Throttle lag problem

[CTgreen]

Here's an unusual problem I have not encountered before. Occasionally when I step on the gas pedal, the engine does not respond, almost like the throttle linkage is not connected. Even if I put the pedal all the way down, the truck stays at idle....sometimes for many seconds, and then all of a sudden the throttle responds. I have checked the linkages, and all are connected, and move the lever on the carburetor linkage. Any ideas what could be the problem? Thanks.

[ZGjethro]

Here is a shot in the dark. Do you have any air leaks in your intake manifold? you might have a fast idle if that is the case. Could there be any blockages in your carb?

[oilleaker1]

The stock Ball in Ball carburator has a finicky accelerator (vaccuum operated) pump. If it gets any dirt at all it plugs up. I took mine off three times to clean it and ended up pumping the cup by hand and it finally expelled whatever the problem was. There also is a governer at the base of the carb which might be malfunctioning. I haven't messed with mine. The carburator manual or book for M37's would be a good item to get and read. Your timing should be 2 degrees ATDC and checked to see if the distributor advances as the engine revs up. If all else fails, read the manual John

[ZGjethro]

Oilleaker, your advice about the accelerator pump is probably better than my shot in the dark. I have to differ about the timing though. I know the manuals mention timing a few degrees ATDC, but I am pretty sure most are timing them BTDC now. At 8000', I am timed ten degrees BTDC, and my truck is running great. I also had a Pertronix ignition installed, and the carb rebuilt.

[CTgreen]

I took off the side cover on the carburetor which houses the (governor?) spring, rocker, plunger setup. There was some dried varnish on the plunger shaft which caused it to hang up. Also, where the end of the plunger rides on the little 'roller' on the rocker, I applied a wee bit of grease, so that they slide over each other better. Works like a champ now. H.

[rc51racer]

I agree with ZGjethro, my timing is around 10 BTDC at 1300'. As Charles has mentioned many times the 2 ATDC in the manual is just wrong.

I used a $10 vacuum gauge from Harbor Freight to get the optimal timing setting, this involved rotating the distributor until maximum vacuum
was achieved.

The vacuum gauge is also useful for checking for sticky valves among other engine ailments.

[oilleaker1]

John B at Midwest Military told me the timing spec. I set mine there and it runs fine. The vacuum gauge is a excellent way to set timing. Where did you tap it at? John

[rc51racer]

I used this vacuum gauge which includes the needed adapter:



available at finer Harbor Freight stores everywhere.

Then just remove either of the brass plugs on the intake manifold as shown here:



with the engine at idle the needle should be steady and read greater than 17" Hg.

The vacuum gauge has a green zone for the correct reading, the only thing I found the timing light useful for was setting idle RPM.

[ZGjethro]

Wow, another spotless engine. I am going to have to clean my 60 year old warhorse up before I post any pictures here. Looks good

[DJ]

Is that the only color the hose for the vacuum gauge comes in?

[rc51racer]

Oddly mine is black, wish I had hot pink!

[DJ]

I'm not gonna comment on that!!!