Runs Like Crap

[ManniB]

Forgive my ignorance, but what do you mean by "have it all in" by a certain RPM? I wouldn't think the advance changes with revolutions, does it? Just trying to learn all I can...

Steve,

mechanical advance is the sum of the initial static advance which you set with your timing light by rotating the distributor and the centrifugal advance which is controlled by your engines rpm.

Initial advance is constant over the rpm range. The centrifugal advance is zero below a certain rpm and starts kicking in usualy at or slightly above idle (typically 500-600 rpm). While rpm increases, the amount of centrifugal advance also increases, reaching its maximum at something like 2300-2800 rpm. That is the point of maximum mechanical advance when it is said to be all in.

- Manfred

 

[sm3570]

Forgive my ignorance, but what do you mean by "have it all in" by a certain RPM? I wouldn't think the advance changes with revolutions, does it? Just trying to learn all I can...

Steve,

mechanical advance is the sum of the initial static advance which you set with your timing light by rotating the distributor and the centrifugal advance which is controlled by your engines rpm.

Initial advance is constant over the rpm range. The centrifugal advance is zero below a certain rpm and starts kicking in usualy at or slightly above idle (typically 500-600 rpm). While rpm increases, the amount of centrifugal advance also increases, reaching its maximum at something like 2300-2800 rpm. That is the point of maximum mechanical advance when it is said to be all in.

- Manfred

Thanks Manfred, good info and now it makes sense! So to elaborate on that, with more advance generally providing better performance that is the reason why the "power band" is typically at that higher RPM range?

 

[Don65Stang]

Good info guys! I like timing via the vacuum gauge but I didn't know the rest of the story. Excellent!

 

[FastE]

FastE, If I remember your set up it is a factory dual diaphragm distributor with pertronix. Set both initial and total mechanical with vacuum line disconnected and plugged. With your gear I'd have it all in by 2600-2800 RPM. Chuck

Thanks Chuck! That was the answer I was looking for. I am running a Mallory Unilite with the vacum advance. I am starting to get the car back to running again.I did the timing with the vacum gauge and picked up a wicked surge at part throttle. I went back to the light, and the car will not Idle below about 10 degr. intial. When I get home this afternoon I am going to go back and do all af my base line timing again. I may have to go into the distributer and back off on how much it is advancing. I may have too much. You don't want more than about 38 total with good gas right? With the temperature finally getting better, I am going to try and go to the track tonight.

 

[c9zx]

FastE, It seems either I need more memory or better retrieval code to keep the parts you are using straight. It shouldn't hardly run at less than 10 degrees initial even with the stock cam (what cam is in it?) Try initial at 16 degrees BTDC with total mechanical advance being 36. There are a lot of variables at work here but, 20 initial and 38 total would be the max I'd consider. Most of the clevelands with Ford iron heads seem to like 34 for max HP and 36 for max torque (mostly determined by the combustion chamber design). The vacuum advance is a wild card. You'll just have do trial and error adjustments to get max benefit (idle quality, mileage) and no "ping" on the street. Let me know how it does at the track. Chuck

 

[FastE]

It is funny you said that about the intial timing.This is my first closed chamber motor.My other Clevelands were open chamber CJ's. They loved to run right at 20 degr. + or -. The service manual says stock 6B ! I just ASSumed that the closed chamber motors could not run that mutch initial due to the compression. I am running a Comp 270 Magnum cam.The specs are,

270 duration

519 lift

intake centerline 106 lobe seperation 110

exhaust closes 21 ATDC

opens 69 BBDC

INTAKE opens 29 BTDC

closes 61 abdc

The card shows 1800- 5800 RPM.

I really did not put enough cam in the car for what I am doing now.It was OK when I was just ideling around town. It really falls off quick after about 5000,not good for those big ole heads. Its a hydrolic cam that almost sounds like a solid.That concerned me at first but Hemikiller said he had run this cam before and they are noise. I am also runing the matching springs retainers,single groove valves,Crane Gold roller rockers. I am going to keep at it.

 

[c9zx]

It is funny you said that about the intial timing.This is my first closed chamber motor.My other Clevelands were open chamber CJ's. They loved to run right at 20 degr. + or -. The service manual says stock 6B ! I just ASSumed that the closed chamber motors could not run that mutch initial due to the compression. I am running a Comp 270 Magnum cam.The specs are,

270 duration

519 lift

intake centerline 106 lobe seperation 110

exhaust closes 21 ATDC

opens 69 BBDC

INTAKE opens 29 BTDC

closes 61 abdc

The card shows 1800- 5800 RPM.

I really did not put enough cam in the car for what I am doing now.It was OK when I was just ideling around town. It really falls off quick after about 5000,not good for those big ole heads. Its a hydrolic cam that almost sounds like a solid.That concerned me at first but Hemikiller said he had run this cam before and they are noise. I am also runing the matching springs retainers,single groove valves,Crane Gold roller rockers. I am going to keep at it.

The cam you have is conservative. Probably better suited to a 351C 2V head due to the Exh/Int ratios of the two heads. The CJ cam was 270/290 Adv.Dur .481/.490 Lift. I don't remember the LSA but it was wide (113/114). how much compression do you have in the current engine? Chuck

 

[JimNiki]

guys, I've read this whole thread ...

Tuning mine has not made me a technician or a"magician"

I've had to resort to being a witch doctor!

It's what you guys say about compromising between:

driveability

performance

economy (what's that?)

hot weather

cold weather

does a full moon affect initial timing pull?

No wonder I struggle to get it perfect ...there is no perfect!

At least I don't feel so stupid now.

good thread guys ...

 

[marks73]

guys, I've read this whole thread ...

Tuning mine has not made me a technician or a"magician"

I've had to resort to being a witch doctor!

It's what you guys say about compromising between:

driveability

performance

economy (what's that?)

hot weather

cold weather

does a full moon affect initial timing pull?

No wonder I struggle to get it perfect ...there is no perfect!

At least I don't feel so stupid now.

good thread guys ...

LOL! would not be suprised about the moon comment!