Hey guys , my son reminded me of a trick we used to use back a long time ago. Just wanted your opinions. Last year I went from a small 1 5/8 to 1 3/4 tube header TTI to a large for the INDY heads W2 big tube headers. The car went almost a 10th slower off the trailer. I jetted the carb up some and got my time back but couldn't help but wonder why such a difference. Anyway fast forward to tonight and my son reminded me of the old header collector extensions we used to put on and mark with a wax pencil to cut at the melt point. How about opinions on weather I should give this a try and do you think it will help ?? I was really hoping that those expensive TTI ILL fitting headers would have made a big improvement in my setup and they never did.
I have a 422 ci X Block with a 652 roller cam and INDY 360-1 heads on it. It runs pretty good but I really thought the headers would have made a pretty good difference.

I can’t imagine on 422 inches a 1.875 tube is too big. I’d start with a 24 inch extension and trim it down from there. If you are running more than a couple degrees of split on cam timing the big headers will kill it. The correct size headers hate big intake/exhaust duration splits. It kills everything in the middle. Also, wide for the combination LSA’s with a bigger header kills mid range power. At your displacement and heads I’d think 111 is as wide as I’d go.

All of this stuff has to work together. I’m not 100% sure from your post if you now have TTI headers or if you took them off for something else. If they are TTI headers their collectors suck poop through a straw. I’ve complained about it several times to them, but they say I’m the only one complaining about them. Unless it’s just a street car and I have to use TTI headers I cut those junk collectors off and buy slip on collectors.

That also has another benefit. You can cut the flanges so you have three pieces per side, plus the slip on collectors. Makes it much easier to get the headers on the car. I’ve asked TTI to make their collectors slip on, but they say they don’t make a true “race” header, except in the description it says “race” header IIRC.

Just my .02 and that’s way more than it’s worth.

Thanks for the info , I did buy another set of TTI Headers and I am not happy with the fit or the performance of them since I bought them. I have to take them loose just to change the darn oil filter. Anyway here is the specs on my cam that was actually built for another engine I had . Stock stroke 340 with a lot more compression. .

FYI, UT also discussed this issue recently

https://www.youtube.com/watch?v=yLudN9E6Nzk&t=1s

ABSOLUTELY run extensions, it can make a huge difference below peak torque. And "too long" really doesn't hurt, too short will kill you.

I'm pretty sure not running collector extensions on a set of headers is where the old "engines like backpressure" myth started.

Uncle Tony's video on the collector extensions and exhaust scavenging were dead on.

12” extensions made a hec of a difference for mine, lost the flat spot on launch, 383 Duster with Hooker fender well headers.

On my car it is huge with Hooker 5903s, I don't have scientific comparisons, but if you want to bench race it feels like a minimum of 30 ft lbs of torque at 2500 or 3000 RPM (stick car). I have seen results others have posted on line of as much as 50 ft lbs.

Motortrend Engine Masters tested this and found something like 25 ft lbs below peak torque on a SBC, the same peak torque, and 10 peak HP by using an 18 inch extension vs nothing. They then cut 2 inches at a time, I don't remember the exact details of each length but essentailly they started trading some of the below peak torque for HP, but i was marginal compared to having an extension vs not having, shifting around something like 5-10 numbers.

Also, I should correct my previous statement. Not EVERYTHING Uncle Tony said was bang on - the grease crayon/paint trick, in my opinion, is an old wives tale. It may coincidentally get you closer, but the compisition of what you put on there, any paint or wax, will be different by brand, color, what they made 40 years ago, etc. And this is going to be a function of your EGT. Raise the EGT and the mark will move futher away, reduce it and it will get closer to the primaries. Your header paint, coating, wrap, etc would all effect it too.

Does anybody have any back to back comparisons ??