Repairing intake manifold fuel distribution issues

General engine tech -- Drag Racing to Circle Track

Moderator: Team

swampbuggy
Pro
Pro
Posts: 490
Joined: Mon Apr 04, 2011 8:54 pm
Location: central Florida

Re: Repairing intake manifold fuel distribution issues

Post by swampbuggy » Sat Apr 14, 2018 6:37 am

Hello Bill C----Would love to see a picture of that manifold, a shot looking into the plenum if possible ?? Thanks Mark H. :)

pamotorman
Guru
Guru
Posts: 2522
Joined: Thu Mar 06, 2014 11:55 pm

Re: Repairing intake manifold fuel distribution issues

Post by pamotorman » Sat Apr 14, 2018 9:45 am

what about a higher intake rocker arm ratio on that cylinder

BILL-C
Pro
Pro
Posts: 307
Joined: Thu Feb 07, 2008 9:57 pm
Location: Oakville, CT
Contact:

Re: Repairing intake manifold fuel distribution issues

Post by BILL-C » Sat Apr 14, 2018 11:51 am

I always prefer to address the problem directly. Carbs sometimes get borrowed for other cars, so i don't want to make a new problem. I'm only interested in fixing the manifold, not any bandaids. Leaning towards making the mouth of the 2 lean runners on the floor wider to suck in a little larger share of fuel puddled on the floor.
Carlquist Competition Engines

User avatar
MadBill
Guru
Guru
Posts: 13156
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: Repairing intake manifold fuel distribution issues

Post by MadBill » Sat Apr 14, 2018 12:29 pm

As alluded to in my previous post, frequently the issue has nothing to do with the manifold, it is because the 90° successive adjacent induction strokes (5 & 7 for a normal Chev F.O.) cause a stronger pulse in the left rear barrel. Manifold changes may help (an IR system for example) but are often not the direct cause.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

pamotorman
Guru
Guru
Posts: 2522
Joined: Thu Mar 06, 2014 11:55 pm

Re: Repairing intake manifold fuel distribution issues

Post by pamotorman » Sat Apr 14, 2018 2:01 pm

i remember chevy cup engines using higher lift rockers on 1 and 7, 2 and 8 to correct manifold fuel distribution problems .

swampbuggy
Pro
Pro
Posts: 490
Joined: Mon Apr 04, 2011 8:54 pm
Location: central Florida

Re: Repairing intake manifold fuel distribution issues

Post by swampbuggy » Sat Apr 14, 2018 6:43 pm

Thanks for sharing your last post PAMOTORMAN----can you remember how far back that was (or) exactly which engine was 23 or 18 deg. maybe ??? Thanks Mark H. Still a NASCAR fan---even though_________. :D

leahymtsps
Pro
Pro
Posts: 282
Joined: Tue Nov 18, 2008 10:20 am
Location: upstate NY

Re: Repairing intake manifold fuel distribution issues

Post by leahymtsps » Sun Apr 15, 2018 7:48 am

Bill,
MadBill wrote:
Sat Apr 14, 2018 12:29 pm
As alluded to in my previous post, frequently the issue has nothing to do with the manifold, it is because the 90° successive adjacent induction strokes (5 & 7 for a normal Chev F.O.) cause a stronger pulse in the left rear barrel. Manifold changes may help (an IR system for example) but are often not the direct cause
While Bill is correct with that statement, the question is what firing order are you using?

"That was confirmed by o2 or plug?"
You didn't answer this question

Tom

pamotorman
Guru
Guru
Posts: 2522
Joined: Thu Mar 06, 2014 11:55 pm

Re: Repairing intake manifold fuel distribution issues

Post by pamotorman » Sun Apr 15, 2018 8:42 am

swampbuggy wrote:
Sat Apr 14, 2018 6:43 pm
Thanks for sharing your last post PAMOTORMAN----can you remember how far back that was (or) exactly which engine was 23 or 18 deg. maybe ??? Thanks Mark H. Still a NASCAR fan---even though_________. :D
it was more than 24 years ago as that is how long i have been retired.

swampbuggy
Pro
Pro
Posts: 490
Joined: Mon Apr 04, 2011 8:54 pm
Location: central Florida

Re: Repairing intake manifold fuel distribution issues

Post by swampbuggy » Sun Apr 15, 2018 8:47 am

Thanks PAMOTORMAN !!! :D

pamotorman
Guru
Guru
Posts: 2522
Joined: Thu Mar 06, 2014 11:55 pm

Re: Repairing intake manifold fuel distribution issues

Post by pamotorman » Sun Apr 15, 2018 9:07 am

swampbuggy wrote:
Sun Apr 15, 2018 8:47 am
Thanks PAMOTORMAN !!! :D
i remember a dyno test at the GM tech center on a NASCAR engine to get equal fuel distribution. the same engine in the race car at Daytona the plugs looked like they came out of 8 different engines. the G forces in the turns have a lot to do with the fuel distribution when using a carb. now you know why NASCAR went to electronic FI

swampbuggy
Pro
Pro
Posts: 490
Joined: Mon Apr 04, 2011 8:54 pm
Location: central Florida

Re: Repairing intake manifold fuel distribution issues

Post by swampbuggy » Sun Apr 15, 2018 12:01 pm

aaaahhhh interesting. Mark H. :wink:

BILL-C
Pro
Pro
Posts: 307
Joined: Thu Feb 07, 2008 9:57 pm
Location: Oakville, CT
Contact:

Re: Repairing intake manifold fuel distribution issues

Post by BILL-C » Sun Apr 15, 2018 6:02 pm

This engine has "C" firing order. 4/7, 2/3 swap. This particular manifold has been on 2 engines that burned pistons on cyl 2 and one that burned up 2 and 6. Too bad, because this manifold makes the most power of any we tried. I have choice of 2 other manifolds that haven't been known to eat pistons. Sorry I'm late getting back to your questions, but we noticed a little water getting in oil, so i've spent the day tracking that down. Now i need to figure out how to stop a leak in lifter valley where block was lightened excessively. There is an area the size of my fist that is .040 thick and weeping. Engine needs to go in car in 2 days.
Carlquist Competition Engines

Big Speed
Pro
Pro
Posts: 253
Joined: Wed Aug 08, 2007 8:14 pm
Location: Paterson N.J.
Contact:

Re: Repairing intake manifold fuel distribution issues

Post by Big Speed » Sun Apr 15, 2018 6:51 pm

WE dyno with 8 o2s on most builds.Will shape runner entry to grab or shear off more fuel.Sometimes will put dam in adjacent port if it is much richer..Firing order does influence distribution.Bill C.
Ceralli Competition Engines & Checkered Flag Machine
Racing engines , CNC head porting and induction development
http://www.checkeredflagmachine.net/

pamotorman
Guru
Guru
Posts: 2522
Joined: Thu Mar 06, 2014 11:55 pm

Re: Repairing intake manifold fuel distribution issues

Post by pamotorman » Sun Apr 15, 2018 7:23 pm

BILL-C wrote:
Sun Apr 15, 2018 6:02 pm
This engine has "C" firing order. 4/7, 2/3 swap. This particular manifold has been on 2 engines that burned pistons on cyl 2 and one that burned up 2 and 6. Too bad, because this manifold makes the most power of any we tried. I have choice of 2 other manifolds that haven't been known to eat pistons. Sorry I'm late getting back to your questions, but we noticed a little water getting in oil, so i've spent the day tracking that down. Now i need to figure out how to stop a leak in lifter valley where block was lightened excessively. There is an area the size of my fist that is .040 thick and weeping. Engine needs to go in car in 2 days.
i had a jim dove cast aluminum BBC that weeped water. used a oil filter with synthnic media that would not swell shut from the water like a paper media one would do and reduce the oil pressure and the car ran all season. drained a few oz of water out of the pan after every race and it never hurt the engine

User avatar
jmarkaudio
Guru
Guru
Posts: 4096
Joined: Wed Sep 26, 2007 11:26 am
Location: Florida
Contact:

Re: Repairing intake manifold fuel distribution issues

Post by jmarkaudio » Mon Apr 16, 2018 9:35 am

Couple of things, there are mini annular boosters that BLP sells if it is a gas carb that improves atomization, distribution for a 4150. And drivability with a Dominator can be just as good if it's built correctly, 2 circuit. Annular boosters on the Dominator make a significant improvement in atomization, that leads to better distribution.
Mark Whitener
http://racingfuelsystems.myfunforum.org
____

Good work isn't cheap and cheap work can't be good.

Post Reply