Quote:
Originally Posted by Mongoose930
I will be pulling my carb off this winter to change the jets and check the float levels. It is a Holley 4150, 850CFM double pumper with two front mount Lemans bowls, each fed individually via a fuel log.
When my engine was being dynoed, my builder didn’t think it was getting enough fuel. He turned up the fuel pressure to 7.5, but then the bowls leaked. I had the NPT fittings that go into the bowl machined to increase the ID as much as possible.
Now I am on the hunt for a larger needle / seat combination. I believe the one I have has an .092 orifice – I will confirm when I remove the bowls. I am trying to find out if anyone makes a Viton needle / seat that will fit into a Lemans bowl and has either a .100 or .110 orifice.
I do have a pair with steel tips that are .128 but I have had a few people tell me not to run steel tip needles on the street. Thoughts on that?
I am also trying to find out what the Holley 2953, 3085 and 3255 used for needles but I can’t find any reference material that will tell me this. They are all 750CFM or larger carbs so whatever they used should work for me, in theory.
Any suggestions / assistance would be appreciated. I am trying to gather as many parts as possible before I pull the carb.
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This guy has a few:
https://www.ebay.com/itm/1963-67-HOL...-/262568900976
Quote:
Originally Posted by FredG
I had a lot of issues with my Holley carb and the reason was the previous owner monkeyed around with it. Running rich. Fuel starvation. Gas smell. I have a 4150 870cfm and it sits atop a Roush 427r with 550hp. I even checked with Roush to confirm it as the correct carb for that engine. I looked at quite a few videos on YouTube about tuning Holley's. I fixed it by taking it apart, cleaning it, rebuilding it and returning it back to factory specs. All the wrong parts were in it. I found 3 things critical. Correct jets. Correct power valves and correct float settings with new needle and seats. The floats are a little tricky to get right. Too low...fuel starvation...Too high...they leak and you run very rich. Fuel pressure is critical on Holleys. They do not like too much pressure. Holley's can be touchy. Correct size power valves are very important when delivering fuel at wide open throttle. The thing runs like a top now.
Good luck
Here is the data for mine which is probably very close to yours.
Fred |
The power valve number is the manifold vacuum opening point and has NOTHING to do with fuel volume delivery. So whether you run a 35 or 85, they will be both open at wide open throttle.
Factory specs are close, but any carb can be tuned up with some jet changing. No carb can be "correct" unless it is listed as to fit "this engine", camshaft etc.
So running out of the box could be good, but you leaving power and drivability on the table.
My custom carbs have opened a few eyes as to how they drive.
I like to run .130 viton needle and seats at 5 psi on the street.
Gary