Has anyone ever heard of the little center punch marks on a timing set for a 390 being off? I replaced the timing set since mine stretched bad and now it back fires through the intake really bad. And yes I have already checked and triple checked to make sure everything is lined up properly. I have more info and pictures posted on the thread "390 compression check" because I originally thought I might have had a bent valve and did compression check to find out. This isn't my primary vehicle, but it hasn't been running in 3 weeks now and I'm running out of idea and getting frustrated with the thing. Please help.:-banged

 

I haven't had a problem "yet"...although I have heard that the late timeing chains are retarded for environmental reasons...but that is just a few degrees..I have had a problem with fireing order ..but you checked that already...when this happens ,,I have a coffee read the boating book ,,to clear my mind...and start at the beginning top dead center ..on the cam and crank the simple answer is the hardest to find...figgered I let you know your not being ignored...

 

yeah you're not being ignored, I'm just about out of ideas is all. lol

Also, no I've never seen one stamped wrong. You sure it's getting enough fuel? I had a fuel line get kinked after I put in a new dizzy, and heads and it did much of the same.

 

yah start at zero...and after you clear your mind..you look to hard and you don't see the problem...well I don't...

 

Are you sure, absolutely sure, that when you put the new set in that the engine was on TDC for #1. The marks will line up for both #1 and #6. If at #6 you would get a backfire for sure. I've done that twice in 25 years on a 302 and mopar 360. The backfire on the modified 302 was spectacular while the stock 360 was only slightly noticeable. If you are not sure you can always move the dizzy 180 and find out.

The 302 took just 1 minute to figure out while the 360 took a few days to come to the realization.

 

"the backfire was spectacular" hahahaha

thats what we were thinking earlier but he's says he's checked like 3 times to make sure its at TDC on #1

 

First off, thank you all for your input, I was starting to get worried that since I'm talking about my galaxies engine and not my trucks engine I might be breaking some rules and getting avoided like the plague And I have the same problem, the more I get stressed and annoyed the more I miss the little ****, hence I haven't even popped the hood today I double checked for top dead center yesterday and when number one comes up, the little dimples are lined up, the dizzy is pointing at spark plug wire number one and according to the rocker arms, both valves are closed. I'm fairly certain that its getting enough fuel, I got ride of the broken mechanical in favor of an electric aftermarket pump. Its back firing enough to blow flames out my carb (very spectacular, specially after dark and it never did that before. Would a bent push rod possibly cause that? The compression test I have done seem to indicate that the valves are good still and most of my low original readings where due to blow by as I suspected. Also, is there a good source for info on tuning the autolite 4100? I have a pdf file of the carb section of the shop manual and the rebuild instruction sheet. Who knows, maybe I don't have the carb tuned in right. It will run and idle, but dies when put in gear. Any and all ideas I'm willing to try cus I'm out of ideas

P.S. When they say you can check the float levels on the 4100 with the air horn off, they should as mention you need to be 100% positive you don't have any back fire Thank god for having a fire blanket 2 feet away

 

And for the record, my truck is a 1977.5 with a 460 bored over. 040 with performer intake, 600 edelbrock, and rv cam sitting on 35's. Looks like **** but its well worth the $1100 I paid as is

 

My backfire was enough fire to singe hair. As for your situation is was Sooooo sure I was at #1 that I wouldn't consider being at #6. Checked everything like you did but flipped 180 many times to please my mechanic brother. Finally a little movement of the dizzy housing to fine tune and the engine started. Then when I put the timing light on #1 I got no damper mark. I had gone back and forth so much I thought let's put it on #6. Bingo, theres the damper mark.This engine is so much harder to get at than a Ford so I decided to leave well enough alone. Now I time off the #6 plug wire. I attribute this one to working in the dark as the car died in front of the house on the street. The amazing thing is I got the front sealed up with nary a leak. No small feat for this 360 where coolant can exit out almost every bolt hole.

 

Oddly enough, I am so out of logical ideas that I was gonna try both spinning the cam 180 and trying it just for the heck of it as well as trying it with the cam gear one tooth each way Who knows, it might work for me too. Its worth a shot anyways.

 

I was just reading in the 385 series section that a guy was having the same problem and 2 solutions suggested there where changing dizzy cap and rotor encased you got a bad one and skip the dizzy one tooth and advance 30 to 40 degrees. Its crazy but I'm ready to try anything

 

Instead of spinning the cam 180degrees, just move the spark plug wires 180 degrees.

Did you do a compression check after doing the timing chain? If so, what were the numbers?

 

I did two compression checks after doing the timing set replacement since I first suspected some bent valves. The first test was dry and the second was with a little oil in each cylinder just to seal the rings. All the results and pictures are posted in the ' 390 compression test' thread. The results of the second test dramatically increased proving that my rings are very worn, kinda expected for a 45 year old engine with 115,000 on the clock. Anyways it ruled out my valves fairly quickly. My one regret is that I never did a test when I first bought it so that I would have kind of a base line to compare things too.

 

but it did run before doing the chain, yes?

I wonder, if there's some weird cam in it, and it needs to be "degreed" ...

 

Well it ran fine one night and then wouldn't run the next day. The timing chain was so stretched that when I pulled the front cover off, the chain was literally sitting on the top of the cam teeth and I was able to pull the chain off without tools and without moving the sprockets. As best as I can tell the engine has never been rebuilt so I would imagine its the factory cam and comparing the old cam sprocket with the new one I put on, all the markings are in the same places and everything is basically the same with the exception that the new one is cast iron and has the integrated spacer and the old one is the aluminium and requires the washer spacer behind it.