Ported Exhaust Manifolds vs Headers, Cam Questions

[Sidewinder]

I was wondering what would kind of differences there would be between the two options (aside from the exhaust manis being free) and which would be better? I have heard that aside from buying headers you can port the exhaust manis.

I've also heard that there is power to be had in the downpipe, is this true? (that may be car specific though)

I also had questions about cams, I hear they add a great deal of horsepower. Now I'm not sure if I will be getting heads at all, and if I do they will probably be stock.

So what kind of cam would I need for ported Upper and Lower Manis, possibly headers/ported exhaust manis, and for a full exhaust from the downpipe to the back of the car? What kind of gains do you think I would get? (guess maybe?)

All of this will be tuned.

Thanks in advance

[bszopi]

To port the exhaust manifolds it a PITA, not only because of their shape, but also because they are cast iron. You will spend $$$ on the bits and come out with something that is only slightly better. Headers are a huge improvement over exhaust manifolds (I have seen 12-17 whp gains on stock engines).

And yes, the downpipe is a restriction on these engines, so if you kept the manifolds, then you would definately need to do the downpipe to see any gains. The headers will replace a good portion of the downpipe, but it can be completely upgraded if you install the headers and the rest of the exhaust system as well.

[IsaacHayes]

S&S headers and new exhaust 2.5" high flow cat and straight through muffler (dynomax ultraflo, etc). Next I'd go with a 3500 or 3400 with 3500 top end and cam. They guys that have done that have reported huge gains. And of course tune it you have ODBII so that's no problem. I can't wait until superdave or 3400-modified goes to a dyno or track to get some numbers!!!

If you don't want to go that far you could get the large port 3400 manifolds (2005 is it?) That would save some time over porting and probably be larger in the end anyways.

[3.5MGB]

What headers were you looking at? I haven't seen anything that looks like it'll tune to maximum efficiency. All the pipes are too short and too fat.

On a separate note: Has anyone seen a set of long tube headers for a RWD??

[Sidewinder]

Holy old thread :P

Well, headers are really few and far between. Right now I'm debating between S&S Headers and Milzy Motorsports Headers. S&S are cheaper, but somewhere along the line things will need to be modified so they will fit into my engine bay. Milzy sells headers that were designed in the 5th gen Monte/Lumina engine bay, they require no modification but cost more.

S&S uncoated are $514.60, and $664.60 coated from their store.

I'm not sure about Milzy's prices. They are listed as:

Headers for 3100/3400 95-99 Monte Carlo - Non Coated: $549.99 Ceramic Coated: $799.99

But are also listed again in the Pre-Order section as just $800 (which could be coated, I guess I should ask him) with no option, so I'm not sure which one to go by. If they are $549 no coated then I would rather get those to fit my engine bay. I have yet to see any pictures of these headers either, and the first guy to buy them fell off the face off the Earth shortly afterwards.

I've decided that if I'm going to do my exhaust, I may as well do everything all at once, since it will be cheaper in the long run. So I'm hoping to do headers, downpipe, and all the way back to the muffler all brand new next year.

[Scott_68B]

What headers were you looking at? I haven't seen anything that looks like it'll tune to maximum efficiency. All the pipes are too short and too fat.

On a separate note: Has anyone seen a set of long tube headers for a RWD??

British Car Conversions http://www.killerbv6.com/ has some long tube tuned headers. They look like a real nice set. Look at the bottom of the "Pictures" section.

-- Scott

[SappySE107]

If you want maximum efficiency, you will need a custom set based on your needs.

[3.5MGB]

Yeah I've looked at the killerb headers. I think the tubes are to short based on prior experiance. (also without measuring the tube length) If the individual tubes ran the full length then they might be 'right' I need to do some anaylsis to calculate the correct length.

I'm probably going to have to make my own, based on my intended application. <sigh> I was hoping someone made these but I'm not seeing it so far. Why pay $1,000 for a set that is only close when I can spend about the same $$ and make my own. BTW the killerb headers for this application are more than $1,000, based on conversation with them. I can make a lot of mistakes for that same $$ (oh btw I can weld, a carry over from my years building ships

[SappySE107]

1000! I know nothing he does is cheap, so I guess I am not that surprised. I would make my own as well.

[3.5MGB]

custom headers are not cheap. no matter who makes them. many of the "headers" on the market are nothing more than tubular exhaust manifolds. The power gains are not what could be expected by the use of correct sizing for the application. I never understood why people will pay good money for an intake / fuel system but fail to understand the importance of the exhaust.

oh and yeah I wish I could find something for 3-400 or even 6-700$$ but I'm not about to pay that kind of money and end up with something that only provides marginal gains. I'm also leary of "header" tests in magazines where they don't follow basic engineering / scientific principles for testing & evaluation. Same goes for any particular test but exhaust and suspensions seem to get short shrift.

[1988GTU]

custom headers are not cheap. no matter who makes them. I never understood why people will pay good money for an intake / fuel system but fail to understand the importance of the exhaust. Same goes for any particular test but exhaust and suspensions seem to get short shrift.

If we all dealt with chevy 350's, headers would be pretty cheap and the gain for price would be worth it. Also many people dealing with these 60*V6 vehicles that most see as grandma/girl cars will not see a very supportive aftermarket world of performance parts. So spending 300 for a UDP (+5hp), homemade true cai (+5hp) AND a mail tune (+10hp) goes a longer way than spending +1000 for a set of headers that might add 20hp and then you'd want to redo the rest of the exhaust system. Also headers may require some real work to install that many beginners will not want to do when the other listed mods can be done relatively easy.


.02