340 Timing / CAM Issue

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MikeAndJack

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We just bought a 72 Dart "project car". We appreciate this forum and have used it a lot already. Sorry for the long post!

First some history as I know it. The motor was transplanted out of a 73. The car was originally a 6 cyl. The project was never finished by the person I bought it from and it was never on the road....maybe a lesson there..
Anyway, here is where we are...

73 340 block and heads from what I can tell
Mopar cam 4452782
Not sure about pistons. Here comp test results
Left front to back - 160-160-160-160
Right Front to back 175-160-160-140
Stock 4bbl manifold
Edelbrock Speed Demon 650

The engine starts but idles like it has a race cam in it.
won't idle below 1500 rpm and 30 degrees advanced.
5 inches of vacuum.

Here's what I have done.
Pulled the front end off and checked the timing gears and everything lines up.
With the marks lined up I pulled the dist cap it appeared that the rotor was 180 degrees off. Bingo! Rotated the distributor and put everything back together.

Would not start and back fired through the carb.

I pulled number one plug and did the finger in the hole till it blows test. Got it to TDC and pulled the cap...180 off!

Pulled the distributor and put it back to where it was and we are back to running but very poorly as described above.

I know my way around cars but this has me stumped. Could it be a wrong cam? Combination of parts? Am I going to have to tear it down?

Thanks for reading and responding!

Jack and Mike
 
That should idle like grandmas car. 700-800rpm and 15+ inches of vacuum

Huge vacuum leak somewhere would be my guess
 
http://proshop.summitracing.com///parts/dcc-4452782

pretty small cam to be called a race cam....you checked the dots are lined up....need to check to see if that cam is degreed in correctly....

went the cam sprocket is a 6 o'clock and the crank sprocket is at 12 o'clock..and the dots line up the engine is at #6 firing ...so it was installed correctly...you put it 180 out....

hate to say this word....Initial advance....how much initial advance is in the timing?
 
Should idle like a stock 340.....cause that's what it is.
 
Pulling the manifold next to check for vac leaks.

We figured out the timing marks after posting but thanks. All is correct.

Tony,
As far as timing, I have the Vacuum advance disconnected but not really an issue since only 5 inches of vac. Not sure if the mechanical is kicking in since I can't get it to idle below 1500. How do I determine initial timing?

I agree it should purr!
 
Vacuum leak, but..........

I'd start with ALL the basics. Check the valve gear even though compression seems OK, and take a look at the valve springs

Along with timing, check that the advance mechanism is working, and are you? (you should not be) using manifold vacuum at the advance. In fact, you might leave the vacuum disconnected until you get this sorted out

Take a good look at rotor, cap, and check the plug wires. Run a "backyard" cylinder balance test, IE short each plug one at a time up at the dist. and look for each cylinder to dump the same RPM or vacuum

Do the carb screws have good effect? My first inkling is a vacuum leak, and don't forget, that can be into the valley area as well

By the way, when you check cam marks, when they are "by the book" at 6 o'clock and 12 o 'clock, that is no6 ready to fire, NOT no1. This is why you thought the rotor was 180 off. The engine won't run at that, and in fact is why you got the fire through the carb.
 
I did a vacuum leak test with propane but it is running so rough, it was tough to get a read. Same with shorting out one plug at a time. I am thinking a vac leak in the valley.
It has a new distributor, pertronix CH-181.
Heads are redone with what looks like new HD valve springs and a new HD rocker assembly.
I was lucky enough to get a bag of receipts!
Thanks for the tips. I will update this post with results.
Jack
 
Have you actually checked where TDC is compared to the balancer using a piston stop, if not you are guessing on the timing.
Are the rocker arms adjustable, it so incorrect valve adjustment may be holding your valves open.
 
DO the vacuum leak test with water. It's much safer and it will show up better.
 
Thanks for all the info. Very helpful.
Today I pulled the intake and found 3 not-so-nice surprises...
1. The cam is wasted. Must not have been lubricated properly on startup. One of the lobes looks like someone took a grinder to it.
2. There is a significant chip in the manifold between cylinders. You can see on the gasket where it didn't seal.
3. This is the worst...I NEED YOUR OPINIONS on this. The block has been repaired with some type of epoxy.
Obviously i need a new cam and intake BUT, is the 340 block worth putting money into it or should I get another engine? It is a 73 340 block bored .30 over.

Hopefully photos loaded.
 

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Oh Crap, that block doesn't look good. Maybe you should pull the motor apart and see what else is FUBAR.
 
Not only does the block not look good but that "chip" between intake ports is no damn good, either.

I'd be talking to the seller first thing

I'd also be lookin for another block. Blocks CAN be repaired, but it's always an iffy business, and that crack is most likely freeze damage, which means it might be weakened somewhere else.
 
Looks like you found your idle problem.
It does not appear to be leaking water.
I would throw a cheap summit cam and lifters in, find a used intake.
Use copper spray on the intake gaskets.
Fire it back up.
 
Damn. I am thinking about sireland67's approach. Slap a cam and lifters in it and see what happens. I am going to try doing a little mig welder buildup on the manifold...got nothing to lose. Keep it cool and build it up slowly.
No water in the oil (I know what that looks like) but like I said the engine hasn't been really run since the "rebuild". Or so the seller said. I will likely stay with the SB so parts are reusable if the block turns out to be crap.
 
VERY popular place for the block to crack. I bet it is. But if it's not leaking.....and it appears its not, you may can leave well enough alone. It's gotta come all the way down anyway, to get all the cam metal out, so you may as well have the block pressure tested. That will tell the story.
 
MikeAndJack said:
Damn. I am thinking about sireland67's approach. Slap a cam and lifters in it and see what happens. I am going to try doing a little mig welder buildup on the manifold...got nothing to lose. Keep it cool and build it up slowly.
No water in the oil (I know what that looks like) but like I said the engine hasn't been really run since the "rebuild". Or so the seller said. I will likely stay with the SB so parts are reusable if the block turns out to be crap.
Click to expand...

You cannot fix a cast iron manifold with a mig, it has to be pre-heated and post-heated and welded with nickle rod.
Just buy an aluminim one used on this site for about $100.00.
You might be able to pick up a used cam and lifters here for next to nothing,
I agree with Rusty on the pressure check, but a running project is better than a push around project.
 
I would change the oil and filter, replace the cam.....a good used one would be ok but use new lifters. find a manifold and run it.

I know that's a Hacked way of doing it. but if you pull the pan, you will need to put a new oil pickup, then rebuild oil pump or replace.....then bearing need to be replace because your in there.

And before you know it you just rebuild a vary questionable block!

IF you put a cam in it and it make a year or two.......then it may be worth a rebuild.

Just a thought.
 
I am very interested in a runner. That's why we bought this car. Cam and lifters, a good oil flush and we will see what happens.
I will keep everyone posted.
 
I pulled the cam and as mentioned before, it is toast. Only one lifter and lobe are damaged. Below is a picture of the lifter. The rest of the cam looks new. Before I drop in a new cam do any of you have suggestions as to the cause of this problem? I don't want to waste a new cam!
 

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Looks like the springs are after-market.
 
stock is a single spring with a damper....anything else is going to be aftermarket...
 
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