it's all in the timming

Kctom · June 10, 2004, 07:44:41 PM

Talked to Barry Grant on setting the chevy 388 c.i. engine in the 38 to work with the 750 cfm Demon carb. The carb run rich, black tail pipes but no black smoke. They want to set the timming at 18 deg.at idle. the Mallory unilite has 24 deg of advance. So will be running about 42 total at around 3000 rpm. The fellow who built the engine is about to have a fit. He wants no more than 32 total. HELP!!!!!!!!!! Will 42 deg. hurt anything? Talked to the mallory people today and they are sending me a set of black colored springs for the mech advance. won't this still give me the same 42 geg but only at a different rpm? and what about adjusting the vac. advance a little? Know very little on this subject.
TOM

SKR8PN · June 10, 2004, 08:05:32 PM

Are you fouling spark plugs? Getting fuel into the oil? Have you tried rejetting the carb? WHAT is leading you to believe the mixture is rich,BESIDES the soot in the tailpipes? I used to run 38 degrees TOTAL timing on my 440,and it was "all in" around 1800 RPM. 42 degrees sounds like a lot for a street engine,but then again,it depends on you compression ratio,camshaft,cylinder head material(aluminum or steel??) spark plug heat range,torque convertor,etc.etc.etc. If it were me,I'd try "sneaking up" on that much total timing. Might try a few degrees at a time and LISTEN very carefully for detonation. Install new spark plugs and READ them often........

tomslik · June 10, 2004, 08:23:53 PM

Quote from: "SKR8PN"Are you fouling spark plugs? Getting fuel into the oil? Have you tried rejetting the carb? WHAT is leading you to believe the mixture is rich,BESIDES the soot in the tailpipes? I used to run 38 degrees TOTAL timing on my 440,and it was "all in" around 1800 RPM. 42 degrees sounds like a lot for a street engine,but then again,it depends on you compression ratio,camshaft,cylinder head material(aluminum or steel??) spark plug heat range,torque convertor,etc.etc.etc. If it were me,I'd try "sneaking up" on that much total timing. Might try a few degrees at a time and LISTEN very carefully for detonation. Install new spark plugs and READ them often........

..and of course there's the unleaded fuel that burns black and sooty no matter what.
42 degrees at YOUR altitude?!?!
sounds like potential meltdown...

up here where there's no air 42 is a good start, ya may need more

enjenjo · June 11, 2004, 12:06:20 AM

Mallory distributors can have the total advance changed internally. There is a slot in the advance plate with a screw in it, by moving the screw in the slot, the amount of total advance can be changed.

As mentioned, 42 degrees for a small block is not really that much, depending on heads, compression, ect.

Kctom · June 11, 2004, 10:11:12 AM

Quote from: "enjenjo"Mallory distributors can have the total advance changed internally. There is a slot in the advance plate with a screw in it, by moving the screw in the slot, the amount of total advance can be changed.

As mentioned, 42 degrees for a small block is not really that much, depending on heads, compression, ect.

Frank, running world products heads 9.5 to 1 steel heads.

wisner955 · June 11, 2004, 11:04:06 AM

KCTom, I agree with your engine builder, 42 deg is too much timing (under load, no vacuum advance).

Take a look at http://members.aol.com/dvandrews/timing.htm

Paul Wisner
KC, MO

enjenjo · June 11, 2004, 11:30:45 AM

QuoteFrank, running world products heads 9.5 to 1 steel heads

Those heads generally don't require as much advance as factory heads. As suggested, sneak up on the timing a couple degrees at a time, and see what you get. With todays fuels, the sooty pipes do seem normal.

Kctom · June 11, 2004, 12:23:05 PM

Quote from: "wisner955"KCTom, I agree with your engine builder, 42 deg is too much timing (under load, no vacuum advance).

Take a look at http://members.aol.com/dvandrews/timing.htm

Paul Wisner
KC, MO

Paul, Thank you very much. This is what I was looking for. This along with all the other great guys here info, helps me alot. Just love this site.
TOM

Kctom · June 11, 2004, 07:51:21 PM

Quote from: "Kctom1"
Quote from: "wisner955"KCTom, I agree with your engine builder, 42 deg is too much timing (under load, no vacuum advance).

Take a look at http://members.aol.com/dvandrews/timing.htm

Paul Wisner
KC, MO

Paul, Thank you very much. This is what I was looking for. This along with all the other great guys here info, helps me alot. Just love this site.
TOM

Ordered a Demon 650 cfm last tues. it came today so put it on the engine. Sure made it run better.Going to a rod run tomorrow will see how it works. Dropped the timing to 12 deg. idle. Seems to like it there.
TOM

Dave · June 12, 2004, 08:00:48 PM

Quote from: "Kctom1"
Quote from: "Kctom1"
Quote from: "wisner955"KCTom, I agree with your engine builder, 42 deg is too much timing (under load, no vacuum advance).

Take a look at http://members.aol.com/dvandrews/timing.htm

Paul Wisner
KC, MO

Paul, Thank you very much. This is what I was looking for. This along with all the other great guys here info, helps me alot. Just love this site.
TOM

Ordered a Demon 650 cfm last tues. it came today so put it on the engine. Sure made it run better.Going to a rod run tomorrow will see how it works. Dropped the timing to 12 deg. idle. Seems to like it there.
TOM

Unless your running a big block with a really hot cam i think a 750 is over kill for a small block. I like the looks of the bg carbs and im thinkin but if i try one it will proly be the 525 or what ever it is for a mostly stock 350.
Dave