All Big Six It's a blast - update

Relates to all big sixes

Frank

Well-known member
Supporter 2021
That sound bite is with the cut out open. I'm running EFI manifolds, two 1.14 2100s on a long runner home made split plenum intake. It's .060 over with 390 Pistons, Schneider 142F solid lifter cam, Smith brothers push rods, and Harland Sharp 3002-7 roller rockers. Ported carb head with big valves. The pistons are in the hole .030 to control compression. The exhaust comes out of the manifolds in 2.25" tubing to a custom y-pipe into 3" tubing then a diesel 3" service muffler then straight out under rear bumper. My old Pixel 1xl sucks at capturing sound. With all the help and guidance I got here it is a blast to drive. My next task is to make some headers. Anyways thanks for the comments and help.
Gover!- post the pic of your fantastic intake again for these newcomers! It is sweet!
 

GPGoverMPG

Well-known member
Supporter 2021
Thanks, it's fun to build stuff and work the bugs out. I'm wondering if headers will affect carb sync like valve lash and fuel mixture.

I'm finishing up my new valves cover. It's a power by Ford but done in Wimbledon white and guardsmen blue. Should look cool when truck gets painted. It's got to spend some time on my rotisserie first. Thanks again.
 

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GPGoverMPG

Well-known member
Supporter 2021
No the only thing like a tube connecting the carbs is 5/16" Y used for PCV. I sync the carbs with a vacuum gauge with the Y removed. The motor is like two three cylinders. It's set up allot like the bikes I raced in the early 80s. I like tinkering so it's loads of fun.
 

GPGoverMPG

Well-known member
Supporter 2021
It may, the carbs are not quite big enough for the cylinder size. A balance tube would let them cover for each other a bit. I might open the 1.14 venturies to 1.33 but I'd need larger diameter boosters. Thanks
 

hodaka100

Well-known member
I wonder if it would run better if the intakes had a crossover or balance tube between the plenums?
I would be very interested to know the same if you have a way to easily experiment the option. I logically agree with the "two three cylinder engines" but my research keeps convincing me a balance tube is necessary.
 

Firepower354

Famous Member
I think the balance tubes are mostly to smooth the idle, if carbs aren't perfectly sync'd?
I can't recall seeing a multi-carb setup without one, though.
I'd like to see an A-B-C-D comparison of the lauded EFI manifolds vs log, HD, and long tube headers. I suspect the headers would do more below the torque peak than above.
 

Toph1821

Active member
Another guy just built a 2 carb intake and he left it out. By skipping the balance tube, precise tuning becomes more important but the pulses from the individual cylinders don't interfere with each other as well as a reduction of the intake plenum volume. This is my understanding of the science anyway, if I'm off the mark, please correct me.
 

Evan76

Well-known member
Took me a minute to see what I was seeing when I opened the photo of your intake.
Man thats freaking badass
 

Frank

Well-known member
Supporter 2021
I would be very interested to know the same if you have a way to easily experiment the option. I logically agree with the "two three cylinder engines" but my research keeps convincing me a balance tube is necessary.
The factory EFI intake is 100% isolated, 3 cylinders/3 cylinders. the large upper plenum has a full wall in the middle. The only crossover is a 1/2" hole between them for PCV and vacuum supply source. They are separated from the air filter to the head. Two intake air tubes, two throttle bodies, two 3 cyl chambers.
In this pic, the front of the manifold is to the right. this view is of the center divider (on the left, in the light) right next to the inlet port from the front throttle.
 

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Dipstik86

Well-known member
The factory EFI intake is 100% isolated, 3 cylinders/3 cylinders. the large upper plenum has a full wall in the middle. The only crossover is a 1/2" hole between them for PCV and vacuum supply source. They are separated from the air filter to the head. Two intake air tubes, two throttle bodies, two 3 cyl chambers.
In this pic, the front of the manifold is to the right. this view is of the center divider (on the left, in the light) right next to the inlet port from the front throttle.

But the efi I take doesn't have fuel flowing through it. Only the last maybe 2in of the manifold sees any fuel.
 

Frank

Well-known member
Supporter 2021
But the efi I take doesn't have fuel flowing through it. Only the last maybe 2in of the manifold sees any fuel.
Correct. Therefore the advantage of isolated chambers and/or individual runners is more evident, not less. Manifolds with fuel flowing with the air are always at least somewhat compromised in order to keep the airstream velocity high enough to keep the fuel in suspension. Port injection intake designs are tuned for ideal air flow, in velocity and resonance since there is no fuel to nurse along the way.
 

bubba22349

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Supporter 2021
Supporter 2019
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X2 yes I think that the injectors are angled so as to point the spray right at the back of the intake valves.
 
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