Ported heads with stock '88 headers - a problem?
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Instructor
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From: Brackley Northamptonshire
Ported heads with stock '88 headers - a problem?
I am currently having my heads ported. The exhaust ports have been opened out and matched to the new gasket. However, I have already over spent this year and cannot afford headers. So my beautiful ported heads will flow out the exhaust gases into a virtual brick wall. Will this just mean that I will only get the maximum out of my heads when I have new headers or will this cause more serious problems?
'88 4+3 manual
1.6RR, 264H Grind Comp Cam, Ported heads, Roller chain, K&N Filter with Opened lid, Fuel pressure regulator.
'88 4+3 manual
1.6RR, 264H Grind Comp Cam, Ported heads, Roller chain, K&N Filter with Opened lid, Fuel pressure regulator.
Melting Slicks
Joined: Jun 2001
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From: Sarasota, FL
Re: Ported heads with stock '88 headers - a problem? (Gareth)
You could also, pretty easily, port out your ex manifolds, this would help considerably. Not like headers, but better than nada IMO.
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From: SE NY
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Re: Ported heads with stock '88 headers - a problem? (Gareth)
I agree on porting the stock maniflods. I did mine in a few hours with a Dremel.
Even if you don't have an exact match it won't do any harm. Actually our stock manifolds are realy SS shorty headers.
Even if you don't have an exact match it won't do any harm. Actually our stock manifolds are realy SS shorty headers.
Safety Car
Joined: Feb 2000
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From: Austin Texas
Re: Ported heads with stock '88 headers - a problem? (Gareth)
You could buy a used set of stock '91 exhaust manifolds and get the same kind of gains. The later L98's had tubular-steel exhaust manifolds that flowed much better than the cast rams-horns. I was told by the local Corvette shop that they flowed "almost" as good as the LT1 shorty headers...not too sure I believe it, but there you go.
I'd imagine there are plenty of them out there seeing how many of us have changed over to headers....
Post it on the C4 parts section and see what you get...someone may give you a set for nothing but the cost of S&H just to clear the garage.
I'd imagine there are plenty of them out there seeing how many of us have changed over to headers....
Post it on the C4 parts section and see what you get...someone may give you a set for nothing but the cost of S&H just to clear the garage.
Pro
Joined: Dec 2001
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From: NYC NY
Re: Ported heads with stock '88 headers - a problem? (Joe90)
QUOTE:
You could buy a used set of stock '91 exhaust manifolds and get the same kind of gains
________________________
Don't know for sure, but you might need a shorter front y pipne if you go this route?
You could buy a used set of stock '91 exhaust manifolds and get the same kind of gains
________________________
Don't know for sure, but you might need a shorter front y pipne if you go this route?
Burning Brakes
Joined: Aug 2000
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From: Cincinnati OH
Re: Ported heads with stock '88 headers - a problem? (Gareth)
Actually if the proverbial "brick wall" was on the "other side", that is often considered to be a good thing. The idea is that if the header ports are bigger than the cyl head exhaust ports, the mismatch (aka "step") would help minimize reversion, which is why you often hear recommendations to not open up the exaust side. But since you have it the other way, I would vote for opening up the manifolds too. The way you have it now would actually promote reversion, I woiuld think. I'm no expert though, just rambling my thoughts.
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From: Brackley Northamptonshire
Re: Ported heads with stock '88 headers - a problem? (65Z01)
Won't porting the exhaust manifolds weaken the welds around where the tube and the bracket attach. I will have a reasonable amount of material to remove - any tips?
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Thread Starter
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From: Brackley Northamptonshire
Re: Ported heads with stock '88 headers - a problem? (Joe90)
There are not so many Corvettes in the UK, but if someone has some headers I could find out how much the shipping would cost - at least I wouldn't get screwed on duty!
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From: SE NY
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Re: Ported heads with stock '88 headers - a problem? (Gareth)
When you remove the stock exhaust manifold you will see the AIR tubes and the EGR tube projecting into the heade tubes. You will also see a buildup of weldment inside each header tube where it is welded to the mounting flange.
I removed all of the AIR & EGR tubind from inside the header tubes. I ground away a large amount of excess weldment. A weld is a joining of metals and excess weldment is not needed to assure strength. Of course I left some weldment but still increased the effective opening size. There are some pics of the finished product on my site.
This won't be quite as good as shorty headers and certainly not as good as full lenght headers (another 20-25hp there) but it is an improvement over the bone stock units and nearly free.
BTW, expect to do this same type of clean up on a set of new full length headers too. They have the AIR tubes into the header tubes and excess weldment as the stock units has. Before installing a set of TES on my IROC I called Edelbrock tech support and the technicial agreed that these mods would increase air flow of their product with no detremental effect.
I removed all of the AIR & EGR tubind from inside the header tubes. I ground away a large amount of excess weldment. A weld is a joining of metals and excess weldment is not needed to assure strength. Of course I left some weldment but still increased the effective opening size. There are some pics of the finished product on my site.
This won't be quite as good as shorty headers and certainly not as good as full lenght headers (another 20-25hp there) but it is an improvement over the bone stock units and nearly free.
BTW, expect to do this same type of clean up on a set of new full length headers too. They have the AIR tubes into the header tubes and excess weldment as the stock units has. Before installing a set of TES on my IROC I called Edelbrock tech support and the technicial agreed that these mods would increase air flow of their product with no detremental effect.
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Re: Ported heads with stock '88 headers - a problem? (Gareth)
Hey people,
I have some sets of '86,'88 and '90 exhaust manifolds.They are all Identical in tubular shape and design,only the egr feed was changed on later years.He wont need to buy newer style ones...theyre already the shorty tube design.Edit*(Unless they changed them in 91 for the last year of the L98,I havent seen the difference myself or at the salvage yards..Joe do you know for sure?)
Yes you can port them out inside a bit and gasket match.The welds arent going to be a problem.Just dont go crazy with the port work.
While the engine would benefit from more headers,it should still run fine since Ive met a few people with a cam,ported heads,RR's and etc run stock manifolds and front Y pipes with no problems.Im convinced here.I know headers are $$$$.Get them later when you can afford them.
:)
[Modified by Bill's86Coupe, 6:03 PM 3/20/2002]
I have some sets of '86,'88 and '90 exhaust manifolds.They are all Identical in tubular shape and design,only the egr feed was changed on later years.He wont need to buy newer style ones...theyre already the shorty tube design.Edit*(Unless they changed them in 91 for the last year of the L98,I havent seen the difference myself or at the salvage yards..Joe do you know for sure?)
Yes you can port them out inside a bit and gasket match.The welds arent going to be a problem.Just dont go crazy with the port work.
While the engine would benefit from more headers,it should still run fine since Ive met a few people with a cam,ported heads,RR's and etc run stock manifolds and front Y pipes with no problems.Im convinced here.I know headers are $$$$.Get them later when you can afford them.
:)
[Modified by Bill's86Coupe, 6:03 PM 3/20/2002]