Who knows cam shafts ?

pearljam724 · Jul 31, 2019

2 questions regarding cam shafts:
My car has a rebuilt 360 in it, with supposedly a mild cam as the previous seller told me. I know it definitely has an aftermarket cam in it. It being mild or not is unsure. The car ran very good when I bought it. It runs very good now. I’ve taken it on 100 mile trips in the last few weeks. I did a major tune up on it shortly after I bought it. I wish I would have checked the timing shortly after I bought it and prior to me changing the distributor cap. But, I didn’t. I checked it a few times afterward. No matter what I do, including removing the vacuum hose. It runs best when the timing mark is 3-4 inches retard ? The closest I can get the timing mark to zero degrees is a little less than 1 inch from zero degrees and it doesn’t run as well there. It runs best severely retard. At first I though it was maybe the cheap gun I bought. But, I bought a new better quality one and it reads the same. My only conclusion is it’s the bigger cam causing it ? Does this sound right to anyone that a bigger cam would cause this vast timing change ?
The second question is. Is it possible to verify the exact cam I have without tearing the motor completely apart ? That’s not very important, but out curiousity. I’d like to know possibly.

khryslerkid · Jul 31, 2019

Are you disconnecting the vacuum advance hose and plugging the carburetors port?

pearljam724 · Jul 31, 2019

khryslerkid said:
Are you disconnecting the vacuum advance hose and plugging the carburetors port?

Yes, sir. And they are correct ports.

Lefty71 · Jul 31, 2019

You can learn a whole lot about your cam by just pulling the valve covers, if you have a dial indicator and some timing tape handy.

khryslerkid · Jul 31, 2019

Could be an aftermarket dampner, or the timing cover is wrong with the pointer being for a different application or worse case the dampner is bad and has slipped. (Spit balling not being up on the small blocks as much)

pearljam724 · Jul 31, 2019

I should have also added that I believe it’s the original distributor with an aftermarket electronic ignition added to replace the original points. My belief is, contrary to what I was told. The cam is bigger than mild. It does some major loping at idle. But, I have no way of knowing. It sounds incredible.

moparedtn · Jul 31, 2019

Before you can question anything the timing mark on the balancer is telling you, it sounds
like you need to verify that the mark itself actually is accurately indicating TDC (top dead center)
of the crankshaft.

pearljam724 · Jul 31, 2019

khryslerkid said:
Could be an aftermarket dampner, or the timing cover is wrong with the pointer being for a different application or worse case the dampner is bad and has slipped. (Spit balling not being up on the small blocks as much)

There’s no doubt in my mind. The dampener is original. Along with the pointer. I’ll have to post a video in a few days. The thing is. Before I messed with the timing. It’s idle speed was the same and the motor didn’t shake at all. After I timed it, it shakes a tad at idle only and set at the same idle speed. I can’t get it to stop shaking, unless I turn the idle higher than I want. It’s currently set at 1k. Which should be plenty enough idle speed. So, I don’t get that part.

pearljam724 · Jul 31, 2019

moparedtn said:
Before you can question anything the timing mark on the balancer is telling you, it sounds
like you need to verify that the mark itself actually is accurately indicating TDC (top dead center)
of the crankshaft.

Yeah, you’re right and that’s a great point. I have a dial gauge that I can check that. Which I haven’t to this point. If it isn’t, how is that corrected ?

1 Wild R/T · Jul 31, 2019

moparedtn said:
Before you can question anything the timing mark on the balancer is telling you, it sounds
like you need to verify that the mark itself actually is accurately indicating TDC (top dead center)
of the crankshaft.

I agree and on a small block it's pretty easy, pull the #1 plug & slip a screwdriver in the hole to see how far down the piston is... It's best if you have a second person you trust either hold the screwdriver upright so it doesn't bind.. Or you hold the screwdriver & have your assistant turn the engine over by using a 1-1/4" socket and a breaker bar on the big bolt securing the front damper... You'll feel the screwdriver either rise or fall... Either way keep turning till the screwdriver comes all the way up & just starts to go back down, then back up to the middle of where it stopped rising & started falling.... The timing mark should be lined up with 0..

1 Wild R/T · Jul 31, 2019

pearljam724 said:
Yeah, you’re right and that’s a great point. I have a dial gauge that I can check that. Which I haven’t to this point. If it isn’t, how is that corrected ?

First you need to make sure the damper didn't slip... Often it's just mismatched parts... If that's the case either re-mark zero on the balancer or find an adjustable pointer that bolts to your timing cover...

pearljam724 · Jul 31, 2019

Thinking back now guys. It was 5 or 6 months ago. I’m pretty sure, I checked that with my dial gauge. But, I’m not 100 percentage positive. I recall the dampener had 2 grooves and I wasn’t sure which to use. So, I used the dial gauge to check which mark was the right one. I definitely remember removing the belts to crank the engine by hand. I’m 99.9 percent sure, but I ll check it again. If anything, maybe I accidentally highlighted the wrong groove. But, I don’t think that was the case. But, it’s a possibility.

Trashdog67 · Jul 31, 2019

pearljam724 said:
2 questions regarding cam shafts:
My car has a rebuilt 360 in it, with supposedly a mild cam as the previous seller told me. I know it definitely has an aftermarket cam in it. It being mild or not is unsure. The car ran very good when I bought it. It runs very good now. I’ve taken it on 100 mile trips in the last few weeks. I did a major tune up on it shortly after I bought it. I wish I would have checked the timing shortly after I bought it and prior to me changing the distributor cap. But, I didn’t. I checked it a few times afterward. No matter what I do, including removing the vacuum hose. It runs best when the timing mark is 3-4 inches retard ? The closest I can get the timing mark to zero degrees is a little less than 1 inch from zero degrees and it doesn’t run as well there. It runs best severely retard. At first I though it was maybe the cheap gun I bought. But, I bought a new better quality one and it reads the same. My only conclusion is it’s the bigger cam causing it ? Does this sound right to anyone that a bigger cam would cause this vast timing change ?
The second question is. Is it possible to verify the exact cam I have without tearing the motor completely apart ? That’s not very important, but out curiousity. I’d like to know possibly.

You replaced the dizzy cap and before that it ran well? Methinks that you misplaced your plug wires by one hole. Try moving them all back one hole and see where the timing mark shows then. HTH

pearljam724 · Jul 31, 2019

Lefty71 said:
You can learn a whole lot about your cam by just pulling the valve covers, if you have a dial indicator and some timing tape handy.

How looking at it, allows you to identify it ? Being a mild cam or a larger one ?

1 Wild R/T · Jul 31, 2019

Well if you do it again you'll either know you marked the wrong groove or the damper is slipping in which case that needs to be replaced before going any further...

moparedtn · Jul 31, 2019

pearljam724 said:
Yeah, you’re right and that’s a great point. I have a dial gauge that I can check that. Which I haven’t to this point. If it isn’t, how is that corrected ?

Use an inexpensive "piston stop" instead. It's much more accurate and makes checking the timing mark a lot simpler.

Install the stop and turn the engine in one direction via the crank bolt until it lightly stops against the tool; mark
where that hits on the dampner.
Reverse the rotation of the engine and when it again stops against the tool, mark the dampner there, too.
The point exactly halfway between the two marks is your true TDC.

This is the one I have:
https://www.summitracing.com/parts/pro-67581

pearljam724 · Jul 31, 2019

Trashdog67 said:
You replaced the dizzy cap and before that it ran well? Methinks that you misplaced your plug wires by one hole. Try moving them all back one hole and see where the timing mark shows then. HTH

I tried that. It wouldn’t even start. Moving all plug wires one hole. I cranked the engine by hand to verify where the distributor pointer was pointing when the balancer was reading zero degrees. I moved the plug wires back one hole to where I had them all along. It fired right up.

1 Wild R/T · Jul 31, 2019

moparedtn said:
Use an inexpensive "piston stop" instead. It's much more accurate and makes checking the timing mark a lot simpler.

Install the stop and turn the engine in one direction via the crank bolt until it lightly stops against the tool; mark
where that hits on the dampner.
Reverse the rotation of the engine and when it again stops against the tool, mark the dampner there, too.
The point exactly halfway between the two marks is your true TDC.

This is the one I have:
https://www.summitracing.com/parts/pro-67581

Yup, the dead stop works very well & is 100% accurate if used correctly.... Unfortunately I've seen a thread where the person used it wrong IE didn't go slow & cracked a piston....

pearljam724 · Jul 31, 2019

1 Wild R/T said:
Yup, the dead stop works very well & is 100% accurate if used correctly.... Unfortunately I've seen a thread where the person used it wrong IE didn't go slow & cracked a piston....

Yeah, my dial gauge is the same exact tool. The needle on the dial rotates one direction. When the piston hits tdc, the dial stops and rotates opposite direction when piston is returning other direction. I like a dial gauge. Because, my particular one goes by millimeter increments. One complete rotation of the dial is 1 millimeter rise or fall of piston movement. It’s very precise.

1 Wild R/T · Jul 31, 2019

pearljam724 said:
Yeah, my dial gauge is the same exact tool. The needle on the dial rotates one direction. When the piston hits tdc, the dial stops and rotates opposite direction when piston is returning other direction. I like a dial gauge. Because, my particular one goes by millimeter increments. One complete rotation of the dial is 1 millimeter rise or fall of piston movement. It’s very precise.

Thing is, at TDC there's about 4 degrees of rotation where the piston doesn't move.... so by using a dead stop bring the piston up till it stops, mark that spot, then rotate the other way till it stops & mark again, now find the mid point between those two marks & you have true TDC...

Who knows cam shafts ?

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