Thread: For Don Shilady

Tweet

HOW TO SET UP (spring + bushing) in MSD distributor for the street?

I'm back, just getting the roadster ready for summer. Actually I ended up teaching as a replacement for a colleague who was seriously ill (passed away a month ago) from November, 2016 through Spring, Summer and Fall of 2017. I did manage to attend a local Friday night meet a few times in the Summer but no long trips. Over the summer the starter began to make a noise more frequently but I let the car sit in the garage over the cold months. Finally the THIRD starter in three years made it very difficult to start so now in the Spring of 2018 I took the car to my favorite shop for a Spring tuneup. It turns out that this 3rd starter was seriously cracked at the gear end. Now for the question. I am mostly sure these three starters all failed due to engine kick back and the engine backfired because the initial timing was too advanced. The distributor is an MSD unit with what looks like L13 on the side. An MSD salesman said all the MSD distributors have the same weights and spring set. He also said Drag racers have a unit which keeps the advance low to start the engine but then the advance is set as high as 42 degrees total for racing. My otherwise excellent shop foreman says the distributor just came ready to install for a street engine and he really is a super mechanic but he also races an aluminum block drag car so I think he may have set the spring too weak. So I ordered a set of six (6) springs and six (6) bushings for the distributor from JEGS. This offers 6x6=36 possibilities for the springs and bushings so I need to learn how to set up the distributor so the engine will start without destroying the starter again and then have enough total advance to get good performance. The cam in the SBC 350 is a very mild grind about 398/410 with 1.5 rocker ratios, shorty headers and a Preformer RPM intake (I know a PES would be better) with an Edelbrock 1406 4-barrel so I would guess I need a strong spring like #5 (?) with a bushing allowing about 34 degrees total like #? Is this a total trial-and-error process or can I do this with a timing light? MY MAIN GOAL is to have a car with a starter that will last for several years of less than 2000 miles/year. I should mention that I am also on my third flexplate but it survived this last starter because it is an expensive billet plate and in spite of a severe disagreement with the starter no gear teeth were damaged on the flexplate. Soooo, How do I pick out a (spring+ bushing) to prevent kick back when starting the engine?

Don Shillady
Retired Scientist/teen rodder

Hi Don, it's good to see you here again. Been awhile I'd say... 8-)

I don't know if your using a chart from MSD.. but I thought the had a write-up saying which springs and weight would allow you to dial in the desired setup.
You can use your timing light and a tach-o-meter to verify the settings. If you know of someone local who has a distributor machine they can do the setup on their machine and give it back to you all dialed in. Not to many shops have them anymore.. kinda like the dinosaurs..

Thanks 34_40,

I was able to print out the chart from MSD.

Don Shillady
Retired Scientist/teen rodder

Originally Posted by Don Shillady

Thanks 34_40,

I was able to print out the chart from MSD.

Don Shillady
Retired Scientist/teen rodder

Sounds like you're good to go! We used to play with mixing the springs and weights to get the settings in between what was intended. It didn't amount to much but it was all good fun! I just saw a Sun distributor machine on Craigslist local to me and figured I should buy it.. then reality smacked me in the head, right between the eyes! Everything I own is electronic now.

Expensive Education

My shop mechanic (Bruce Orlandi of Performance Transmissions, Ashland Va) swears he has the correct spring in the "Big End" electronic distributor sold by MSD but I ordered the correct set of springs just in case I need a different spring. However after three (!) flex plates and three starters in five years he has found the problem but perhaps not the solution. The distributor shaft allows engine gear thrust to gradually advance the timing! I have never seen/heard of this before but it fits the facts. After each of the previous (expensive) repairs of a destroyed starter and/or flex plate the car started easily for about two months and then gradually increased kickback. I never dreamed the advance setting would wander and in fact you cannot rotate it by hand. Apparently vibration and the natural tendency of the cam gear link gradually increases the advance until the engine kicks back enough to destroy the starter. Now I have a very expensive competition starter with three bolts and a billet flex plate. This last time the starter broke but there was no damage to the billet flex plate. Sooooo, How can I improve the hold down clamp to make sure the distributor shaft does not turn to advance the ignition? The only answer here at present is to mark the position of the shaft (now set at 10 degrees initial with a maximum of 28 additional degrees when running) and check it frequently, maybe every week and set it back to initial the 10 degree mark.

Don Shillady
Retired Scientist/teer rodder

Don, your explanation doesn't make sense to me unless you've got bad bearings, a bent shaft or something else that's putting resistance in the rotation of the distributor shaft relative to the distributor housing. If the housing, bearings, and shaft are in good working order, the shaft spins in the housing with very little resistance, and thus the shaft puts virtually zero rotational force on the housing. There's just nothing there to make the housing "creep" on the block, and it doesn't matter how much vibration it sees, which on your engine should again be virtually zero. It just doesn't compute that your distributor housing is moving in the block because of gear forces. There is just no way for those forces to affect the housing, seems to me, unless you've got bigger problems with that distributor.
What I did experience was that on my SBF (yes, Ford, and I know your's is Chevy) my distributor housing was quite tight in the bore on the intake and I failed to note that when I stabbed the distributor the housing was slightly raised, not firmly seated against the intake surface. When I set my timing to the base 10BTDC it was precise, UNTIL I tightened the hold down, which pushed the distributor down about 1/16" to 3/32" and advanced my timing three or four degrees due to the helical cut of the gears. I felt really, really foolish when I realized the source of my timing problems.

Don, what motor are you running?

I'm not up to much on the later stuff, but it seems several years ago a friend of mine mentioned to me that they had a new (Camaro ?) that kept coming back into the dealer he worked at and the timing was all over the place. They finally figured out that the factory had left out the cam button and it was allowing the cam to go back and forth changing the timing.


.

Mike P,

That is very interesting! My engine is a rebuilt 1976 L-48 two bolt 350. At only .030 overbore some builders tell me the block is like gold. The person who built the engine is now deceased but he built a lot of engines for circle-track racers. He shaved the stock heads, gave them a three angle valve job and cleaned out the exhaust ports. I will investigate the cam button theory. The short block was rebuilt with a 0.010 grind on the crank and used a hypereutectic set of pistons. The cam is the same as the stock 1976 Z28 with Z28 springs. The heads were cced to get a 9:1 CR. This is a very mild engine but the fiberglass roadster body is light enough for good street performance, at least for me! Actually the initial acceleration is probably due to the low gear in the 700R4 trans although the 3.55 rear takes away some acceleration Thanks for the idea.

Don Shillady
Retired Scientist/teen roder

I believe I would seriously consider finding a good stock HEI dizzy and throw that MSD in the trash. My 76 Vette has the same basic engine that you're dealing with and nowhere near all the problems and my starer is a combination of a 400 and 350 starter with a new solenoid. I would also look for a second opinion as it appears to me that your current "mechanic" regards you as a cash cow.

NFTDAY,

You are correct, but i was just 80 and have found that rolling around on the floor of an unheated garage in the winter leads to severe sinus infections, I guess from floor dust and low temperatures. Thus I have found Mr. Orlandi who now knows almost everything about my car. I have a brand new HEI dizzy still in the box but the diameter would require cutting more out of the 'glass "firewall" and I already had to clearance the trans tunnel before it was painted. Although taking off the electric water pump and timing chain gear will probably be another cash cow event I will have to do that if it starts to kick back again. Maybe checking the cam button presence or not offers the possibility of finally solving this problem. Thanks for your comments.

Don Shillady
Rerired Scientist/teen rodder (a long time ago!)

Are you running a gear drive? Why electric water pump? MSD's claim to fame was "perfecting" capacitive discharge ignition which I put in the same class as Sony's one gun picture tube.

Don,
What Mike said is that without the cam button the timing was "...all over the place." This means that as the cam shifted fore & aft, the cut of the gears shifted the timing. It does NOT say that it caused the distributor housing to move relative to the block, changing the timing. I'll say it again, if your distributor housing is moving on the block, you've got a distributor problem. There shouldn't be ANY torque transfer from shaft to housing.

JMHO, a starter can not spin the motor fast enough to advance the mechanical advance weights and cause kick back, thus ruling out distributor springs as a culprit. Also, if your distributor’s bearings are stiff enough to allow the housing to move from rotational trust your cam gear would have failed way before four staters and flex plates. So if the intial timing (should be checking total timing too) is creeping up and causing kick back, logic would dictate that something is going on inside the distributor, such as a sticking or damaged vacuum advance plate….

Hello again,

The possibility of a missing cam button makes better sense than the shifting distributor shaft. I can see that if the cam shifted fore an aft to allow allow the distributor to skip at least one tooth that would make a big difference in the timing. I guess I will have to wait a month or so for good weather to take off that water pump and front cover. How long do those nylon buttons last compared to an aluminum button? Of course I originally tried to set up a mild rebuilt engine with NAPA accessories keeping everything almost stock but I had to find a distributor small enough to clear my firewall and started out with a 327 points distributor with an electronic kit but that wore out fast and yes my mechanic does tend to put in expensive racing components and I did switch from the first guy who took off my belt water pump and installed two electric fans and the electric water pump. Each time I thought it would get better. My original set up did work and kept the engine cool in February but not in July so it has all been a continuing expensive learning process. I would note to NFTDAY that finding stock parts designed for the car is easier for an existing Corvette than to adapt many parts to a smaller engine compartment in the 1929 replica and make a lot of adaptations along the way. At the very least there is more opportunity to make learning mistakes along the way when you have to make adaptations as you go along. Maybe the lack of a cam "button" is the final problem but probably not even now! For what it is worth the distributor that does fit my firewall is from "Big End" that is only a MSD product because Big End was absorbed by MSD, it is electronic and smaller than the HEI unit.

Don Shillady
Retired Scientist/teen rodder

Sometimes the motor doth protest too much (starting ). It doesn't necessarily mean the timing is too far advanced, just too far advanced to start.

HUH?

What I'm saying is the problem might be the engine at startup is turning too slow for the base timing. Install a kill switch on the ignition, and "fire it off" only after the engine is spinning. You can even use oil pressure as your signal to flip the switch and start the beast.