Collector Extension

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. .

The 5 degree split is getting there. That’s quite a bit for a good set of headers. You may want to call Cam Motion and talk to them since it’s their cam. I’m trying to think through in my head if advancing the cam will help get blow down going earlier and help with that extra split, but it’s still early and I’m not fully awake yet!

With extra exhaust duration, you are increasing scavenge time. Yep...too early. Let me think about it. Or better yet, call CM and see what they say. It’s funny...I became a CM dealer in 1999 and I was running an 8 degree split from another well known cam grinder. The car was a pig in the gear change. Once we had all the numbers out on the table, the first question was why the big split. I said that’s what that grinder picked. So we knocked it down to a 2 degree split and that was only because I was on alcohol.

That was almost 22 years ago, but I doubt much has changed in the way of split duration cam timing and quality headers.

I agree Kindafast: I replaced my Tubular Automotive headers with TTIs a few years ago, not happy with them , don't like taking the suspension apart to put them in, they fit to close to the trans and trans shield, I had to modify my T/A shifter cable bracket to clear the collectors. the only thing I gained was not having to use a 90 degree oil filter adapter. They might be ok for a street car but not a race car the motor comes out of once in awhile. For the close to a grand they cost I expected better I am probably going back to Tubular Automotive brand the next time the motor comes out.

FYI, UT also discussed this issue recently

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

Thanks , I think that is the video my son watched and called me on. It makes sense to give it a try . I haven't even thought about extensions in years.

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.

Been thinking about this myself .

So if you run crankcase evacs do you move them to the end of the extension , or leave them in the collector?

Thanks , I hope it helps a little . At least make me think those TTI headers were worth all the money and grief . LOL

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

Does anybody have any back to back comparisons ??

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.

EGT does affect the speed the gas travels and expands at too so perhaps a combo that generates higher EGT's would respond favorably to a longer extension?

Way above my amateur engineering skills and pay grade... lol

Kevin

Yes but no record, we were at the track divisionals and to get in I had to run in the heavy class, 12.50 or slower. My car ran 11.6, so was trying different ways to slow down, bagging wasn’t consistent so ‘hey let’s take the extensions off’ wrong, bogged so bad and came on when the engine wanted too, but did knock off 3 tenths but couldn’t get a consistent number to run. Finally bagged, ran the number and so did the other guy but he had a couple thousents better light. That extension made one heck of a difference. Might add this was well sorted out with my combo.

on a car with a full 3" exhaust, having a collector diameter of 3 1/2" x 4" [approximately] long, would adding length to the collector size before necking down to the exhaust size be of any benefit ?
as always, TIA !

Every Mopar V8 motor I've added collector extensions to at the races help them, BB, Hemi, and SB motors with automatic and even stick shift SS/A Hemi cars with 4.0 inch H pipe collectors extensions
Depending on the track conditions, weather, elevation and tuning can make a difference on which length will work the best that day at that track
Marking them with crayon or soap stone helps you find out where to cut them off at for that day and track, I know several NHRA class racers that have 6.0 inch, 12.0 inch, 18 inch and even 24 inch long collectors in their trailers and swap them as needed

Thanks everybody for the replies , Must be a weak moment on my part not to build the extension and just buy them. 106.00 total for two 18" Long 3.5 " collectors. LOL hope they work.

We tried 12" extensions on ours. Didn't make a noticeable difference ET or MPH wise but maybe other factors were prevelant. It did however, help stabilize the AFR readings though. It's pretty much a moot point for us now though, we have a 120db limit at the track in our class but we've now gone a little faster and quicker with a full system and silencers

Just wanted to update all on the header extensions. Last year around this time I went a new best with my much lighter 8.75 rear end @ 6.51 at 104.8 miles per hour. After that pass I installed a new Strange Dana 60 and the car couldn't get out of the 60s 6.62 6.63 and so on. Well I installed 18" header extensions last week and went to the track today. Right off the trailer the car went 6.50 @105.26 and backed it up with a 51 and a 52. same MPH. The car went 1.41 60' time where it was high 1.40s last year. All I can say is that was the best 100.00 I have spent in a long time to buy those header extensions. 6.40s here I come.

did you change the collector or just add extension.

I have a set of hooker headers 1 5/8 with 360-1 head planning on a new set 1 7/8 in the future I was considering cutting off the 3 in collector and replacing it with 3 1/2 wondering if that would help or hurt the scavenging

[quote=BigFish69]did you change the collector or just add extension. [/quote

I didn't change the collector. TTI Had 3.5" Collector. I just added 18" 3.5" extension. Really happy with the pick up.

Evac tubes stay put............gas velocity is fastest just past the merge and you generate the most negative pressure there.

Look into these extensions. Hendren Racing anti-reversion mufflers

Awesome! I bet you're feeling better now!

Yes sir I am. All last year I backed up and went slower. LOL it was nice to see an improvement starting this year . Thanks

I thought I remembered years ago when racers ran collector extensions that they used to say cut it off where you see it making a ring on the collector ? I believe these were 24" collectors but I never tried it. Ron