Looking for recommendations regarding the size of the header primary tube.

Intended use is (M-body in the sig, 3600 lbs race weight): weekend driver, not a drag racer, a typical street/light-strip car. W2 based 408 stroker, forged crank, H-beam rods, 10.5:1 CR, hydraulic roller cam, 6500 max RPM, 4k converter, 4.10 rear end ratio.

I am moving to the TTI headers, specifically looking at the 340W2 (1-5/8" primary) or 340W2-17835 (1-7/8" primary) setups.

Previously I have only ran 1-5/8" tubes, always on a stock displacement motor (360"), these worked well on the car. The remainder of the exhaust are dual 3" pipes with X-pipe, all feeding into Hooker MaxFlow mufflers.

Given the move to a stroker (408) and the cost of these headers in particular, I am wondering whether I should be looking at the 1-7/8" tubes in order to get some "room to grow"?

While I always aim for max-performance effort within a particular combo, this is not a motor that will spend a lot of time in the upper RPM, it simply is not a drag race vehicle.

My original thinking was to stay with the 1-5/8 tubes, but given the extra cubic inches that the stroker brings, the fact that at WOT I push the converter to the 4k stall and with the 4.10 gears it'll buzz real quick I am now wondering what the best option is. What do you recommend?

I run 1.875 tubes on a 340 CID street car.

That would be the minimum size I would run.

I would look at 1 3/4(if you can find them
or the 1 7/8) being that its a street ride

For comparison, when I was testing my 383....... Unported 906's, rpm intake, solid cam....... Going from 1-3/4 x 3 headers up to 1-7/8 x 3 headers picked up power pretty much everywhere(within the tested range).
More tq and more hp.

I don't recall the amount off the top of my head..... Around 15hp iirc...... On a motor smaller than what you're building, and with much lesser flowing heads.

The info is in the tech archives if you're curious.

Well, sort of late to the game with this info, but I did call TTI when I got some free time to get their recommendation. The gentlemen I spoke with literally said: "...if over 600 hp then use 1-7/8" pipe...".

Even when I asked him for the "room to grow", it all came down to that seemingly magic 600hp mark.

Alright, a bit weird I think, because as I've been scouring the net tonight trying a learn a bit more about this, I am universally seeing that 600 level being more of a 500 mark. Again, these are just numerous posts from folks like you and I.

I did come across a decent Header Ho-Down article, where 4 different sized pipes were compared. Even on a smaller displacement engine (that was a Chevy 383) it appears the big 1-7/8" primary pipes posted some impressive dyno numbers throughout the combo powerband. So seemingly counter-intuitive to the "smaller primary pipe nets more torque".

How is the clearance with the 1-7/8" header install on a SB look like?

I have 1 7/8 TTI W2 headers on an Abody. They fit tight but they fit great. The one thing the instructions lack is they only tell you to jack the car up. They do not tell you that you need to jack the car up really really really high, but do that and they go right in.

With 1 7/8 you shouldnt have any problems..
you might want to run 1 7/8 but with a 3.5"
collector.. will make more torque.. I'm running
1 7/8 with a 3.5" collector on my 416... It does
go back down to a 3" after the collector but I
also run electric dumps right after the collector
to help reduce back pressure
EDIT
this is with a full exhaust out to the bumper

I agree on the 3.5 inch collector. I forgot to mention that.

I would also make sure you have 18 inches of collector. Maybe a bit more.

No doubt I'd go with the 1-7/8" primary tubes. I have the same on my W2 408 and it made good torque and hp with a 950cfm 4150 on a single plane Indy intake. I was surprised when it picked up everywhere by adding a 1050 dominator (thanks again Thump!). This combo is not set on kill but it shows they like to breath.

See if TTI will make you a set of 1 7/8 to 2.0 step headers with 3.5 inch collector
This is to make sure you have enough pipe for real future growth AKA go big now instead of later How much does a 150 HP NOS kit cost now

Just thinking, how would step 1 3/4 to 1 7/8 work? I know 1 5/8 to 1 3/4 work very well on a 500 hp 408 build.

I have 410" stroker with W2 heads. I have TTI headers with 1 7/8" primary tubes. Works great for my 3100 pound Barracuda with 3.23 gears and 27.5" tires. Drove from Carson City to Las Vegas and ran 12.34. I think that it would run 12 0's at sea level. I am please with the setup.

I have to agree with the 1 7/8 with a 3 1/5 collector. I'm currently running a 2" tube with a 4" collector on my 408.

I've never seen a step header make more power than a straight header if the straight header was correct.

I don't feel the 3.5 collector is the right set-up for the OP's combo.

Ideally, I would want 1-3/4 > 1-7/8 stepped primaries with a 3" collector for that combo if I had the choice.

IMO, the 1-5/8 primaries and w2 heads doesn't make any sense.......well...... Maybe on a 318.

I have tested a 1 3/4-1 7/8 step header on my
W-9.. it made more low end torque.. then I
went to a 3 step.. 1 3/4-1 7/8- 2.00.. still
had the low end torque and better on top end..
I ended up building the 3 step

Take a look at the prostock and nascar guys anytime you want,they do and pay anything to make that last fraction of a hp.

no fitment problems with 1-7/8'' TTI's. that's what i run with zero issues.

go with the 1-7/8'' and never look back

A long time ago the late Jere Stahl told me that headers were a 5% deal. That is from the best to the worse you are talking about 5% of your power.

I don't know how much the difference between a header that is good compared to a header that is great, but you probably are not going to help or hurt things a whole lot.

And then there is the "Engine Masters" episode where they beat the daylights out of a set of headers and have little effect.

Bill

I don't know about primary tube but if the collector is too small (where it doesnt allow the motor to achieve it's natural torque peak RPM) it will limit top end power....(so to me) that could likely be more than 5% of the potential peak power. Stahl was also likely talking about an open header/race situation which is obviously very different from a street/strip type application. In other words the peak torque limit of a too small collector could very likely lower the HP trajectory/rate of rise/curve from that RPM all the way to peak....that being said.... (cont'd below)

My 440" W2 is a big torque motor but I'm discussing (with a fabricator buddy whose been doing some awesome work on it) whether it might be more practical to put a set of undersized shorties (Made by sanderson) in it because the chassis (66 A body) is so tight. It'll cost me big time up top but the combo just has so much torque in a 3000 pound car I doubt I'll miss it very much. I basically have a mopar version of a Buick 455 Stage 1 motor in terms of torque already, and then maybe 100+ HP on top of that....in a 1000 pound lighter car. At some point I'm asking....how much is enough? I keep reminding myself...the FAST BBMW and SBMW guys run high 10's with worse than that.

Sanderson will make a set of their DD-9 (63-66 A body) in 1 1/2" x 2.5" collector but with a W2 flange very reasonably. Not ideal....but it fits. I tried to get TTI to make a set of their full length step header but with the W2 flange but they wouldn't do it. I know the std vs W2 port mismatch really isn't that big a deal though, also I left my Exhaust port outlets well ported but essentially sized As cast

Ideally I would like to duplicate/improve the shorty design but in a 1 7/8" tube 3" or bigger collector, if it would fit an Early A it would fit any chassis, then maybe market them for any stroker small block combo. I think there could be a big market for big tube shorties for both ease of install plus when you run a full exhaust it's really hard to optimize a header anyway, so the diffesrnce from "ideal open header/collector" to undersized will be a whole lot less of a % difference with a reasonably quiet street exhaust. In 'real world" sense, if the collectors don't essentially free-flow at WOT all the way to the power peak (for whatever the reason) the "dyno" arguement loses a lot of its validity.

I doubt that it matters much so if it was me I'd buy the set that fits the best. If the 1 7/8 headers fit nicely and allow you to pull the starter and get to all 8 plugs then I'd go with them. If you have to use the 1 5/8 headers in order to get to everything then use them.

Thanks everyone for the great feedback. I am actually suprised that so many of you said "...do the 1-7/8"...!!!", but real world feedback is what matters.

My budget is already stretched on this project, so I may actually hold off on the TTI purchase, run another season with my new stroker but old LA headers (1-5/8"), and then move to the 1-7/8" pipes...the benefit would be that I should actually be able to roughly tell the difference between these sizes (disregarding the hit for the port miss-match between the LA and W2).

How many rpms do you turn.. I ran a 1 3/4 set on my w-2
and it wasnt bad.. I was turning 7800 rpms.. I cant say
if there was any power loss but the time slip didnt see it
but the conditions might have been different(I dont remember)

Oh my!!!

No no, no chance of me buzzing this thing up that high...I have the following Comp Cams custom hydraulic roller cam lined up: 240/248 @ 0.050, .547/.544 lift, 112 LSA. Basically the XR292HR grind, but 112 LSA instead.

With a 4k stall converter, 4.10 gearing in a 3600 lbs ride I would like it to top out at 6500 RPM, that has been the ceiling for my current 360 hydraulic flat tappet build and it seemed to work fine.

Why a 112?

With that heavy of car, only 4k convertor, with that 112 cam it will be a pooch out of the gate unless its like 15 to 1.

RobC & B3422W2:

Well, a 112 because this is a 2nd hand purchase. I picked up the cam for $150 a while back when I was contemplating trying the "roller thing" out and replacing my Hughes HE3844AL in the current 360 motor.

The feedback the two of you provided was similar to my previous old post on the subject of trying this out in my 360 motor.

Now that I am building a stroker engine however, I am thinking that the extra displacement will more than make up for any lost grunt due to the 112 vs 108 LSA. I guess I am looking for the 112 LSA to improve the street manners somewhat (the car has to run power brakes), while the 4k stall on the converter should give it a get-up-and-go when needed.

Beyond this, I used to run a Crower 31243 (224HDP CompuPro) hydraulic flat tappet some years ago in a street 360 build. That was a 112 LSA and about two steps smaller than this roller - 228/238 @ 0.050, .480/.504 lift. This cam worked well in my ride at that time, and that was with a 2300 stall converter. Going to the Hughes cam even required me to ditch the newly built 2800 stall in favour of the 4k, which has been one of the greatest improvement in the combination since I finished the car.

I was initially concerned about the LSA, but repeated calls and emails to Comp Cams tech-line resulted in these guys telling me that in a street combo the 112 will actually work better. No doubt the 108 or 110 grind would be more 'explosive', but that's most visible at the race track.

This is the first (and most likely not the last) time I'm going to try a roller though, so if the 112 is a totally wrong way to go about it I would love to understand this better. But ultimately, the budget is limitted, I have all the parts here already and if I'm about to give up a tiny amount of torque which in my street application will never translate to a noticeable impact, I will accept a bit of compromise.

I have 1-7/8 TTi's. Everything I read said that W2's liked to breath and most guys who ran them said they saw gains in the 1-7/8"s.

You will want to run a smaller spark plug so your socket can clear the header flange.

I needed motor mount shims http://www.engine-swaps.com/Pages/ProductsYear/67.72aBody.html to help clear a torsion bar

Your starter wires will be close to pipes, so you plan on some insulation

I run a 106 LSA Comp Cams roller cam and only have 10" of vacuum at idle (I hadn't planned on fuel injection) compression is 10.4 to 1. Hot Rod had a cam comparison article that actually showed how LSA difference's effect performance in June of 2017.


Do you run power brakes? The wider LSAand higher vacuum will help there if so.

I swapped from a 107 lsa cam to a 112 a few years ago in an 11.5 compression 416 stroker.
It killed the 60 foot.
The guy who designed the cam knew the exact specs of my motor and old cam.
I didnt care about vacuum, just how the car ran.

I dont really see any problems with the 112lsa in the OP's proposed build.

Hmm...my car today has terrible 60' time, best being 1.87s...but that is because it is not setup for 1/4 mile racing at all. Instead the suspension is pretty stiff, HD leaf springs, sway bars, etc all in an attempt to make it stick to the road, lol, as much as an amateur build 3600 lbs vehicle can.

I'm curious though, so what were the before & after 60' times like?

In your case you were focused on max performance, and knowing the difference a move from 107 to 112 LSA had is pretty good stuff! Was the LSA the only change?

fast68plymouth was kind enough to spend some time with me on the phone and through several emails to try to figure out the best options. Granted, and he was very up-front about this: the solid roller would be the top pick from a performance stand point, but given my indended use - this primarily being a street vehicle - it was reasonable to try the 112 LSA first.

Dwayne specced the comp flat tappet cam. Car ran best ever 10.38 with it. 1.41 ish 60 foot
Straightline guy specced the 112. Car ran 10.55 best with it.
60 foot was off 6 or 7 as i recall. 107 cam 260/266, 112 was 259/268. Car didnt go anywhere till it was in high gear
Admittedly, the car lost almost no mph, just wouldnt ET near as good. I suspect with more squeeze and convertor the 112 might have shined, but i stated i was leaving that stuff alone, and was told it would still run better. It flat didnt.