Cam advance question-again?

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aracer01

aracer01

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I asked this before, but I didn't have the timing chain removed until today. I have a Purple shaft cam .484 lift with 108 overlap and I want to use the the 4* key and the 4* gear set for a total of 8*. This is a 1972 factory rebuilt 340 @ +.060 pistons with the deep valve cut forged pistons. The 2.02 J heads were milled .060, with thin steel .020 MP gaskets coated with copper spray.
The pistons are down .100 too. Is it too much to advance it to 100 degrees (8*)? It was run for 20,000 miles at 108 advance and had 128 lbs of compression on the dial gauge. Now I would like more low end torque. I know the proper way is to check clearance, but technically speaking, is 8* OK , if there's clearance?
 
No that's not too much. Just use a degree wheel. Don't assume the keys will get it where you want it without the wheel.
 
Done it a bunch with those cams in low comp engines. 100 is a good place.
 
I have the wheel and stop to check the out come before I close, Thanks for the fast reply, now back to the garage!
 
I've never done this, but before you resort to keys, you might try intentionally offsetting the chain a tooth, then experiment with the sprocket crank key positions.
 
Easy enough to double check the piston-to-valve clearance: Put some very light springs from the hardware store on a cylinder's valves; make sure they are light enough to not compress the lifter pistons down into the bottom of the lifters. Rotate the crank through TDC at overlap for that cylinder, stopping every few degrees, and push down each valve and see how far they move.
 
Nothing wrong with offset keys, I've used them on just about every small block I've every built. One thing to remember, 1º at the cam is 2º at the crank.
 
I ran the 292/509 cam in my 367. I ran it at 112,108,and104. On the street,I could hardly tell the difference. And here I think is why; At 180psi, my cylinder pressure was high enough to spin the tires all the way through the first two gears with 3.55s and 295s. The engine wasn't really loaded until I hit well past 60mph, which put me into speeding territory.
At 128psi your 340 is seriously compromised.A quick calculation, puts your engine at 8.28Scr/6.32Dcr. That .100 deck clearance is over 21CC and it's killing your compression.Advancing that cam will bring the Dcr up to about 6.74, and I don't think you will gain 10 psi in cylinder pressure.But zero decking and a 104 ICA might put your compressions to around 10.33Scr/8.1Dcr.This will bring your cylinder pressure closer to 165psi. This pressure will really wake up your 340.
I know pistons means a do-over, and may not be in your budget. But advancing your current cam, IMO won't solve your torque problem. From what I learned in moving mine around, I wouldn't put the time into it, unless the front was already off. IMO a smaller cam with a much earlier ICA would be a better solution and costs a bit less.But of course you are free to learn at your own pace; that is to say, all the best to you.
 
To the OP, ask Muddog if my installed centerline of 100 suggestion works on that cam. :)
 
I used the 4* cam key and the 4* CAM advance position with the Cloyes chain. I would like to say it was a ***** to mount the cam gear with the MP chain tensioner in the way. The trick is to use the bolt and washer to steady the thing while you find the keyway. I used the crank nut tool to move the chain for position and again to align it. The other styme was the chain cover and the oil pan rubber seal. Trick is to pry down in the upper bolt hole on each side to start the threads. I don't like this job either that's why it took so long to do it.

I saved the stock 340 cam it came with, but I still drag race and this one is good for hi 12's since 1982. With a stock 1970's 340 cam using the 1.6 rockers it's @ .474 intake lift.

It looked like the cam gear "marked" tooth is about 1/3 of a tooth advanced from previous set up, so the whole tooth thing would not work. That would be in the 80 to 90 CL range. IT is now at 101 CL due to original 1 degree error using the original 1982 wheel readings.
I tried to start it today. It ran for about 4 seconds and would not start. Cranking was tight. It needs less timing. The same effect when setting the distributor up. This will take a few minutes and the fumes will get in the house. Tomorrow my friends.
 
what did the degree wheel tell u ? usually the 4* crank sprocket moves the cam 8*. if a naturally aspirated mopar v8 does not like an intake centerline of 104-110 something is wrong
 
8 degree cam advance from the crank on a Cloyes True roller? You other guys can sort this last statement out.
 
when u finished playing around what did the degree wheel say? and what I say is in my experience the 3 keyway crank sprocket moves the cam 8 degrees
 
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