Distributor issues from NCRS West. Reg.

[Duke W.]

Re: Distributor issues from NCRS West. Reg.

You should be able to get a stable hot idle at about 1000-1100, and you should go through the idle mixture adjustement procedure. Then read the idle vacuum. You want at least 9". Raise the idle speed if necessary to achieve at least 9"

The window surface should be perpendicular to the vehicle centerline. A line normal to the window should be very close to centerline. Said another way the window should be pointing straight ahead.

At 2500 and above you should be reading about 50-54 degrees total timing with the vacuum can connected. A proper Delco vacuum can should be stamped "236 16". The NAPA/Echlin VC1810 (stamped B28) is functionally equivalent - 0@4", 16@8".

It sounds like you've got a lot of issues. Get your shop manuals out, read up on the distributor and follow my general instructions from the above post.

Duke

[Michael H.]

Re: Don't shoot the messenger!!!

Jack,

I know we're a long way from the original distributor subject on this but I agree with you 100% on the judging. If cars were to be judged strictly by what was in the book, it would have to be nine inches thick to cover all the items typically looked at and judged. There's a lot more to judging than just going down a list of items. The manual couldn't possibly describe all of the things that COULD be incorrect about an item or it's installation so the judge has to have the knowledge and common sense to make decisions on his own.

As far as accuracy, I know there are several incorrect items in the 63 manual and again, an experienced logical judge will judge accordingly. An example would be the style and head markings on a 63 F.I. air cleaner "S" tube mounting screw. The manual calls for the later high hex 1/4" design for late production 63 but most experienced 63 judges know that the late 1/4" screw didn't appear until early 64 production so they don't deduct for this. If this item was judged according to the manual, owners would be going home and changing to the incorrect screws.

It takes the manual AND common sense with flexibility to be a good judge.

Michael

[Duke W.]

Re: Distributor issues from NCRS West. Reg.

I'm not convinced that "201" is the "correct" vacuum can. The parts manual lists 1116163, and there would be no reason to change the service number. The OE vacuum advance spec for all '63 engines is 0@8", 16@15", and this was a common vacuum can for fifties and sixties engines. See a problem here?

The '63 SHP/FI engines only pull about 12" at 900, so the vacuum can is not "locked" at full advacne. It will "dither" varying the advance, which leads to idle instablility.

The fix is to install the 1116236 vacuum can used on SHP/FI engines beginning in '64.

I made this modification to my '63 L-76 in the late sixties and the idle quality and stability improved dramatically.

Duke

[Michael H.]

Re: Distributor issues from NCRS West. Reg.

Actually, the 201 IS the correct vac advance unit for all 63 Corvettes. It was replaced in late 64 with the 163, if I remember correctly. I agree that if the incorrect vac unit was installed, that might give the point plate a new starting position but with the correct original in place, I'm not sure what the problem is. There are a few possibilities but none that are likely. I'm still thinking about the problem on Timothy's 63 but I know I've seen a lot of this exact problem on F.I. cars.

Duke, I thought you had a 63? Your supposed to know about that "201" vac unit.

Michael

[Duke W.]

Re: Distributor issues from NCRS West. Reg.

No, you don't remember correctly, and the vacuum can will not change the orientation of the breaker plate. They all have the same "rest" position with zero applied vacuum, so regardless of the installed can, the initial timing will not change.

Yes I have a '63 L-76. I'm the original owner.

Did you read my previous post? The 163 can is the service replacement, and I believe the originally installed vacuum can on all '63 engines, even though it was not properly engineered for SHP/FI engines; '63 was the first year that vacuum advance was used on mechanical lifter cam engines and Chevrolet didn't get it right!

They corrected this in '64 with the 236 can for SHP/FI, and I recommend this can be retrofited to '63 SHP/FI if you want better idle quality and no overheating. The 163 can continued on 250/300 HP engines.

I don't know the specs of the 201 cam, but I would wager a fair sum that it is NOT "correct" for '63 engines.

There are at least a half dozen errors in the current '63 JG, beginning with the plug in the clutch cross shaft. All '63s had a zerk fitting from St. Louis. Then there is the JG coil untilization...

I submitted a letter with backup documentation nearly two years ago. Never heard anything more about it.

Duke

[Michael H.]

Re: Distributor issues from NCRS West. Reg.

Ok, I thought you said "I'm not convinced the 201 is the correct vacuum can" but I probably read it wrong.

The 201 is the correct original equipment vac adv unit but you're correct, it has little to do with it's effect on base timing but it also has nothing to do with the initial position of the distributor, other than a possible degree or two because of assy tolerances. The original problem being discussed was the fact that some distributors seem to be in the correct clock position when installed with the gear in a non correct mode and the vac adv unit has nothing to do with that. I don't know the answer to the original problem but I do know it has nothing to do with the vac adv unit.

I've had an original 201 on my 63 FI car for the last 20 years that I've owned it and never had an unstable idle or surge problem. Maybe just lucky I guess.

I agree, the manual needs a little work but it'll get there. It most of all needs accurate information submitted and it will get this.

[Duke W.]

Re: Distributor issues from NCRS West. Reg.

On what basis do you claim a 201 can is "correct" for '63 engines being as how the parts catalog calls out a 163 which is also called out for all 59-62 Corvette engines that had vacuum advance?

The '63 vacuum can specs (all engines) is 0@8", 15@15.5", and I believe you will also find this as the specified vacuum advance in the ST-12 manual.

What is the spec for the 201 can - or, if you have a Mightly Vac or equivalent, what is the start and end point for your installed 201 can.

The 201 can is not listed for any Corvette engines in the P&A catalog.

If you don't have idle stability problems it might be because the 201 can yields full vacuum advance at less than idle vacuum. This will keep the vacuum can plunger locked at full advance at idle. With the OE '63 vacuum can that does not pull the plunger to the stop at idle it will absolutely, positively guarantee you that the SHP/FI engines will not idle stably.

My L-76 idle stability was a constant problem until I installed (circa 1966) the 1964 SHP/FI 236 can that locked in full advance at 8". Once it was installed my idle problems disappeared.

The 1963 SHP/FI vacuum can - same as the base 250/300 HP engines is one of the few true "engineering errors" on these cars. It was corrected for 1964 SHP/FI engines, but Chevrolet left 1963 owners to deal with it on their own.

Duke

[Michael H.]

Re: Distributor issues from NCRS West. Reg.

If you were looking in an original 1963 printing of the parts book, you would see the 1116201 listed for all 63 Corvettes and several pass cars and some trucks with 283 and 327 engines. My May printing does indeed show the 201 and at that time, there is no such thing as a 1116163 at all. The first 1116163 was spec for the 65 model year and the 1116201 was replaced by the 1116163 in Jan of 1965. At that time, all the new 1965 parts books showed the 163 as the correct unt for 63.I don't have the 201 specs here but I should dig them out just to compare the two and see if there is a substantial difference. If you have the numbers for the 163, I'll send the numbers for the 201 so you can compare.

The 63 and early 64 7017375 F.I. vacuum advance system, as I'm sure you know, is not the same as the system for the 64-65 7017380 F.I. because the vacuum source was different. That would partially explain the change in the part number and specs for the vac adv unit for the 64-65. The new 346 cam specs would have changed it also. I have to assume the new Holley carburetor for 64 worked off the same new vacuum source as the FI unit. As I'm sure you know, the new 236 operated on a totally different system but I don't remember if it was more sensitive or less sensitive.

I'll dig out the specs on the 201 and send them to you.

Michael

[Michael H.]

Re: 201 vac adv specs

Found the numbers Duke. The 1116201 is supposed to be 0 @ 8" and 15 @ 15.5". I don't remember the numbers for the 163 but as you said, I'm sure there different. Let me know if they're substantially different.

[Duke W.]

Re: 201 vac adv specs

Okay, I believe it now. The 201 can specs you quote are the same as in the shop manual. I don't know what the 163 specs are, but they are probably very close, which is why the 163 can could have replaced the 201.

It's been said that '63 FI system have "ported" vacuum advance, so there is no vacuum advance at idle. As far as I know, all '63-'67 SHP engines whether AFB or Holley equipped have full manifold vacuum to the can under all operating condition, including idle.

My recommendation for '63 FI engines is to use a full manifold vacuum source and the 236 vacuum can that was used on '64 (except very early) and '65 FI engines.

Duke

[Michael H.]

Re: 201 vac adv specs

I should know this but I can't remember if there's vac at the can at idle on the 375 unit. I'm thinking no but I'm not sure. I believe the vac takeoff is ahead the throttle plate but just can't remember. (old age)

I'll try to dig out the spec's for the 163 unit and we can compare the numbers but that's going to have to be a project for tomorrow.

I think I remember a dramatic change in the mechanical adv from 63 to 64, at least for the FI in 64. Seemed like it was all in at a much lower rpm than 63. I suppose that had a lot to do with the new vac source for 64.

[Timothy B.]

Re: 201 vac adv specs

Michael/Duke,

Thanks for all this info. from this thread. I can't figure out why my car is like this but I'll bet there are many midyears with this same problem. I will go back into my reciepts and check the cam gear (timing chain) part # as this part may not be cut properly. I can tell you that the little dimple marks on the timing chain gears are lined up as I am very careful with things like this. What's strange is how everything lines up so nice with the distributor gear turned 180 to correct position.

I am also curious as to why a FI car would be any different than a lower HP car. The vacuum advance still has to be in the same position relative to the coil bracket and plenum. I am sure that the 201 can is correct for 1963 models but I think it is replaced by the 163 can and the specs are almost exactly the same.

Thanks again and if anyone has any suggestions as to why my distributor dosen't want the rotor tip lined with the dimple let me know because I don't think the problem is with the timing chain gears.

[Dick W.]

Re: PS

I personally do not think the "Augusta Midget" abides by "if it is not in the book, we do not judge it" I believe that there is a failure to communicate here. I have had cars judged when he was there as team leader, and have had the pleasure of judging for him.

[John H.]

Re: 201 vac adv specs

Tim -

Do you know for a fact that your cam is original? Chevrolet OEM cams were ground with a precise drawing specification that related the position of the pitch centerline of a given drive gear tooth to the dowel at the front of the cam, which was the master gage location baseline for grinding the cam. I doubt that any aftermarket/replacement non-GM cam grinders pay any attention to this particular spec at all, as the gear "only drives the distributor" and "you just turn it to set the timing"

[Patrick H.]

Re: 201 vac adv specs

John,

That's a VERY interesting fact.

It's be interesting to know if any of the major cam mfrs even pay attention to this.

Patrick