[INchief]

I know this is going to sound like a dumb question but I'm trying to confirm that initial ignition timing is set to 5degrees BTC with the vacuum disconnected from the vacuum advance canister. I'm going by the original manual from 1955 and it doesn't state to disconnect the vacuum line, that I can find. The page I'm on is 12-23 and the reference page for the specs are page 12-46. The rest seems pretty straight forward to set the ignition timing.

I am trying to make sure I follow the correct process since I'm troubleshooting a problem. I have always disconnected the vacuum advance on other engines to set the initial timing, but I'm not sure if there is something I'm not aware of on setting the ignition timing on this 287.

Side note - someone mentioned I should pay attention to manifold vs ported vacuum. My impression is that an engine before the mid-60's would be only manifold vacuum. I don't see any other ports other than what is already being used on the car. It's running the original 2bbl carb with a small vacuum manifold at the base of the carb. I've set timing on later model (70's) SBC that had port and manifold, but I don't think this applies to my situation. I also have electronic points and a mild (RV) cam. I'm not thinking either of these make difference in following the original shop manual specs.

Thanks for any help you can provide.

[Bill Hanlon]

I just read through those pages and did not find any reference to disconnecting the vacuum line or not. Any "ported" vacuum connection would be in the carb's base.

Where does your vacuum line connect to its vacuum source?

If at the manifold, I would disconnect the line, block off the passage to the manifold, set the timing and reconnect the line.

If at the carb base (Master Parts Catalog doesn't show a connection), I would set the timing to the specified value (5 BTC), set idle speed to 500 rpm (where mechanical advance starts), and then check/reset timing to 5 BTC again before reconnecting the vacuum line. Then reconnect the vacuum line and see if the idle speed and/or timing changed (they shouldn't).

[Bill Hanlon]

By the way, does your "RV cam" have the proper oiling holes drilled in the #2 and #4 journals?

[INchief]

Originally Posted by Bill Hanlon

By the way, does your "RV cam" have the proper oiling holes drilled in the #2 and #4 journals?

Hi Bill - yes, that's how I wound up with this cam. Other replacement cams didn't have the oiling holes.

I went out and adjusted timing to 5 BTDC, it was at TDC. I found the vacuum line to the advance canister was coming from the base of the carb, not the manifold. After timing to 5 BTDC with vacuum connected, I disconnected the vacuum advance and it stayed the same.

I went to 2400 RPM and the timing was in spec in the intermediate range. I was at 25 BTDC.

I moved on to check the vacuum advance. I put a vacuum pump on the canister and it won't hold vacuum and has no effect on timing - bad vacuum advance. Which I guess would also be a vacuum leak. I put a vacuum gauge on the line to the canister and it was around 6-8 hg of vacuum at 500 RPM. So it pulls vacuum, just not as much as the manifold. I assume that makes it a "ported vacuum source". Learned something there.

I pulled the vacuum canister to check the fittings and test it on the bench - tightened fittings and looked it over, still won't hold vacuum.

I'm currently looking for a vacuum advance canister and not having much luck with the auto parts stores or internet, at least nothing I really trust on the internet.

I am also thinking that a new (modern tech) distributor would be an option. I drive this car a lot and I really need reliability. I checked with several sources like Pertronix and they list compatibility 1955-1980 model engines, but not the 287. Will the same distributor fit from a 301 for example? Do you know of a solid replacement that is modern technology?

I'm not versed enough to cross reference this myself so I'm looking for any help available.

Thank you

[Bill Hanlon]

I don't know Pertronics' complete line of products, but I think they do not make complete distributor replacements. The Pertronics parts I am familiar with replace the points and condenser inside your distributor.

I think (but don't KNOW) that a 301 Pontiac would have a GM HEI distributor. I've heard (but again don't KNOW) that there isn't enough room for the larger diameter HEI to fit in your '55. Firewall and throttle linkage (especially if your '55 has a HydraMatic) get in the way.

I think a slightly newer ('57 through early '70s) points style Pontiac distributor would be small enough diameter to fit and would also provide easier points adjustment.

[INchief]

Originally Posted by Bill Hanlon

I don't know Pertronics' complete line of products, but I think they do not make complete distributor replacements. The Pertronics parts I am familiar with replace the points and condenser inside your distributor.

I think (but don't KNOW) that a 301 Pontiac would have a GM HEI distributor. I've heard (but again don't KNOW) that there isn't enough room for the larger diameter HEI to fit in your '55. Firewall and throttle linkage (especially if your '55 has a HydraMatic) get in the way.

I think a slightly newer ('57 through early '70s) points style Pontiac distributor would be small enough diameter to fit and would also provide easier points adjustment.

Right, I have the replacement points and condenser. Their tech support called me back and you are correct, the replacements they carry won't work/fit my car.

I'm waiting for a call back from a distributor repair shop. I'll ask them about compatibility with a later model distributor. Thanks for the information. I really appreciate it.

[Bill Hanlon]

Physically, any Pontiac V8 distributor from 1955 through the last real Pontiac V8 in 1981 will plug into the 287. All may have different advance curves than your '55 distributor. The vacuum advance specs will most likely vary too. The driven gear at the bottom of the shaft may be made of different material which would not be compatible with the 287's cam gear.

And as I said above, HEI distributor caps may be too big in diameter and try to occupy the same space as the firewall and throttle linkage.

I put a '77 Pontiac HEI (last of the non-computer HEIs) in my '57 GMC (factory stock, Pontiac-based) 347" V8. Plenty of room to the firewall, but I had to put a slight kink in the throttle linkage. Worked great for many years.

[694.1]

Got a Vac Adv unit for '57/58 I could send you for the shipping. NIB aftermarket.

[INchief]

Originally Posted by Bill Hanlon

Physically, any Pontiac V8 distributor from 1955 through the last real Pontiac V8 in 1981 will plug into the 287. All may have different advance curves than your '55 distributor. The vacuum advance specs will most likely vary too. The driven gear at the bottom of the shaft may be made of different material which would not be compatible with the 287's cam gear.

And as I said above, HEI distributor caps may be too big in diameter and try to occupy the same space as the firewall and throttle linkage.

I put a '77 Pontiac HEI (last of the non-computer HEIs) in my '57 GMC (factory stock, Pontiac-based) 347" V8. Plenty of room to the firewall, but I had to put a slight kink in the throttle linkage. Worked great for many years.

Thanks for the information. I read your post on pontiacsafari.com about the HEI conversion. My thoughts lean toward keeping the car running with original equipment as much as possible. Mainly for the reasons you mentioned in your reply. Changing anything leads to more changes and I really just like driving the car without a lot of extra steps. I am very cautious about doing anything that changes the relationship between the throttle linkage and the transmission. The engine and transmission work really well together right now and upsetting the delicate balance seems like a bad idea.

I asked the shop that did my transmission work if they knew anyone that could help with this distributor/vacuum advance rebuild. They have a guy that used to work there that retired and he is interested in doing the work on the side. Apparently he's a "Pontiac Guy". So, it isn't coming together as quickly as I wanted but that isn't new with anything these days.

Again, thanks for sharing your knowledge. Over the past 6 years I have learned just how much I didn't know - especially about 1955 Pontiac's.

[INchief]

Originally Posted by 694.1

Got a Vac Adv unit for '57/58 I could send you for the shipping. NIB aftermarket.

OK, I can message you with my address. Thank you