Lt1 Headers what Do i get 1 3/4 Primary's or 1 5/8??

[LoudLT1]

What's the difference???
can someone explain???
I'm planning on installing them myself what primary is easier to install if there's sucha thing ??
thanks,
Ed

[soCalTA]

Unless you do some serious motor work I would stick with the 1 5/8. I think they are good for about 400-450 hp. I have them on mine currently.

[Injuneer]

The key to increasing volumetric efficiency (= more power) is "scavenging"... allowing the exiting exhaust pulse to "pull" the incoming air/fuel charge into the cylinder. You get scavenging from high exhaust velocity. A smaller tube keeps the velocity high at lower rpm. That "fattens" the low end torque curve. But it can limit breathing at the top end, because the smaller tube becomes a "choke point". A larger tube will flow better at high rpm, but may provide poorer bottom end torque.

A 1-5/8" primary is good for a stock 350. A 1-3/4" tube is good for a stroker. What you use in between is sort of a toss-up. If you ever plan to push your setup to 400-500HP, and particularly if you ever plan to use nitrous, get the 1-3/4" primaries.

I started with a set of 1-5/8" JBA's, and they did keep the bottom end toruqe up, but even with a mild bolt on engine they never seemed to allow the engine to breathe above 5,500rpm. Current setup is 1-3/4" AS&M's.

[LoudLT1]

guys thanks for the replies......
i plan on porting stock heads , intake , adding a mild cam and 3,200 stall in the near future. should i still stick with 1-5/8 primary's? i think so from your posts....should i look for a 58mm or 52mm throttle body?? OR can a stock Throttle body be ported to match the intake????
ed

[Injuneer]

A 52mm TB will be adequate for up to 500HP. You can buy a new one, or there are people who will "port" your stock TB to 52mm.

I would put 1-3/4" headers on it, if it were mine.

[soCalTA]

well with all the things you have outlined to do I would kick it up a notch and head for the 1 3/4