406 SBC Wont start - Team Camaro Tech
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post #1 of 29 (permalink) Old Dec 7th, 19, 06:52 PM Thread Starter
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406 SBC Wont start

New build wont start. Wont even sputter or try to run.
406 SBC, hydraulic rolller cam, 10-1 static compression, 65 cc heads and dished pistons with .010 deck, 49 quench, 780 carb, small HEI.
We are getting fuel to the cylinders.
We are getting spark at the plugs. Cranking speed is a bit slow but not bad.
Valves are not too tight.
Plug wires 18436572 verified.
Exh opens and closes, intake opens and closes at at this point the timing marks on balancer are at timing tab.
Distributor pointer is at plug wire number one.
Only thing we find is that compression checks on two cylinders show 40 pounds.
Beginning to think cam not phased right?
Any ideas appreciated.
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post #2 of 29 (permalink) Old Dec 7th, 19, 07:54 PM
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Re: 406 SBC Wont start

Am I wrong in thinking that if the cam was phased that far out that a piston would hit a valve? If I'm wrong, you could be right. But I would think that 40 lb. compression would move around. I'm interested in what's going on here as well. It should at least try to fire.
I'm also thinking very weak spark. I've had spark before but was too weak to fire motor.

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post #3 of 29 (permalink) Old Dec 8th, 19, 04:27 AM
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Re: 406 SBC Wont start

You have the distributor at #1 during the Compression Stroke? You could be 180 degrees off.

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post #4 of 29 (permalink) Old Dec 8th, 19, 04:41 AM
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Sounds like you have more than one problem.tge compression is crazy low. If it's got the correct amount of spark it should at least sputter. 180 out would backfire or pop out of the intake. Possible the plugs are gas fouled, but that doesn't explain the compression loss. Sure the timing mark on the balancer is correct? My 409 uses a 350 balancer and flywheel.

You need to figure out if the timing is indeed correct, and then figure out what's up with the compression . Then worry about the spark.

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post #5 of 29 (permalink) Old Dec 8th, 19, 07:25 AM
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Re: 406 SBC Wont start

Dizzy may be 180 off

Pull plugs. Are possibly fouled. If so clean them well and blow out with compressed air.

Pull plugs

Compression. Valves may be too tight. Pull rockers on the low cylinders and check compression.

Crank speed may be due to timing being too far advanced which would also keep it from firing.

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post #6 of 29 (permalink) Old Dec 8th, 19, 07:45 AM
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Re: 406 SBC Wont start

My guess would be distributor out 180

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post #7 of 29 (permalink) Old Dec 8th, 19, 09:54 AM
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OP days it will not even sputter. If it's 180 out it will backfire . Not bragging, but done it a few times when trying to cut corners. Valves could be too tight, but he has more than one problem.
eville and R/T like this.

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post #8 of 29 (permalink) Old Dec 8th, 19, 11:05 AM Thread Starter
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Re: 406 SBC Wont start

Quote:
Originally Posted by Brettallen59 View Post
You have the distributor at #1 during the Compression Stroke? You could be 180 degrees off.

Brett.....
Yes, verified a number of times with covers off.
Thanks.
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post #9 of 29 (permalink) Old Dec 8th, 19, 11:11 AM Thread Starter
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Re: 406 SBC Wont start

Quote:
Originally Posted by X-77 keith View Post
Sounds like you have more than one problem. We certainly may.
tge compression is crazy low. Agree
If it's got the correct amount of spark it should at least sputter. Agree
180 out would backfire or pop out of the intake. Agree
Possible the plugs are gas fouled, but that doesn't explain the compression loss. Agree
Sure the timing mark on the balancer is correct? My 409 uses a 350 balancer and flywheel. We think so. With cover off and piston at TDC according to rocker positions, the mark on the balancer is at the tab.

You need to figure out if the timing is indeed correct, and then figure out what's up with the compression . Then worry about the spark.
Agree. Beginning to wonder if cam is out of phase just enough to affect compression, but not contact valves. We used a degree wheel and too our time, but beginning to wonder. Stumped right now.
Thanks!
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post #10 of 29 (permalink) Old Dec 8th, 19, 11:14 AM Thread Starter
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Re: 406 SBC Wont start

Quote:
Originally Posted by Vega$69 View Post
Dizzy may be 180 off

Pull plugs. Are possibly fouled. If so clean them well and blow out with compressed air. We pulled them, smelled like gas but not wet and dont believed fouled. Will blow off for sure.

Pull plugs

Compression. Valves may be too tight. Pull rockers on the low cylinders and check compression. All pushrods can be rotated with fingers with pistons at TDC, so should not be too tight.

Crank speed may be due to timing being too far advanced which would also keep it from firing.
Yep. We started out with mild advance, then more advance, then retarded. Nothing helped.

Thanks.
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post #11 of 29 (permalink) Old Dec 8th, 19, 12:06 PM
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Re: 406 SBC Wont start

Not a fan of adjusting the valves by rotating them. I have better luck moving them up & down to find zero lash.

What valve lash did you use? 1/2, 3/4, 1 turn down?

Are you using a timing chain or is the gear drive?

When you installed the timing chain (I'm assuming you went that route), did you advance or retard the crank gear?
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post #12 of 29 (permalink) Old Dec 8th, 19, 09:50 PM Thread Starter
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Re: 406 SBC Wont start

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Originally Posted by bob15 View Post
Not a fan of adjusting the valves by rotating them. I have better luck moving them up & down to find zero lash. I think that method works too. At this point we are satisfied that the valves are fully seating and not too tight, but we will continue to recheck. We don't mind being wrong.

What valve lash did you use? 1/2, 3/4, 1 turn down? Just over 1/2 turn.

Are you using a timing chain or is the gear drive? Cloyes chain.

When you installed the timing chain (I'm assuming you went that route), did you advance or retard the crank gear?
For this build, we installed everything straight up, no advance or retard. At the time our checks with the degree wheel showed the intake begin to open just as specd on the cam timing card. Stumped.
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post #13 of 29 (permalink) Old Dec 9th, 19, 12:41 AM
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Re: 406 SBC Wont start

What is the compression of the other cylinders?

A cam being a tooth or three out of time won't necessarily lead to piston/ valve contact but compression will be off for sure and especially when comparing one bank to the other. But compression should be constant throughout that bank (Normal/ low... etc) and not wonky on just two cylinders.

That being said two cylinders with low compression still won't affect the other six trying to fire.

Fuel wash/ glazed cylinder walls, wrong size rings, or valves not seating are all good ways of having low compression and not fire, and too small of rings and it definitely won't sputter or try to start.

Checking the cam timing is an easy-ish place to start though and makes sense.
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post #14 of 29 (permalink) Old Dec 9th, 19, 09:46 AM Thread Starter
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Re: 406 SBC Wont start

Quote:
Originally Posted by Dash808 View Post
What is the compression of the other cylinders?

A cam being a tooth or three out of time won't necessarily lead to piston/ valve contact but compression will be off for sure and especially when comparing one bank to the other. But compression should be constant throughout that bank (Normal/ low... etc) and not wonky on just two cylinders. If the cam is off a tooth or two, it seems that all cylinders would be the same, and not vary one bank to the other??

That being said two cylinders with low compression still won't affect the other six trying to fire. Yep.

Fuel wash/ glazed cylinder walls, wrong size rings, or valves not seating are all good ways of having low compression and not fire, and too small of rings and it definitely won't sputter or try to start. Cylinder walls really looked good back from fresh bore with and hone with torque plate. Beginning to wonder about rings. We remarked when putting this engine together how easily we could rotate it through the process. Rings were marked right size, and seemed to install with normal effort. But, I think a leak down test may tell us a lot more.

Checking the cam timing is an easy-ish place to start though and makes sense. We have been checking this with valve cover off by getting #1 cylinder at TDC after exhaust valve closes, then watching balancer come over to timing marks as intake opens, and it certainly seems where it needs to be to run. Do you have another way you recommend to check timing, short of pulling the cam cover and re-verifying the setup? We are getting closer to doing that, if nothing else pans out.
Thanks for your help!
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post #15 of 29 (permalink) Old Dec 9th, 19, 10:26 AM
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Re: 406 SBC Wont start

We have been checking this with valve cover off by getting #1 cylinder at TDC after exhaust valve closes,
then watching balancer come over to timing marks as intake opens, and it certainly seems where it needs to
be to run.

If you are seeing the intake valve opening then you are not on TDC of the compression stroke. The plug
needs to fire at TDC (actually slightly before) on the compression stroke. Both valves closed. Not as the
intake valve opens.

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