66 : 327 / 350 hp. distributor

[Jim S.]

I took my Distributor to a recomended shop for rebuilding .

Since I had read several post on this site about pinging and such, from incorrectly set up distributors , and not knowing what the "Infamous Bubba"
may have done to mine , ie. it had an after market Vaccum advance on it , I left specific instructions . "I want it set up exactly like the 66 327 / 350 hp. Corvette was originaly". I handed the front desk guy the distributor, a brand new #236 Vacuum acvance, and that message. He said to pick it up this wednesday.

I arrived there late Thursday only to be told that They were more than happy to build it anyway I wanted . They were not sure however what exactly the correct specs were. So apart from the #236 V/A ,which is the only thing I knew for sure , what should I tell them ?

If it matters , I intend to rebuild the motor as close to original as possible with a 10.5 to 1 compression ratio, correct pistons, ect . ect.

Thanks,

Jim

[Joe L.]

Re: 66 : 327 / 350 hp. distributor

Jim------

The basic specs of the GM #111156 distributor is as follows:

mechanical advance:

0 distributor degrees @ 450 distributor RPM

15 distributor degrees @ 2550 distributor RPM

vacuum advance:

inches of vacuum to start= 4"

maximum advance= 8 distributor degrees @ 8" vacuum

The above are basic specs. Folks with a distributor machine should have more complete specs and complete advance curves. If they don't, I'd be a little leery if they really know how to use the machine.

[Duke W.]

Re: 66 : 327 / 350 hp. distributor

The 236 VAC is correct, but a 12" VAC will actually do the job and have less tendency to detonate.

The OE advance curve is slow and better low end torque is available with lighter springs to quicken the curve, but too quick and it could detonate.

Establishing the best centrifugal curve is a matter or road testing, and using lighter springs until you reach the detonation limit.

Most rebuilds just involve disassembling the dist., cleaning it up, checking shaft end and side play, checking for breaker plate wobble, replenishing the upper bushing grease well and assembly.

Most DIYers can do the complete job except changing the bushings if this is required.

Taking it to a shop and telling them to "set it up stock" is a crapshoot IMO. I've seen to many distributors that were set up by "experts" and they were all wrong.

Duke

[Jim S.]

Re: 66 : 327 / 350 hp. distributor

Joe and Duke !

I fiqured one or both of you would be the ones to respond. Thanks guys !

Joe , I now have the basic stats for them to work on !

Duke , "Taking it to a shop and telling them to set it up stock is a crapshoot ..I've seen too many that were set up by experts that were all wrong ".

I know ! I've read too many post on this Forum about that very thing . Thats why I wanted the specs. Since I however , dont want to tackle it myself it sounds like I should start with the basic rebuild. Then , if I understand you correctly , perhaps ask for a few extra sets of springs for experimenting with once the car is running .

Sound like a good plan ?

Jim

[Duke W.]

Re: 66 : 327 / 350 hp. distributor

Yes. Using the OE centrifugal curve as a baseline is a good starting point. You can have the shop use different springs to create a quicker curve - say all in at 3500 instead of 5100, but make sure you they clearly document what springs create what curve.

Or you can buy a kit from the hot rod parts vendors with different springs, and use a dial back timing light to characterize them. Then road test and set up the most aggressive curve that the engine will handle without detonation.

The worse case for detonation is a hot summer day.

Being as how your distributor provides 30 max. centrifugal run the initial timing at 6-8 for all spring combinations. This will yield 36-38 max centrifugal. Then is just a matter of getting it in as quickly as possible with detonation being the limiting factor on how quick it can be.

Duke

[Joe C.]

Re: 66 : 327 / 350 hp. distributor

Jim,

Either invest in a dial-back timing light, or install a degree tape on your harmonic balancer. It's not rocket science to "set it up to spec", as long as you know what that is. The best, and probably only way to check the distributor off-the-car, is with an ole' fashion' Sun Distributor machine. There are very few of those around, anymore. Without it, or something similar, it is indeed, a "crap shoot". So, you're much better off doing it yourself, "in-situ". By the way, you should tailor it to be more aggressive than spec......as long as it doesn't detonate, the more and faster-in advance, the better.

Joe

PS: you can use the good ole equation: pi x balancer diameter/360
to determine each degree demarcation on a homemade balancer tape. OR You can pop for about 5 bucks and buy a real nice one at your local speed shop. Tell ya what I did. I photocopied it into my computer, so I can make as many as I need (wanna buy one......mine's for an 8" diameter balancer ) I then "permenently" installed the original on my balancer, and "laminated" it with clear "Scotch" tape.

[Mike M.]

Re: 66 : 327 / 350 hp. distributor

Where do you buy the springs? I've looked a couple times and no luck. Mike

[Joe C.]

Re: 66 : 327 / 350 hp. distributor

Mike,

Speed shop is probably your best bet. They usually have "Accel" , "Mr.Gasket" etc.
distributor spring sets in "bubble packs". Usually 2-4 different pairs per set. LICS also sells a 2-pair spring package. I used the softer "hi-perf" springs with good results. They are more aggressive than stock, but the engine handles the advance with no deonation.

Joe

[Jim S.]

Re: 66 : 327 / 350 hp. distributor

joe,

I would like to place an order for two ! Do you include the tape , and how does that judge at an NCRS event ?

Seriously though , good point !

As always , Thanks again to all for some great feedback .

Jim

[Duke W.]

Re: 66 : 327 / 350 hp. distributor

Two readily available from hot rod parts vendors distributor curve kits are Mr. Gasket 925A and Moroso 72310. There are probably others. These kits include three sets of springs, weights, and a limit bushing. There are reports that the weight pivot holes wear rapidly because they are not hardened, so use the original weights.

The springs do not have to be used in matching pairs, but avoid using one very heavy and one very light spring.

End play shim kits are also available - Mr. Gasket 2820 (2-010", 1-.020", 1-.050") and Moroso 26140 (2-.010", 2-020", 1-.053")

Shim and dress thick shims as required to achieve .001-.007" end play, and I prefer the lower end of the scale right down to .002-.003".

This data is all off the internet from the Mr. Gasket and Moroso online catalogs.

Duke