383 SBC?

[Old Buzzard]

A couple questions for anyone with the 383.
Engine is a 10:1, Edelbrock alum heads, mild cam, Holley 750, MSD dist/coil/6A box, headers.
In a 55 sedan.
4L80E trans, with lock up.
The owner is insisting on running what I consider "weird" timing values.
Seems his engine guy has told him to run timing @26* @ 3000. Lock it down, and drive it.
The owner is reporting 8-11mpg.
My observations include the ceramic coating, on the header tubes has turned dull, near the heads.
A couple plug boots are toast, etc.
[The headers were recently coated].
I've advised him that 26*, at road speeds of up to 80mph, is too low.[Engine rpm at/near 3K].
After all the background info, the ?'s
1. What are you running for initial and WOT timing?
2. At what rpm do you see max timing?

I've been doing this for a looonnng time, and totally disagree with the tune specs.:rolleyes:

[markm]

I don't know what being a 383 has to do with it, but generally speaking I would want 36 to 38 total at 3000. What cam and rear axle ratio would be nice to know as fuel mileage is not good. I am a check the plugs and change the plug wire person.

[Rick_L]

At 26°, he's giving up not only economy, but quite a bit of power. Plus he's ruined his headers.

[55 Rescue Dog]

Too much unknown to even guess. Do you have vacuum advance, and is connected to ported, or full vacuum? You must run a vacuum advance on the street. It can put the timing up into the 40+ degree range which is what you want for light throttle cruising, and fuel economy. At idle it keeps the plug temp up to help prevent fouling. Connected to full vacuum it adds a lot of advance at idle at a lower throttle plate opening. A simple vacuum gage can tell you a lot also. I always set the timing around 35 degrees mechanical with no vacuum connected which is what happens at wide open throttle, when there is no vacuum. And then tweak the base timing as needed, which seems to be in the 12 degree range. Fuel makes a difference too. I love 110 race gas, but at $8+ a gallon, I blend it since my 1970 vintage 11:1 350 LT1 can get by with a little less.

[Old Buzzard]

At 26°, he's giving up not only economy, but quite a bit of power. Plus he's ruined his headers.
This is a case of "ask for help", ignore same.
I've been over these same comments/suggestions, with the owner.
As of yesterday, he's back at it, using bogus info....:rolleyes:
Thanks all, for the replies.

[enigma57]

A bit on the generic side as to timing curve, but for a typical engine in a road car, you want 8 - 12 deg. BTDC initial timing (set with vacuum advance plugged) and a total of 34 - 36 degrees when 'all in' running the swill diluted with 10% ethanol that passes for pump gas now of days. An exception to that would be L31 Vortec heads which because of their combustion chamber shape are said only to need 32 degrees total timing. Typically, advance curve should bring timing 'all in' around 3,000 - 3,300 RPMs whether distributor has vacuum advance or is all centrifugal advance.

Locked timing is a 'race thing' and even the majority of race cars do not run locked timing. And when they do, they lock in total timing...... Not 26 degrees. See if you can get this across to him before whomever he is listening to damages his new engine!

Just shaking head,

Harry

[Old Buzzard]

"A bit on the generic side as to timing curve, but for a typical engine in a road car, you want 8 - 12 deg. BTDC initial timing (set with vacuum advance plugged) and a total of 34 - 36 degrees when 'all in' running the swill diluted with 10% ethanol that passes for pump gas now of days. An exception to that would be L31 Vortec heads which because of their combustion chamber shape are said only to need 32 degrees total timing. Typically, advance curve should bring timing 'all in' around 3,000 - 3,300 RPMs whether distributor has vacuum advance or is all centrifugal advance".
Exactly what I told the owner.
His engine builder's "suggestion" of 26* is exactly why he's having issues. [ This bogus info, leads me to wonder what else may be going on inside the engine].:rolleyes:
Your "generic" info is what I was looking for... Guess I didn't make that known, when I made the thread.

Thanks!

[markm]

I would buy the builder wants 10-12 on the wheel and 26 in the dist.

[enigma57]

Happy to help. Locked timing...... Especially 26 degrees...... Even on a race engine that will operate only in an extremely narrow RPM range is a clue that whomever the owner of this engine is listening to...... Isn't giving him sound advice. Do what you can to set him straight before he does irreparable harm to the engine. But however it goes...... Keep in mind that you can lead a horse to water, but you cannot make him drink.

Happy Motoring,

Harry

[Old Buzzard]

For sure!
"Keep in mind that you can lead a horse to water, but you cannot make him drink".
So true with this guy! :D
I'm at the point now, that I make a reply 1 time...After that, there's no more "back and forth".

[markm]

In the early 70s I bought the Chevrolet Power book at the dealer parts room, been following its plan ever since.

[Rustaddict]

For sure!
"Keep in mind that you can lead a horse to water, but you cannot make him drink".
So true with this guy! :D
I'm at the point now, that I make a reply 1 time...After that, there's no more "back and forth".

I love to bench race and talk tech in person, but see people beating their head against a wall and refusing to quit so many times because one guy gave them some bogus information or they simply don't understand what you are telling them but won't admit it that it has caused me to keep whatever I know to myself. Maybe its not the best way to be but it sure is more peaceful.