TI distributor advance curve

[Jerry G.]

Re: TI distributor advance curve

I appreciate that Mike. I do not have a part number band on the distributor. It came with the race car and 20 years ago the guy i bought the car from told me it was an L-88 distributor. It does appear to have a partial not double oil groove. I would be happy to send you detailed photos of any portion of the distributor to help ID the unit. My use is strictly road racing. The motor is a racing 327. Soon to be with Rochester fuel injection. Calculated 14/1 compression ratio. Highly modified original 461 heads. Headers, 14 quart wet sump oiling system etc..etc. my rough logic is to get all the advance in around 3000 RPM and have a timing at lower RPM that will allow it to idle. This may be the wrong approach. No real drivability issue. It's either WOT or on the brakes. There is some modulation in the corners but the RPM rarely falls below 3500 RPM.

[Mike Z.]

Re: TI distributor advance curve

Jerry-sounds like a wild ride-we got to stay young somehow, and you maybe onto something.
Send me pics; top, side and lower portions-couple of each from different angles and I can probably nail it down for you. Send them to mike_zamora@hotmail.com, or attach them in a discussion response.
On the curve-sounds like the idle & max advance info I gave you may just be enough to do what you need. So, if you have an advance feature on your timing light-you are golden, or a degree tape on the balancer. Remember, contrary to some other's comments-these units will keep advancing to about 5500-6000RPM engine speed-based on my "Sun" testing. You are, I am sure running racing fuel (with 14:1 C/R), but you still probably will see best performance at no more than 40-42 degrees total at 5000+ ft above sea level (Denver)-back off to 36-38 at sea level.
I am a little concerned about your comment regarding the partial groove housing-sounds like an early BB housing-do not, read do not under any circumstances, use that type of housing in a "mouse" motor-the partial groove on the lower housing, just above the camshaft gear is/was intended for 65-67 BB only oiling issues. I will be able to tell from the pics, but if you are curious, check out some of my listings on E-Bay-there are several pictures of what I am talking about in the 65-67BB model listings. My handle is: MichaelZ505.

Mike

[Jerry G.]

Re: TI distributor advance curve

You've got mail. Your welcome to share all photos with anyone and everyone on the board. I'm technically challanged or I would post them here. Jerry

[Clem Z.]

Re: TI distributor advance curve

Jerry-sounds like a wild ride-we got to stay young somehow, and you maybe onto something.
Send me pics; top, side and lower portions-couple of each from different angles and I can probably nail it down for you. Send them to mike_zamora@hotmail.com, or attach them in a discussion response.
On the curve-sounds like the idle & max advance info I gave you may just be enough to do what you need. So, if you have an advance feature on your timing light-you are golden, or a degree tape on the balancer. Remember, contrary to some other's comments-these units will keep advancing to about 5500-6000RPM engine speed-based on my "Sun" testing. You are, I am sure running racing fuel (with 14:1 C/R), but you still probably will see best performance at no more than 40-42 degrees total at 5000+ ft above sea level (Denver)-back off to 36-38 at sea level.
I am a little concerned about your comment regarding the partial groove housing-sounds like an early BB housing-do not, read do not under any circumstances, use that type of housing in a "mouse" motor-the partial groove on the lower housing, just above the camshaft gear is/was intended for 65-67 BB only oiling issues. I will be able to tell from the pics, but if you are curious, check out some of my listings on E-Bay-there are several pictures of what I am talking about in the 65-67BB model listings. My handle is: MichaelZ505.

Mike

the original TI setup with a distributors with original weighs and springs would retard the timing abour 2 degrees after 6000 engine RPM. were they designed that way i don't know but you could see it happen using a timing light on the engine

[Jerry G.]

Re: TI distributor advance curve

Mike has identified it as a 263 distributor. Thanks for your help. Jerry

[Paul Y.]

Re: TI distributor advance curve

Jerry, Lars up in Lafayette has a Sun Distributor machine and is a genius with advance maps and specs. I also have a manometer to calibrate your injector if you need to. If you want his contact information I can get it to you. My # is 303-520-6363. Paul

[Mike Z.]

Re: TI distributor advance curve

Jerry, just to share with the crowd. The pics you sent me were of a #1111263 with the partial groove lower housing (you might post your pics #1, #2 as a minimum), which by all accounts was designed/intended for early (65-67) BB only. These units were available "over-the-counter" through the Performance Catalog only, never as an OEM unit. They were intended as a racing distributor, but were never installed at the factory on any model OEM, including the L-88. It is my understanding, these distributors found their way to life through the "back-door" racing that GM had going in the late 60's, early 70's-primarily for race teams like Penske (TransAm & CanAm).
These units were available in four versions, co-incidentally all with the same part number-at least that is my experience of owning and studying these units: 1) early BB w/partial lower groove CCW rotation, 2) early BB CW-I assume for the direct cam gear drive early L-88 & ZL-1 like Penske ran in his CanAm effort, 3) later BB & all SB CCW and 4) late BB & all SB CW. They are a unique unit, because they ran bearings vs. bushings, the advance plate was fixed to the housing and did not have a provision for a vac canister, unlike the OEM L-88 units, which all used the #373 vac. I have in stock a #1 & #2 above and have had a #3 in the past--all with the same P/N on the ID band.
The unit you have Jerry, is a # 1-early BB CCW. As I mentioned to you in our direct messages, it was intended for the early BB, which had a unique oiling issue partially resolved with this unique lower distributor housing. You have indicated you have run this distributors in your SB motor for some 15 years. I would like to get the opinion of others! What is your experience or thoughts of running the partially grooved distributor in a small block motor???????????
I have recommended to have the lower groove machined to be fully grooved. I am not saying it will not run; I am saying, I believe potential oiling problems could become reality-opinions please!
Jerry, once you machine the lower groove (or not), the advance curve mapping for this unit expressed in distributor RPM (half engine speed) is:
450= 0-2 degrees, 800= 6.5-9.5, 2000= 11.5-13.5, 3000= 10.3-13.5. I would be happy to check it on my Sun Machine, or as indicated by Duke, one can possibly check it in the car, with an advance feature in a timing light or degree tape on the harmonic balancer. And, contrary to what others have said; my Sun machine tells me, these units advance clear up 6000RPM engine speed, so be careful!
Good luck with the racing!

Mike Zamora

[Duke W.]

Re: TI distributor advance curve

Assuming this dist. does not have a provison for the FI pump drive, how can it be run in Jerry's engine, which he says is going to have a FI system?

Duke

[William C.]

Re: TI distributor advance curve

Given the intended use of this engine, a set of the lightweight "boy racer" springs might be all that is needed to get into the more "race friendly" timing map.

[Clem Z.]

Re: TI distributor advance curve

Assuming this dist. does not have a provison for the FI pump drive, how can it be run in Jerry's engine, which he says is going to have a FI system?

Duke

good point that never crossed my mind.

[Duke W.]

Re: TI distributor advance curve

Yeah, see - you're loosing your analytical capability, old buddy. I'm still just a kid with a razor sharp mind.

Duke

[Clem Z.]

Re: TI distributor advance curve

Yeah, see - you're loosing your analytical capability, old buddy. I'm still just a kid with a razor sharp mind.

Duke

i am not a FI guy as the price back then would have put my next new corvette out of reach

[Duke W.]

Re: TI distributor advance curve

While we're on the subject, it's always been my impression that you can convert a single point dist. to a TI (and vice versa) since both use the same housing.

The stationary pole piece/pickup coil mounts in the place and in the same manner as the breaker plate, and one would need to replace the cam assembly with a TI rotating pole piece.

Thoughts?

Duke

[Clem Z.]

Re: TI distributor advance curve

While we're on the subject, it's always been my impression that you can convert a single point dist. to a TI (and vice versa) since both use the same housing.

The stationary pole piece/pickup coil mounts in the place and in the same manner as the breaker plate, and one would need to replace the cam assembly with a TI rotating pole piece.

Thoughts?

Duke

yes you can you just need the part including the brass washer under the pole piece. i don't know the rules the racing assoc that jerry is running under BUT the TI was never used till 1964 so if jerry is racing a 63 corvette is it OK to use the TI ?

[Clem Z.]

Re: TI distributor advance curve

Jerry, just to share with the crowd. The pics you sent me were of a #1111263 with the partial groove lower housing (you might post your pics #1, #2 as a minimum), which by all accounts was designed/intended for early (65-67) BB only. These units were available "over-the-counter" through the Performance Catalog only, never as an OEM unit. They were intended as a racing distributor, but were never installed at the factory on any model OEM, including the L-88. It is my understanding, these distributors found their way to life through the "back-door" racing that GM had going in the late 60's, early 70's-primarily for race teams like Penske (TransAm & CanAm).
These units were available in four versions, co-incidentally all with the same part number-at least that is my experience of owning and studying these units: 1) early BB w/partial lower groove CCW rotation, 2) early BB CW-I assume for the direct cam gear drive early L-88 & ZL-1 like Penske ran in his CanAm effort, 3) later BB & all SB CCW and 4) late BB & all SB CW. They are a unique unit, because they ran bearings vs. bushings, the advance plate was fixed to the housing and did not have a provision for a vac canister, unlike the OEM L-88 units, which all used the #373 vac. I have in stock a #1 & #2 above and have had a #3 in the past--all with the same P/N on the ID band.
The unit you have Jerry, is a # 1-early BB CCW. As I mentioned to you in our direct messages, it was intended for the early BB, which had a unique oiling issue partially resolved with this unique lower distributor housing. You have indicated you have run this distributors in your SB motor for some 15 years. I would like to get the opinion of others! What is your experience or thoughts of running the partially grooved distributor in a small block motor???????????
I have recommended to have the lower groove machined to be fully grooved. I am not saying it will not run; I am saying, I believe potential oiling problems could become reality-opinions please!
Jerry, once you machine the lower groove (or not), the advance curve mapping for this unit expressed in distributor RPM (half engine speed) is:
450= 0-2 degrees, 800= 6.5-9.5, 2000= 11.5-13.5, 3000= 10.3-13.5. I would be happy to check it on my Sun Machine, or as indicated by Duke, one can possibly check it in the car, with an advance feature in a timing light or degree tape on the harmonic balancer. And, contrary to what others have said; my Sun machine tells me, these units advance clear up 6000RPM engine speed, so be careful!
Good luck with the racing!

Mike Zamora

the oil gallery that runs thru the dist hole in the block is offset towards the center of the engine so if the dist is installed with the grooved part facing that side of the engine you should be ok. i used the BBC ball bearing dist in SBC race engine with no problems after changing the bottom gear.