Hi all,
I’ve been racking my brain and trying everything I can think of but my 505 build pings pretty good under load. The motor only has 1500 or so miles on it but the issue seems to be getting worse as it gets driven more. Here’s the list of things I’ve tried:
- I have a Wide Band O2 gauge that shows 10-11.5 under load and the plugs also show no lean conditions. Rejetted the carb every way to Sunday.
- Tried 110 VP race fuel. This did quiet it down a lot but it was still there under heavy load. Normally I run 93 with a mix of 100LL AvGas
- I backed the timing off considerably and limited the overall advance to 18 total (starts at 10 goes to 28) with the heaviest springs. It has an MSD ProBillet distributor and a 6AL box
- Took the PCV system off and replaced with a couple breathers on each valve cover
- Checked for vacuum leaks with a smoke machine. Capped off everything. No heater controls, not power brakes, no PCV.
- Pulled the heads and had them checked. No issues found
- Lowered the compression from 10.5:1 to 10:1 with thicker Cometic MLS head gaskets.
- Reset the cam timing to straight up.
- check and rechecked valve preload.
- tried colder spark plugs
Details of the engine build are as follows:
Some other symptoms I’m seeing that may or may not be contributing factors
I have a complete handwritten list of all the assembly measurements I checked as I built it along with the cam card that I’ll try to attach here somehow.
Any advice would be appreciated.
I’ve been racking my brain and trying everything I can think of but my 505 build pings pretty good under load. The motor only has 1500 or so miles on it but the issue seems to be getting worse as it gets driven more. Here’s the list of things I’ve tried:
- I have a Wide Band O2 gauge that shows 10-11.5 under load and the plugs also show no lean conditions. Rejetted the carb every way to Sunday.
- Tried 110 VP race fuel. This did quiet it down a lot but it was still there under heavy load. Normally I run 93 with a mix of 100LL AvGas
- I backed the timing off considerably and limited the overall advance to 18 total (starts at 10 goes to 28) with the heaviest springs. It has an MSD ProBillet distributor and a 6AL box
- Took the PCV system off and replaced with a couple breathers on each valve cover
- Checked for vacuum leaks with a smoke machine. Capped off everything. No heater controls, not power brakes, no PCV.
- Pulled the heads and had them checked. No issues found
- Lowered the compression from 10.5:1 to 10:1 with thicker Cometic MLS head gaskets.
- Reset the cam timing to straight up.
- check and rechecked valve preload.
- tried colder spark plugs
Details of the engine build are as follows:
- 77 440 RV block bored, clearanced and checked by LRB performance in Franklin, NJ
- Edlebrock RPM heads (60185) w/ 88cc chambers
- Eagle Competition Rotating Assy (B21202030) stroker crank, rods and pistons
- Mahle BBM475350F08 pistons (part of the Eagle kit)
- Comp Cams 23-712-9 hyd roller cam and lifters (Duration 286/294, Lift .544/.541)
- Hughes 1.5 roller rockers
- Edlebrock RPM air gap intake manifold
- AED 950 carb
- TTI 1 ⅞ headers
- Edelbrock Performer RPM Street Fuel Pumps 1723
- All ARP hardware
Some other symptoms I’m seeing that may or may not be contributing factors
- Coolant keeps getting dirty/muddy. I flushed the block several times but it keeps coming back. Tested for combustion gasses in coolant but it showed none. No water/coolant in the oil.
- Blow-by over 3k rpm. This is tested under no load. I don’t have a dyno so it’s really hard to test this under load at any higher rpm
- Scoring on the lower cylinder walls at the 12 and 6 o'clock positions. It’s not very deep although I can feel them with my fingernails but not catch on them.
I have a complete handwritten list of all the assembly measurements I checked as I built it along with the cam card that I’ll try to attach here somehow.
Any advice would be appreciated.