GT350 intake w/o headers

Has anyone put a GT 350 intake on with out headers. What was the results? Thank you for any constructive information.

sub'd, interested as well.

I did.

Last year...stock manifold with headers 11.7 @ 119mph.

This year...GT350 manifold with STOCK EXHAUST MANIFOLDS/CATS 12.0 @ 116mph

I now have cat-less headers so looking to get back to higher mph with better et soon.

eesh, 3mph is no joke, that's a decent power loss. I would guess at least 30whp loss using stock manifolds. Why did you switch back, noise?

I was going to trade the car in so I put the stock manifolds back on. Decided to keep it and bought the GT350 stuff shortly after my decision. Ran it a handful of times like this and was not impressed. I now have a race tune and catless headers. I haven't been back to the track with this new setup.

Not worth it. Barely even worth it, if at all, with headers installed IMHO.

I can tell you my maf reading is 2lbs more air with headers vs stock exhaust...with no other changes. 49 vs 47 at 7600rpm.

wildcatgoal said:

Not worth it. Barely even worth it, if at all, with headers installed IMHO.

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I'm confused by your statement above.

Are you saying the GT-350 manifold is not worth doing at all; with or without headers?

11.60 at 119.71 here with OUT headers, I have MAK Cat Deletes.

If you plan on going turbo later, don't waste money on headers. I kind of wish I would have went GT350 mani first and saved for an ON3 kit. Way easier install too. When I added a GT350 mani to my car after headers, I picked up 2-3mph. Doing dirty 30 rolls were much improved too.

I did a numerous amount of dyno and some quarters:

Car UK GT PP with 3.55 manual

Stock: 410HP / 13.3 @ 107mph
JDM Tune: 440HP / 13.1@ 110mph
Lund / PMAS CAI: 470HP / 13.1 @ 113mph
Lund / GT 350 IM, 350 CAI, stock TB: 505HP / 12.9 @ 115mph (also switched to bigger 20", less grip) (WITH 350 TB it made 516HP, but the cars throttle is way too touchy for me with 350 TB).

So it helps, remember UK cars are handicapped with 2mm narrower header on the RHD side, which kills power and I've never done drag racing in my life so I not only suck at it but I baby the car.

However on the road the GT 350 shines, the car is so potent from a roll in 3rd and 4th, its great fun, pulls several car lengths on a stock UK GT PP.

I am heading back to strip in September, I am on 19" lightweight wheels now and my 350 tune is better, so hoping for more 12s times and to breach 116mph terminal.

Also I am hoping ARH will do me a deal on some 3" direct connect RHD headers for my Corsa system, which might get me upto around 120mph some of you guys are seeing.


P.S. My power figures are crank, EU Maha dyno which measures crank, all pulls done in 5th.

I am running the GT350 manifold with steeda intake and stock TB. Stock exhaust other then a catback. It has been a great mod. I love it. I pulled on a headers only 2016 GT by about a car for comparison. It just makes the car so much more fun to Rev to 7800rpm with little to no power fall off.

My MAF readings Max at 49 with my setup.

djpheer said:

I am running the GT350 manifold with steeda intake and stock TB. Stock exhaust other then a catback. It has been a great mod. I love it. I pulled on a headers only 2016 GT by about a car for comparison. It just makes the car so much more fun to Rev to 7800rpm with little to no power fall off.

My MAF readings Max at 49 with my setup.

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To also update my maf readings:

Stock: 42
Tuned with panel filter, big mouth: 44
Tuned with PMAS: 44.5
Tuned with 350 IM stock TB: 47
Tuned with 350 IM, 350 TB: 47.4

Remember UK cars have restrictive headers. If I had un-restrictive stock USA headers I'd also be around 49.

Hoping if I get ARH I will see 49-50 on the maf flow which should be good for another 30 or so horsepower at the crank, so around 530-540HP crank.

bobbyh said:

I'm confused by your statement above.

Are you saying the GT-350 manifold is not worth doing at all; with or without headers?

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I see people get to basically 450-460 after spending literally thousands for parts and tunes to get from 380 to that 460. Let's say you got 100 hp and you spent about $2K total at a minium. Is 100 hp worth $2,000 (likely more)?

I'd rather keep the money, pile it together for FI, preferably turbo so I can control boost electronically as opposed to via a pulley. Although a centri can do that too technically. For me, I'm just not seeing the value, but I don't street race or drag race and my track days aren't really for competition. I've been in cars with the GT350 manifold or the Cobrajet. They're fast, but not $2,000+ faster (to me). Just not there yet mentally I guess, haha.