300 worth rebuilding?

[tbyro1]

I'm running a 300 4bbl with petronix and dual exhaust on a 66 skylark convertible. Starting to have lifter noise on one side. Would like more power. Is it really worth rebuilding with performance cam upgrade or maybe swap out for a buick 350?

[Dr. Frankenbuick]

350 is hard to pass up as a drop in replacement. You will have to do some exhaust work though. They have different exhaust manifolds since the valve arrangement is changed from the 300/340.

[LARRY70GS]

I'm running a 300 4bbl with petronix and dual exhaust on a 66 skylark convertible. Starting to have lifter noise on one side. Would like more power. Is it really worth rebuilding with performance cam upgrade or maybe swap out for a buick 350?

Is the noise on the driver's side? All the lifters? Might just be a worn front cam bearing. Oil goes across the bearing from the passenger side galley to the driver's side lifter galley. When the bearing goes it clogs the feed holes starving the driver's side lifters.

[tbyro1]

It is on the drivers side. No noise when cruising or idle. Ticks when accelerating or under load. Not sure if its one or more of the lifters.

[telriv]

In that case it sounds like a timing issue to me.

[LARRY70GS]

It is on the drivers side. No noise when cruising or idle. Ticks when accelerating or under load. Not sure if its one or more of the lifters.

That is detonation/ping. Do you know what that sounds like?

[tbyro1]

That is detonation/ping. Do you know what that sounds like?

I'm not much of a mechanic. I believe I set the timing between 8 and 10 degrees and I do use 91 octane although probably not necessary.

[Dr. Frankenbuick]

The limiter bushing in the distributors eventually fail. This means the initial timing may be spot on, but the mechanical advance is no longer limited. There will be way too much total advance when this happens and detonation will result. You have to power time it to find out if this has happened. We have a helpful link to timing here: http://www.teambuick.com/reference/engine_timing.php. If you have a dial back timing light, you want dial back 30* of advance and see if you have 2-5* advance as full mechanical advance is achieved at 3500-4000 rpms with the vacuum advance line off and plugged. If the initial is set correctly and there is well over 35*, then the limiter bushing is MIA and needs to be replaced. Then you can re-time it once the bushing is replaced.

Also, the initial advance on the 300 should only be 2.5* - not 8*. That may be the cause of your pinging right there.

[LARRY70GS]

I'm not much of a mechanic. I believe I set the timing between 8 and 10 degrees and I do use 91 octane although probably not necessary.

The limiter bushing in the distributors eventually fail. This means the initial timing may be spot on, but the mechanical advance is no longer limited. There will be way too much total advance when this happens and detonation will result. You have to power time it to find out if this has happened. We have a helpful link to timing here: http://www.teambuick.com/reference/engine_timing.php. If you have a dial back timing light, you want dial back 30* of advance and see if you have 2-5* advance as full mechanical advance is achieved at 3500-4000 rpms with the vacuum advance line off and plugged. If the initial is set correctly and there is well over 35*, then the limiter bushing is MIA and needs to be replaced. Then you can re-time it once the bushing is replaced.

Also, the initial advance on the 300 should only be 2.5* - not 8*. That may be the cause of your pinging right there.

To add to what Steve said, the stock specs only apply if the engine has the same part number distributor it left the factory with. How likely is that in a 45-50 year old car? Lots of small block distributors will fit and function in your 300, but over the years, they differed in the amount of mechanical advance built into them. Most guys just assume they are all the same, and they only check and set the initial timing, then think they are done. The only time the engine runs at the initial setting is when the engine is at idle. Once the RPM goes above idle, the mechanical and vacuum advance add timing. You have to check that, and it is easy if you have and know how to use a timing light. The springs that attach under the rotor control when the weights move out to their furthest position and timing tops out. Most stock springs don't allow that until 4000 RPM, and that makes checking total timing more difficult. Getting some light springs, commonly available in re curve kits, and installing them lets you check and set total timing at a much lower RPM.

Years ago, I got tired of answering the same timing questions over and over again. What I did was author a Power timing thread over on V8Buick. That was back in 2005, and to date, it is 27 pages long, with over 180,000 views and 652 responses. It is one of the few threads with a 5 star rating, whatever that means. Now I just link it when I see timing questions. I'll link it for anyone who cares to read it, http://www.v8buick.com/showthread.ph...-your-Buick-V8

In any case, you can't just run any initial timing you like, or whatever your neighbor Joe Blow down the street runs, without checking where the timing tops out at. Most Buick V8s like between 30 and 34* of timing at wide open throttle(WOT). Since vacuum advance does not function at WOT because vacuum is at or near zero, the total timing at WOT will be the sum of initial advance and the maximum amount of mechanical advance built into whatever distributor you happen to have installed. That is why it is a good practice to just set the total WOT timing. Once you do that, the initial timing ends up where it has to be depending on the distributor you are using, and the total timing you have decided to run. Most replacement aftermarket distributors like the MSD and Mallory units have an adjustable mechanical advance so you can run more or less mechanical advance and therefore more or less initial advance, but with the stock distributors, you don't have that option.

If you decide to adjust your timing, always check and adjust point dwell first if you are running points. Dwell affects timing, Timing DOES NOT affect dwell.

Have a look at my Power Timing thread. There is a WORD attachment describing how to use a timing light to set total WOT timing. There is also pictures showing how to modify the vacuum advance canister, which you must do if you decide to bring in mechanical advance earlier to boost low end performance.

[65specialconvert]

Add to the confusion...I have heard exhaust leaks that sound like lifter noise on the 300's Might be cracked or warped manifold since the 300 didn't use an exhaust gasket.