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Old 02-09-2013, 01:20 PM
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Cam Question

Ive been pulling my hair out for a couple weeks now because of a SBC Ive put together from some parts I had laying around. Its a crate motor short block with a set of 2.02 stock heads. I cant get the thing to run and it is spitting up fuel from the carb. My instinct was a timing issue so I checked my dist. at TDC and I was dead on. Ive checked compression and all cylinders were at 150. When I was turning the motor over by hand I noticed I could hear a pretty big hissing sound coming from the intake. I was convinced I had leaking intake valves and that was the culprit for her spitting up so I pulled the heads and tested them. There was no leaks at all!! After scratching my head some more I turned the motor over with the heads off and noticed that my intake lifter was not down all the way before the piston was on its way up. As a matter of fact it is coming up about an inch before the lifter is fully seated. My question is "Is this normal?" I know different cams have different lift and durration but shouldnt the intake valve be fully seated before the compression stroke starts? I appreciate any insight you guys might have on this.

Thanks,
Andre

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Old 02-09-2013, 01:45 PM
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I did set them dot to dot. I even double checked it yesterday. So a hissing sound coming up through the intake is normal?
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Old 02-09-2013, 02:05 PM
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Sounds like the timing chain is off either 180 out or a tooth off.

Might want to pull the cover and make sure the cam is timed right.

Also double check the wiring it is the most common start up issues plug wires crossed. Even seasoned mechanics do it from time to time. With the hold downs and all the wire close to each other its not hard to get one mixed up. I always make it a point to check it agaist the chart on my wall for firing order and which cylinder is which and cap position for the cyl. One wire off it runs fine one wire crossed it could stop the engine from starting if its always firing at the wrong time.
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Old 02-09-2013, 02:11 PM
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Thanks, it must be somthing stupid. Ive tried a couple different carbs because I noticed excessive fuel in the intake when I removed it. Got a edelbrock off a running vehicle and installed it with no better result. When I took the heads off a few of the cylinders were flooded with fuel! I cant remember if I had the plugs out and turned the motor over after I pulled my bad holley so Im hoping it was just extremely flooded.
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Old 02-09-2013, 02:18 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
after installing the cam and timing gears dot to dot. You must rotate the crankshaft 1 revolution, before
installing the distributor. just like the cam install instructions (that you did not read) tell you. or the spark timing is 180deg out.
and it will not run.
it is fireing on the overlap . make it fire at TDC on the power stroke by installing the distributor correctly.
I understand that the dot to dot position is the compression stroke for #6 and I have verified that I am on the compression stroke for #1 when dropping in my dist.
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Old 02-09-2013, 02:21 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
You are likely hearing it leak past the piston rings. If the cranking compression is 150 its good.

On a stock OEM cam the intake is not fully closed until 40deg ABDC +/- The piston is approx 1/3 past BDC

The bigger the cam the later the intake closes (generally)

Did you verify accurate timing tab TDC location, using a piston stop to find true TDC?
often a issue with non stock aftermarket parts. inaccurate timing setting is the result.

what cam?
It is a stock cam from the crate motor short block.
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Old 02-09-2013, 02:30 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
after installing the cam and timing gears dot to dot. You must rotate the crankshaft 1 revolution, before
installing the distributor. just like the cam install instructions (that you did not read) tell you. or the spark timing is 180deg out.
and it will not run.
it is fireing on the overlap . make it fire at TDC on the power stroke by installing the distributor correctly.

I never uninstalled the cam. Just replaced the chain and gears. Ive been keeping an eye on the oil and It is contaminated. Not my first time. Ive put a sbc together many times on my racecar but it has been about 5 years. Thats why this is so frustrating!
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Old 02-09-2013, 02:43 PM
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Sounds like maybe the cam is wpied a lobe or maybe you have a timing chain set withe the 3 different settings and you have the marks wrong.
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Old 02-09-2013, 02:45 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
what crate motor? they do not all have the same cam in them?

what else did you change.. everything...
Just put a set of fresh 2.02's on and a Q-jet intake. New cap, rotor, wires and plugs. The lower end came from a buddy that had a problem with it so he just bought a new long block. I tore it down and found 3 burnt intake valves. He told me it only had 12,000 miles on it and compression was good. As for the cam specs. I dont know. Is it possible the lift/durration is incompatable with these 2.02 heads?
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Old 02-09-2013, 02:48 PM
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Quote:
Originally Posted by Richiehd View Post
Sounds like maybe the cam is wpied a lobe or maybe you have a timing chain set withe the 3 different settings and you have the marks wrong.
Only 1 keyway in my crank gear! Its my understanding that with that setup it is impossible to be so far off that it wont run as long as the dots are lined up. Would you agree?
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Old 02-10-2013, 01:42 AM
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Think I found the problem. Had the intake off and checked my lifters. Sure enough they were all stuck up. This motor sat in my shop for a couple years and that must have done them in. Gonna throw a new set on in the morning and see what happens.
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