Thread: Need to pick your brains about headers

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Originally Posted by poncho62

As the Irish guy said..........vacuum leak. If you are not using the other 2 carbs, it would be best to seal off those carbs. A simple sheet metal plate under the carb between 2 gaskets would do it.

Yes they have been plated )sealed off) already by last owner, who reverted to that to solve the problem. He tried to make the progressive linkage work, but the car would not idle right, it ran OK once going faster. He ran out of money and gave up LOL. He did not have money really and that is why he sold the car when he moved to Northern CA. he couldn't keep it financially. Anywhoo, this is WAY down on my list of "to do" things but I like to start investigating ahead of time so i am ready when the funds are.

Engine runs good, never stalls. It does seem to idel a bit rough (possibly - but not sure) and may be eating up too much gas (about 10 to 12 miles per gallon). Otherwise powerful and pretty fast.

Originally Posted by HiboyGal

Yes they have been plated )sealed off) already by last owner, who reverted to that to solve the problem. He tried to make the progressive linkage work, but the car would not idle right, it ran OK once going faster. He ran out of money and gave up LOL. He did not have money really and that is why he sold the car when he moved to Northern CA. he couldn't keep it financially. Anywhoo, this is WAY down on my list of "to do" things but I like to start investigating ahead of time so i am ready when the funds are.

Engine runs good, never stalls. It does seem to idel a bit rough (possibly - but not sure) and may be eating up too much gas (about 10 to 12 miles per gallon). Otherwise powerful and pretty fast.

I'm with Mike P, what is the vacuum reading, the idle speed and where are you sourcing the gauge from?


One experiment you could do would be to try each carb in the center position with the outer two carb mounts blocked off by a plate.
Sounds like you already have plates that would work.

If all the carbs function ok why not run them with straight linkage?
I've had many different multi-carb setups and ran them all with straight linkage.

Progressive linkage is ok . . . if you get a good one . . . there's a lot of junky stuff out there posing as progressive, but some of it is downright dangerous.
One setup I see now and then is nothing more than bent wire for the sliding part.

You can make a high quality straight linkage for about $30. - $35. for parts and a little time with a hacksaw, grinder and die.

Depending on what you're running for a throttle control (cable - ok, rod- best) you could make up a nice throttle rod setup to match.

HBG,
What you need to find is a greybeard that can tune a real motor.
Three two's should run fine on your 350 with straight or progressive linkage. If it has a stock cam (which I suspect) that would explain why it runs so well with end carbs. blocked off. Vacuum leaks and the way the pvc and breather are installed is something that should be checked. I have used a vacuum gauge to tune for years and it is how you adjust a carb. and I use it to set timing (although a race motor is another story). Some folks will probably not agee with this method but there's more than one to skin a cat.
I adjust carb. for higest vacuum reading (adjusting mixture and idle speed) and adjust dist. untill I get the highest reading. I usually have to back off timing a hair if I have trouble starting, but that is usually not a prob.
So much for my rambling. I hope you figure it out soon.
Keep on Truckin' (Roadsterin' )
Jim
P.S. 12 MPG sounds awfull low, 18-20 seems more in line with your combo.

There have been numerous dyno tests on the SBC with 2 fours and with 3 twos ... a single 4 barrel carb on a aluminum performance intake always made more power ... gave better mileage and was a LOT easier to live with ...

That's why most folks use them ... over the old outdated multiple carb systems ...

They ( single 4 barrel setups ) also have less vacuum leak issues ... and are easier to tune
I would buy a new 600 CFM Edelbrock and a Edelbrock aluminum intake for it ... seal up the intake well and you would be amazed at the power gained and the mileage improvement ...