Hey Guys, I've been talking with Leo at Weber and I'm ordering up one of their LS2 shortblocks for my F-body.

At first I decided to go with a 365ci, stock crank, 4.005" bore, -11cc pistons. Now I'm having second thoughts and think a better choice may be a 403ci, forged 4" crank, 4.005" bore, -15cc pistons.

My car is 95% street car. I'm going to run a Vortech T-Trim with a 2.75" pulley, and 8.00" crank pulley, so it'll be maxed out. The blower will supposedly support 825fwhp/1200cfm. I've seen good numbers with the T-Trim, of Late, "Navy" making 730rwhp.

So, my question is about longevity of the engine. With the blower, both engines should be capable of making the same power, with the 403 probably making a little more power under the curve, with less boost.

Would there be a benefit of running the 403 at say ~10-12psi vs. the 365 at 14-16psi? The boost numbers don't matter to me, so If I can have a 403 making the same power with less boost, wouldn't that be the way to go for reliability and longevity?

You Procharger guys are more than welcome to give me some insight too.

Thanks in advance

 

Depends how much low end/off boost torque you want.

If you want more, go bigger, if it doesnt matter, stick with the smaller.

 

Right, I understand that part of it. But what about problems with reliability, and tuning for more boost on the smaller engine? Wouldn't the slightly larger engine be easier to work with and a little more reliable while running less boost?

 

Are you seriously overspinning T-trim?

If I recall right, I have 8" balancer and 3.125 pulley and already at 6600 I'm way over the recommended limit...

 

Whats the internal stepup on the T ?

 

Not sure off the top of my head, but it's rated for 55,000rpm. Overspinning it a little won't hurt it. Heck, guys on here have been doing it for a while now. Although, the 2.75" pulley is the smallest RMCR recommends.

Anyway, back to the original question...

 

Obviously a bigger, less stressed engine has better long term prospects for reliability

 

Have you had your current combination to the track? Mine is very close to what yours is right now and I havnt had mine to track. I have a T-trim waiting to go on as well.

 

Get the 403...the one in my signature to be exact!

 

I haven't had it to the track in a couple of years. I was running the G-Trim and have no good #'s to show because I was running regular street radials.

I currently still have the G-Trim on the car, and have been collecting parts, ie: T-Trim, fuel system, suspension, rear end, etc. The engine is pretty much one of the last things I need to buy.

The more research I do makes me lean toward the 403 now.

 

I would have seriously considered it, had I not already given the OK to Weber to get started.

 

My opinion, I'd run bigger cubes for a street car keeps the revs down.

 

I have to agree with PSJ. When you have boost and bigger cubes you scoot around so much easier due to having more tq and power under the curve. In my car I quickly short shift and get into 5th. I can pass in 5th with no problem...

 

I'm in the market, I just really wanted 15cc vs 20cc... I'll keep this in mind... how much was shipping from Texas to you? as I'm in Texas, should be similar $

 

Thanks for the replies everyone. I think you've helped me make my decision to go with the 403. I'll call Leo at Weber in the morning to discuss it.

Mr.Big, that really is a great price on Mr.MartySone's engine. It even comes with head studs which run another couple hundred dollars! In my original post I mentioned -15cc pistons, but when I looked into it a little more I realized -20cc would net around 9.7:1 compression with a 65cc combustion chamber, which is where I want to be. Like I said before, If I hadn't already made arrangements with Weber Racing, I probably would have bought this engine.

 

Are you getting the noisier T-trim (the V-1) or the Superquiet V-2 version? The internal stepup is a little different - V-1's are 3.4:1 and the V-2's are 3.61:1. All the T-trims have a rated redline of 55,000rpm.

I like your choice of the bigger motor. That will be a great combo.

Jim

 

It's the V1 T-Trim, the noisy one haha! I bought it over a year ago and have been picking away at everything else since then. I figure the motor should be one of the last things I buy.

 

I would do some research....years ago i read hear on the forums that it you run a supercharger that its better to not run that much stroke. that is why i am looking to go with the 365 or 370 vs a 402 with my procharger d1. i will try to find the link for you..