Hey guys kind of bored and wanted to see what some of you more experienced boosted guys think of my tune up. I know the only real way to tell is to put it on the dyno or do street pulls and read plugs but that realistically won’t happen for a while.

Gen 1 stock bottom end SBC, stock rods pistons crank etc. Lightly ported vortec heads, good springs, small flat tappet cam and roller rockers. single plane intake, CSU 650cfm blow through carb, D1Sc procharger, longtubes 3” exhaust.

That’s all in an 81 Chevy C10 probably 3800 lbs. 3.73 gear, th350 Trans, PtC 3200 converter.

Right now I’ve got the distributor locked at 30 degrees and at 10lbs of boost it’s at 22degrees total and at 12lbs of boost it’s at 20 degrees total. Pump 93, no intercooler, no meth. Air fuel ratio is 11.8:1, rev limiter set at 5700 rpm.

Do you consider this a safe setup or more towards the aggressive side? think I’m leaving power on the table with that timing set up?

If I were to switch out the pump 93 for 110 race fuel where would you have the timing at?

Thanks guys

 

Im kinda surprised you're getting away with that much timing.

 

That’s what I was afraid of lol. I was reading up on spark plug reading all day yesterday, maybe I should just back it down another 2-3 degrees until I can find time to make some WOT runs and attempt to read plugs

 

Stock headed sbc's like timing, but with no form of charge cooling, and pump gas, I think you're asking for trouble starting where you think it needs to be. Back it down to the mid/upper teens, and creep up on it.

 

Maybe I’ve been getting lucky with it so far but it’s been on this same tune for a year now, I just honestly haven’t beaten on it much at all due to some other non related issues (vibration at speed and front end alignment). I did however make a couple WOT 1st and 2nd gear pulls yesterday and it’s still together (knock on wood). I think the only thing that’s helping cool the intake charge is the carb itself and the outside temps yesterday were 50F. Going to pull some plugs here in a bit and make sure I don’t see specs of aluminum on them lol, also will probably make a timing curve so it’s at 18degrees total at 12lbs I’d boost and try that.

 

Last year just for experimenting I would mix in some race fuel, not even sure what brand or octane it is, I know 5-6 years ago it was 100 octane unleaded but could have changed to 110 leaded.. anyway.. at a 50/50 ratio of pump 93 and this race fuel it ran fine (obviously no increase in power since I didn’t change the tune up). But at 100% race fuel it would misfire at WOT like it didn’t have enough timing in it to ignite the fuel.

 

There's a good chance it may want more timing than you're at currently, but if you guess, and guess wrong, bad things happen. Also, quick 1st, or 2nd gear pulls may not show an issue like a long high gear pull.

 

Yeah, I know that’s why I’ve been scared to do a long high gear pull so far lol. I guess the smart thing to do is back off the timing a few and buy a fresh set of plugs and find a place to do a long pull and then attempt to read plugs right after the pull. Hopefully I’ll be able to get a clear reading on the ground strap to see if it wants more or less ignition

 

Smarter thing is to do it at the track. Safe, and mph gains/loss.

 

True, I will to try and get to the local track in the next month or so. I just pulled all 8 plugs just to have a look... didn’t see anything majorly concerning to me, but I am new at the plug reading thing. Saw one plug that possibly could have had 3-4 specs of aluminum on it but also could have just been debris from me handling it. Also saw #1 cylinder looked like the ground strap was being eaten away (porous & corroded looking) but I’m thinking it was some type of deposits on the metal of the ground strap as 95% of it came off with a wire wheel and brake clean.
See pic.

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Here’s a plug after cleaning.

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1st plug is useless. 2nd plug shows safe timing but it still doesnt count. Need to use a fresh plug and shut off after hit or at the end of track.
I personally dont like going super low timing on Gen1 sbc. Keep the timing reasonable and limit your boost since you are octane limited. Motor will be happier and wont end up making a bunch of heat because of excessive low timing that is just a bandaid for shit fuel.

 

Yeah I plan to get a set of fresh plugs in the near future and pull them out after a WOT High gear pull. I also made another timing curve which is 2 degrees less than than what I had in it.. so at 12psi it would be at 18degrees timing. If it feels like power fell off I will probably put my other timing curve back in it. Unfortunately I can’t get any less boost than I have now I already have a 4.25” pulley on the blower and don’t have any larger diameter pulleys to put on it. It only sees 12psi around 5,000 rpm and up, right at the stab of the throttle it’s probably closer to 9-10. Also found a BP station right by my house carries “recreational” 93 octane... going to give it a shot, supposed to be additive and ethanol free I think