Initial timing too advanced

[Mr Roadrunner]

My father in law recently purchased a 68 Road Runner 383 auto. 3:23 gear. Overall nice car. It ran good enough for a 2 hour drive home, but needed some tuning. Long story short, this engine wants 30 degrees initial timing. It has a lumpy cam, but the only specs I have are .471 lift intake and .489 exhaust. I had the intake off, and checked lift with a dial indicator. This is assuming a 1.5 ratio rocker arm. Engine pulls around 11” vacuum at 750 rpm idle. I initially had a mopar performance distributor in it, but just changed out to a MSD ready to run. This engine runs best with 26-30 degrees initial advance. Starts fine hot. I checked the timing marks with a piston stop, and marks are spot on. I then installed a timing tape, as initial timing is off tab on factory marks. I am fighting with this because setting initial this high, the engine starts breaking up at higher RPM. I know very little about this engine build, but I am wondering if the cam being installed advanced/retarded too much could cause this issue?

 

[Don Frelier]

What is your total advance?
Is the distributor locked out?
It may need to be or you've got to really limit your mechanical advance.

 

[RemCharger]

Dial it back to 8 degrees mechanical advance in the distributor.

 

[Mr Roadrunner]

I can adjust to get total to around 36 degrees I think. I can’t see how it would need this much initial.

 

[turbine68rt]

You could always put the MP distrib back in and use an FBO limiter plate to avoid too much total timing. Do you have a timing light with adjustable advance?

 

[moparedtn]

When you say the engine "wants" or "runs best" at a certain initial timing, by what means are
you determining that?
Highest vacuum reading? Highest RPM?

 

[Mr Roadrunner]

Both

 

[Mr Roadrunner]

The mopar distributor was the same, except timing wasn’t stable “ in the curve”. Was jumping around 10 Degrees until it hit max advance.

 

[PurpleBeeper]

I think these guys are right. Just check (& maybe limit) your total timing. Your vacuum isn't the greatest and you said the cam is lumpy....so, maybe it does need that much initial timing. What if you idle it at 900-1000 rpm?

 

[65-440]

I agree, you need to figure out how much mechanical advance you have. At 30 initial who the hell knows how high it is at 3k rpm! The 340 in my dart really like 24 initial but it stops at 36 total !

 

[383man]

For the cam specs if accurate that sounds like a lot of initial no matter what the mech advance. What balancer is on the crank ? I have seen stock ones slip and have TDC off. For a reference my cam is 264 & 270 and .585 & .592 lift with a 110 LSA. Its in my eng on a 106 ICL. Mine likes around 24 degrees initial and I run 36 total. Your eng should not need that much initial but make sure the balancer is true and has not slipped which will give you unaccurate timing readings. Ron

 

[Nate S]

Seems like a lot of initial timing, cam doesn’t seem that big. Might want to check cam CL. Sounds like it might be retarded a bit.

 

[Mr Roadrunner]

I started with a new MP distributor. I set total timing at 36 degrees and using a FBO limiting plate, the initial was 26 degrees. It came with 1 spring on 1 of the advance weights, and would hit total advance around 1750 rpm. Also as stated above, the timing was jumping around as much as 10 degrees while it was advancing, and only was stable after hitting full advance. I could not find springs to slow down the advance, and I had an off idle stumble that I could not work out. So I started over and bought an MSD ready to run, and installed it. I started the engine and set the timing by ear. I advanced the timing until I noticed a change in the engine, and then retarded it until it smoothed back out. I then put a timing light on it, and found my initial now at 30 degrees. I checked the balancer with a piston stop. It hasn't slipped. I agree that this engine should not need this much initial. I know I can limit the timing to get the total where it needs to be, but this is pointless if the cam is installed wrong. I am looking for experience as to why an engine with a mild cam would want this much initial. The performance of this engine sucks!! No power. As Nate S said I am suspecting an assembly error with the cam, and was looking for experience with this. I have always heard of a cam being installed a tooth off on the timing set. I would love to hear if an engine would even run this way, and what kind of symptoms it would have. I also know that several of the new timing sets have multiple keyway bottom sprockets and can be pretty confusing to assemble. The only way to know for sure, is to tear into the engine and check things out, but this is a lot of work for "volunteer/free" labor. I am looking for experience as to what could be wrong to back up my suspicions. Also I don't have a cam card, so unless I can identify the cam with it removed, I could not check centerline. I have checked online for a cam with my lift specs, and have found nothing matching yet.

 

[dadeo]

Well I got to ask, are you running vacuum advance and if so are you checking timing with the vacuum advance plugged? Assuming you're not the best way to check to see if your timing chain was put on wrong without taking everything apart, cam retarded would be to do a compression check on one cylinder because the intake closing that late will drop your compression reading down quite a bit explaining the loss of power.
Andy

 

[65-440]

Don't take this the wrong way but pulling the timing cover to verify the installation isn't exactly hard work nor an all day job. Drain the coolant and pull the water pump and crank pulley, easy ! I think at this point it's pretty much your next step, get it over with.

 

[RemCharger]

Lumpy cams+low compression+383= hard to keep running at idle+ shitty power brakes. I have a 10 to one 383 with an XE284,, and it needs the dist advance severely limited. I havent done it because I barely drive it anymore. Its a two-footer, which i can live with.

 

[hunt2elk]

I started with a new MP distributor. I set total timing at 36 degrees and using a FBO limiting plate, the initial was 26 degrees. It came with 1 spring on 1 of the advance weights, and would hit total advance around 1750 rpm. Also as stated above, the timing was jumping around as much as 10 degrees while it was advancing, and only was stable after hitting full advance.

I would think with only 1 spring, that's what was causing your timing jumping around until it was at full advance.

 

[Nate S]

You don’t need to tear into it to check cam CL. Just pop off the drivers side valve cover and use a dial indicator. Degree wheel is nice but I’ve done this successfully with a sharpie and a tape measure. Part of the job is already done now that you know the timing mark on the balancer is correct.

 

[1967coronet]

I agree with the guys wanting you to ck. The balancer, got to get #1 up to tdc , check your mark and cover tab.
Just me but I would go back to the mopar dizzy with a 9.5 plate in it and both springs.
Vaccum seems pretty low mabey chase around the intake and under with a propane bottle and piece of hose ?

 

[Mr Roadrunner]

I have checked timing marks. Used a piston stop. Confident spark timing is reading correctly. No vacuum leaks that I can find using carb/choke cleaner. We have decided to pull engine. The steering box is leaking, small oil leak from engine also. He wants to inspect engine internals, and I will check valve timing while it is on a stand if I can identify the cam.