ok ok ok .....I searched and couldnt come up with anything helpful. Just wanted to make sure. Ive been reading lingenfelter's book on sbc's. He states that you really dont need 1 3/4 size headers on a 350 unless your making around400 hp. But everyone here seems to think that if you have a 305 go with 1 5/8 and if you have a 350 go with 1 3/4.

Any opinins?

 

As far as I know, the only 1 3/4" shorties available for our cars are the SLP's but they're also the most expensive. I bought a set a few weeks back and after installing them, I noticed a major power increase from 3500+ . It was actually very surprising at just how much harder the car pulled compared to the factory manifolds.

https://www.thirdgen.org/forums/exha...p-1-3-4-a.html

I didn't notice any decrease in the low-end torque department as I expected going with the bigger primaries, it pretty much stayed the same, so that was definetely a pleasant surprise.

1 5/8 primaries though, I'm sure, would have made a bigger difference down low as that's generally been the case in my (and other's) experience with that size header (1 5/8). They generally make a lot more torque in the lower rpm's.

1/58 should be more than enough to support 450+ HP. Seen it done 100's of times already, but if you're going for 500+ you might want to consider 1 3/4 (SLP's)

Most go with the smaller primaries because they're much more readily available (more companies make them), more cost effective and provide bigger gains down low than bigger primary headers like the SLP's.

If you have the money and plan on really building up your engine, go with the SLP's.

If your only planning on making somewhere in 450-475 area, 1/58 will do just fine.

 

Most times there talking about long tubes. Theres a difference...

 

What was said in the 100 previous threads on this topic that you're unsure of?
1 5/8" shorty headers for a stock engine, 1 3/4" shorty headers for a 350 or larger engine with heads/cam, nitrous, blower, etc.