I'm soon going to start on a second 3.1 stroker motor. This one is going to be bored .030 over, Custom JE flat top pistons, Ported heads and intake, Crane 2030 cam, Darrell Morse TB, double roller timing set,1.6 roller tip rockers, Sprint exhaust manifolds. Should give it about 10:1 compression ratio that I hope will still be compatible with pump gas, but is it worth the exta expense to go with the stainless SI valves over stock?

I'm not sure with the 1.6 rockers I will have enough clearance with the flattops either without modifications to the pistons.

Anyone car to share their thoughts?

Thanks

[This message has been edited by Mike Murphy (edited 12-19-2004).]

I don't think the valves will matter. The biggest air flow restriction is the intake manifold, even with Darrell's porting it's not going to be much better. Your compression ratio is likely to create detonation problems IMHO, even on 93 octane.

With the Fiero intake system I feel the best approach is to build for low and midrange torque rather than high end power.

JazzMan

watchout! 10:1 compression on iron heads will require 92+ octane heck 94!
ditch the Crane 2030...it does make good tq but not hp.... Just go with light 1.5 or 1.52 roller tipped rocker arms and get PAW's v6 60 degree cam, that sucker has some nice lift!

oh and I used the Fiero Store's SI valves and that did seem to help the breathing despite the fact that I didn't have a ported TB at the time on my original .060 over 3.1 rebuild...ofcourse I was using a higher lift cam than that 2030...that motor liked revving to 5500...

[This message has been edited by lou_dias (edited 12-19-2004).]

I just did a similar rebuild last year, check my sig. Just make sure if you exceed about .420 lift, you let whoever's doing the head work know because you'll need different valve springs. There's VERY little room left with the stock valve springs for additional lift.

If you read through some of the older threads here you'll see a few guys had rebuilds that self destructed in a couple thousand miles from overlooking that item. www.gmpartsdirect.com had a good deal on the h260 cam, .427/.454 if i remember correctly.

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88 Formula, T-Tops,auto, 3.2 V6, roller chain, roller tip rockers, h260 cam, Darrell Morse throttle body, 19lb injectors, Spintech muffler, K&N ,

[This message has been edited by 88 Formula (edited 12-19-2004).]

I'm with everyone else here - use a bigger cam to open the valve - not 1.6 rockers - the results are the same, with less strain on the push rods.

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1985 Fiero SE - Plain Red V6 Coupe
3.1 Crane 272 MSD 4.10-4spd

Mike,
I'm running 9.5 compression after milling heads and having block decked, no problems running premium pump gas. One thing I did that really made the engine smoother was having the rotating assy balanced. Mine will rev right to redline without hesitating, but I try not to since I haven't even put 1000 miles on since the rebuild.

I agree with the others, there's no reason to go w/1.6 rockers if you're changing the cam anyway, just buy the cam that has the lift you want. 1.6 rockers only make sense when you're trying to avoid pulling the engine to change the cam.

I forgot to mention that I did have everything balanced. I have the Crane 2030 but also a Competition Cams although I don't remember which one I will have to check. From what I'm hearing I will probably not use the 1.6 rockers if I go the right cam. Hear they are hard on valve guides anyway. The 10:1 ratio and detonation do concern me as these pistons are not dished like the normal ones for the 3.1 stroker with cast iron heads. JE told me 10:1 would be what I should expect.

The cam you choose should have a recommended range of compression ratios, you should follow that, my h260 cam recommended up to 9.5 cr. so that's what I used for my target. I think the 2030 cam is one step less aggressive than the h260 (I also considered it) so I would expect the recomended cr to be a little less, it may not be, but I would check it out.

Hey Mike,

I have one of the PAW high-lift cams, and probably won't use it. I decided it's a little too aggressive for my rebuild. It's unused, still in the packing grease. Specs are as follows:

Gross Valve lift -- 0.443" intake / 0.465" exhaust
Lobe Seperation -- 112 degrees
Duration @ 0.050" lift -- 214 degrees intake / 224 degrees exhaust

You WILL need aftermarket valve springs with this cam. It's recommended for compression ratios up to 10.5:1. It was designed for mid-to-upper range torque. You'll lose some low range torque, and the idle will be a little rough. But it'll be really happy in the 2500-5000 RPM range.

If your Comp Cams one happens to be the 260, I'd happily trade.

[This message has been edited by Blacktree (edited 12-20-2004).]

I'll check it out and let you know. Sounds like a plan.

Thanks