MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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tdskip
Tom Deutsch

(14 posts)

Registered:
02/20/2011 07:18PM

Main British Car:


For a 302 conversion - pro/con of headers out the wheel well?
Posted by: tdskip
Date: January 14, 2016 08:13AM

I think I am leaning towards not cutting metal (planning phase only here) but wanted to ask for some coaching on the pros and cons of using a set up that goes out the wheel well.

Any tips on cost difference on headers and where to source?


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1078 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: ex-tyke
Date: January 14, 2016 09:04AM

AFAIK, Fast Cars Inc is the only commercial source for blockhugger or through the fender exhaust headers.
[www.fastcarsinc.com]
Blockhuggers for the Ford 302 conversion are hard to design because of the restricted space available for a downpipe - Fast Cars solved the problem by utilizing an oval sectioned pipe at the restricted area.
It is generally believed that through the fender designs, being less restrictive, deliver more power....however the Fast Cars blokhuggers are of excellent design and quality.....you'd be hard pressed to feel a difference!.

Dan Masters uses the FCI blockhugger design in his 302 conversion.

DanMasters-GA.jpg



Edited 1 time(s). Last edit at 01/14/2016 09:58AM by ex-tyke.


Moderator
Curtis Jacobson
Portland Oregon
(4411 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: Moderator
Date: January 14, 2016 11:10AM

Holes cut in your inner fenders vent (hot) air from the engine compartment to the wheel wells. So, typically through-the-fender installations are easier to cool. A cooler engine bay is a bit more important if that's where your engine (carberator?) will draw from.


danmas
Dan Masters
Alcoa, Tennessee
(573 posts)

Registered:
10/28/2007 12:11AM

Main British Car:
1974 MGBGT Ford 302

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: danmas
Date: January 14, 2016 12:06PM

It is my understanding that the fender well headers flow better and provide better under-hood cooling than blockhugger headers. However, the difference in performance between the two is not enough to overcome my sense of esthetics. Fast Cars blockhuggers provide, as they say, "adequate" performance. Very adequate. Unless you are driving in competition where even one more horsepower matters, it's a matter of personal taste, I think.

I don't know how much power I'm losing with blockhuggers, if any, but I'm still left with plenty, and cooling has not been a problem.


tdskip
Tom Deutsch

(14 posts)

Registered:
02/20/2011 07:18PM

Main British Car:


Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: tdskip
Date: January 14, 2016 04:06PM

Thanks guys, appreciate the info


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5812 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: BlownMGB-V8
Date: January 15, 2016 11:23AM

As a proponent of good, effective headers I'd like to add my opinion that all available headers for MGB conversions are woefully inefficient and will rob power. The only reason to not notice it is because there isn't anything to compare it with.

I've had long tube true equal length headers on my car from the very beginning back in the early 80's. They were difficult to design and build but well worth the effort, enough so to make them worth stripping and re-coating on the last upgrade. But, I did have to build them myself. At the time, I had 80 hours and $750 in the exhaust, including the header mufflers, all of which was coated.

Jim


danmas
Dan Masters
Alcoa, Tennessee
(573 posts)

Registered:
10/28/2007 12:11AM

Main British Car:
1974 MGBGT Ford 302

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: danmas
Date: January 15, 2016 11:45AM

Quote:
As a proponent of good, effective headers I'd like to add my opinion that all available headers for MGB conversions are woefully inefficient and will rob power.

Agreed, although I'm not sure I'd use the term "woefully." I was comparing my blockhuggers to fender well headers. I'm not willing to pay the price of asthetics to go with a good set of headers.



MGBV8
Carl Floyd
Kingsport, TN
(3727 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: MGBV8
Date: January 16, 2016 09:22AM

How bad can a Buick 215 block hugger header be if it will support 300RWHP? We need some dyno headers tests!

I'd bet Adrian's are not woeful at all & are better than most Buick/Rover headers.

http://www.britishv8.org/MG/AdrianAkhurst/Exhaustonshow.jpg


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1078 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: ex-tyke
Date: January 16, 2016 09:46AM

I’ve brought this subject up before, but equal length primaries for a V-8, according to Dave Vizard, are not critical to more power.
Quote:
“What we find in practice is that a V-8 is very much primary length insensitive. If the primaries are somewhere between about 28 and 40 inches, things work out fine. This is also a reason why getting all the pipes the exact same length for a V-8 is something of a waste of time. It’s best to make sure that all the bends are a big radius and the route to the collector is the least tortuous.”


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5812 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: BlownMGB-V8
Date: January 16, 2016 11:49AM

So where did you ever see a 28" primary on an MGB? I know of only one.

Jim


danmas
Dan Masters
Alcoa, Tennessee
(573 posts)

Registered:
10/28/2007 12:11AM

Main British Car:
1974 MGBGT Ford 302

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: danmas
Date: January 16, 2016 12:26PM

For engines other than the BOPR, dyno tests have been done and have shown conclusively that header design has a significant impact on power out put.

The headers on my car are an excellent design from the standpoint of getting blockhuggers into the available space, but not as good from the standpoint of maximum power.

I can live with it because I'd rather have the exhaust out of sight than a possible few more horses and having the exhaust stick out the fender wells. Just my personal preference.


Scott68B
Scott Costanzo
Columbus, Ohio
(541 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: Scott68B
Date: January 16, 2016 02:14PM

Quote:
So where did you ever see a 28" primary on an MGB? I know of only one.

I had 34" primaries on my V6.....equal length within about 1.5".

I don't think Ed, from Headers by Ed, would agree with Vizard about equal length not being important.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5812 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: BlownMGB-V8
Date: January 16, 2016 05:56PM

No, he certainly would not.


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1078 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: ex-tyke
Date: January 16, 2016 08:05PM

Quote:
No, he certainly would not.
Ed is in the business of selling exhaust parts - he is obviously going to promote anything that sells his product!

Here's an article by Vizard on exhaust design
[www.superchevy.com]



Edited 1 time(s). Last edit at 01/16/2016 08:14PM by ex-tyke.


Burrogs
Matt Burroughs
Houston, TX
(37 posts)

Registered:
01/18/2016 02:19PM

Main British Car:
1970 MGB GT V8 Conversion Ford 331ci

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: Burrogs
Date: January 19, 2016 10:25AM

I've got the Fast Cars Blockhuggers on my BGT, they look great (because I can't see them), and seem to do the job well. That said they are super crammed, and are REALLY close to the frame, even though it has been "massaged" to gain some more clearance. They have developed some hairline fractures near the collector that will need to be addressed. Mine are black and appear to be mild steel. As I understand it, they no longer offer the stainless version.

My question is do the through the wing "wheel well headers" impede on the front wheels themselves? Something tells me that my 17x8's with 225's up front would rub at least some of the time (bumps and whatnot).



MGBV8
Carl Floyd
Kingsport, TN
(3727 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: MGBV8
Date: January 19, 2016 11:33AM

The tire will bump the header with most fenderwell exit headers, 302 or 215/3.5 engine, at full lock.



Edited 1 time(s). Last edit at 01/19/2016 11:33AM by MGBV8.


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1078 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: ex-tyke
Date: January 19, 2016 03:47PM

Quote:
The tire will bump the header with most fenderwell exit headers, 302 or 215/3.5 engine, at full lock..
Not so hasty with that assessment, my friend....... My 15x7 Panasports and 225 rubber did not hit Ted's headers at all. Ted made a real design improvement from the early (first design Coyote) headers) and brought the collector forward as much as possible.
I've since switched to 205 rubber (based on availability) but 225 was not an interference issue.

EDIT: I'll add another comment to the effect that interference with the front sway bar is more probable than interference with the FCI fenderwell headers..



Edited 1 time(s). Last edit at 01/19/2016 03:52PM by ex-tyke.


MGBV8
Carl Floyd
Kingsport, TN
(3727 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: MGBV8
Date: January 20, 2016 10:38AM

Glad to hear they have been improved. Over the years I have heard from both 302 Ford and Buick/Rover V8 owners that the tires did touch the headers at full lock.

If the front sway bar has the proper bend for tire clearance it's a non-issue. I had to return one bar because of this.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5812 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: BlownMGB-V8
Date: January 20, 2016 01:01PM

I don't see a lot of conflict with Vizard's article in practical terms where we are concerned, because, when did you ever see even a 24" collector primary in an MGB? However, current thinking which looks at a so called reflecting pressure wave may not be too accurate. To my mind more attention needs to be given the the low pressure areas in between the exhaust pulses. A properly sized primary tube will cause the distance from the end of one pulse to the end of the next to be around 36" with a pulse length close to 8". If the tube opens at that point the low pressure area (Vacuum pulse) is preserved. If it opens at 18" it is lost. Modern trends towards smaller collector diameters and "merge" collectors in effect increase the effective length of the primary, which is why a 24" primary can work. But without an effective collector it won't. But how far back you can push primary length is a valid question. At some point the turbulence in the collector is going to disrupt the vacuum pulses in the primaries and the headers will quit working and begin to act more like a simple log manifold. In all fairness, Ed Henneman began addressing this issue back in 1962 before anyone else even had a clue it could be important, and conducted ground breaking studies over an extended time period. I do not think he and Vizard would be in serious disagreement, except perhaps on the topic of primary tube equal length, and I suspect the merge collectors have muddied the water on that topic quite a bit. Anybody here running merge collectors? (Henneman, btw is the best single point resource I know of for anybody wanting to build their own exhaust and from my experience was easily accessible by telephone. I believe his son is now running the business.)

On the topic of equal length tubes, a simple question seems to be in order. If the exhaust is 5 times more effective at moving air through the system than the intake (Vizard) and we are concerned with charge balancing in the intake (which we obviously are) is it reasonable to think we can disregard it on the exhaust? I'll leave you to make your own judgements on that, but just comment that intake imbalance can be the result of exhaust imbalance.

Now as for the practice of analyzing the system in terms of reversion pulses or reflected waves, that practice has it's roots in microwave theory and while such things as resonant frequencies and harmonics do apply to the system as a whole and to the mufflers and chambers, in terms of gasses moving through the headers and collectors it seems to be not that good of a fit. How, for instance do you make a gaseous reversion pulse travel through a vacuum? (or near vacuum) Until that question can be answered satisfactorily it will be seen that there is no real evidence that reversion pulses or standing waves, or reflected waves can exist inside the primary tube.

What can exist is a partial vacuum of variable density and a slug of gasses moving at high velocity, also of variable density, each merging into the other, and the partial vacuum can exert more or less influence against the following pulse. But to look at it as a wave traveling back up the tube is clearly in error except strictly as an analytical tool and not a factual condition. In practical terms it probably makes no difference though, EXCEPT that once the exhaust pulse moves beyond the end of the tube (or virtual tube in the case of a well designed merge collector) the vacuum is broken and the tube can no longer act as an extractor. And THIS is the fundamental principle that the header operates on.

Jim


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1078 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: For a 302 conversion - pro/con of headers out the wheel well?
Posted by: ex-tyke
Date: January 20, 2016 01:51PM

Sorry Jim, ya lost me at "I don't see......."
If someone were in the business of maximizing engine horsepower (at a particular RPM) I could understand exhaust designs being very critical. For we "street racers", over the counter exhaust systems are more than adequate.
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