That cam should be OK in a near-stock 307. Make sure you check all the simple stuff. Timing, as mentioned. What about the lifter preload? Is it possible that you are running them too tight and hanging valves open? What kind of vac*** is it making at idle? Is the vac*** gage reading steady?
Hydraulic lifters? Adjusted properly and not too tight? Easy check with minimum teardown. Novadude types faster than me!
I had a similar problem when I built my 355 - sounded mean as hell but would only casually loaf its way through the gears. Turns out the 'rebuilt' distributor I picked up had frozen internals thus keeping it from advancing the timing (centrifugal advance). Have you increased the RPMs while watching with a timing light? If the mark continues to align with the cover, we've found your problem.
The rubber cone-type compressiontesters are fairly common. Just press harder while someone else is cranking the engine. Also, remove ALL sparkplugs first before testing. If this turns out OK then start turning the distributor. A 'lazy' engine probably has late timing. Advance the timing. Engine RPM should pickup aswell a bit. If you adjust the ignition so the engine idles the fastest, the timing is too early. Do not drive the car like that because the engine will ping itself to death. Better get someone experienced with you while wrenching on the car.
Do this first before changing anything. Get #1 up on top dead center by cranking it over with a socket on the dampener bolt. Use something like a piece (long like a foot or so) of 1/8 or so in welding rod or something similar to stick through the plug hole and feel the piston go up an down. With a bit of effort you can tell when the piston is at top dead center. On some cars you can shine a light down the plug hole and see the top of the piston move and do it that way. When you figure out where top dead center is put a new timing mark on the dampener right where the 0 is on the timing tab. Paint, magic marker or what ever to do that. Now reset the timing using that mark and see what happens. Remember to set the advance with the vacuum hose disconnected and plugged. Also it's a good idea to check the vacuum advance to make sure it is working. An easy way to do that is to just pull the hose going to the advance off the carb and **** on it and see if you get a resistance. You can usually tell if the advance is moving and if you are just ****ing air the advance is bad. We ran a 307 with power pack heads a mid 70's Z28 cam, 300hp 327 intake and Holley spreadbore in my oldest sons 70 Chev C-10 and it ran pretty strong. You need to get the timing squared away first and then go on to resolving any other issues that the engine may have. You might want to check the casting numbers on the heads and look on one of the many Small block cylinder head charts floating around and find out what the capacity of the combustion chamber is and compare that to either the stock 307 heads or the earlier power packs.
This man is right on target with the balancer being a top mark version What you need to do now is invest in a piston stop and find true top dead center. Then permanantly mark your balancer where zero falls on the timing tab. Right now your timing accuracy is probably +/- 10 degrees by gut feel method. No wonder it runs like ***. There's no need to do anything else til you can trust a timing light. That's absolutely your #1 concern. Good luck!
Two things: 305 heads are notiously restrictive on anything but a 305, so don't expect any power over about 3000 rpm. The other usual problem, which can happen with any smallblock, is the inertia ring slipping on the balancer, which means the timing marks are off, hence the timing is off. I'd hook up a vacuum guage, rotate the distributor to the highest reading and then back it off one inch of indicated vacuum. Then drive it. It'll probably feel the same, given all you've done. Like I said, the heads. Yes, I did it as well. good luck!
305 heads **** not to get off subject here but ive known guys that put 305 heads on a 350 and have nothing but overheating problems they restrict coolant flow im pretty sure
***uming all the basics are covered, like lifter preload, valve sealing, no broken parts, etc. then yes this is true. Did you remove vacuum advance when you did this swap? It's really important for normal around-town operation. That's what it sounds like to me. Summit and Jeg's just want to sell parts, they don't care how well your car actually runs. Don't buy those distributors with no vacuum advance... I wouldn't expect very much power from a 307 with smog heads and a mild cam.
make sure you don't have the valves adjusted to tight. I'd suggest adjusting them with the engine running
305 heads aren't going to completely kill power on a 307. BTW... I've never seen a 307 with a timing pointer at 12-o-clock. I don't think they started doing this until 76-77 when the 305 came out. However, w/ a 305 balancer and a standard timing tag... that would cause issues.
WHAT 305 heads did you use? That WILL make a big difference. the 601 castings have the smallest combustion chambers (53cc), smallest ports, and valve sizes; the 416 castings have slightly larger ports, 58cc chambers, and possibly 1.84 intake valves (they also came with the small valves), there are a couple of other 305 heads, but the 601 and 416 are the most common. You did'nt use 187 swirl port/ramp port heads that only flow to about 4500 rpm did you? Are the valve springs good? Something is'nt right here, you already know that. Are you getting enough fuel? Butch/56sedandelivery.
Do you have taper seat spark plugs? The 307 heads take a washer on the seat and a 13/16 wrench (autolite #86) The 305 heads take a taper seat with no washer, 5/8 wrench size (autolite 24 colder or 25 stock). Jeff
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