does anybody have any experience or comparisons of ported exhaust manifolds vs headers. I hear that fitting headers in a 67 gs can be a bit difficult. So what are the approx hp or et gains of porting vs stock vs headers. and what are the approx costs? Its always cool to have the stock look but if headers are 300 bucks and porting is 600 then i might have to rethink the whole subject. btw im running a basically stock 76 455 in my 67, with the except of a converted dist, and a modified 800 q jet with 75-44's.
i'm by no means an expert but i have heard buick guys say that ported manifolds are just as good as headers. I heard about a service that you send the intake, heads and exhaust manifolds to and they port them all together or something like that. my dad told me about it.
Contact Greg Gessler on this board. He does the porting service. Do they work?well Gregs GS has gone 11.50`s through manifolds:TU:
There was a thread from Tri-Shield/Jim W. where he got like 5oo horsies from a stage 1 Al head motor with untouched exhaust manifolds. Do a search on it. He talked/compared headers, to shorty headers, to manifolds. He also said that What was true for the new Al heads may not carry over to iron. Interesting comparison, though.
thanks i read that post too, but it was a little confusing. was it using stock manifolds? there was another post where a similar question was asked and i believe jim said that he was going to use the full out race version of gregs manifolds. To typical guys stock means stock, untouched, but i think to an engine builder stock would at least mean gasket matching. nobody should just expect to bolt on a part and have it fit correctly.
First off, let me say that Greg does some great work on his head, intake porting, and exhaust manifold porting. I have had an opportunity to work with quite a bit of his stuff this year. Second disclaimer: The dyno is not the car, with it's full exhaust system. The Superflow dyno we use does have a full 6" exhaust system, that runs out of the cell, and up to the roof, thru two 8" truck mufflers. So anything I say here needs to be tempered by the fact that there are cars out there working very well with ported exhaust manifolds, Greg's is certainly one of them. On to the question: No, an exhaust manifold will never be a header. Period. Headers will always be 15-30 numbers better on both the torque and HP. Yes, we used a set of old crusty totally untouched exhaust manifolds on that STG 1 Alum motor, as well as both versions of Greg's manifolds, and TA shorty and long headers. The shorty and long headers were very close in power, but the clear power champ is still full length headers. On that particular motor, there was minimal power gains with the ported manifolds. I attribute that to the fact that the stg 1 Alum heads have such a good exhaust port, that anything that does not provide scavenging (like headers do) to the individual cylinders works pretty much the same.. that head has sufficient exhaust flow, so whatever is bolted onto it, that simply decreases backpressure, doesn't really affect the engine's performance.. at least on the engine I tested, with the particulars of that engine... different combo's will yield different results, for sure. I will be re-running that testing on an upcoming ported iron head motor, to evaluate the exhaust combo's with the iron heads. One thing to keep in mind... and over-simplifying this, any exhaust manifold will always be a backpressure situation. With a manifold motor, when an exhaust valve opens, it is exposed to back pressure. With headers, that exhaust valve is exposed to suction, which is the result of what is know as "Scavenging". Headers will always make more power, due to this fact. We have seen this be true with any type of header. JW
Since originality does not seem to be a priority, the headers are probably the way to go. I have ported manifolds, and while I like the effect it has when I open the hood after dusting a heavily equipped car, I have to say that it has been expensive and frustrating. Working and scraping for every single horsepower when I could easily bolt on 20 or more in an afternoon keeps me awake at night!! I've had to mill the manifolds to get them flat enough to seal, and after years of messing with various coatings, paints, etc., I finally broke down and had them Jet-Hot coated. The finish is beautiful, but of course not "original", which was kind of the purpose in the first place. In all, I guess I've got about $350 in the manifolds. (The porting was free; brother's a tool and die maker!) If you do get headers, consider that Jet Hot option....very durable.
at this point and budget, originality isnt important. im saving my 400 block for that. but looking stock certainly has its plusses. id certainly love to run a 13.0 with manifolds. ive got the converted points dist, and even the 455 with 400 valve covers to help with the stock look. plus it must make our buicks look even better when a "stock" car runs so well.
thanks for the clarification jim. so those 460 horse numbers were with al heads, a small cam, and stock manifolds? awesome. since im paying my way through grad school im still on a tight budget and looking for the best way to spend a few hundred bucks. maybe ill wait til your dyno results with the iron heads. im trying to do the best i can with the budget i have, but i guess thats what tuning is all about. now that ive got a stout ignition and ive read all i could find about qjets and spent some time modding one, ive gotten just about all i can out of my stock combo. without spending major bucks . i do have a set of 67 400 heads. maybe putting them on the 76 block and installing a new cam will give me some noticeable results, while still staying in the 300 buck range? any ideas.
300 bucks, eh? I'd say spending the 300 bills on getting your early heads together would be the ticket - get that 8:1 compression up a bit. Maybe do a 3-angle valvejob and some bowl cleanup. A cam/lifter combo would probably not be as effective with your low compression, plus you'd probably want to be carefull about wiping out your stock cam bearings.
On a 12.0 car headers are worth .3 sec. and 3 MPH in the quarter over stock manifolds. (both- closed up thru 'good 2.5" exhaust system) I have found ported manifolds to generally run a tenth of a second faster than pure stockers. I say generally because every car/combination is different. It IS nice to open the hood and have it look ALL STOCK!:grin:
About ten years ago Duane and I spent a couple of days on the dyno with all the different exhaust manifold castings Buick ever made, and compared them to headers, and exhaust manifolds that were stock, and various ones we ported. There is an article on our testing in one of the GS-XTRAS. I am still looking for our Dyno sheets from that testing. The article in the GS-XTRA should be easy enough to find.We did some cam testing along with that too. One thing about an exhaust manifold it won't scavenge the exhaust like a header will.
Headers were 25hp better (435 vs 460) on Mandys Motor over the Gregs ported manifolds. I think camshaft selection has a lot to do with how much hp loss you have also.
I tried home porting my exhaust manifolds. I can't isolate the benefit because I swapped the converter at the same time. I went from consistant 13.80's and best time of 13.50 to consistant 13.50's and a best of 13.21. Most of this probably came from the converter. Mph went from best of high 102's to close to 104, so maybe I picked up 10 hp or so with the manifold porting. All I did was a port match and hog the exits out to about 2-1/4" diameter. Stock manifolds may be as small as 2" diameter outlet. That's a lot of grinding, especially on the passenger side - you have to go about 6" into the manifold! I used a cheap air powered die grinder and a coarse stone about 2" in diameter, just kept working in and out and around the circumference of the exit. I used a roll of electrical tape for a gage - unrolled enough of it so it was just the diameter I was going for, then ground until it slipped in and out. I spent at least one Saturday on this. If you do it don't forget to sweep up the driveway. I did not clean up after myself and I now have a couple of huge red stains where the grindings rusted! ou: Worthwhile effort, and definitely low buck, but lots of work!
Putting headers into the early chassis is not that big of a deal. Poston's newer headers fit very nicely. Just as a side not, we recently installed headers and a 2.5 inch x-pipe system into a 66 lark with a 300 inch motor, very noticeable power gains even with the stock 300 incher. Jim Burek P.A.E. ENTERPRISES
good to know jim. i guess its sort of up to me to decide which way ill go. obviously id like to get the most hp, well torque, for my buck. ive got a skylark 4dr with a 340 and a cracked exhaust manifold. as you might know its not easy to find new manifolds. so maybe the poston headers are the way to go.
