t4 will easily hit your mark.

As for pistons if your taking it to a machine shop theyll know where to get em otherwise youll have know the measurements to give to a piston company to lower compression.

[ezrollin]

The 2.8's from about 86 up has the bigger journals and can easily make 300 hp @ flywheel. Be warned,you need to do a lot of research before doing a turbo project. Selecting the right turbo for intended use is critical,you will have fuel and ignition management issues. TurboKits,if one is even built for your vehicle are exspensive,.If you do some "searches" on this site and on fullthorttlev6 and thirdgen.org you will get the knowledge to piece together a proper kit and save lots of money.