3.1, 3100, 3500?? build options

[Mach 5]

ok so I just asked about the 3500 crank size... now I have a few questions to ease my confusion before I go buying parts

All build plans will be using my gt3071r turbo and gen 2 ported heads and intake unless noted otherwise w/ manly 3500 valves and a 60mm throttle body. all builds will have Proform billet main caps to help with block twist also SBC rods H-beam(lighter where it needs to be) and JE Pistons. Trans is a Getrag 284 w/ EP LSD

Build #1- 3100 bottom w/ a 3500 crank rod journals modified to accept sbc rods and 3.1 race bearings and stroked to 208ci w/ 3.1L gen 2 heads and intake

Build #2- 3400 bottom with everything else same as Build #1 except journal size on 3500 crank modified to de-stroke crank.. bigger bore of the 3400 to help with deshrouding of valves but destroke to increase rev limit

Build#3- 3500 bottom w/ 3500 crank ground down and de-stroked again to help deshroud the valves, allow use of oil squirters..


Build #4- 3500 motor top and bottom end but w/ a custom plenum and the crank would be de-stroked to allow sbc rods..

Build- # 5+6- oh and after thinking what abouit 3500 heads and lower intake along with the 3500 crank stroked .240 on a 3100?? Is this possible? This would make 208ci on the 3100 bore. or just leaving the stroke the same but still using the 3500 heads and intake and just grinding the rod journals down to accept sbc rods??

question(s)- I noticied a difference in part #'s regarding bearings between the 31xx and 34xx in comparison to a 3500. If the journal size were the same is the 2 other motors the will I be able to use those sealed power H series race bearings?? I didnt know how much the block differed.. On paper it looks do-able.

I have heard that you cannot use Gen 2 3.1 top end intake and heads on a 3500. How much truth is there to this?

Last question for now..- the Turbo Race Cam thats on here http://wot-tech.com/shop/gm-60v6/rac.../prod_275.html
what is the power band like and has anyone used this before?? My machinist after showing him the cam selection liked this cam the most and stated that it should help with lag down low which is better because I have traction issues and pull harder up top. My old 3.1 had an Engle mild turbo cam I can post specs later. max power with my old setup before I changed the downpipe was 309hp and 362tq peak power around 5100rpm. the tune was far from being done but I lost my motor due to a failed oil line

Thanks
-Jarek

[geoffinbc]

There is no shrouding problem with the splayed valves of the aluminum heads. Also changing stoke will have no effect what so ever on de shrouding the valves. Only increasing the bore and relieving the combustion chamber can do that.

If your building an N/A motor and have a chance to add stroke then do it. Do not de-stroke a crank with such a small stroke. If it was a 3.75" stroke and you were looking for 8000+ RPM then sure it might be a smart move to de-stroke it. But with less than a 3.5" stroke making it even smaller is not a smart move.

A descent set of rods will be fine at an average piston speed of 4500ft/min. So to figure out your max RPM for a give stroke we go Stroke (3.31) divide by 6 which is 0.552 then divide that into the mean piston speed of 4500ft/min. 4500/.552 which is 8152RPM so you can see that increasing stroke will still allow you to spin the engine up just fine.

So I would use a 3500 top and bottom end and offset grind more stroke and use SBC rods.

[Mach 5]

I understand the difference between bore and stroke. Im would want the bigger bore size to get the valves deshrouded a little better even though Im sure its not an issue. Im also gonna be running 25psi through the motor and I want it to rev. de-stroking it will make it easier to rev and make power a little higher and smoother.

Im def considering the 3500 but only if I do a custom intake manifold.

[ericjon262]

why a custom manifold?

[Mach 5]

my mindset is that if i cant have a gen2 manifold on the car the one that says 3.1 Turbo on it then its got to be custom. That being said then I can also modify the throttle body placement so that its sits like factory. My main goal with this car is to have a stock appearing car while having the most power I can squeeze out of the stock engine. If I were to go with a 3500 then I would have to make a custom manifold solely because its a swap and its not the original motor. I can definitely make a cool looking manifold that will work just as good if not better than the factory one. It sounds crazy but Im crazy like that. My main concern with this 3500 motor is the bearing selection. I do not want an aluminum bearing I want a race bearing since Im going high boost high revs and I see that the only bearings available are shitty aluminum bearings which I dont trust.

[Mach 5]

The only reasons why I even considered the 3500 motor is that they have a forged crank which I wanted to use for the other build ideas, the oil squirters, and the fact that I cant seem to find a 3100 or a 3400 around here thats not available for just parts. The have a bunch of low mileage 3500's going for $400 and the 3100's and 3400's are going for that or more for what I feel could potentially be a bad motor

[Superdave]

I used the Teflon coated SBC cam bearings in my 3500, still stock rod/main bearings though. IIRC WOT-Tech was working on something for that though.


As for 3500 VS a 3.1 top end.. This picture is appropriate.



gasket matched 3500 LIM vs a 3.1 turbo LIM (also gasket matched)


The 3500 plenum is pretty plain looking, 90% of people (who aren't 60v6 gurus) wouldn't be able to tell the difference between it and a gen 2 plenum.

[ericjon262]

I used the Teflon coated SBC cam bearings in my 3500, still stock rod/main bearings though. IIRC WOT-Tech was working on something for that though.


As for 3500 VS a 3.1 top end.. This picture is appropriate.

wow, I knew the gen 2 lower was a bad design, but damn, I didn't know it was that bad...the runners don't even look close to the same length! wow.

[Jonpro03]

wow, I knew the gen 2 lower was a bad design, but damn, I didn't know it was that bad...the runners don't even look close to the same length! wow.

Coupled with the UIM they are the same length.

[ericjon262]

Coupled with the UIM they are the same length.

either way, look at the size of the runners! wow, I mean really gm, what were you thinking? "lets choke this thing down as much as we can and make sure it has absolutely no balls at all..."

[Mach 5]

Im sure that if I had the machine shop grind down the rod journals for use with sbc rods I could use the smaller 3.1 bearings. Im really curious about the mains. Whats the difference between the 2 motors?? I looked at the specs on paper and they look the same so I should be able to just use a 3.1 tri metal P bearing in place of the 3500 aluminum bearing.

Thanks for the pic I do like the style of those 3500 runners better but I think the plenum is just more for myself than anything else. Besides a couple of my friends and the guys on here and w-body I agree most people couldnt tell the difference I just dont like the design of it. plus I think I could come up with something that will allow use of different throttle bodies to be used and different lengths.

[Superdave]

Mains are the same, GM went with the aluminum coated ones in the 3500 but measurements are the same. Of course you should check all your clearances on assembly though. Grinding the pins down for the SBC rods will work fine and it's a great time to add some stroke to it. you could get up to around 3.7 liters out of it.. maybe a little more.

Just keep plenum volume in mind when building your own, that's where the 3500 plenum shines. For the gen3's, it's the best out there.

[Mach 5]

gotcha, I have been studying plenum design for a while now so I think I can come up with something different. I may actually just use this thread as my build post..
Thanks for the verification of those main bearings I was confused because of the different part# but now I know why. I would actually rather want to de-stroke it.

example of why.. besides my experience with my small stroke 4age 20v ae86

http://www.youtube.com/watch?v=5B1uqQWdw6A&feature=related

[geoffinbc]

Not gonna happen sorry. Your not going to spin a pushrod motor that high and have it last. If your strictly drag racing then go for it. But if it is a street/endurance motor its not going to run for long spinning that high. Start building a realistic motor for your car and not something your going to dump $15,000 into on fancy parts that do nothing to increase reliability. 7000 RPM potential is more than enough for any street/endurance motor. If you want to make a few trips north of that then it can be done. But get 8000RPM+ street motor dreams out of your head. Stroke the motor it will make more torque all over the RPM range and the small increase is not going to hinder high RPM performance at all.

If you really need a motor that can perform at 10,000RPM then you should start with a 2.8L or 3.6L DOHC 60 Degree V6 and not any of the pushrod motors.

[Mach 5]

I never said 10000rpm but I was taking the idea that all of the high powered motors like the supra and the skyline heck even the vq series 350 and 370z's all have in common are short strokes. i think having a little lower torque can actually benefit me since I have traction issues out of the hole.. that and my stock 5700 redline of my old motor kinda made my shifts very short and the high torque gave me wheel spin in the first 3 gears after the downpipe change. Im sure a tuned suspension can help greatly I still need to do the Koni upgrade

I was thinking a realistic goal would be between 6800- 7500rpm with a destroked crank. I dont even think the stock oiling system could hold more than that anyway. I already have a high rpm screamer in my ae86.

example:
RB26- 86mm bore 73.7mm stroke
RB30- 86mm 86mm

1JZ- 86mm bore 71.5mm stroke
2JZ- 86mm 86mm

VQ37VHR 370z
95.5mm bore
86mm stroke

VQ35HR 350z
95.5mm bore
81.4mm stroke

granted these are all 4valve motors but just the concept of small stroke large bore and they peak around 7000- 8000rpm

GM 60 degree v6

2.8- 89mm bore 76mm stroke

3.1- 89mm bore 84mm stroke

3.5- 94mm bore 84mm stroke