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| | | | Joined: Feb 2009 Posts: 128 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2009 Posts: 128 | I have a freshly rebuilt 235 and on occasion I get some slight backfiring through the carb that sounds like popcorn popping. Any ideas why? Once the engine is warm and I throttle down, most times it stops, but the last time it backfired loudly and the engine shut down. ALSO, when I have the throttle wide open, my oil pressure is over 20 pounds, but as I back the throttle down to idle, the pressure drops to around 10 pounds. Is this normal? Thanks guys.
1946 2 Ton Flatbed
| | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | Check the timing, may need to be advanced.
Yes, the oil pressure will fluctuate with engine rpm.
Bill Burmeister
| | | | | Joined: Feb 2009 Posts: 128 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2009 Posts: 128 | Thanks Bill. I'll try advancing the engine in the morning. I figured as much with the oil pressure, but I just wanted to double check.
1946 2 Ton Flatbed
| | | | | Joined: Feb 2004 Posts: 29,798 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,798 | That top end pressure is a bit low for a fresh rebuild. You might want to check the oil pressure relief spring in the pump if you happen to have the oil pan off again for some reason. The pressure isn't dangerously low, but unless you're running very thin oil, the hot cruise RPM pressure should be a little higher, 30 PSI or more. 10 PSI at slow idle isn't bad, but it could stand to be a bit higher, also.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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| | | | | Joined: Feb 2009 Posts: 128 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2009 Posts: 128 | I'll check my oil gauge again to make sure. What rpm should the engine be at when the oil pressure is at 30? What's the best way to read rpm? Is there a test gauge I could buy? I don't have my gauge cluster hooked up just yet.
1946 2 Ton Flatbed
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