If you mean in your pic 2 pages back. #1 tdc firing is WRONG. The way you show in pic is #6 FIRING TDC.
Where's the Wow?
- Thread starter Freezerman
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nm9stheham
Well-Known Member
I can't resist......
Sounds from this that the damper marks are 20 degrees off. If the OP referenced the 0 timing mark on the cover instead (which is 10 degrees CW from the 10 BTDC mark on the cover), that 0 timing cover mark would line up with the 50 BTDC mark on the damper tape at one end of the motion, and 10 ATDC at the other end of motion. With a 60 degree stop-to-stop range, then the zero mark on the damper tape would be 20 degrees further CCW than it should be.
That would put the crank 20 degrees further CW than true TDC when the damper mark 0 aligned to the timing cover 0. Ignition timing would then be 20 degrees retarded (a great cause for crappy performance). This should not effect cam timing IF the chain set is set dot-to-dot AND the sprockets and crank keyway are machined right (as it would be impossible to get the crank sprocket dot straight up). So the damper marks being off will throw off ignition timing...and be useless for cam timing. Get this: Damper marks are not intended for cam timing. They don't possibly cover the range needed for finding ICL for example.
At this point, the OP should be using the piston stop to:
1) Check crank keyway and sprockets being right or wrong and find true TDC. At the middle of the stop-to-stop range (forget the actual damper or degree wheel readings, just get to the exact center of the stop-to-stop range), then a correctly machined crank sprocket dot should be perfectly straight up and lined up on a line from the crank centerline to the cam centerline.
2) Then at that crank position, find where the 0 mark on the damper lines up to the timing cover and note that particular timing cover mark as the reference point for ignition timing in the future.
THEN the degree wheel gets used to set up cam timing.
Freezerman
Well-Known Member
#1 TDC exhaust stroke.
Excellent explanation thank you.
Excellent explanation thank you.
nm9stheham
Well-Known Member
Just to be sure this is all understood.... this cam has 4 degrees of of ground in advance and would have an ICL of 106 degrees (110 LSA) if installed straight up with dot-to-dot on the sprockets. So another 4 degrees advances from dot-to-dot would put it at 102 degrees ICL. (All assuming everything is machined accurately.)
Don't let me put the wrong words in your mouth RRR but I think this is where you are advising the OP to go. Yes? No?
OP, note the repeated statement of 'assuming everything is machined accurately'; that is one of the key advantages to using the degree wheel and going fully through the cam timing and finding ICL; that process uncovers any parts inaccuracies that can throw off the cam timing many degrees, and allows you to compensate for them.
No problem. TDC should be at end of compression and start of power stroke. Not exhaust. I cant believe pushrods havent been bent yet.
Before buying ANYTHING. I would find TDC #1 Firing with piston stop. Then post pic of crank n cam gear.
My 2 pesos
Before buying ANYTHING. I would find TDC #1 Firing with piston stop. Then post pic of crank n cam gear.
My 2 pesos
Freezerman
Well-Known Member
LOL, it's not as bad as that, I used the wrong term. When the dots are together the rotor is pointing 180 Away from #1piston.
LOL..... this thread, the longer it gets, the more cross-eyed I get. 
nm9stheham
Well-Known Member
A FABO specialty.... LOLLOL..... this thread, the longer it gets, the more cross-eyed I get.
Ok so we will go with "180 off". So put distributor cap on and mark the wire the rotor points to. Is that wire running to #6 cyl?
Freezerman
Well-Known Member
Yes
Cool so that is good then.
cookietruck
Well-Known Member
so freezerman, looks like you didn't have the cam in wrong. you had decent cranking psi for yr static compression and it looked like the dots wanted to line up with a slight rotation.
is the cam in straight up with 4* advance ground into it?
looks like your balancer might've been off, so your ignition timing wasn't ideal.
what's your plan? check the cam with the degree wheel then put it at tdc compression #1 (crank dot at 12 o'clock and cam dot at 12 o'clock if i'm not mistaken)
then put that new balancer on and make sure the tdc mark matches you timing cover and see how it runs?
if i were you, one thing i'd be thinking about is that converter that sounds like it's really tight.
also did you say the motor didn't want to rev much past 4000rpm or so???
is the cam in straight up with 4* advance ground into it?
looks like your balancer might've been off, so your ignition timing wasn't ideal.
what's your plan? check the cam with the degree wheel then put it at tdc compression #1 (crank dot at 12 o'clock and cam dot at 12 o'clock if i'm not mistaken)
then put that new balancer on and make sure the tdc mark matches you timing cover and see how it runs?
if i were you, one thing i'd be thinking about is that converter that sounds like it's really tight.
also did you say the motor didn't want to rev much past 4000rpm or so???
Yes,but also using the compression gauge as I outlined.
Freezerman
Well-Known Member
So this is what it looks like at TDC found with a piston stop. The disappointing part is that my balancer is only a few degrees off. So now I will recheck the cam with a degree wheel and see if I still have some offset keys
nm9stheham
Well-Known Member
Just on thing to consider: The OP's description of the head and gaskets and pistons leads to an SCR of no better than around 8.3-8.4. I suspect he would not see 160 psi (on an accurate gauge) even with 30 or 40 degrees of cam advance; he is just starting too low in SCR. (Plus he is at around 1000' altitude). It looks like he will be doing great to have a true 140 psi cranking pressure with 10 degrees of cam advance.
(Heck, we get a 160-ish cranking compression with a true 10.0 SCR and a similar ICL and closing angle at 2400'.....3.31" stroke though.)
Freezerman
Well-Known Member
The most I had was 150 on #8 the rest were 140 to 145 for cranking compression
nm9stheham
Well-Known Member
OP, do you still have that same crank sprocket? Using the slot with the triangular 'roof' should be for +4 degrees cam timing.
Interesting on the damper. (I did not expect that from you initial report.)
Please take the time to verify the ICL with the degree wheel.
If it is all on time, it is back to the ignition timing, TC and the low SCR..... Am I understanding it right that this is an untouched 1974 bottom end....43 years old?
Interesting on the damper. (I did not expect that from you initial report.)
Please take the time to verify the ICL with the degree wheel.
If it is all on time, it is back to the ignition timing, TC and the low SCR..... Am I understanding it right that this is an untouched 1974 bottom end....43 years old?
nm9stheham
Well-Known Member
If the gauge is correct, then you have more SCR than thought. Trying another gauge would be worthwhile IMHO.
Freezerman
Well-Known Member
After checking the cam it is at 106 CL as the card says. The crank sprocket does have different keyways so if I move it to the other way with the "roof" that will give me the advance I want?
Yes it is original short block. It had no ridges on top of the cylinders and they looked good. The bearings looked fine. Had limited funds at the time so I threw it in.
Yes it is original short block. It had no ridges on top of the cylinders and they looked good. The bearings looked fine. Had limited funds at the time so I threw it in.
Is the cam at 106 installed straight up? If so, then yes, advancing it will bring the cylinder pressure up.
Freezerman
Well-Known Member
Yes it is. Thank you
Then that right there should tell you it needs advancing more........OR you need a smaller camshaft. Since you have the one you have now installed, it would seem advancing it further would be the more economically friendly thing to do.
Well, lobe centers 110 ICL 106 means 4deg adv are ground in as it sets.................................
20-223-3 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts
20-223-3 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts
Yeah, I think that's been cleared up. Like even before this thread. 4* ain't enough advance for THAT cam in THAT engine. THAT is the point I am making.
Lol, I'm just letting the OP know where He's at & where He's headin'...............................4deg plus whatever He's adding.....probably another 4.......................
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