1-5/8" headers in a 393w stroker??

[afterglow]

Would it be a no-no to use 1-5/8" headers in a 393w stroker?? How much would I be giving up over 1-3/4" headers???

 

[rbohm]

that depends on how you build the 393. remember you dont need the same rpm capability to make power with a 393 that you do with a 351. it also depends on where you want to make your power. at low and mid range rpms you will actually do better with the smaller tubes, though it will choke the engine off at rpms above 4500-5000 rpm. understand though that this applies to a normal street build. if you are planning a very healthy street/strip engine, then use the larger headers.

 

[afterglow]

It's purely a street car so emphasis will be on low to mid rpms. Planning to go with AFR185 heads, 750cfm carb, Compcams XE274H, Weiand Stealth, 9.5CR.

Desktop Dyno says 434hp@5500/456ft.lbs.@4500.

 

[rbohm]

in your case then i would go with the 1 5/8" headers tubes, and a 3 1/2" collector.

 

[86bluecobra]

The 1 3/4 inch headers will give you room to grow should ever choose to do so. The smaller tube headers will give you more torque. I have 1 5/8 shorty's on my car and I have got a 11.5 time slip under my belt. Maybe I could have done more but I'm pretty happy with what my 351w has done. If i was building a stroker I would be looking at buying 1 3/4 in longtubes. I guess as long as I had the money that is.

 

[Helmantel]

I think 1 3/4 would be the better choice.

Look at it this way: a 1 5/8" header on a 393 is like a 1 3/8" header on a 302. I think most would agree this would be way too small for a performance 302.

 

[SoCalCruising]

Go buy this months HOTROD and read what Marlin Davis has to say in Pitstop.

 

[rbohm]

I think 1 3/4 would be the better choice.

Look at it this way: a 1 5/8" header on a 393 is like a 1 3/8" header on a 302. I think most would agree this would be way too small for a performance 302.

to a point i agree. but since he is building a street engine, the smaller header is better. i am going to build a 300hp 289 for my 66 mustang, and i am going to use a 1 1/2" tube tri-y header because i want the fat low end and midrange torque.

 

[htwheelz67]

I've seen some buildups (chevy 383) that made best power with 1 5/8, 1 5/8 would be fine for a mild stroker with 185 heads.

 

[Helmantel]

to a point i agree. but since he is building a street engine, the smaller header is better. i am going to build a 300hp 289 for my 66 mustang, and i am going to use a 1 1/2" tube tri-y header because i want the fat low end and midrange torque.

Smaller tubes are indeed better for the street, but you need to take the engine size into account. It's a 393, which is 35% larger than a 289, hence the pipes cross section should be increased accordingly. Believe it or not, but making the cross section of a 1.5" tube 35% larger results in a 1.75" tube

A 393 is a big block (cube wise), so think in big block terms

 

[Helmantel]

Double post

 

[rbohm]

Smaller tubes are indeed better for the street, but you need to take the engine size into account. It's a 393, which is 35% larger than a 289, hence the pipes cross section should be increased accordingly. Believe it or not, but making the cross section of a 1.5" tube 35% larger results in a 1.75" tube

A 393 is a big block (cube wise), so think in big block terms

again i agree to a point, but look at the heads, cam, and carb that he is using. all are geared towards a low to mid range rpm power band, and the 1 5/8" headers will compliment that nicely, especially since that motor is not likely to see the high side of 5000 rpm very often. on the other hand, had he choose an 850 carb, and the 205 heads, then i would agree that using the 1 3/4" header is the better way to go. his motor is going to make maybe 450hp, but the torque curve is going to be fat flat and low.