AgentEran

I am going to purchase some Long Tubes for my LT4..

I am looking at the trick flow/stainless works headers with 1 5/8th primaries and the American racing headers 1 3/4 primary headers.

I heave read that 1 5/8ths was too small for LT4 and Id want more..

But I have a concern that I would loose some bottom end torque if I go as big as 1 3/4. Bottom end power is more important to me than top end..

Anyone that possibly has experience with both care to chime in?

pologreen1

1-5/8 is not too small. 1-3/4 may help on dyno or track, but 330-400 needs 1-5/8 imo.

vader86

I highly doubt you would notice any difference between the two primaries sizes. In your case I would go with the 1 5/8" though.

1993C4LT1

Please, get us exhaust clips.

AgentEran

I most certainly will.. this will not be another case of the disappearing OP.

1993C4LT1

Thanks!

pologreen1

Also; I and I mean I would try OBX first before I bought those over priced things.

AgentEran

I would absolutely love to spend 700 vs 1600 & 1700, have concerns about the fitment and quality I read about in this thread:

https://www.corvetteforum.com/forums...uy-unless.html

dizwiz24

1 5/8" is absolutely too small for your high revving lt4 motor.

in fact it pisses me off that stAinless works makes a 1 5/8 for corvette lt1 but 1 3/4 for camaro lt1 ....

i ran 1 3/4" on my lower revving lt1 with ported heads and hotcam. made 353 rwhp and 353 rwtq

i did not dyno beforehand though.

do not make this mistake and choke down your engine for future mods.

this is not an l98 intake that only revs to 4000-4500 rpm.

btw. i ran tpis 1 3/4" ceramic coated TPIS steel headers. these were the best fitting header i have ever had on my 93 6spd. there were no points of contact and even cleared swingouts on my canton road race 7 qt oil pan.

now i run the arh 1 7/8 stepped header and exhaust on ny supercharged 93. these are a good quality header but do not fit as well as the tpis did (which is to be somewhat expected as these are bigger 1 7/8 tubes). these headers did not clear the swingouts of my canton road race pan and i needed to add spacers to space them off the head a little bit to get to fit.
the american racing headers were also needlessly heavier, due to an extra thick mounting flange they boast about - but im not sure why thats good. to me it just needlessly adds an extra few pounds of weight and gets in the way of spark plug changes.

where arh shined was the matching exhaust x pipe they sold custom tailored with or without cats. they also added an extra wideband o2 bung.

i also had mine swain tech coAted to keep underhood heat down

if you want a perfect fit, track down tpis 1 3/4 headers but you will need custom fab to tie in with rest of your exhaust

grandspt

I have the ARH 1 3/4" headers and cats on my LT4 and they have been great. No loss of low end torque that I can feel and the car feels real strong ( no tune done).
I also think 1 5/8" headers are a bit to small on a LT4. Good luck with your choice.

TorchTarga94

Either will be better than the stock manifolds. Pick which one suits you the best.

cv67

Its a stock 350 how does he need big headers?

1-5/8 here opinions will vary
Buy what you can afford I guess people will argue all day long over this one and what kind of oil to use

BacknBlack

I use 1 5/8 headers with no cats and an SLP catback that is straight through. I have a H/C setup(stock cubes) that revs to 6500rpm and runs 11.7s. No problems with top end, it hauls ***.

pologreen1

He might forget he has 2 times the hp most guys do here and their combos will be a little different.

I have 1-3/4 with about 700hp n/a and now looking at adding a blower and I still won't go 1-7/8" even though it's justified, I'll wait until I see how it runs. I don't have low gears.

OP there is a chart out there, but 1-3/4 if for higher hp cars, but to each their own.

blackozvet

while everyone is in the midst of this discussion, have a look at this,

pologreen1

I seen that one too. That says to me too large is the way you don't want to go, it's proven to only be good at the highest end of the power band where most these cars will never see for more than 30 seconds a car ride.

JrRifleCoach

Max power.... Okay they proved a point. Nice to know.

This will drive the purists just wack crazy!!!

Sleazy Rider

if you are thinking about stainless works, I would look else where's. I had to fight with them for a couple of months last spring/summer and ended up costing me another $200 to get things half *** straight and they still are not correct. your emission's fittings will be 15 deg tilted and the hard line will not line up or connect, and they said their fixture was correct. maybe in their world.

pologreen1

lol, yeah OBX looks like a good choice then.

AgentEran

Firstly, just let me say thanks to all you guys for the input. I seriously LOVE this forum!

SO I have been reading ALOT and still feel stuck with the decision. I would like to go 1 3/4 as a compromise, but cant seem to find any OBX in that size, just 1 5/8th and a whopping 1 7/8th.

So my choices are now between the 1 5/8th with 2.5 collectors and 1 7/8th with 3.0 collectors.

Before I pull the trigger I figured I would get one more feeler between those two options. My gut is telling me to go 1 7/8ths (figure too big is better than too small).. But I worry about killing my low torque

So if you had a bolt on LT4 and had to pick between the smallest size and the largest size, what would you do??

Also, I will be upgrading my ring and pinion to 4:11 at the same time as the installation of the headers. So this def has an impact on this decision..