Valve Float or Points Gap

[33 IMP]

Well, the cap and rotor sure are! I don't know yet about the points and condenser.

 

[khryslerkid]

When you have 30-32-34 dwell what’s the gap? I will say setting GM points dwell is nice with the window in the cap. Seems these you need to try different gaps to get to the dwell. I was at 26 and I closed the gap .001” @ .016”and it went to 28.

This is my first one of these carbs and if the floats aren’t right out of the box then it’s likely running out of gas. I assume when they’re low?

I'm not exactly sure what the point gap is mainly because I don't use feeler guages. I'll eyeball the gap, hook up the dwell meter, hook up a remote button to the starter relay and crank the engine. This is with the dizzy cap off. Then open or close the points to get the dwell you want. It's much easier than using a feeler gauge and the most accurate.

Yes, if the float level is too low the carb can starve at WOT. I believe the setting is 9/16". I'll try to find the diagram where to measure to.

It's 7/16". Using a drill bit works the best.

Like Bob R mentioned, check float drop also. 15/16" to 1"

 

[RJRENTON]

I'm not exactly sure what the point gap is mainly because I don't use feeler guages. I'll eyeball the gap, hook up the dwell meter, hook up a remote button to the starter relay and crank the engine. This is with the dizzy cap off. Then open or close the points to get the dwell you want. It's much easier than using a feeler gauge and the most accurate.

Yes, if the float level is too low the carb can starve at WOT. I believe the setting is 9/16". I'll try to find the diagram where to measure to.

It's 7/16". Using a drill bit works the best.
View attachment 979480

Like Bob R mentioned, check float drop also. 15/16" to 1"
View attachment 979484

EXCELLENT GRAPHICS....one additional item to CHECK....MAKE SURE the float's pull clip is installed. Thus is an often overlooked part. It attaches to the needle valve stem AND the float's arm near the pivot pin's "ears". The purpose is to insure the needle valve starts to open as soon as the float starts to drop. This little item helps to maintain a constant fuel level and accurate metering.
BOB RENTON

 

[beanhead]

Ok. Ignition components have all been changed, springs check out okay, reported symptom is valve float at WOT...let us know how the fuel system checks out. Although, fuel issues and valve float at high rpm are two different sounds/feelings, and as you've said it feels like valve float, no breaking up or missing..and you did report close to .600" lift and hydraulic lifters. With that kind of lift the springs should be pretty stout. I've suspected the lifters since page 1 and still do..

 

[69L48Z27]

Here’s the cam.
http://www.hughesengines.com/Index/...dWxpYw==&level3=U3RyZWV0L1N0cmlw&partid=30257

These are the lifters
http://www.hughesengines.com/Index/products.php?browse=search&search=5003&partid=11033

All items including springs all spec’d with the cam. I’m not sure I follow how the lifters would hang the valves open. If they collapse they wouldn’t open the valve as far, right? I have .050” lash on them. Rockers a Harland Sharp 1.6.

 

[Bad B-rad]

"At high speed, hydraulic lifters may “pump up” and hold the valves open causing the valves to float. This can happen if the valve springs are not strong enough to maintain normal valve control, or lifters are failing and the lifters try to take up the slack that really isn’t there. This overextends the plunger and prevents the valve from closing all the way."------Quote from engine builder mag.

 

[69L48Z27]

I’ll report back once it’s all fixed up and let you know what I find. I would really hope Hughes isn’t selling ‘high performance’ lifter that hold open at 4500 RPM with only .050 preload. Hughes seemed to be of the opinion these lifters would run to 6500 with no problem.

 

[khryslerkid]

I’ll report back once it’s all fixed up and let you know what I find. I would really hope Hughes isn’t selling ‘high performance’ lifter that hold open at 4500 RPM with only .050 preload. Hughes seemed to be of the opinion these lifters would run to 6500 with no problem.

One question I wanted to ask was what preload are you using. Now I know. If all else fails and you happen to have adjustable rockers you could try .020 That's what I'm using.

 

[Jerry Hall]

I’ll report back once it’s all fixed up and let you know what I find. I would really hope Hughes isn’t selling ‘high performance’ lifter that hold open at 4500 RPM with only .050 preload. Hughes seemed to be of the opinion these lifters would run to 6500 with no problem.

My opinion is when you find the problem, it will be relatively simple. You are methodical in going through the systems, and have not skimped on quality components. I can't say what you will eventually find but I'm staying tuned. Best of luck.

 

[Bee1971]

I have been dealing with the same issue on my 383/432 for a few years

5000 RPMs and up inconsistent on the street , power goes flat fast and just falls off

3:91 Gears and a 383/432 Stroker - RPMs come on fast very fast on the street/highway

Comp cams XE275 HL and lifters

Fast rate ramp camshafts

I have talked about it with a few on this webpage along with Moparts

There are numerous threads on the same subject , valve train and hydraulic lifters falling off after 5000 RPMs


Different carbs

Fuel pressure

Ignition ECUs

Coils

New Firecore distributor (That definitely helped my inconsistent missing RPMs between 3500-4500)
Wore out bushings and shaft on old Chrysler distributor

Checked fuel pump rod twice

I taped a fuel pressure gauge to my windshield (No issues) - Different float settings on Edelbrock 1912 800 AVS 2 - 7/16"/5/16" - Float drop down to 1.25"
Changed needle and seats to .110

Put everything back to factory stock now on the Eddy 1912 last week

Nothing helped Or changed honestly , other then a new Distributor helping my inconsistent miss

Some good threads and articles out there on hydraulic lifters

 

[beanhead]

Yes lifter pump-up is what I was suspicious of, not collapse.
I would double-check that your .050 preload is okay for those. I thought those were supposed to be run closer to .000 preload (but I could be thinking of the other non-standard hydraulic lifters.)

 

[66 Sat]

What about a restriction in the exhaust? Are you running manifolds or headers? What about the cam itself - have they got any other grinds that top out power wise by 5000 rpm and you accidentally got sold the wrong cam? Just trying to think outside the box.

 

[69L48Z27]

One question I wanted to ask was what preload are you using. Now I know. If all else fails and you happen to have adjustable rockers you could try .020 That's what I'm using.

Yes lifter pump-up is what I was suspicious of, not collapse.
I would double-check that your .050 preload is okay for those. I thought those were supposed to be run closer to .000 preload (but I could be thinking of the other non-standard hydraulic lifters.)

The first time I had this together I went a quarter turn which would be .025”. Same issue. When I spoke to Hughes they said they could be run at zero (race application only) but would be noisy. Cam card says close to .095, I questioned that and they said 1/2 turn is good compromise. On the 20 pitch thread that would be .050. I’ll run them at zero just to see if the fuel stuff doesn’t pan out.

 

[69L48Z27]

What about a restriction in the exhaust? Are you running manifolds or headers? What about the cam itself - have they got any other grinds that top out power wise by 5000 rpm and you accidentally got sold the wrong cam? Just trying to think outside the box.

You’re right about the exhaust, thought of that the other day. I’m running manifolds and I know they’re clear and the heat riser is gone. Then it’s the factory H-pipe, I know that’s clear. From there it’s a pair of old Flowmasters and tailpipes. There could be some restriction in a muffler or tailpipe but I don’t get the noise from clogged exhaust. I’ve had cars in the past where the catalytic converters clogged and you get that restriction noise.

What ever it is, it recovers very quickly when the RPM drops.

 

[khryslerkid]

The first time I had this together I went a quarter turn which would be .025”. Same issue. When I spoke to Hughes they said they could be run at zero (race application only) but would be noisy. Cam card says close to .095, I questioned that and they said 1/2 turn is good compromise. On the 20 pitch thread that would be .050. I’ll run them at zero just to see if the fuel stuff doesn’t pan out.

Reading the link you posted on the lifters it stated not to have the preload at zero? Keep doing what you are doing, one thing at a time

 

[dvw]

After reading this thread I believe it has a fuel delivery issue. As stated it doesnt miss, just wont pull at upper rpm range. It recovers quickly when the rpm drops. This would not any kind of valve train issue. No misfire tells me the it's getting spark. Have you done a volume test at the carb inlet? How much fuel will it pump in 30 seconds. Why a .600" lift cam fancy rockers with points and a stock style fuel pump?
Doug

 

[69L48Z27]

After reading this thread I believe it has a fuel delivery issue. As stated it doesnt miss, just wont pull at upper rpm range. It recovers quickly when the rpm drops. This would not any kind of valve train issue. No misfire tells me the it's getting spark. Have you done a volume test at the carb inlet? How much fuel will it pump in 30 seconds. Why a .600" lift cam fancy rockers with points and a stock style fuel pump?
Doug

I’m working on fuel stuff this week. I have the carb apart now with gaskets on order. Everything inside is bone stock for jets and rods and floats were not that far off. I think I was the first person inside the carb. Pressure are on the list to check.

How do you check volume with a mechanical pump? Pressure is simple enough but I’m not sure what volume numbers I’m looking for.

This car came with a ‘race’ engine and PO bracket raced it. 3500 stall converter too with 3.91s. He had the rockers on the engine already. I’m trying to keep the car as stock looking as possible and I don’t see the need to throw a bunch of parts at it. Shouldn’t need aftermarket pumps and ignition to go have some fun at the track. I had to replace the cam but he had a similar one in there when I got it, he said the setup went mid 12’s with slicks, he was using a ThermoQuad.

 

[dvw]

[QUOTE="69L48Z27,

How do you check volume with a mechanical pump? Pressure is simple enough but I’m not sure what volume numbers I’m looking for.

This car came with a ‘race’ engine and PO bracket raced it. 3500 stall converter too with 3.91s.


.600 lift with 3.91 and 3500 stall sounds like a mismatch. But usually .600" lift would be up around 250@.050". To test delivery run the carb line into a can and run it for 30 seconds. I'd like to see at least a quart.
Doug

 

[69L48Z27]

.600 lift with 3.91 and 3500 stall sounds like a mismatch. But usually .600" lift would be up around 250@.050". To test delivery run the carb line into a can and run it for 30 seconds. I'd like to see at least a quart.
Doug

Why is it a mismatch?

How do you ‘run it’, are you just cranking the starter for 30 seconds? I would also assume if there a volume problem I would also see the pressure fall off too when the car stops pulling?

Thanks for the input.

 

[dvw]

It should run for 30 seconds on just the fuel in the carb. If not crank it.
Doug