I’m hoping you guys can help me sort out some problems with my 283. When I bought the car, it had a big solid cam in it that was installed straight-up, sounded great at idle but really no power in lower rpm’s. It also would make you tear up from the fumes. It has 10.5-1 comp, camel hump heads that have been polished, a knock-off performer RPM intake and a 650 double pump Holley with headers and a Mallory Unilite distributor, MSD ignition and a Accel coil. When I tried to set the initial timing it was running at about 32 degrees after. When I tried to back it down it wouldn’t run hardly at all. I just replaced the cam this weekend with a mild hydraulic and got it running last night. I still can’t set the initial timing much lower than 23 degrees. When I raised the rpm’s to 2500 to break in the cam it started to backfire thru mufflers continuously and got worse the higher I went. It does not backfire at idle. At this point I’m not sure where to go, the distributor seems to be in correctly. I want to convert it back to a standard vacuum tach drive distributor and coil. In fact I bought a Delco tach drive dist off ebay but when I got it, it turned out to be a non-vacuum advance unit so I still have the Mallory in. Any ideas would be much appreciated.

 

It might be worth it to verify the TDC in case you have a mismatch between the balancer and timing cover/timing tab. On the 327 in my 61, I found it had the early 8 inch diameter balancer but a late model (69-newer) timing cover which will give you a false timing reading of about 8 or 10 degrees (forget exactly which).
Mike T.

 

I tried to set the initial timing it was running at about 32 degrees after.
Does this mean it is at 32 degrees ATDC, or it was at 32 degrees BTDC after you set the timing? Are you setting the initial with timing the vacuum advance connected?

 

32 atdc, and it's a mechanical advance distributor

 

I could be wrong and it wouldn't be the first time, but shouldn't the initial timing be around 10 degrees BTDC at idle?

 

Verify TDC and then re-install the distributor correctly cause there's no way it's in there right at 32 degrees after TDC.

 

there is a mis match or something wrong with your balancer mark or you are timing on the wrong cylinder
i seriously doubt the mill would run at 32 retarded.....need more info

find tdc first as was posted earlier, then verify the timing marks...tdc on compression stroke first cylinder on the drivers side ( closest to the radiator)

 

Thanks Mike, I'll take another look when I get home but when I installed cam and timing chain and then put cover on everything was at zero.

 

Sorry guys I'm saying it wrong, it is 32 degrees advanced. The line on balancer was almost straight up.

 

Start here.

 

The 'backfire' in the exhaust -- really called 'afterfire' means raw gas is igniting in the hot tailpipes. As the timing advances when you throttle up it gets worse as you've noted.

A clear indication of valve timing being off ... as others have said get that straightened out then go from there.

 

The items above, with the exception of the camshaft could cause your spark plugs to become gas fouled and cause the backfiring out of your exhaust. If the backfiring is ryhtmic, it's not plugs. Sporadic, likely.

Apparently, your engine isn't running much beter after the cam change than before?

"Backfire" means your exhaust is barking out the back end of the car! Others call it something wierd!

I'd take a look at the plugs.

 

Non-advance dist is probably from a '62. A better curve than vac advance ones.

 

All good ideas, also check your firing order is correct, it will run with 2 mixed up, and backfire when you rev it. And like Frankie says, valve lash should be checked also.
Balancers can slip on the hub, so verify your tdc first either with a dial indicator, or by putting a longish bolt into the plug hole and rotating it front to stop and backwards to stop, and measure half way on the balancer, which is where the line should be, or mark your balancer at that point.

 

#'s 5 and 7 are likely candidates.

 

Actually its running worse. It didn"t pop out of the exhaust before the cam change. I'll get around to all of the suggestions over the next few days. I was also wondering if a vacuum leak at the intake would cause the problem.

 

I had a 29 ford roadster with a 265 Chevy got 5 and 7 switched and did same thing.
Took it to this old (79) hot rod builder and he found the wires switched.

 

backfire could come from a engine that is way too fat...the double pumper could be that problem...especially running it up and going back to idle......burning the fuel in the pipes instead of in the cylinders........a distributor without a vacuum can is simple to set...the distributor will normally be internally set for a total of 24...the 24 with a 8-12 initial lead would place the engine 32-36, an acceptable total......

the only other factor is some valve lash is too tight, however that's a little remote....but check the carb for internal leaks

 

How did you stab the distributor after the cam change? If you installed the timing chain with the gears dot-to-dot (the usual method), that sets the engine at #6 top dead center on the compression stroke; from there, you either have to install the distributor with the rotor pointing at the #6 wire tower, or you have to turn the crank one complete revolution (both dots at 12 o'clock) to set the engine at #1 TDC on the compression stroke and install the distributor with the rotor pointing at the #1 wire tower.

Here's the diagram they should have put in the Shop Manuals; none of them explain it, assuming the tech knows it from experience.

 

John, now I'm really confused! I have built several small blocks and 1 427 over the last 30+ years and have never heard that! And honestly, never had an issue with them running bad. Now I admit I haven't touched an engine since 1995 when I restored a 69 big block vette, and my wife is telling me I'm going senile, but I from what I remember I always dropped the distributor in with the dots facing each other and the rotor pointing to #1. If this is wrong, why does it start and idle without a problem? I'll try moving it, I hope this is the only problem cause I checked the wires and none are crossed.

Bob