1967 435 vacuum reading and timing

[Mark F.]

Good Evening,

In the last year I purchased a 1967 435 convertible. 100% stock, with about every award available. I purchased it and only have run it a few times. I had to send the carbs out to be looked at due to an idling issue I had. They came back perfect, and the car now idle great. Being in MN I drove the car briefly this winter to relocate it to another facility of mine. About 20 min. Ran great. Now in July I got the car out just to exercise it a little on a 83 degree day. It ran great for about 20 min of running slowly on a back country road. All gauges looked fine. As I was pulling into my neighborhood, I noticed it starting to stumble a little. By the time I pulled it in my garage it struggle to even idle. After about an hour, I tried starting it and it would not start and labored to turn over almost like the battery was weak. I left it sit over night and in the morning tried to start it and it fired right off and idled fine.

After reading an archived thread on the NCRS site about "427 overheating" it was clear I was not the only one having this issue. The discussion in the thread circled back to the vacuum advance can on the distributor, timing advance and Hg vacuum ported or manifold. Due to how this car was campaigned and Judged all the components are 100% original including the B20 vacuum can. My questions are this: 1. The vacuum line going to my vacuum can comes directly off the bottom plate of the center carb. Is the manifold or ported? If ported I don't see a direct manifold place to hook up to. 2. Using the vacuum fitting at the bottom plate of the center carb, my engine at idle ( 800-900 rpm) pulls 5 Hg (10 cm) inches. At 3500 rpm it pulls about 17-18 Hg inches (45 cm Hg) The timing advances using the mechanical as it should. Are these vacuum readings normal?

[Stewart L.]

Re: 1967 435 vacuum reading and timing

The first thing I would check is the coil. The symptoms you describe sound like an aftermarket coil. When they heat up they can cause problems like you describe. When they cool down the next day everything is back to normal.

[Mark F.]

Re: 1967 435 vacuum reading and timing

Thanks for the reply. Yes, I have heard this same thing about the coils heating up. However, I did not hear anything about this issue being related to aftermarket coils. It has a Delco Remy coil with a Red Label on the side with the Delco Remy name along with some other words in black. With the level of judging this car has been thru, I would be surprised if the coil is aftermarket. Are you aware of the part number for the proper coil?

[Danny P.]

Re: 1967 435 vacuum reading and timing

Good Evening,

In the last year I purchased a 1967 435 convertible. 100% stock, with about every award available. I purchased it and only have run it a few times. I had to send the carbs out to be looked at due to an idling issue I had. They came back perfect, and the car now idle great. Being in MN I drove the car briefly this winter to relocate it to another facility of mine. About 20 min. Ran great. Now in July I got the car out just to exercise it a little on a 83 degree day. It ran great for about 20 min of running slowly on a back country road. All gauges looked fine. As I was pulling into my neighborhood, I noticed it starting to stumble a little. By the time I pulled it in my garage it struggle to even idle. After about an hour, I tried starting it and it would not start and labored to turn over almost like the battery was weak. I left it sit over night and in the morning tried to start it and it fired right off and idled fine.

After reading an archived thread on the NCRS site about "427 overheating" it was clear I was not the only one having this issue. The discussion in the thread circled back to the vacuum advance can on the distributor, timing advance and Hg vacuum ported or manifold. Due to how this car was campaigned and Judged all the components are 100% original including the B20 vacuum can. My questions are this: 1. The vacuum line going to my vacuum can comes directly off the bottom plate of the center carb. Is the manifold or ported? If ported I don't see a direct manifold place to hook up to. 2. Using the vacuum fitting at the bottom plate of the center carb, my engine at idle ( 800-900 rpm) pulls 5 Hg (10 cm) inches. At 3500 rpm it pulls about 17-18 Hg inches (45 cm Hg) The timing advances using the mechanical as it should. Are these vacuum readings normal?

Mark , your vacuum port is on the lower base plate by it self to the vacuum can on the dist. like the photo of my L71, vacuum gauge reading should read about 14-15" @900 i set my timming at 10 degrees, about the coil if you just install a new Delco Coil in a Delco box but there made in China, they break down and get hot at about 20 mins. of running there junk, find yourself a good used coil that you know is good and try it and see what happens , Danny

17 Original and born with Tri- Power and Dated Carburators fully factory restored to spec.jpg

[Mark F.]

Re: 1967 435 vacuum reading and timing

One correction. I had the vacuum gauge hooked up to the center carb base port. I t'd it into the choke vacuum line and at 900 rpm the vacuum is 10 hg in.

[Mark F.]

Re: 1967 435 vacuum reading and timing

Thanks Danny. Good to hear from you again. I did run the vacuum gauge off the port at the base of the center carb. That gave me 5 Hg in at 900 rpm. I then plugged that port and t'd in the choke vacuum line to the gauge and I got 9-10 Hg in. When guys on this forum are saying "direct manifold" vacuum" vs. "ported" vacuum, where are they pulling direct manifold vacuum from? And, when they refer to "port vacuum" are they referring to the port where my vacuum line connects for the vacuum advance can? As far as the coil is concerned, I'll pull it off and take a look at it. I've been over this car fairly thoroughly, and I have found no evidence of "cheaping out" anywhere. As I mentioned, it's been NCRS judged at every level, plus Bloomington Gold, Bloomington Triple Crown, Duntov Award, etc. I know that doesn't necessarily rule out everything, so I'll check the coil and see what that does. Do you know of there is a correct part number for the coil? By the way, any opinion on the OE vacuum advance B20 vs. using the B26? A thread that I review here with a guy that was having the exact same issue ultimately resolved it by going to the B26.

[Mark F.]

Re: 1967 435 vacuum reading and timing

Thanks Danny...Do you know of there is a correct part number for the coil? ...

Mark,

The GM-specified coil number is 1115263263

[Mark F.]

Re: 1967 435 vacuum reading and timing

Hi Danny,

I pulled the coil and it looks like I have a "hens tooth" as I suspected. It is the embossed 263. In your opinion, do you think it could still possibly be the coil? One thing I did notice, once it cooled down and I was able to re-start it, I checked the timing, it was way too far advanced even at idle. I pulled it back to where it should be. Maybe I should test it now with the timing back where it should be. Any thoughts?

[Stewart L.]

Re: 1967 435 vacuum reading and timing

Original coils look very similar to the reproductions. Originals have magnetic studs and the nuts take a 11/32 socket to remove. Repro have metric nuts and threads and the studs are non magnetic. That would be a quick way to check.

[Mark F.]

Re: 1967 435 vacuum reading and timing

...I pulled the coil and it looks like I have a "hens tooth" as I suspected. It is the embossed 263. In your opinion, do you think it could still possibly be the coil? One thing I did notice, once it cooled down and I was able to re-start it, I checked the timing, it was way too far advanced even at idle. I pulled it back to where it should be. Maybe I should test it now with the timing back where it should be. Any thoughts?

Be sure you have an air gap between the bottom of the coil can and the intake manifold.

IOW - you don't want those two parts touching each other - too much direct heat transfer from the intake to the coil

[Mark F.]

Re: 1967 435 vacuum reading and timing

Thanks Mark. It may have been touching, not sure. When I put it back on I will be sure to make sure their is a gap.

[Mark F.]

Re: 1967 435 vacuum reading and timing

The nuts are 11/32. Thanks for the tip!

[Gary S.]

Re: 1967 435 vacuum reading and timing

While I know very little about big blocks and can't come close to the knowledge base of these other gents, is it possible that your carb float levels are set too high? I know you had them rebuilt but the symptoms sound similar to what I had a while back on a small block. My floats were set high and flooded the engine so it wouldn't idle well. At near full throttle it ran quite well. After sitting all night, it ran well for a bit and then repeated the symptoms.

Just a thought.

Gary

[Danny P.]

Re: 1967 435 vacuum reading and timing

Mark,

The GM-specified coil number is 1115263, which was used on all 1967 Big Blocks with K66 Transistor Ignition (and K66 was mandatory with L71 435).

If you have a FOEM coil, the last three numbers embossed on the side of the “can” would be “263”.

These coils are rare as hens teeth, so if you have one – never let it go 

I don’t believe repro coils have the 3 numbers embossed on the “can”, but others may correct me on that.

So if you pull yours out to look at it and it doesn't have embossed numbers on the side it's probably a repro - no matter how realistic the labels may look.

Mark , the reproduction 263 coil on the left and the Delco box they come in are from China and there junk , the 263 coil on the bottom is a original one that i have on my L71, it a different embossed number, there very hard to find and very expensive and if there good or not ?

46 Original Coil 263 AC Delco (2).jpgIMG_5913.jpg46 Original Coil 263 ignition coil.jpg

[Mark F.]

Re: 1967 435 vacuum reading and timing

Mark , the reproduction 263 coil on the left and the Delco box they come in are from China and there junk , the 263 coil on the bottom is a original one that i have on my L71, it a different embossed number, there very hard to find and very expensive and if there good or not ?

Thanks much, Danny,

I was not aware repros had embossed numbers...good to know.

If I ever find one (meaning a real 263 that's working), I'd probably try to buy it if not outrageously priced.