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My '58 with the original 3-speed has a '73 307 in it. It starts great and moves off the line pretty good but really seems to lag in 2nd and 3rd gear. I push the accelerator and hear the engine open up but it seems to take a few seconds before I feel the truck start kicking in. It gets going plenty fast enough on the freeway so it does'nt seem gas starved. I had the stock? Rochester 2-barrel rebuilt and see gas pumping into the barrels when I push the throttle. Vacuum is good and I used the vacuum gauge to set the carb at idle and the timing which I think is about 10 degrees BTC. My compression seems good with all cylinders at 145-160 lbs. My plugs seem to be burning well, tan, and I bumped up the gap to about.040. I have a aftermarket electronic distributor which I assume works O.K.-it doesn't miss obviously. I once had a slightly hopped up 283 in a truck like this that was much quicker. I wish this truck was a little more responsive to the accelerator. My best guess is just that the carb is a dog. Any other ideas? thanks for any input. Bob

The timeing chain might be getting sloppy. These had plastic teeth on the cam gear & if they wipe out you are in trouble. Also check for resticted exhaust.

It may be that the power valve in the carb is stuck. The power valve enriches the mixture under low vacuum to give the engine some power and then leans out once the vacuum comes up. I had a Willys Jeep with a Buick 225V6 with a 2GC and I found a bent power valve piston hanging up in the bore that intermittantly caused crummy acceleration and terrible gas milage, because it would stick closed for a while, break loose, and then stick open for a while.

Also, check the total mechanical advance of the distributor at 2500 rpm, you may not be getting enough ignition advance to make any power. The weights may be stuck or rusty and hanging up. If the distributor sat for a while it could happen.

Did you unhook the vacum advance when you set the timing? You could get a false reading if you didn,t. Really sounds like slow timing.

I also go with carb. A "bog" is generally caused by the engine not getting a big gulp of air and not enough gas. Don't complicate this problem. Check the carb FIRST.

If the balancer ring has slipped, your timing could off, even though it looks on. Try power timing it. Advance it a bit, drive it and if it doesn't ping on heavy acceleration, advance it some more. Keep going until it pings then back it off a hair. Crude, but effective.

IMHO if the timing were the problem the motor would lack power throught the rpm range. If it just bogs when you stab it, then boogies, that says, "carb" to me.

Use a delay-flash timing light to set the total timing at 2500 RPM to 36-37 degrees BTDC with the vacuum advance disconnected. With the advance connected, no-load advance at 2500 should be 42-43 degrees. Set this way, the advance at idle with the vacuum disconnected should be somewhere in the 6 to 8 degree BTDC range at normal idle speed (500-600 RPM). If you want more initial advance to help low-speed acceleration, you'll need to restrict the centrifugal advance to prevent over-advancing at high speed. On the race engines with a radical camshaft, I up the initial timing to about 12 degrees BTDC, and restrict the centrifugal advance enough to give a max of 37 degrees at speed. One degree over-advanced drops as much horsepower as 5 degrees late; I've proved it repeatedly on the dyno. It sounds like you're over-advanced on the initial timing, and the engine is trying to run backwards on acceleration.
Jerry

I think you guys are over-thinking this problem. I knew a guy with a hot-rod, 69 Camero. He would punch it and it would really bog badly. You could hear the motor gulping huge amounts of air and stammer for a good three seconds, until the carb mixed in enough gas. Then it would run strong. My guess is that the accelerator pump needs rebuilding. Do the easy stuff first, then move on.

Thanks to everyone for the ideas. That last post by Tab does sound like my problem. I had the carb rebuilt by a local repair shop. Should I assume they unstuck the power valve? or that the accelerator pump works? Like I said I can see gas squirt into to barrels when I push the accelerator. Should I tear the carb apart myself?or buy a new one? The air cleaner element is a 9-inch diameter, 2inch tall which I would assume is big enough for this relatively small carb. I did the timing with vacuum disconnected and I do notice the timing does advance with rpms. I can check to see if it's in the 36-37 degree range at 2500rpm with vacuum disconnected. I have tried moving the advance up and down some without really noticing a significant change in the problem. What would be restricting my exhaust? When I bought this truck it was smoking heavily out both pipes. After oil change and some high speed driving it doesn't smoke at all!-happy about that. Thanks again. Bob

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Kustoms-and-Sleds