Thread: my 355 sounds like a diesel
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10-20-2004 04:43 PM #1
my 355 sounds like a diesel
Please help I have a 350 small block, with angle plug dart heads,flat top forged pistons, steel crank, floating rods and crane energerizer cam and lifters block is 30 over crank is turned 10/10. Motor has 35 psi oil pressure at idle, motor has 1 hr. on it cam was broke in proper, my problem is motor sounds like it's dieseling sound seems like it's coming from under intake really bad when engine is cold but still there when engine is warm. Has anyone else had a problem like this? P.S ready to tear motor back down.
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10-20-2004 11:28 PM #2
What is your ignition advance? What is your compression ratio? Are the pistons loose in the bore? The oil pressure is good which leads me away from excessive bearing clearance. The fact that it gets better as the engine warms up makes me think it's piston related. Are you using forged pistons? Forged pistons expand more and must be fit loose in the bore so they have room to expand as they warm up. When the engine is cold, the skirt will slap the cylinder wall making a diesel noise. Did you use hypereutectic pistons? I have heard stories that some brands of pistons run tighter clearances than standard pistons, but some shops forget to take this into account and machine the bore for standard pistons. This results in piston slap/diesel sound.
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10-21-2004 05:50 AM #3
Thanks for the input 76GMC1500 my ignition advance is 10 degrees advanced compression ratio is 10/1 cranking compression is 185 and i am using trw Forged pistons wall to piston clearance is 5 thousand noise is still there when engine is warm but not as bad
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10-21-2004 05:56 AM #4
Re: my 355 sounds like a diesel
Originally posted by 4onthefloor
my problem is motor sounds like it's dieseling
Sounds like you may have a mismatch between your static compression ratio and your valve timing.www.brownsperformance.com
Performance By Design
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10-21-2004 06:07 AM #5
cranking compression PSI is 185
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10-21-2004 06:33 AM #6
Originally posted by 4onthefloor
cranking compression PSI is 185
You might try dumping some racing gas in it and see if it quiets down. If it doesn't you should probably look for a mechanical cause.www.brownsperformance.com
Performance By Design
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10-21-2004 08:46 AM #7
I had the same problem with my 350 rocket in my truck. This is gonna sound stupid but check your vacuum that's what mine was. If that ain't it check your timing and compression ratio thats all I got to say on the subjectBrad
If It runs like a deer it's to slow.
Going slow is just a crutch for the people who can't deal with real power.
If it ain't classic or Chevy it's junk.
Ford = Found On Road Dead
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10-26-2004 10:30 PM #8
Did you lube the cam or lifters when the engine was assembled?Lifter noise can cause a lot of noise. Also check the fuel pump rod ive seen it cause a lot of noise also. Just some simple thing to check before you tear it down. Sometimes its the simple things that cause a lot of problems.
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11-26-2004 11:16 PM #9
larry tell me what thinkLast edited by 4onthefloor; 11-26-2004 at 11:23 PM.
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11-26-2004 11:55 PM #10
Originally posted by j*b
I'm not familiar with the Crane cam you're using but if it is designed for low RPM torque and your static compression ratio is around 10 or 11-1 that could possibly be your problem. The "torque" cams are designed to be more volumetric efficient in the lower RPM ranges and generally work best with static compression ratios ranging from 8.5 to 9.2-1.
You might try dumping some racing gas in it and see if it quiets down. If it doesn't you should probably look for a mechanical cause.Last edited by 4onthefloor; 11-30-2004 at 05:49 AM.
Welcome to CHR. I think that you need to hook up your vacuum advance. At part throttle when cruising you have less air and fuel in each cylinder, and the air-fuel mixture is not as densely packed...
MSD 8360 distributor vacuum advance