which is better the smaller 1 5/8 or 1 3/4 inch headers? I think the smaller daimeter piping would be better for velocity. What do you guys suggest?

 

1 5/8 for a 305, and a near stock 350 should be fine, 1 3/4 for anything more.

I'm running the 1 5/8.

 

Who else besides SLP makes 1 3/4" headers? Other than the long tube variety. Hooker makes a 1 5/8" shorty type header, why no 1 3/4"?

 

1-3/4" is good on our cars to make up for how compromised the rest of the system is layed out. Another car with good exaust layout is probably fine with 1-5/8s like a ton of Mustangs are.

 

i run the SLP 1 3/4" on my 305.

 

Go 1 3/4" so you only have to do them once.

 

haha, i agree. if u get 1 5/8" and start modding your engine, your gonna be choking that engine.. unless its a 305..

 

Just go with the 1 3/4's. TPI already makes lots of TQ, this will help out the HP some.

 

With a 305 or a stock easy-going daily driven 350 go with 1 5/8", plan on doing mods later or already have mods go with 1 3/4"


I have 1 5/8" because I got them cheap a long time ago ...I'll probably be putting on 1 3/4" long tubes after everything is back together.

 

i did notice a slight loss in that awsome low end torque my car used to have.. it MORE then makes up for it in mid\high end.. but i guess i just got used to the low end torque pushing me back..

 

No flame intended, but do you guys have any dyno results to back up your comments about 1 5/8" headers "choking" a 350 or about 1 3/4" being a better choice? I'm not convinced that this is valid statement whatsoever.

I see this stuff posted all the time..."Get 1 3/4" headers, 1 5/8" will be a restriction when you do big heads/cam, yada yada."

Here are 2 guys with 1 5/8" headers who have pulled 116 and 120 mph 1/4 trap speeds with them. I haven't seen many people on this board who have hit those trap speeds....period.

Check out Ralph on here:
http://temp.corvetteforum.net/c4/bea...enSetups.shtml

And I'm sure you've all seen this post:
https://www.thirdgen.org/techbb2/sho...hreadid=103711

It makes you wonder who to listen to, doesn't it? I just think there's a lot more to this than "bigger's always better". What it comes down to is what makes you put the best torque AND horsepower to the ground throughout EVERY rpm range while you're racing. Peak numbers don't mean squat compared to the AVERAGE.

Do I have any backup on this one? Come on now, it's not very often I get drinking and feel compelled to post!

 

It doesn't seem to me that 1 5/8" headers are holding anyone back here. SLP is the only company out there that makes 1 3/4" primary smog legal headers for our cars. Of course they're going to recommend 1 3/4" inch headers for 350's so they can put that thought in the back of your mind. Don't get me wrong they're nice headers but SLP's have small 2.2" collectors vs. most headers which have at least 2.5 to 3" collectors.

 

If you are gonna be modding 1 3/4's is what to get. If its gonna be near stock or lightly modded 1 5/8's should be good, I say go for the 1 3/4's just incase.

 

Good point, Red. I didn't know that.

Our combos are only as good as our biggest restrictions. I think we've proven here that 1 5/8 primaries are by no means the restriction.

Hmmm. Very interesting.

 

Anything under 350HP shouldn't need 1 3/4". However, once you are pushing around 400+ HP 1 3/4" primaries are proven to increase top end significantly. Car Craft does several buildups on 350's and one combo with stock rockers and 1 5/8" primaries made 390HP. Later they added 1.5 roller rockers and 1 3/4" primary headers and got 417HP out of the same motor - with very little difference in low end torque.

esams - If those guys put a set of Hooker Super Comps (1 3/4") on they would probably gain another 2-3 MPH. Once I put my new SLP's on I'll post the results. I'll guarantee they are good for another 10-15 over these crappy Edelbrocks

 

I researched on this site and others before purchasing my headers and I found that 1 5/8 headers will flow up to about 400hp. I don't think my car will ever see 400hp, so I went with 1 5/8 on my L98.

 

This debate is ongoing and my vote is for the 1 5/8" headers.

My proof stems from a Chevy High Performance article a few years ago where they took a 406, put the budget trick flow heads on and made 450 HP and 500 ft/lb of torque with 1 5/8" headers...

Do you think they can handle over 400HP? Also, the HP peak was at like 5300 rpm.

I think that you should be fine with 1 5/8" headers cause like every other street engine...build for torque.

 

OK, here's another question....

Up here, in Salt Lake, we're at over 4000 feet elevation and we put out about 80 less horsepower and run .8 sec and mph slower than those at sea level.

Does that mean that 1 5/8 headers would be even more "forgiving" up here and not become a restriction until even higher power levels, like 400 up here? (480 at sea level)

 

anything is better then stock...

 

I would think that you would want to build the combo as if you were at sea level...just to do it right.

It depends on your combo and what you want for the future too.