I may be crazy!

gmanrides

gmanrides

Senior Member
Is it possible for a flathead to over run? Driving my Model A I have noticed that when coming to a stop if I don't downshift and lug it down the idle wants to run up around 1000-1200 rpms. Last Sat I did around 150 miles and going up a typical TN hill I was running in 4th gear around 1900 rpms somewhere mid 50's mph and pulling good. Slow down towards the top to make my turn downshifted 3rd then 2nd and 1st as I started to accelerate throttle took off up to 3000 rpm before I shut it down. Coasted to a stop got out and checked linkage, return spring everything seemed fine. Started it up and it ran fine again.
Here's the current setup, 59AB, .030 over, 400JR cam, dual 97's on slingshot intake. T5 transmission 1352-145, 2.73 diff and 8.20 x 15 Cheater slicks that specs say are 30.5 diameter. I know the diff is not ideal but it is on the list to change. Engine temp runs around 170. Am I barking up the wrong tree? Any ideas? Other than that it starts and runs fine. Thanks Gary
 
Your car looks way cool from the top!!! I would oil all of the bosses on the carburetor and all of the connecting linkage and make sure nothing is hanging up anywhere. I'm sure others with more tech knowledge with modifieds will chime in.
 
My experience has been that a runaway idle is usually caused by either sticking linkage, a sudden lean fuel condition, or advanced/incorrect spark timing.
 
Also check for vacuum leaks at manifold, manifold to carb adaptor and carb bases. Now here's a strange one for you, make sure you have a good engine to frame ground. I've seen parts of the carb linkages stick when theres a bad or no engine ground strap. The engine can find a ground through the linkages causing them to arc and stick. Also linkages can stick if there tight or on the edge of binding with engine torque on the road, but are fine whilst the car is stationary.
Check everything, make sure of good throttle return spring.
Martin.
 
Most likely a linkage problem . If you are using rod ends (hiem's) , make sure that they are not binding or sticking at all . I had a car once that they would bind on , but only when it got warmed up . A good test for a linkage problem would be to put on a 2nd return spring on . If problem goes away - it's the linkage .
 
Thanks guys, I'll check it out. Seems fine when it's cold or prior to engine temp running up. I have the throttle shaft springs on each carb and then one return spring on the linkage. I'll get it warm and check though.
 
Just had that problem - with a nicely rebuilt carb. I put on a slightly stronger return spring and the problem vanished.
 
I got a chance this evening to actually look at it. So simple, it's embarrassing. Everything on the carbs are new including throttle pedal. WD40 fixed it! Pivots where the rod links together. I didn't have time to look at it Sunday being Mothers Day and all, back to work Monday and all week kept thinking about it (too much). Got home today and presto.Geez!
 
If your running a 400JR cam your idle is going to be about 1000 rpm. I might be a little crazy but it keeps me from going insane. Walt
 
Walt Dupont--Me. said:
I might be a little crazy but it keeps me from going insane. Walt
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I am with you on this Walt, except in my case, I may be a litte insane, but it difinately keeps me from going crazy.

I also agree with 40 Deluxe, WD40 is often used as a lube which it is NOT. I once made the huge mistake of using WD40 on a gun mechanism and later wondered why that mechanism was all gummed up and completely non functional.
 
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Lee. a life long friend from high school, an aircraft quality assurance tech for Continental Airlines, says, 90% of the problems are lack of lubrication, and that also applies to social issues.
 
russcc said:
Lee. a life long friend from high school, an aircraft quality assurance tech for Continental Airlines, says, 90% of the problems are lack of lubrication, and that also applies to social issues.
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Welllllll..........One of the reasons Continental is actually no longer with us is likely because not enough lube was applied when it was most-needed. DD
 
Rock on Terry! I'll put some good lube on it. WD40 was handy on the bench. Walt I've been running it at about 850. Sounds good I'll give it a test tomorrow, headed to Nashville for the Goodguys show. Should be fun. Thanks again everyone.
 
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