MadRacing19 Posted July 30, 2004 Report Share Posted July 30, 2004 Ok maybe someone can figure this one out ? Half way thru the feature motor started banging top end . Tach would got crazy ,thought it was electrical. Changed battery ,dist., wires ,plugs, carb, checked all the wiring found no problem or solution . Motor will free rev to any rpm but under a load above 5000/5500 motor trips out . Today I checked valve springs for a broken one and found no problems . Atleast that you can see. Now I am pulling intake now to see if maybe a lobe on the cam went flat. If this is not the problem then mabye someone else has an idea. The motor is a flat top .40 bore with 58cc heads. Solid cam . Roller rockers blah blah blah. Some help would be nice. Thanks. Link to comment Share on other sites More sharing options...
hotstock74 Posted July 30, 2004 Report Share Posted July 30, 2004 I know you said you changed dist.,I had module cause this problem.It might also be weak valve springs. Link to comment Share on other sites More sharing options...
jracer98 Posted July 30, 2004 Report Share Posted July 30, 2004 Cheap idea--->disconnect the tach and drive it. I had a tach go bad and cause similar grief once. Jay Link to comment Share on other sites More sharing options...
VictoryLane Posted July 30, 2004 Report Share Posted July 30, 2004 Check your timing at 3-4k , and see if the mark is jumping around. Check your Ground to your Distributor. Victory Lane Link to comment Share on other sites More sharing options...
Truck99 Posted July 30, 2004 Report Share Posted July 30, 2004 You mentioned that you check the valve springs visually for broken ones. Your problem may still lie there if you have one or more of them getting weak. If it's valve float you're feeling, the problem needs to be fixed soon before it leads to bigger problems. The other suggestions are all good also. Also check your float level - should just trickle over the bottom edge of the sight hole at idle. ss99 Link to comment Share on other sites More sharing options...
SVCMNGR1 Posted July 30, 2004 Report Share Posted July 30, 2004 Do you have stud girdles on it? Link to comment Share on other sites More sharing options...
MadRacing19 Posted July 30, 2004 Author Report Share Posted July 30, 2004 The tach was one of the first things I did. I forgot to mention earlier. Changed jets, checked float level, checked for timing being off at high rpm , Changed dist. again(3rd time) Checked for flat cam lobes and now we have the heads off. Valve springs look weird . Inner springs maybe broken. Going to put new heads on in the morning. I do run stud gurdle. Thanks for all the help so far I will try almost anything about now. Will be back tomorrow to let everyone know is the head change did it or not. Link to comment Share on other sites More sharing options...
Pacecar Posted July 31, 2004 Report Share Posted July 31, 2004 The high-speed air bleeds (the smallest ones) in the carburetor may have a small piece of dirt in one of them. Take the metering block off. Cover your windshield. Spray carb cleaner spray (using straw nozzle) thru all holes in carb body and thru metering block. Should have a good stream of cleaner flowing thru the air bleeds. Air blow dry. Reassemble metering block. P.S. Carb spray will damage your lexan windshield if you clean the carb while it is still on the engine. Link to comment Share on other sites More sharing options...
hobby74 Posted July 31, 2004 Report Share Posted July 31, 2004 I had this same problem and it was vapor lock. I had the fuel line near the head. Link to comment Share on other sites More sharing options...
ups88john Posted July 31, 2004 Report Share Posted July 31, 2004 weak valve springs will cause a high rpm miss, aka valve float. if this is the case you will drop a valve and destroy the motor. you need to check the seat pressure and open pressure, if you dont know how take it to a good machine shop and have them check it. big john p.s. flat cam will run like crap at all rpm. Link to comment Share on other sites More sharing options...
The Shrimp Posted July 31, 2004 Report Share Posted July 31, 2004 I had the same problem last week, valve springs were extremely weak. Thank the lord we found them could of cost us the motor this week. They were real bad. Link to comment Share on other sites More sharing options...
MadRacing19 Posted July 31, 2004 Author Report Share Posted July 31, 2004 OK ,thanks for all the help ! I found the problem. Weak broken valve springs. Well atleast now I know my car got a gooooooooood check up. Thanks to all for advise. Link to comment Share on other sites More sharing options...
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