You’ve got questions, we’ve got answers. We work with the Summit Racing tech department to help you tackle your auto-related conundrums. In this week’s Mailbag, we’re helping a reader troubleshoot spark plug, carb-jetting, and timing issues in a small block Chevy 350.


putting the cap on a distributor for a 355 cubic inch chevy small block v8
(Image/Jeff Smith)

Q: I have a .030 overbored, balanced and blueprinted Chevy 350. It has a 9.5:1 TRW pistons, .507/.510-inch lift COMP Cams camshaft, Trick Flow heads, an Edelbrock Performer intake with a Holley 750 (#71 primary/#82 secondary jets), and an MSD 6AL ignition with coil.

The engine is not performing as I think it should. There is no color on the spark plugs—they burn white. I have the timing set at 10 degrees before Top Dead Center. Should I switch to a different spark plug? I am currently using AC #45TS plugs gapped at .045 inch. Should I go up a size in secondary jetting? What should the timing be set at?

A: Your combination looks pretty good, except for the spark plugs.

The AC 45TS plugs are a .460-inch reach plug with a tapered seat. Your Trick Flow cylinder heads require a 3/4-inch reach plug with a gasketed seat. In other words, the plugs are not far enough into the combustion chambers.

Here are Trick Flow’s spark plug recommendations:

Keep the plug gap at .045 inch and put initial timing at 35 degrees total advance. We would stay with the carburetor jetting you have for now. Once you change the plugs, you should be able to fine-tune the 350 for the performance you want.