1965 Belvedere II 318 poly tuning

[R. Shackleford]

Hey all, got a coupe questions about my poly 318 tuning. Engine has been rebuilt in the late 90's and currently has about 5800 miles. It has a 198-264 cam in it (unknown brand) with solid lifters and a Carter 4 barrel 9635sa (I know, I know, its a chevy setup carb that previous owner put on) on a cast manifold. It's been running good but a bit rich and a little rough idle, probably from the cam. Yesterday I went to tune the carb a little leaner. Ide mixture screws were out about 4 full turns from seat. I set them in to 1.5 turns to start and set the ide around 800rpm (roughly) and I noticed the timing mark on the HB was about an inch retard from the timing mark (not sure how many degrees that is). Now I'm not sure if that's set due to the cam or not. I advanced it to line up with the mark then went back to tuning the carb. Carb doesn't seem to like havin the mixture screws less than 3 turns out in order to smooth out a bit. Its not perfect but close. Then my timing light I've had for many years decided to die on me (leading to another question about whether it was working properly at all). I have another one sitting on my porch as we speak. I guess my question is with the 264 cam am I needing to leave the timing a bit retarded? Also the carb seems a bit off to be out 3+ turns in order to smooth out. This is my first Carter, I'm more of a Holly kinda guy. Any advice would be welcome. Thank you!

 

[R413]

First thing? Adjust the valves.

Timing retarded is just that with a bigger cam
The timing needs to be advanced.
Does it ever ping? Advance till it does and back it off.

 

[R/T Boy 67]

If your timing was really that far retarded, it would idle and run very poorly. You need the check the accuracy of your timing marks.

 

[toolmanmike]

My 64 Poly has the stock cam and 2 barrel and starts and runs fine at 10° before. I can imagine with a little cam 10-15° would be it's happy place. Remember, the more initial you have, the more total advance you get. At 3000 rpm it should be around 32° with the vacuum advance disconnected at the distributor and plugged. Speaking of which, make sure your advance isn't hooked to manifold vacuum. The port on the carb should be the higher one (if there is 2). The lower one is manifold vacuum and the higher one is ported vacuum (above the throttle plates) You should have no vacuum at idle. There is more, Let me think.

 

[toolmanmike]

Here's how I feel about tuning a street cruiser. Not too much is needed. As long as it starts well, runs smooth, doesn't ping, and doesn't hesitate, you are good. A race engine is different. You are trying to get the last few horses out of it, although that isn't really necessary if you are ET racing. Tuning on the dyno can be easier. Sometimes adding a extra degree or two of timing will net you 4 or 5 horsepower. See, not all that important.

You can pull #1 plug, stick your finger in the hole and bump it over until compression want's to blow it out. That should be close to TDC and the mark on your balancer should be close to lining up. If it does, you should be good, if not your balancer may be old and has slipped. Then your timing light won't be close at all.
Speaking of timing lights, I hope you got a digital advance light. Non advance lights won't allow you to read total timing unless you have a degree tape on the balancer. Dial advance lights can be inaccurate. Halifaxhops calibrates lights and has worked on many dial lights that were way more than a degree or two off. Digital advance lights are the most accurate between the two designs.

Give it 10° and test drive it. If it doesn't kick back against the starter when you hit the key and doesn't ping on acceleration or cruising, you could be good to go. Or, you could add a degree or two and re-test. Just remember, a few degrees isn't going to make a whole lot of difference in performance on a mild street cruiser.

 

[RemCharger]

I agree with the valve adjustment.

 

[R. Shackleford]

If your timing was really that far retarded, it would idle and run very poorly. You need the check the accuracy of your timing marks.

That was part of the issue as well. I'll need to do my own TDC and make sure the mark is correct

 

[R. Shackleford]

Ok thank you all for the advice. I will try and mess with it a little tonight and see what I can come up with. Does the 3+ turns out on the idle mixture screws seem a bit much? Or do you think that'll change when in proper time?

 

[R. Shackleford]

Here's how I feel about tuning a street cruiser. Not too much is needed. As long as it starts well, runs smooth, doesn't ping, and doesn't hesitate, you are good. A race engine is different. You are trying to get the last few horses out of it, although that isn't really necessary if you are ET racing. Tuning on the dyno can be easier. Sometimes adding a extra degree or two of timing will net you 4 or 5 horsepower. See, not all that important.

You can pull #1 plug, stick your finger in the hole and bump it over until compression want's to blow it out. That should be close to TDC and the mark on your balancer should be close to lining up. If it does, you should be good, if not your balancer may be old and has slipped. Then your timing light won't be close at all.
Speaking of timing lights, I hope you got a digital advance light. Non advance lights won't allow you to read total timing unless you have a degree tape on the balancer. Dial advance lights can be inaccurate. Halifaxhops calibrates lights and has worked on many dial lights that were way more than a degree or two off. Digital advance lights are the most accurate between the two designs.

Give it 10° and test drive it. If it doesn't kick back against the starter when you hit the key and doesn't ping on acceleration or cruising, you could be good to go. Or, you could add a degree or two and re-test. Just remember, a few degrees isn't going to make a whole lot of difference in performance on a mild street cruiser.

It is a digital advance

 

[66 Sat]

Speaking of which, make sure your advance isn't hooked to manifold vacuum. The port on the carb should be the higher one (if there is 2). The lower one is manifold vacuum and the higher one is ported vacuum (above the throttle plates) You should have no vacuum at idle.

I'm interested why you don't like manifold vacuum advance. Mine runs better on MVA than PVA. Idles cleaner, better off-idle response. I switched a few years back.

 

[RemCharger]

I'm interested why you don't like manifold vacuum advance. Mine runs better on MVA than PVA. Idles cleaner, better off-idle response. I switched a few years back.

Then really all you needed was a higher mechanical initial

 

[66 Sat]

Then really all you needed was a higher mechanical initial

No, I'm running similar initial and total whether it's on PVA or MVA. About 12° initial, 32° all in. Maybe I can squeeze 14° in the winter when it's cooler. The car idles fine with Ported at 12° but idles much cleaner with Manifold vacuum (at probably 20°+, I've never put the light on it with it connected). Less exhaust smell too.
I've tried to run 18° initial which was great at idle/off idle response except then it would ping.
The only thing with MVA, even though in theory it should drop off when the throttle is cracked open and be equal to the advance with Ported, it seems to hold more advance for a period, so I've had to limit the vacuum advance with spacers under the arm.

There's been a lot of debate on here about the benefits and drawbacks - I was curious as to why Toolmanmike was against it.

 

[R413]

Forget all the timing lights and timing marks.

Advance it till it pings and back it off. Then tell us how much better it runs.

 

[Geoff 2]

No, you don't advance it until it pings.....
You need to do things in the correct sequence...
Man or auto?
Vacuum at idle?
Valve lash?
Are the passages in the carb base fully covered by the carb mounting pad? If not, you get air leaks.
First, you need to get some timing marks on the dampener.

I am reading the cam info as 264* advertised, 198 @ 050. If this is correct, then it is a reallllllly small cam & should idle smoothly with plenty of vacuum [ 13+"]

 

[Geoff 2]

Another thing to check is the float level.