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Norbert Sliwinski
(28 posts)

08/11/2012 05:20PM

Main British Car:
1973 MGB GM 2.8 V6

DIY Exhaust
Posted by: NAS1966
Date: December 12, 2018 02:20PM

Hi All,

I am looking for data for a DIY header and exhaust pipes for my 2.8 V6 for my '74 MGB restoration project.
There where a bunch of people who made their own but no one gave pipe sizes i.e. primary and secondary
OD pipe diameters.

According to my calculations the primary ( header ) pipes should be 1 5/8 ID or 1 7/8 OD and the main
exhaust pipes after the collector should be 2 ID or 2 1/16 OD

Also I saw one set-up which had a couple of nice rectangular mufflers - does anyone have data for those?
Can anyone concur with these above pipe sizes or which size pipes should I be using?

Carl Floyd
Kingsport, TN
(3978 posts)

10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: DIY Exhaust
Posted by: MGBV8
Date: December 13, 2018 08:06AM

IMO, your primaries are too large. Except for all out high RPM efforts, smaller is better. I run 1 5/8" primary headers on a 400hp 350 V8.




Scott Costanzo
Columbus, Ohio
(549 posts)

10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: DIY Exhaust
Posted by: Scott68B
Date: December 13, 2018 04:48PM

I used 1 1/2" primaries on my 3.1 headers with 2 1/4" collectors. I got guidance from Headers by Ed when I sized things.

Rob Ficalora
Willis, TX
(2686 posts)

10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: DIY Exhaust
Posted by: rficalora
Date: December 13, 2018 04:54PM

For the mufflers you referred to, check out [spintechmufflers.com].

I use their cruiser series on my car. They are great for clearance, but I wish the sounds was a bit deeper.

Norbert Sliwinski
(11 posts)

08/04/2018 08:01PM

Main British Car:
1973 MGB GM 3.2l V6

Re: DIY Exhaust
Posted by: 7399MGM
Date: February 20, 2019 03:51PM

Thank you for your input

Dan Jones
Dan Jones
St. Louis, Missouri
(269 posts)

07/21/2008 03:32PM

Main British Car:
1980 Triumph TR8 3.5L Rover V8

Re: DIY Exhaust
Posted by: Dan Jones
Date: February 21, 2019 05:04PM

If your 60 degree V6 doesn't have unevenly spaced pulses competing for space in the collectors, you want them to be smaller in diameter than what would be run in an equivalent 90 degree non-flat plane V8. I'll have to check my notes but we are running well over 600 HP through 2 1/2" ID collectors with out 180 degree headers instead of the usual 3 1/2" ID for a 4-into-1 header.

Dan Jones

Carl Winterbauer

(9 posts)

09/07/2019 04:07PM

Main British Car:

Re: DIY Exhaust
Posted by: BeemerNut
Date: September 07, 2019 08:30PM

great to hear the name SpinTech pop up again as it isn't mentioned than much these days. Dyno muffler shootouts and sound clips sold me. Out of app 13 different brands SpinTech was rated 2nd and 3rd behing a 454 on the dyno in Hp & Tq numbers.
I run a pair of them now called the 8000 series "Truck RV mufflers 4" x 10.5" x 20" 2 1/2" in / out in aluminized steel on the 68 F250 with 410, 427 heads and intake. Original Doug Thorley headers out back to a custom built 4 piece "X" cross all ceramic coated inside and out. Made a copy of their "X" pipe, [burnsstainless.com]. pissed them off after finding the exact venturi restriction cross sectional area they dyno created. It took 34 pieces of tubing and mandrel bends to complete my exhaust system. A lot of mockup, tack and Mig welding hrs spent. WTH a custom DIY system a one off vs expensive muffler shop hacks.
Do not believe these Truck RV's are that quiet, they are rather loud at least with my engine and the exhaust ends out the back. Going silent above 3,200 rpms or 85 mph not pleasing with the cops. Long coned out to 4 1/2" dia long tips. It barks plus causing negative pulses all the way back to the O2 sensors an inch after the header flanges, they scale full lean to full rich at around 2,350 rpm's.
Before this a pair of Edelbrock's stainless RPM Series 5510 2 1/2" "LIfe Time" mufflers back in 02, made your eardrums chatter at a certain rpm drone zone hence the swap to Spintechs. Same problem not as bad. Cool sounding Borla's Cat Back SS system on the 95 Disco 1 with a slight drone zone right at 58 to 64 mph in main highway traffic with back set family ending up in 4th vs 5th gear to remove that drone zone.
Next step adding Vibrant's SS "Silent Resonators" I have in storage to both vehicles toning therm down a little. I say little I like to apply throttle listening to exhaust music but not that stupid drone. Disco sounds like a 289 with Glaspacks while stirring the stick.....~~=o&o>.......

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