SIMON HOLTBY

Is there anyone out there who has made big horsepower gains by swopping cam etc and still using the stock TPI manifolds?

I'm not going to pay big bucks for SLP headers to gain less than 10 horse power. Whats that about a 4% gain! I dont like the idea of fitting cheaper headers as they will surely rust away. Then there is all the hassle of fitting, starter motors failing from increased heat.....

Thanks

Simon

Mark A Shields

You don't have to get SLP, you can get Hooker or Edelbrock.

Once you start modding the car, cam/heads etc, that's when you notice the benefits of headers the most.

SIMON HOLTBY

Thanks Mark, my car is stock and I'm thinking of doing some mods but I often read of people spending big bucks and doing lots of work to gain a few horsepower. Plus living in the UK things cost twice as much as you pay.
I think if I change anything it may just be the cam or I may just settle for what I have got.

Simon

Mark A Shields

To answer you're question though, there is someone on here, I forget his scn name but he has a built 350 cam/heads and other work, runnin with LS1s with stock manifolds. 86iroc350 or something like that is his name. I talk to him on aim a lot thndriroc.

CamaroDriver

I've seenn in a mag were a guy ran 11.7 ET in an '87 IROC with all stock internals including heads and cam, and a 12 PSI ProCharger and a 150HP shot of NOS!!!!!!!

He was running stock manifolds with a Random Tech y-pipe and a 3" cat-back.

So obviously they're not at restrictive as people think.

Mark A Shields

Well, hmmm I guess not with 12psi and 150 shot, they'd probably reach 10s with headers.

HrdRockA4305

The way I see it, there isn't really a "wall" you'll hit on the manifolds as far as HP goes. Its more like a % loss kinda thing. You can keep stuffing more and more air through them, but it'll be keeping your motor from reaching its full potential. Other than if the cost overseas is prohibitive, I see no good reason not to get them. I mean heck, if they made a very noticable SOTP difference in my stock 305, they'd really make a difference on a motor that actually was making some power. With shorty headers as far as I know you won't have any starter heat issues since the routing is about the same as the originals. My dad was so sure I'd be having starter trouble from headers... never have.

82z28122

iTrader: (1)

After doing my cfi to carb swap on my 350 I had the stock cfi manifolds and exhaust still on my car, and I couldnt break 15s. Now I can beat my friends car that runs 13.8, but I also had a clogged catylytic converter, and that was probably the main problem.

Mark A Shields

Yep, that will do it.

SIMON HOLTBY

I replaced the cat with a straight bit of pipe some time ago and noticed quite a gain. Will fitting headers give a bigger gain? Anyone done this in this order?

Will I also need a new set of shorter plugs and a 90 deg plug lead set with most headers types?

It would be nice to know other 3rd gen owners to compare cars. but there aren't many of us in the UK.

Thanks

Simon

HrdRockA4305

Yes I did have to go get new plug wires, but kept the plugs. I had straight boot wires on but needed the 90 degree ones to fit with the hedmans. I'll assume this goes for all brands. Just another $50 I didn't really plan on spending during the install, oh well. Always good to have a nice set of wires anyway.

iceman02

iTrader: (1)

On a pickup truck I had, long tube headers burned starters left and right, but I also had a '91 Z28 with shorties on it and never had a problem. Could never get the damn things to seal at the collectors though, maybe a prefab y-pipe built for the specific headers would help. I just had a muffler shop rig them into my stock y-pipe and, as I said, didn't work too well.

poorboy8

I would say that headers generally make you about 10 to 15% gains in your current horsepower.

Another words if you have a 200hp car you would take that and times it by .1 or .15

200 X .10 = 20
or
200 X .15 = 30

NOTE: This is not fact, this is just my observation from SOTP and seen dyno runs!

SIMON HOLTBY

Thanks for the further information. I'm now thinking that the best idea is to save for new heads a cam and headers and change them all at once. Kind of easier to get everything done at once and should see a good gain for my work. From reading this site it appears that stock heads cant handle the valve lift of a big cam and the extra airflow would then benefit from headers. Thing seem to be interconnected.
I'm at the crossroads of decideing between stock and throwing some money at the car to liven it up.

Thanks

simon