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  • 1 Post By Gaz64

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  #1 (permalink)  
Old 12-03-2019, 06:27 PM
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Default Needle / Seat For Holley With Lemans Bowls

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 didnít 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 Ė 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 canít 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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Old 12-04-2019, 06:46 AM
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Default Carb

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

Last edited by FredG; 12-04-2019 at 06:55 AM.. Reason: add
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Old 12-05-2019, 01:35 AM
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Quote:
Originally Posted by Mongoose930 View Post
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.
This guy has a few:

https://www.ebay.com/itm/1963-67-HOL...-/262568900976

Quote:
Originally Posted by FredG View Post
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

Last edited by Gaz64; 12-05-2019 at 01:42 AM..
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Old 12-05-2019, 11:30 AM
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Check out the quickfuel power vales they are made better in my opinion . They should work with your Holley but check first.
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Old 12-05-2019, 02:51 PM
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Check out the Quickfuel power valves, they are made better in my opinion . They should work with your Holley but check first.
Yes, they do.

I run high flow PVs in anything, especially over 400hp.
The PVCRs are the restrictions, so the Power Valve should alsways flow better than the PVCRs total area.

Don't just look at the windows, that is not the restrictive area of the valve, it is the valve stem to body clearance.

Gary

Last edited by Gaz64; 12-05-2019 at 02:56 PM..
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Old 12-05-2019, 03:01 PM
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Default I respectfully beg to differ.

The Holley carb that came with my 427r ran the best when brought back to factory specs. Having the wrong power valve or one that stuck open will definitely affect performance when accelerating and the vacuum drops. Open throttle is a different story but the vacuum will have to catch up to the throttle and that is where the power valve comes in till it does. Wrong jets are another issue.

Fred
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Old 12-05-2019, 03:42 PM
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Originally Posted by FredG View Post
The Holley carb that came with my 427r ran the best when brought back to factory specs. Having the wrong power valve or one that stuck open will definitely affect performance when accelerating and the vacuum drops. Open throttle is a different story but the vacuum will have to catch up to the throttle and that is where the power valve comes in till it does. Wrong jets are another issue.

Fred
Your carb must have been a long way out.

A power valve stuck open will affect fuel economy, but not outright power.

The only way that can happen is if the diaphragm has hardened from lack of use. A ruptured diaphragm becomes a fuel leak into the PV cavity, which is then a fuel leak into the manifold vacuum port of the throttle body.

Manifold vacuum responds in inverse proportion to throttle movement, so vacuum does not need to "catch up" with throttle movement.

Gary
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Old 12-05-2019, 04:43 PM
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Default

Thank you all for your responses. I think the unique challenge that I have right now is the Lemans Bowls. I am certainly no carb expert, but if I can't get enough fuel into the bowls to start with, then nothing else downstream will work. So far the viton tip needles I have found are pretty small -.092 orifice and the larger size needles are steel - .128. I ordered a set of the Daytona float needles today and I think I will give them a try. I am hoping that by replacing the needles, setting the floats and changing the jets to a more appropriate size for my engine, that it will run even better in the spring. I will keep you posted on my progress.
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Old 12-05-2019, 05:23 PM
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Default A loooongway out

It was a long way out because the previous owner messed with it. Given the car was 4 years old and only had 1100 miles, it needed a good cleaning. For anyone who has experience working on carbs, its pretty easy to tell when someone was in there ahead of you. Wrong jets, wrongpower valves, accelerator pump out of adjustment. Floats out of adjustment....etc. I entertained replacing it but enjoy a good challenge. One full rebuild kit,hi flow power valve for the primaries and blocked off the power valve for the secondaries. I even contacted Rush because I thought an 870 cfm would be to bigon a 427r. Runs like a top now.
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Old 12-06-2019, 12:48 AM
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So if it had wrong jets, and now you have added a sec PV plug, did you increase sec main jet size from the factory jetting to compensate for no sec PV?

Did this carb even come with a sec PV to start with?

Sorry to the OP for thread deviation.

Gary
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Old 12-06-2019, 05:42 AM
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Default PV plug

Yes. It comes with one from the factory. If you block it off, rule of thumb is 8-10 higher.

Last edited by FredG; 12-06-2019 at 05:51 AM.. Reason: text
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Old 12-06-2019, 01:53 PM
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Yes. It comes with one from the factory. If you block it off, rule of thumb is 8-10 higher.
Yes, that's correct, rule of thumb, just checking, didn't want you going lean.
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