MTFCA Forum

Ever since I rebuilt my engine, I have had a problem with climbing steep hills. The car (26 with cowl tank) would sputter like it was running out of gas. This was especially noticeable with low RPM such as right after shifting gears, whenever I opened the throttle. If I backed off on the gas, it would run better. I have tried adjusting the float level and the mixture, with no avail. I replaced spark plugs , no relief.
A number of years ago, I had received a "high volume intake manifold as a door prize on one of our tours, and when I rebuilt the engine I had installed it.
Today I installed a stock intake manifold and took the car out on several hills. I could climb a hill in high which formerly needed Ruckstell. It runs smoother at all speeds and idles better.
This is what I think my problem was. I had a stock engine and exhaust system which would create low vacuum when the throttle was opened. This was similar to pursing the lips and blowing out VS blowing out with lips open. The volume of air was higher, but the speed was slowed down. With the open throttle, there was simply not enough vacuum to suck in the gas! This would have been no problem if I had a modified engine with higher compression, higher valve lift or longer valve duration. And a dual exhaust, all of which would have increased airflow.
Anyway, for those who are experiencing this same problem, this might be the answer.
Norm

Or install a fuel pump Norm

A fuel pump is not necessary. The tank is high under the cowl. I have another 26 and can climb a hill about 10% grade in low Ruckstell. The change in manifold fixed the problem. The problem is not getting fuel to the carburetor, but it is getting enough vacuum to suck it into the manifold with an open throttle. No problem anymore. This car runs just like the other one now.
Norm

Glad you got it fixed Norm !

However the high flow intake is an early design if I’m not mistaken.
I would be more inclined to think you possibly had a gasket leaking.

Norm

Good work to find the cause of poor power.

As for the repro high volume, found something similar when installed one of those, had it powder coated red for flash. But found later the aluminum casting is oversize too at the ports, and my issue was seating of the gasket at the upper side, hard to know the intake wasn't seated well.

So after this photo, removed the aluminum high volume, and ground a flat at the top of the upper exterior of the ports, where it was slightly impinging on the repro exhaust manifold and allowed leaks. That fixed it. Don't have photo of the part ground off, but just something else that may have been going on with yours.

I don't think I want to speculate too much on this one. I have never had one of the high-volume intake manifolds to play with.
However, I have known several people that weren't all that happy with the high volume intakes. While they do seem to give some improvement on the high speed end, quite a few people have had low speed issues. Whether it was strictly due to the slower air flow at low end not vaporizing enough fuel? Or leaks because the manifold didn't seat properly? I just don't know.
I do suspect that different models of carburetors would likely suffer different amounts of deleterious effects from the reduced airflow.
One could possibly adjust the fuel mixture to compensate for the reduced airflow. But having to do so every time one changes from uphill to downhill to level and back to uphill or idling at a stop would be a p i t a.

On this car I have only used a Holly NH and over the years tried different float levels. Yesterday when I replaced the manifold, The copper 0 gaskets were very well compressed. so I don't think I had a vacuum leak. It ran very smoothly at idle or when going high rpm on level. It was slow starting in low and after shift to high. The farther I pulled the throttle, the more it misfired.

I left the exhaust in place by rotating the front and back clamp so it would hold the exhaust and removed the center two clamps. I took out the bolts holding the carburetor and left the carb and all fittings and rods in place. Then I placed the standard intake manifold with new 0 gaskets and tightened everything up. It started right up and with about 1/8 turn of the richness adjustment ran smoothly at all speeds and all throttle openings including pulling hills.

It might have been different with dual exhaust and other modifications to the engine, so I won't criticize the manifold, just didn't work very good in this application. This engine is completely stock including cylinders sleeved back to standard.
Norm

While I have never used the aluminum high volume intake, but I did try an original type aluminum one which has somewhat larger inside passages over the cast iron type. I was never really happy with the performance on a stock engine (see note*) even after trying several different carbs. I wonder if it had to do with the type of carb used with them originally; Holley H, G or Kingston 4 ball and how fuel was supplied by those carbs. I know some could argue that theirs run fine with later carbs, could be what they expected and how they drove the car, but my seat of the pants OP says different. Mine came off and I went back to stock intake which is what (in my OP)most T type bolt on carbs (aftermarket or stock) were designed to work with unless they came with their own intake manifold. After I installed the stock intake, performance was back up. If you look at, for example, the Zenith setup, the runners on it are rather small. I tried one with a Stromberg OE-1, varoom!! So maybe there is something to be said about the vacuum inside the smaller passages working better with the stock T' engine.
*My engine in these cases had a touring grind cam and 6-1/2 degree advance timing gear with stock head, valves and pistons.

I had to do same as Dan did on mine. On another one it leaked about 3 inches up the leg with many minute holes in a 2 " area, couldn't see them but I could feel the gasoline , covered area with epoxy & still running.