James Montigny

iTrader: (13)

So, I'm looking at my 1-3/4" Hooker LTs wondering why on earth I would need 1-7/8".
There has to be a reason people step up to them that I am not seeing.

The exhaust ports on an LT1 head are 1-1/2", maybe 1-5/8" at the most.
The only things I see bigger primaries doing is reducing velocity and scorching a larger part of the gasket.

Now, someone tell me why I am wrong here and what obvious detail I am missing.

BlackScreaminMachine

iTrader: (17)

Exhaust flow is a critical part of making power.

I would say having a LARGER collector and merge, especially a velocity spike will help more.

I got a bud who runs a 402 LS2 w/ 150-300 shot of juice, He has a 1-7/8 stepped to 2", he did not see a increase over a 1-3/4" primaries. EVen after the tune was corrected.

At best his power band moved, but didnt gain or lose.

If your running a stockish LT1, 1-3/4 is fine enough.

James Montigny

iTrader: (13)

Heh, not quite "stockish"
Building a 383 with a rather agressive street/strip cam and ported Dart heads.
It will probably see a healthy amout of N20 in the near future.

Sorry, should have mentioned that in the original post

I was actually just looking at LPP's post about their stainless LTs.
If I did buy them, I'd probably break the new motor in with my current Hookers then switch.

NightTrain66

iTrader: (7)

The "stepped" headers are good for helping out against reversion. This is helpful on cams with overlap (tighter LSA, lots of duration, etc).

Lloyd

James Montigny

iTrader: (13)

That's what I needed, Thanks.

This one fits both of those catagories LOL

BlackScreaminMachine

iTrader: (17)

Yea I had a 383 LT1 w/ 11.25 to 1 comp, ran 1-3/4 Jet Hot headers with good success. Like Lloyd said the cam will dictate alot on header choice.

1989GTA

I would say the 1 3/4" headers would be good enough. However if you are running a big shot of nitrous that would change the equation.

James Montigny

iTrader: (13)

I'm thinking I will break the motor in with the existing 1-3/4, then upgrade to stepped headers later.
(that way, I don't ruin new headers in the break-in phase)

The square exhaust ports on these heads should mate a little better with the larger tubes.

That's actually an important note for anyone considering TFS VS Dart.
I'm not sure what the TFS exhaust ports looks like, but it seems like
round or D-shaped would be more header-friendly.

Bersaglieri

iTrader: (13)

This question has come to my attention lately. I ported my exhaust gaskets so there was no restriction on the exhaust side of the head. I then laid the gasket onto my Hooker LT's and found that the flange welds are going to hinder exhaust flow from the head. I'm going to start looking into getting measurements from people with different header brands so we can archive them online.

Anyone who wants to give pictures of their header ports and measurements please post them up. I'll be making a thread with pictures soon.

-Dustin-

ThreeHonks

iTrader: (10)

I ported out my headers at that area to smooth out the welds

Ed Wright

iTrader: (1)

Depends on a lot of things. My 383" loved 1-7/8" tubes. Like a full tenth quicker and over a MPH compared to 1-3/4". A milder engine would not. I was tempted to try 2" but never got around to it. The size of the port versus the tube size has little to do with it. Well, I guess, as long as the tubing is not smaller than the port.

Most NHRA Stock Eliminator LT1s like 1-3/4" to 1-7/8" steps with 3" collectors.
So far my 358" Lt1 Super Stocker doesn't seem to care.

Bersaglieri

iTrader: (13)

See that's my problem, I'm worried about the welds cracking and leaking there...which headers do you run?

-Dustin-

Ed Wright

iTrader: (1)

Your header gaskets were smaller than, or covered part of your exhaust ports? I've never seen that.

Bersaglieri

iTrader: (13)

Well kind of. See if you matched up the port holes they were fine, but if you actually used the header bolts to align them there were a few spots that needed cut back to be sure they wouldn't interfere. I then laid the gaskets onto my headers and found the header ports were noticeably smaller than the gasket. I have pictures but they are on my buddy's camera. I'll try to get a thread going about it tomorrow. I thought Hedman's might fix it, but they look even smaller at the flange...

I've been pretty meticulous with building this motor, maybe I'm just going overboard...

-Dustin-

Ed Wright

iTrader: (1)

What brand header gaskets are you trying to use?

quik95lt1

iTrader: (7)

what do you think my best bet would be??? I've got 1 3/4 Primary 3" collector hooker super comps on mine now......i know its choking the motor......the engine is a Naturally Aspirated 385 w/ 13.9:1 Compression AI TFS 215 cnc heads a large Solid Roller cam 258/264 .710 lift on a 107LSA and a Edelbrock Victor Single Plane w/ a elbow and 105mm monoblade wit a fast xfi.......im thinking stepped 1 7/8 to 2" with a 3.5" Collector is my ticket? what do you think???

T/ALT1

iTrader: (3)

I would like to know this also.

Ed Wright

iTrader: (1)

As heavy as you are, and no bigger than your cam and heads, I can't really say. I would try them.

quik95lt1

iTrader: (7)

Yea thats the only thing im worried about is loosing too much low end of course it shouldn't be too relevant with the 5000 converter in the car now. Another issue is....MAN are those suckers expensive!!!! Like 1400 for the set!!!

Ed Wright

iTrader: (1)

It's relevant with a 6000 RPM converter. Got to get that heavy sucker moving, no matter what a dyno tells you. Has to recover from gear changes also. If it doesn't really charge when it drops into the next gear, it ain't gonna be as fast as it should. We don't race dynos, flow benches, or engine modeling software. If it doesn't show up on the scoreboard at the finish line it aint' right.

The 1-7/8" Hedman Hustlers are cheaper than that. They aren't step headers, but if it wants bigger tubes a set of those will tell you. If you run open headers it could very well like extentions on the collectors. I hung 8" on the collectors and found a tenth with a powerglide car I used to race.

You need to log some passes, you want to get out of 1st gear quicker than second, but you don't want it "falling back on the converter". In other words, it should not drop back to your converter flash RPM. If your converter flashes to 5000, don't let it drop below 5200 or so. For example, if you have been shifting it at 7500, try shifting low-to-second at 7100 or so. If it drops to 5000, raise the 1-2 shift RPM a couple hundred. I shift mine at 7600 and 7200.