I have a chevy 307 that ran fine except for a slight rod knock, I took it apart put in a 262/272 cam 305 heads and an edelbrock 1405 600 cfm carb on a edelbrock performer intake. It ran fine, sounded great but it wouldent make any power under load. I put the original cam back in, no change. I put the orig**** intake and carb back on, agian no change. I oiled the advance weaights in the distributer and checked to make sure they moved freely, agian no change. I tested the compression and it was a consistant 150psi. The moter does have a lot of blow-by. I noticed scoring on the number 7 cylinder wall when the moter was taken aprt. The moter sat for about a year apart before I could put it back together. I have no clue what is wrong with it, I think I'll just have to give up on the car.
No offense intended but did you ever consider that your motor might just be wore out? Instead of throwing supposed speed parts at it you might just try an overhaul. Putting an aluminum intake on a clapped out 307 is like putting a jewel in a pigs snout. Kinda ***y but basically useless.
yeah I kinda just took it apart for the hell of it. When a motor is worn out it's because it looses compression, right? But it cranking 150psi not less than 100
How much vacuum is the engine pulling? Secondaries opening? Is the vacuum advance working? How much of a load are you talking, just driving or pulling a trailer or???? Trans slippin?
I don't have a vacuum guage but it idles well, so I ***ume that it has decent vacuum. I don't think the trans is slipping because it doesn't feel disconnected. It feels like less than 50% of the power it had before.
Only leaves fuel , I guess, Check the plugs after a strong pull for color, check the exhaust for color inside pipes, Make sure your fuel lines are open and flowing properly, check your fuel pressure, check your float level in the carbs. Keep looking! Traderjack
Did you check and make sure it is getting full mechanical advance out of the distributor say at 3000 rpm your getting 32* or more?
Dang,I read the ***le of this thread and I thought it was about shooting your help.I had some suggestions,but..........nevermind.
I guess I am looking at this the wrong way and don't take this the wrong way but why the hell did you spend all that money on speed parts on an engine with a "slight rod knock " ????? That makes no sense to me at all ! If the rod knocks you have a bad bearing with means bad oil pressure from bearing blocking the hole on the crank . Sounds like you should have rebuilt the engine too ! RetroJim
does anyone have any suggestions? I don't have money for a new motor and if I can't fix the 307 I'll just have to sell the car
What carb is on motor .307 were lousy motors .I tried to make a performance motor out of one and blew it up.7 and 8 The pistons looked chrome when took a part.
Being you said one cylinder had a score I would venture to say you have a bad piston, cracked colapested skirt etc. That would make a noise that "could be ' mistaken for a rod knock. Once a rod starts making noise in a small block they die real quick in my experance. When you installed the cam you may have got the cam timing off a tooth or 2 ,that would make for poor running. With the cylinder issue if you can't afford to at least pull and replace that bad? piston you might as well sell the car. You spent money already on it ,but in the wrong places.
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