Modified A will not run at higher RPM

50Trucking

50Trucking

Member
I built a 31 coupe and raced it at TROG last year and it ran fine. This year I painted the car and converted it over to 12 volt. As part of painting, I repainted the motor. To do that I removed the exhaust and intake manifold. Every since I put it back together it does not run right.

The engine is bored 60 over with a Burtz 6.1 head, FSI electronic distributor, dual 81 carbs and Red's headers with a lightened flywheel and a V8 clutch and a 39 transmission. I am running the stock gas tank with a 3-6 lb. electric pump and a regulator set at 2.5 pounds.

It cranks great and runs but at high rpm it just does not keep pulling and running properly. It wants to run but something is not letting it calihute.

Calihute is a word I heard my father say when he was talking about engines that he was working on. He would tune an engine by ear, listening and when it was right, he said it was calihuting.

The Stromberg 81's do not have power valves. I just had them rebuilt by Vintage Speed. I have checked for vacuum leaks. Removed the intake and exhaust and replaced the gaskets and coated with gasket sealer, sprayed carb cleaner on manifold and and carb bases (only place air could in) to check for leaks to no avail.

The spark advances about 30 degrees but stops at about 2600 RPM. I will check with FSI on the spark curve

I am using a Spectre Performance 2518 Fuel Pressure Regulator for Amazon about a $30.00 regulator.

If it cranks on the first turn idles around 650 RPM, pulls good in each gear about half way through the power curve and then stops pulling and starts sputtering and running rough what else could be causing it.

How does an engine operate and sound if it starves for gas at higher RPM?
How does an engine operate and sound if the timing does not advance enough as the engine makes higher RPM's?

Doesn't it have to be gas or timing? What else can it be? All cylinders have 115 lbs compression so the valve are seating. I have extra strong valve springs. This motor was completely rebuilt with larger valves and new piston rings with less than 10 hours of running over a years period

Calihute is a word I heard my father say when he was talking about engines that he was working on. He would tune an engine by ear, listening and when it was right, he said it was calihuting.

I am not aware that the Stromberg 81's have power valves. I just had the carbs rebuilt by Vintage Speed. I have checked for vacuum leaks. Removed the intake and exhaust again and replaced the gaskets and coated with gasket sealer, sprayed carb cleaner on manifold and and carb bases (only place air could in) to check for leaks to no avail.

The spark advances about 30 degrees but stops at about 2600 RPM. I will check with FSI on the spark curve

I am using a Spectre Performance 2518 Fuel Pressure Regulator for Amazon about a $30.00 regulator.

If it cranks on the first turn idles around 650 RPM, pulls good in each gear about half way through the power curve and then stops pulling and starts sputtering and running rough what else could be causing it.

How does an engine sound and run if it starves for gas at higher RPM?
How does an engine sound and run if the timing does not advance enough as the engine makes higher RPM's?

Charlie did put adjustable jets in the carbs when he rebuilt them.

Doesn't it have to be gas or timing? What else can it be? All cylinders have 115 lbs compression so that points to good valve seating. This motor was completely rebuilt with larger valves and new piston rings less than 10 hours of running over a years period

Any help is appreciated
 
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Re: Modified A will not Calihute

First off if that word is slang I've never heard it before:
"Calihute" is not a recognized word in the Merriam-Webster Dictionary. It is very likely a misspelling.

Have you put a vacuum test gauge on it?

What kind of fuel pressure regulator are you using. There are lots of really crappy ones out there.
 
Re: Modified A will not Calihute

Convert to 12 volts ( is the FSI 12 volt ? they are polarity sensitive ! along with the coil ! ) Paint is an excellent insulator ! do you have good grounds ? clean shiny and tight ! As stated above , check if you are getting full timing advance at high rpm .
 
Re: Modified A will not Calihute

If it ran good before pulling the manifolds then I'd wonder about that. Vacuum leak due to a crack. Did something get inside there during assembly? Did a carb catch something in a jet?

Sometimes things happen while a car is down. Sticky valve? who knows what it may be. If it idles good but falls off a cliff at higher rpm then it could be a carb partial blockage, a power valve gone bad, a cracked or weak valve spring, or something else.

With a stock engine, it would likely be easier to troubleshoot but were not talking about a stock engine.
 
Re: Modified A will not Calihute

I agree with the vacuum test. Will help show an intake manifold leak or carb to manifold leak. Also agree with verifying advance at high speed.
 
Re: Modified A will not Calihute

What is the definition of Calihute? Is it a regional term or am I completely missing the boat here. :)
 
Re: Modified A will not Calihute

Flathead said:
What is the definition of Calihute? Is it a regional term or am I completely missing the boat here. :)
Click to expand...

Maybe he means "Cahoot" as In cahoots with the other parts? Just guessing, I have know idea what he is talking about!
 
Re: Modified A will not Calihute

Check with FSI for the proper advance curve for your head, carburetor and header setup. The distributor advance may not be curved correctly for your setup.
 
Modified A

Charlie put adjustable main jets in the carbs when he rebuilt them. I am going to open them up and see if that helps. If I could determine whether it is getting to much fuel or not enough it would make it a lot easier. I raised the fuel pressure and the carbs started getting fuel on the outside of the body from around the gasket. I matched the coil with what Shawn recommended when I went from 6 to 12 volts

Any ideas on how to get this puppy to run is appreciated
 
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Re: Modified A will not Calihute

John said:
Check with FSI for the proper advance curve for your head, carburetor and header setup. The distributor advance may not be curved correctly for your setup.
Click to expand...

Bingo! Years ago I experimented with all manner of modifications on Volkswagen Beetle engines. Each additional tweak to carburetors, engine displacement, camshaft, and exhaust resulted in a some improvement in performance. It was only after the addition of one of the various Bosch centrifugal distributors available that it tended to go the other way. The typical result was that the engine would **** out under a load, especially when accelerating through the gears. These distributors were typically sold as an improvement to performance but apparently that only happened when the advance curve was in alignment with all the other elements of the ensemble.

****: sounds like "crepe"!
 
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Re: Modified A will not Calihute

At 115 PSI your engine is great (as it should be). I’m not a big believer in coincidence I seriously doubt the removing the manifolds created a carb problem or a distributor problem (30 degrees is too much advance however, with a 6:1 head you should be in the 24 degree range call Shawn at FSI and talk to him, he is extremely helpful).
81’s do indeed have a power valve but it’s mechanically operated not vacuum operated (you mash the pedal to the floor and it opens another jet. With 2 81’s I doubt you will ever activate the power valves unless you try hard to do it). Your problem sounds for all the world like fuel starvation to me. Try bumping the fuel pressure up a bit maybe to 3.5 psi. I do not know how the removal of the manifolds could create a fuel problem either however something is clearly wrong and fuel is my thought.
 
Re: Modified A will not Calihute

The 81 (as well as a 97 and a 48) power valve is operated in this way: when the accelerator pump reaches the bottom of it’s stroke the rod pushes on a needle valve and opens the power valve. The stock power valve is a 71.
 
Re: Modified A will not Calihute

The painting suggests that you should make sure the engine is well grounded. I run a wire from where the heavy gauge battery cable is bolted down to a head bolt. Copper is a much better conductor than steel and the distributer needs good electricity at high RPMs.

Another thing, easy to check on Zeniths and probably the 81s also is full fuel delivery. If you remove the carb drain you should get more than 5 fluid ounces of fuel per minute gushing out. Anytime you remove the carbs you stand a chance of dislodging a piece of dirt in the lines, I would check the jets in the carbs.

Good luck. I try to look for the simple explanations first because it is tiring to think through the complicated obscure possibilities.
 
Re: Modified A will not Calihute

Point bounce? Back in the 70's I got an optical kit for my Mustang V6 just to eliminate having to adjust the points. Should be one for a 4 cyl if they're still made.
 
Re: Modified A will not Calihute

It does sound like a fuel starvation problem to me if you keep your ' in it long enough it'll probably start popping back through the carburetors from being lean I would check your fuel flow Obviously you have enough fuel flow for the lower RPM ranges But it sounds like it's restricted somehow also check your float levels maybe they're improperly set.
 
Re: Modified A will not Calihute

I don't see any reference to the coil that you're using with that FSI distributor. As suggested in post #12, when you talk with Shawn confirm the coil that he recommends for the distributor.
 
Re: Modified A will not Calihute

I found this posted by WUGA . He said he installed a Brierly head on his banger using the FSI distributor. It was getting way too much advance. When he talked to Jim, he told him that FSI makes two distributors, one with 28 degrees of advance and one with 18 degrees of advance for use on high compression heads. he had the 28. He sent the distributor back to FSI and they recurved it to 18 degrees. Problem solved. Could this be the problem?
 
You might be on to something, flatheads don't want a lot of advance, and 28 sounds like a lot in this case. :)
 
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