I built my engine/truck in stages as money permits and got myself into a high compression on pump gas situation.

351W - stock iron block
Solid/Mechanical Roller
236/242 @.050 and 608/610 lift on 110 LSA (IVC @ .050 is 44)
in a 1954 F100 that weighs roughly 3200 lbs with me in it
T56 6 speed manual
4:10 gears (posi)
AFR cnc ported heads with 58cc chambers (Alum)
pistons head volume +11 cc (scat rotating assembly)
4.030 bore
4.030 gasket bore @ .040 compressed thickness (MSL)
pistons are .010 in the hole
rod length is 6.2 in. and the stroke is 4 in.
I am getting 190 - 210 psi on compression test
650 CFM holley ultra XP
air gap intake
1 3/4 primaries long tube headers
electric fuel, fan and water pump. no power steering or AC. only belt is for alternator.
Use: just as a hot rod that I sometimes drive to cruise-ins and tear up back roads.

The above engine specs give me a static compression 11.52:1 and dynamic of 9.61:1. I currently have the full-in timing at 30 degrees. Generally I run 93 Octane. Everything I find on the internet and in discussions with experienced engine builders and hot rodders is that 10.5:1 static (dynamic should stay under 8.5) is the most on pump gas but also depends on a lot of other details (engine/trans/rear end/vehicle weight).

Because I am riding around in 69 year old truck there are rattles, pings, and such very similar to what everyone says is spark knock. Not sure if I have ever heard spark knock but maybe I have and it has been very faint. Everyone that I have talk to says it is noticeable at load but also could be faint.

All that aside, I put myself out there in hopes from specific people that I have worked with before that have provided valuable insite and advice. My initial thought is I am fine due to my truck being light, with a manual transmission and low gears. Before I go out and spend $$ on a new set of heads with 72 cc chambers I wanted to see what the experts think. I welcome your thoughts.

Thanks

 

After driving around a while, see if the spark plugs look like they've been gapped with a hammer.

 

good idea. I have been keeping a good eye on those. Everyone says that the only true way to tell the health is to read the spark plugs. I have studied how to read them from many sources. I think I have a basic understanding. I have about 1,500 miles on the current plugs. Yesterday I pulled them and they look good aside from #7 looking a bit richer then the rest. I checked the gap and it has remained at my installed setting (.045).

 

Your only real option if you don't want to rebuild the engine with different pistons to get the compression lower would be to change the cam and put in more duration. I think that your current cam choice would be pretty good if the compression ratio was lower, 10-10.5 but in your case a cam with another 10 degrees or so at .050 would probably do ok on premium pump gas. The cam could also have the lobe separation moved out to say 112 or 114 so that you could move the intake closing back farther. If the ICL is 106 now making it 110 would make a big difference in the cylinder pressures.

Plug reading is mostly fallacy especially on unleaded fuels and if there is any part throttle running. It won't tell you anything about the mixture.

 

I was thinking of checking the plugs for signs of detonation, like broken insulator or vaporized electrodes.