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Discussion Starter · #1 · (Edited)
I recently had a machine shop in OKC rebuild my 350 small block for my 1936 Chevy streetrod. They chose Speed Pro CS-1014R Camshaft for this application. Engine rebuild was non-eventful as well as re-installation. The engine parts additional info is this:
GM Factory HEI ignition
Hydraulic Lifters
Engine bored .20 over.
Edelbrock Performer Air Gap 7501 manifold
Holley 4160 .600 CFM Carb.
Chevy 1969 performance '041-x' .194 cylinder heads
ceramic headers attached to 2.5" pipe, and excelerator mufflers

Issue is this. at idle, the timing is at 12deg. at excelleration the timing advances to 56 deg. which I feel is way too much. The mechanic at the shop states it must be a HEI distributor issue and that the distributor needs to be modified (recurve kit) to bring the advance down to where it needs to be. Vacuum for HEI advance is coming off of the intake manifold. Should the vacuum advance be moved to a timed port on the carb, or is this possibly an cam/crank timing issue or is this truly a issue with the standard chevy HEI? can any one help with possible diagnosis. Thanks, Robert in OKC.
 

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It's a common issue with Smog era HEI's, they were set up for very low initial advance settings(0-4°) on the crank at idle, and then add a lot with rpm on those slumbering low performance 70's engines.

You were checking the mechanical advance with the vacuum disconnected from the distributor, right?? Base timing setting(initial advance) and total mechanical advance are always checked with vacuum off the distributor.

Low 50°s advance with vacuum advance connected to manifold and checked at 3000 steady rpm would be normal for a stock distributor. Should be no more than 36-38° Total from just the mechanical advance, then 12-16° added by vacuum to improve mileage.

It may/likely needs a recurve and to have the total amount it adds limited with a stop screw or shortened travel slot.

Will likely need an adjustable vacuum advance can also. This kit will take care of the vacuum side and the mechanical springs, then you just need to limit the mechanical advance slot or add a stop screw. Crane Cams #99600-1 :http://www.cranecams.com/333.pdf

Here is HEI info from our Crankshaft Coalition Wiki at the top of the page, Section 15 will be of interest to you : http://www.crankshaftcoalition.com/...g_or_locking_the_mechanical_advance_mechanism.

You may also be facing worn out holes in the advance weights and worn out pivot pins adding to the too much advance problem, if so you would be farther ahead to just get a new performance replacement HEI.
 

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HEI advance

For the last few years I have been purchasing the Summit HEI's. They are about $90.00. I have had no issues and they work great in numerous SBC 355's and BBC 461's. I have had no issues. For the money, it's not worth the headaches. I have used some of the cheap chinese made HEI's but have had problems with the top plate that the advance mechanism mounts to being pressed on and moving on the shaft causing missfiring. The Chinese made HEI has a machined shiny housing. The summit HEI's have a cast housing appearance and look like they are a stock GM made distributor. I have a Summit HEI in one vehicle since 1996 with no problems. Just my opinion, from experience.
 

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... The Chinese made HEI has a machined shiny housing. The summit HEI's have a cast housing appearance and look like they are a stock GM made distributor. I have a Summit HEI in one vehicle since 1996 with no problems. Just my opinion, from experience.
I've seen that shiny plating flake off of those Chinese distributor and it only flakes off on the inside of the motor. I really don't want pieces of chrome or whatever floating around in my oil.
 

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retard it

I would retard the timing 2-4 degrees and also check your idle speed(750-850), you may need a adjustable vacuum advance canister as mentioned before, and recurve mechanical advance. Might be easier to buy a new distriburtor with those options already installed. As mentioned before most SBCs respond well to total timing at 3000 rpm of 36-38 degrees. Some even respond better to lower say 32 -34 total degrees.
 

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Discussion Starter · #6 ·
Thanks to all of you with your comments and ideas. This is my first occasion to have a distributor problem as such. I never imagined that changing from the total stock cam to the Speed-Pro CS-1014R would insert this new issue with timing. It's been a learning experience, that I hope to be able to pass on to other hot-rodder fans such as myself. Thanks again. wrench up, get dirty, and have fun doing it...
 

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I also built a 360(.060 over 350) with a CS1014R Speed-Pro cam and about the same parts that you have in your truck and it developed a timing issue, too much advance! My 72 Chev. truck has an Excel HEI distributor that has an adjustable vacuum advance and along with a few advance spring changes( I had to play with a couple different combinations) we finally reined in the timing advance issue! Good old try it and test it see if it works! the only other thing is base timing and idle, on this motor so far it's 0 deg @ 650rpm, so far starts good, runs good, launches good, Sounds Great, turns a lot of heads, Great Street Motor not done yet got a lot more to do to the old girl and we( my son and a good friend) should have a Sweet 72 Cheyene! I hope this will shed some light on what to try, Good Luck Old School is where it's At!!!
 
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