I have a 95 firebird that is going to need a rebuild soon and had a few questions regarding how to build it. I want to use stock bottom end and forged pistons. First how should I port the heads in order to achieve good flow and lower lift. I dont want a dyno queen i want uasable power. Any tips on where to start so i can match the parts? I cant figure out which parts i should get first then work from there. I know it all in the combination but i cant figure out where to start. any recomendation on heads will be helpful. what size valves should i use for power under 6500 whats the most important thing on the heads flow/velocity?

 

essentially, what you want is high VE and low RPM.

tuned intake runners and high "displacement."

I put "displacement" in quotes because in terms of VE, boost = displacement.

Boost, big cubes, efficient engine.


achieve High VE in a big cube motor and put it where you want it. what racing is all about

 

Assuming you are staying NA:

What you seem to want is "area under the curve" both torque and hp curves. That's pretty much what the Engine Masters contest looks for. They have displacement limits and measure the average torque plus average hp from 2500-6500 (for small blocks). The first year (2002) it was 366 cube small blocks. The winners got great numbers, but they did peak power about 6500, and peaked torque around 5000. What is surprising is ths amount of torque some folks got from below 3000. With an A4 and a 2800-3000 stall converter, that's where you should be looking. With an M6 is should be very driveable off the line.

You could look at what folks like Joe Sherman did to win and adapt some of the thinking. Basically they had excellent flow without excessive port volume, which keeps velocity up. They also had carbed single plane intake runners about 5-1/2 inches long. That's going to be a problem with an LT1 or LT4 intake, so you might have to work around that. Remember they were going for the untimate output and spent tons of money.

Generally, you'll want as much compression as your gas will allow, good flow with moderate sized ports, and a very specific cam and valvetrain designed to maximize your engine's torque/power curves IN THE RPM RANGE YOU PLAN TO USE THE ENGINE. This applies whether you stay with 355 cubes or stroke it to 383 or so.

If you stay at 355, I'm not sure you'll need forged pistons. Hypereutectics might be sufficient. Spend your money on the heads and valvetrain, and maybe the intake. Get professional design advice also. The combo has to work together very well to achieve your desires.

I'm sure others will have ideas. Good luck!

 

Super Ram, Lingenfelter produced a Super Ram intake for the LT1 a while back that made gobs of TQ at lower RPMs. Because iof the longer intake runners the SR makes a lot of power at lower RPS then the shorter LT/Mini ram, style of intakes.

 

i still vote massive quantities of boost.

 

That would undoubtedly work, but wouldn't it involve ma$$ive quantitie$ of $$?

 

Yes it would, and he already said he's planning on using the stock bottom end so, IMO, that's out of the question for long-term reliability.

 

I wonder if anybody has ever tried putting a TPI setup on an LT1?

 

I wouldn't be surprised if someone out in the woodwork has tried it, but the TPI system would kill your top end power.

 

thanks guys for the replies it helped out alot, came up with a few ideas

 

two words....... TWIN SCREW

 

There's no replacement for displacement.. hp is a function of torque x rpm, so to increase the hp in lower rpms, you'll need to increase the torque. Longer stroke would be the easiest way to that.

Then get with your cam grinder and get a cam designed for the rpm range you want to run in, with the port size you choose. Smaller, stock sized ports will be best, concentrate your work in the bowls and chambers..

Of course, you could always consider a power adder.. my turbos peak torque with a stock LT1 was at 3400 rpm...

 

I wish I'd said that.

 

God let's hope not! Cheston put that crack pipe down! This guy wants power AND torque not just torque. The TPI setups are probably not THAT bad but if you have any kind of real engine they just totally choke it. On a 447 incher I did I gained 100+ RWHP with the change to a Vic Jr. from a ported TPI and only lost around 20 foot pounds of TQ down low. The really good aftermarket long runners might not be as bad as I think though?

 

Well if he wants more power everywhere low and top end cant you have headwork done that makes the runners more efficient? Like rather than enlarge the ports more consentrate on areas that dont reduce velocity any and simply help low mid and high lift flow, as well as swirl and all that good stuff? Then have a cam that is more efficient than the stocker but produces power in relatively the same rpms like an XE version of the stock cam matched to the new heads? Seems like a neat idea that probably not many have tried... IF anyone made a 1 5/8" longtube for the lt1 that would probably help a bit too, but I dont know Ive never seen a test comparing the 1 3/4" primary longtubes against a set of 1 5/8" primary longtubes on a relatively stock lt1...that might be interesting, sure would be easier to fit and tighten the headers bolts