Thread: Chevy 350, zero compression. engine not starting

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Just received a rebuilt long block from a local mechanic. 1972 block, 96 vortec heads. hydraulic lifters, roller rockers. Prelubed it by using an old diff till oil came out of each rod. installed diff, and tried to start. not even a cough. checked compression in cylinders 1, 3, and 2, zero compression. pulled the valve covers and rechecked the hydraulic lifters on cylinder one by going to TDC and making sure both valves were closed. backed off till loose, tightened to zero play and then preloaded 1/2 turn. Also plugged in my air compressor into the spark plug hole using my compression tester adapter and heard no leaks. Any clues guys? Did the mechanic install the timing chain incorrectly maybe? How can I tell? arghhhhhh......

TBC ??????????really????????? needs top dead center TDC

Originally Posted by jerry clayton

tbc ??????????really????????? Needs top dead center tdc

typo.... Tdc.


and all cylinders are zero compression... taking it apart... thinking maybe it's the timing chain?

well, pulled the timing cover... uses the 3 slot cloyes type crank gear... it is on the standard slot, no advance or retard. lined up the "O" mark and the cam mark is sitting at 10 o'clock or there about. figuring it should of been 12 or 6 o'clock... so adjusted the cam gear / chain to 6 o'clock matching both marks... putting her altogether... maybe find out tomorrow if i have compression... ugh.

You can test the compression by cranking it over-don't need to put the front back together-just screw in the tester and crank 'er----------

When you have the cam gear installed at 6PM and the crank gear installed at Noon, the motor is timed to fire #6 spark plug. Before you button up the timing cover, turn the motor over one complete revolution, so that the cam gear is at Noon and the crank gear is at Noon. That will have both valves closed and the ignition set to fire #1 spark plug. Pull the dizzy and re-insert it with the rotor pointing at 5:30PM as viewed from above the motor. Leave room between the vacuum cannister and the intake manifold/firewall so that you can twist the dizzy body to advance or retard the ignition timing after the motor is running. Run #1 plug wire from the 5:30PM position of the dizzy cap to the #1 spark plug. In a clockwise order, insert each subsequent wire according to the firing order 1-8-4-3-6-5-7-2. Condition your brain so that you know 1-3-5-7 are on the driver's side and 2-4-6-8 are on the passenger's side. Your 2 longest plug wires will be for cylinders 1 and 2. Shortest wires will be for cylinders 7 and 8. Here are some wiki articles that I either wrote or had a hand in writing that may help you......
http://www.crankshaftcoalition.com/w..._compatibility
I know you said you're running a roller cam, but you should still know this info in the event you ever build another flat tappet motor......
http://www.crankshaftcoalition.com/w...ips_and_tricks
http://www.crankshaftcoalition.com/w...op_dead_center
http://www.crankshaftcoalition.com/w...stment_SBC/BBC
Please pay particular attention to the valve adjustment tutorial. I'm thinking you have the valves too tight.

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first thanks for the reply...

but oh no. I just read this and she's all buttoned up..... almost ready to fire...

As I said before the crank was at 12:00, the cam at 10:00 so i rotated the cam from 10 to 6:00 so the two marks were lining up... that was per some youtube vides ???? Looks like the attached link but I think you get the picture.

https://encrypted-tbn2.gstatic.com/i...lDvkrhJ5nZ_9gQ

The dizzy was installed so the rotor points towards the #1 mark from the cover... and generally pointed to the #1 cylinder...

but from your reply I have totally screwed up... argue so my option is pull everything apart again...

p.s. it's not a roller cam, it's only a roller rockers and I have prelubed everything using a oil pump tool... I adjusted valves by going to TDC, loosening and retightening till the slop was gone then applying a preload of 1/2 turn... as I understand it the performance guys preload 1/4 turn usually and the factory to one turn... saw a lot of recommendation to 1/2. I'm going to go read all your links.... thanks...

check out the video below at 11:17.... ? I'm so confused

https://www.youtube.com/watch?v=R-Y-bIEtegE

if you have the two marks together at 12 & 6 ( way I do it) you just need to set the dist on #6

I don't know why you would be confused. That video is showing the same thing I told you, cam gear at 6PM, crank gear at Noon, then rotate the crank one complete revolution so that the cam gear is at Noon and the crank gear is at Noon. Now the motor is ready to run the spark plug wiring and phase the rotor at 5:30 PM, firing #1

Chevrolet engineers opted to line up the dots at 6 and noon to fire #6. They could just as easily have lined up the dots to fire #1, without having to turn the crank 360 degrees, but they didn't. You can also assemble the motor with the cam gear at Noon and the crank gear at Noon, so that the motor is ready to fire #1 without turning the crank 360 degrees, but it's harder to see the relationship between the cam gear dot and the crank gear dot with both the dots at Noon because they are too far apart.

Perhaps you're confused because you don't realize that the cam gear, being twice the diameter of the crank gear, rotates 1/2 as fast as the crank gear. For every rotation of the cam gear, the crank gear rotates twice. For every rotation of the crank gear, the cam gear makes half a turn.

I didn't mean for you to pull the motor apart is it was back together. With the cam gear at 6PM and the crank gear at Noon, as assembled, it is only necessary to turn the crank one complete revolution to get the motor timed to fire #1. You can do that when the motor is completely assembled, you don't have to disassemble to turn the crank. You just have to pay attention and make a 360 crank rotation.

Jerry's explanation works also if you pay attention. It has always been easier for me to assemble on #6, then turn the crank to #1.

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ok, so instead of pointing the rotor at the #1 cylinder I'll point it at the # 6 and slide the dizzy in that way? or do I just make the #6 the #1... sorry... feeling very stupid and mislead by youtube video's.

ok, little more reading... so with it setup this way my #1 is at top dead center of the exhaust stroke... i guess I could rotate it and bring it up on the compression stroke ar as suggested set it up for # 6.. I'll read up on that... thanks... you actually made my day

If you are going to time on #6, you would not turn the crank at all and would install the rotor at the 11:30 position, running the wire from that rotor position to the #6 spark plug. Then you would continue plugging in wires at the cap in a clockwise rotation according to the firing order, 5-7-2-1-8-4-3. This will end up having the #1 spark plug position on the cap at 5:30, just like if you had turned the crank and timed on #1 to begin with.

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ok, so just reinstall the dizzy with the rotor 180 from what it is now and leave the wires like they are. Roger on that.

I've never paid much attention to where the dizzy rotor is pointing, and didn't know I could get to #1 tdc by putting gear dot at 12 (after chain is on). I've just left plugs out, and spun the crank with a ratchet, feeling for compression with a finger. Then, I'll put the timing to about where I want it, and set the distributor in place, making sure the dapshot has plenty of room. Next. Put power to dizzy, and rock it back and forth, looking for spark. ( laying a plug on the manifold ). I guesstimate the exact place where the dizzy sparks, and snug it down. Put plugs in, lace the plug wires, prime the carb, and fire it up.

This method puts the engine within 5 degrees timing, confirms spark, confirms compression. Usually fires on first crank.