72 360 first start question

-
Actually when I have done rockover I have had the intake off & I go by the lifters themselves (not that I recommend that you go back in there). I dont have the final word on the compressed or uncompressed (from the oil) & I hope others can chime in on that. yes you want em both moving & go back & forth on the dampener bolt till the height is the same. actually I'd start with the slit at TDC & see how close that gets you for a start then work the height/movement
 
I guess I'm a little confused as to what I'm looking for. I thought the hope was that both the springs were equal height when uncompressed and that would signify that the timing marks were indeed lined up. But maybe I'm missing something.??
 
ok I'll give it another go tomorrow. So if my springs aren't moving like you said what would that indicate? The springs are dead on exactly at at TDC. I'll look at it again and note when each springs starts to move after TDC exactly. This one's not going down easy, thanks for the help.
 
I thought the hope was that both the springs were equal height when uncompressed
Click to expand...
when #1 or #6 cyl is on TDC compression the cam will be on base circle and you will be able to move the dampener aways a bit either way from the slit being at zero (TDC) without there being any spring movement. If that is the case then going (1) turn on the dampener will put the slit back to zero (TDC) and you will now be on overlap which is what we want then at that position you can move the dampener till the springs are (1) the same height (compressed amount) and they both will be compressed SOME (2) & going back & forth a bit on the dampener they both move. (3) at that point get em equal & see where the slit is at
 
Mophile said:
ok I'll give it another go tomorrow. So if my springs aren't moving like you said what would that indicate? The springs are dead on exactly at at TDC. I'll look at it again and note when each springs starts to move after TDC exactly. This one's not going down easy, thanks for the help.
Click to expand...
Let me give you more procedure detail to work with:

1. DON'T look at the timing mark on the crankshaft until step 4. Turn the crank CW and watch #1 exhaust valve & spring. As you rotate the crank, the exhaust valve will open (spring compresses), peak out at maximum opening and then start to close (spring opens up).
2. At this point, slow down your rotation speed waaay down to a few degrees per movement of the crank, and watch the exhaust closing AND watch for the intake valve and spring to start opening. The intake will start to open before the exhaust is fully closed.
3. Stop at the exact point where the exhaust spring is compressed the same amount as the intake spring. You may have to slightly move the crank back and forth and measure the spring heights carefully to find this point.
4. When you find this point where intake and exhaust valve springs are compressed equally, measured as precisely as you can, THEN look at the mark on the crankshaft. It should be about 4 degrees in advance of TDC. If it is anywhere far off, then the cam is off some number of teeth.

This is supposed to be an approximate, quick check of cam timing, and, as said, depends on the lifters not bleeding off. (You have been given some tips on how to check for this.) I'll suggest at this point that if this procedure is not clear, you may be better off just taking off the timing cover and checking the dots on the sprockets.

Part of what may be confusing you is that there are 2 TDC events in a 4 cycle engine; in other words, TDC is reached TWICE in a complete cycle of the cam and valves. It sounds like you are finding the 'other' TDC point, where both valves are closed, and need to find the right one, where 2 valves are both open equal amounts. Find that point first, and then and only then look at the mark on the crank.
 
Ok that makes a lot more sense. I was measuring TDC when the valves are closed and springs uncompressed. Which i thought was kind of pointless because the valves were closed, how would that tell me anything. Now I'm on the trolley. I'm gonna go give it a shot now. keep you posted. thanks.
 
Ok so i followed your procedure to the tee. and it looks good. I measured my valves at exactly that moment when the exhaust valve is closing and the intake valve begins to open on the non compression stroke and at 2-3 deg. BTDC they are exactly the same 1.770 inches. It's difficult to get a caliper on the springs so i used a feeler gauge held tight up against the spring touching the seat and made a mark on it with a sharp awl. I was careful to make sure that i put the feeler gauge in exactly the same position on the other valve. then I measured the marks with the caliper. So does this suggest that my cam is not out of phase? Here's hoping.
 
I also measured several times with several different feeler gauge strips just to be sure.
 
Why would you hope your cam was not out of phase? If its in right you still have a unknown problem. JMO
 
So after the rock over test, I went back and retightened all the intake bolts and ports. It's been run a dozen times now so just to make sure. I set the initial at TDC this time and ran it pretty damn good. It started needing a lot of advance and throttle but I let it run for a while and slow backed each one down. I was able to get it to run at 10 deg advanced with the throttle resting. It still feels like it's gonna snap my neck when i put it in gear but it's running pretty solid at this setting. I think it may still be a tooth off. I'm gonna reset it again tommorrow, but pretty damned pleased at this point. Thanks for sticking with me through all this. I think it was a combo of missed timing and vacuum. I'm gonna do vac. test tomorrow as well.

it's beer thirty.
 
First you're 'on the trolley'....now you're 'off the wagon' LOL.

Well, your test results sound good as long as you did it without reference to the crank mark while measuring the valves and then looked at the crank pointer afterwards. I just emphasize this 'cuz it needs to be a blind test in a way, so you don't fool yourself; cam timing is an easy place ofr anyone to foll themselves. At some point, if I was you, I would learn how to use a degree wheel and recheck the intake valve for what is called 'intake center line' (ICL) which is a precise spec on your cam timing and is no the cam card. Just do this to be sure on the cam timing.

Maybe you are getting it licked now. BTW, were the heads shaved in the rebuild or the block decked? I ask as any intake sealing issue will often start with either such operation being done, without the necessary matching machine work in the intake.
 
I see what you mean about the crank mark. I actually did it by looking at the valves and then measured, and then moved them and remeasured to see where they changed size. The heads were shaved and the block was decked. I'm not saying that i don't still have a vacuum leak but everything seemed to start working better after i retorked the intake. It's getting there.

thanks
 
Mophile said:
I see what you mean about the crank mark. I actually did it by looking at the valves and then measured, and then moved them and remeasured to see where they changed size. The heads were shaved and the block was decked. I'm not saying that i don't still have a vacuum leak but everything seemed to start working better after i retorked the intake. It's getting there.

thanks
Click to expand...
OK, well how much were the heads shaved and how much was taken off the block? If more than a certain amount, and especially if not done at the proper angles, and the intake was not machined to match, that could cause intake sealing problems.

If the intake angles are not right, then you may well be fighting this over and over. Here are pix of how well matched the intake and head angles are on our build with new heads and intake; these are prior to any torquing of the intake bolts, and on block decks no more than .002" from square to the bores vertically and pretty much perfect-on horizontally.
 

Attachments

  • DSCN1730.jpg
    66.1 KB · Views: 122
  • DSCN1738.jpg
    57.4 KB · Views: 118
i think we're really close, gotta do a bit more but it's running on it's own without being pegged and crazy advanced. So right now I have the initial advance at zero and when i ran it originally it started running with around 25-30 deg advance on the timing light. Then i was able to back it down to about 12 deg. and lower the throttle. It sounds pretty good at this setting but what do you all think i should be shooting for with this cam timing wise?

thanks again
 
Ya know I think that's exactly what's going on. I noticed what appeared to be an uneven amount in one corner and tried to correct it with sealant. After I retorked everything it seemed to help so hopefully it's air tight now.

thanks
 
Mophile said:
Ya know I think that's exactly what's going on. I noticed what appeared to be an uneven amount in one corner and tried to correct it with sealant. After I retorked everything it seemed to help so hopefully it's air tight now.

thanks
Click to expand...
So do you have the numbers on how much the heads were shaved and how much the block was decked? Just trying to use those to help you make a judgement on how much you ought to worry about this.
 
My stock 83 318 was at 18 initial on ported. I would say 15-20 in your case & that'd likely require shortening the mech adv amount but you'd be OK with that amt for now for your basic troubleshooting to get it running. FBO sells a plate for $25 to your door that lets you easily take care of limiting the advance. What idle speed are you able to get it down to now? I'm hoping low enough so we are on ported. So the cam is correct and it was a vac leak & they are a real pain to deal with & you may or may not still need to pull the intake but we're getting there!
 
unfortunately I don't know how much they took off when they decked the block and worked on the heads. I remember he told me he took off as little as possible but got it good and flat. I wasn't thinking about the intake fit then. hindsight's got high beams.
 
it would appear to have been vacuum and the fact that Iwas setting it off the incorrect timing mark. Right now like i said the initial is at zero. I'm gonna go try and set it at 15 and see if it'll go. keep you posted.
 
ok so here's my new question, regardless of wether the dampener set at zero or 15 or 30, Am i meant to point the rotor at the tooth that is approaching #1 cylinder ) basically (#3CYLINDER) or directly at the #1? If I'm directly at #1 with the dampener at 15 deg. it doesn't wanna run that well. but pointing at #3 approaching #1 it wants to run all day. I still can't get it to a reasonable idle. At the above described setting i can get it to run with no throttle screw advance, and backing the diet. down all the way to 12-24 deg. advanced. That sounds fine but it's still sounds like it's gonna snap my neck if i try and put it in gear. If i back the dist. down one more degree it suddenly sounds like a good idle but then wants to die. super close but still confused????
 
You must log in or register to reply here.
-

Back
Top