406 new build SBC wont start - Chevelle Tech
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post #1 of 14 (permalink) Old Dec 8th, 19, 1:14 AM Thread Starter
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Steve
 
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406 new build SBC wont start

New build won't start. Won't 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. Haven't checked voltage but nice big ignition feed wire from switch to coil.
Cranking speed is a bit slow but not bad.
Valves are not too tight, push rods can be rolled with fingers with valves closed.
Plug wires 18436572 verified.
With #1 piston near TDC, distributor pointer is at plug wire number one.
Only thing we can find is that compression checks on two cylinders show 40 pounds during cranking rotation.
Beginning to think cam not installed right? We had a degree wheel on it and thought we had it dead on??
Any ideas appreciated.

TXCR13
1966 Chevelle 300 2dr Sedan
385, Flat Top Hypers, Performer RPM, S.M.I. 750 Q-Jet, 72cc Dart Platinum 200cc runners, U.D. Harold 223/233 112 LSA Cam, 700-R4, PS, Manual Disc Brakes, AC, Hedman headers with 2-1/2" exhaust.

1946 Studebaker Coupe- street gasser finally underway!
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post #2 of 14 (permalink) Old Dec 8th, 19, 5:52 AM
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Re: 406 new build SBC wont start

hi
accel pump working
fuel pump ,pumping fuel

spark at dummy plug and earthed to motor

compression with known good gauge

compression stroke No1 piston TDC

Is distributor pointing to no1 cylinder

crank to cam timing, timing chain marks /sprockets installed properly
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post #3 of 14 (permalink) Old Dec 8th, 19, 8:06 AM
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Bob
 
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Re: 406 new build SBC wont start

left out the piston rings? seriously you need to use air pressure like a leak down tester to determine if compression is escaping past the valves, or the head gaskets or crankcase, have you spun the engine with the valve covers off?
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post #4 of 14 (permalink) Old Dec 8th, 19, 1:16 PM Thread Starter
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Steve
 
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Re: 406 new build SBC wont start

Quote:
Originally Posted by swampy 6x6 View Post
hi
accel pump working Yes
fuel pump ,pumping fuel Yes

spark at dummy plug and earthed to motor Yes

compression with known good gauge Yes

compression stroke No1 piston TDC Yes

Is distributor pointing to no1 cylinder Yes

crank to cam timing, timing chain marks /sprockets installed properly
No longer sure about this, as stated at end of my post. Trying to figure it out.

TXCR13
1966 Chevelle 300 2dr Sedan
385, Flat Top Hypers, Performer RPM, S.M.I. 750 Q-Jet, 72cc Dart Platinum 200cc runners, U.D. Harold 223/233 112 LSA Cam, 700-R4, PS, Manual Disc Brakes, AC, Hedman headers with 2-1/2" exhaust.

1946 Studebaker Coupe- street gasser finally underway!
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post #5 of 14 (permalink) Old Dec 8th, 19, 1:21 PM
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Eric
 
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Re: 406 new build SBC wont start

Go back to basics, an engine needs air, fuel and a well timed spark to run. Make sure all of it is correct.

Your just jealous because you can't hear the voices!

1967 Olds Cutlass 468 BBC/T400
1963 Plymouth Fury 440/Torqueflite
2007 Ford Mustang GT (momma's car)
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post #6 of 14 (permalink) Old Dec 8th, 19, 1:23 PM Thread Starter
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Steve
 
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Re: 406 new build SBC wont start

Quote:
Originally Posted by pbcbob View Post
left out the piston rings? Are those the little square shouldered circular thingys???

seriously you need to use air pressure like a leak down tester to determine if compression is escaping past the valves, or the head gaskets or crankcase, The only leakdown we have checked is with the cranking compression. I haven't timed the bleed down rate, but it seems to be quite slow. If you have any specifics on psi to use/leak rate/etc pls let me know.

have you spun the engine with the valve covers off?
Yes indeed. As stated, valves not too tight. Rockers seem to be getting full travel, no evidence of coil binding or rocker issues.

Thanks!

TXCR13
1966 Chevelle 300 2dr Sedan
385, Flat Top Hypers, Performer RPM, S.M.I. 750 Q-Jet, 72cc Dart Platinum 200cc runners, U.D. Harold 223/233 112 LSA Cam, 700-R4, PS, Manual Disc Brakes, AC, Hedman headers with 2-1/2" exhaust.

1946 Studebaker Coupe- street gasser finally underway!
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post #7 of 14 (permalink) Old Dec 8th, 19, 2:52 PM
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Bob
 
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Re: 406 new build SBC wont start

what does the timing light show on the balancer when cranking? does it change if you move the distributor? the point of looking at the valve train is the sequence-does number 8 follow number 1 etc.
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post #8 of 14 (permalink) Old Dec 9th, 19, 12:42 AM Thread Starter
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Steve
 
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Re: 406 new build SBC wont start

Quote:
Originally Posted by pbcbob View Post
what does the timing light show on the balancer when cranking? does it change if you move the distributor? the point of looking at the valve train is the sequence-does number 8 follow number 1 etc.
Haven't tried the timing light yet.

TXCR13
1966 Chevelle 300 2dr Sedan
385, Flat Top Hypers, Performer RPM, S.M.I. 750 Q-Jet, 72cc Dart Platinum 200cc runners, U.D. Harold 223/233 112 LSA Cam, 700-R4, PS, Manual Disc Brakes, AC, Hedman headers with 2-1/2" exhaust.

1946 Studebaker Coupe- street gasser finally underway!
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post #9 of 14 (permalink) Old Dec 9th, 19, 9:23 PM Thread Starter
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Steve
 
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Re: 406 new build SBC wont start

Never mind! I found the problem, and it was me.
Long story fairly short, I reviewed all my receipts for machining and parts.
I ended up with +030 rings for a 350 in my +030 SBC 400.
Sooo...gotta pull it down and change em out.
Nope, this time didn't check the end gap when I started, and it bit me. Hard.

TXCR13
1966 Chevelle 300 2dr Sedan
385, Flat Top Hypers, Performer RPM, S.M.I. 750 Q-Jet, 72cc Dart Platinum 200cc runners, U.D. Harold 223/233 112 LSA Cam, 700-R4, PS, Manual Disc Brakes, AC, Hedman headers with 2-1/2" exhaust.

1946 Studebaker Coupe- street gasser finally underway!
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post #10 of 14 (permalink) Old Dec 10th, 19, 9:45 AM
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Bob
 
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Re: 406 new build SBC wont start

my piston ring joke turned out to be accurate, the messiest screw up I ever had was leaving the oil filter off, I was spinning the primer with a drill while wondering if the oil pressure gauge was bad when I finally noticed the oil flowing all over the driveway
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post #11 of 14 (permalink) Old Dec 10th, 19, 12:20 PM
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Re: 406 new build SBC wont start

Quote:
Originally Posted by TXCR13 View Post
Never mind! I found the problem, and it was me.
Long story fairly short, I reviewed all my receipts for machining and parts.
I ended up with +030 rings for a 350 in my +030 SBC 400.
Sooo...gotta pull it down and change em out.
Nope, this time didn't check the end gap when I started, and it bit me. Hard.
This really doesn't make sense. The difference in bore from the 350 to the 400 is .125. Multiple that times pi (.125x3.1416)gives you a ring gap of .393. Stevie Wonder could see that large of a gap during assembly and know something wasn't right. The 350 rings would be so much smaller they would not rotate in the piston grooves when you offset the end gaps during assembly if they would spin at all. I really don't think you could have gotten a 350 ring on without breaking it. All cylinders would be down on compression, in fact you should have no compression.

I think you should check again and see if you don't have some valves too tight.
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post #12 of 14 (permalink) Old Dec 11th, 19, 12:52 PM Thread Starter
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Steve
 
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Re: 406 new build SBC wont start

Quote:
Originally Posted by sleeper View Post
This really doesn't make sense. The difference in bore from the 350 to the 400 is .125. Multiple that times pi (.125x3.1416)gives you a ring gap of .393. Stevie Wonder could see that large of a gap during assembly and know something wasn't right. The 350 rings would be so much smaller they would not rotate in the piston grooves when you offset the end gaps during assembly if they would spin at all. I really don't think you could have gotten a 350 ring on without breaking it. Rings are 1/16, 1/16, 3/16 so had a fair amount of flex to them. First time I had used these rings and I remember they extended very little beyond piston o.d.

All cylinders would be down on compression, in fact you should have no compression. Haven't checked them all, but believe yes all cylinders are down on compression, around 40 psi.

I think you should check again and see if you don't have some valves too tight. I'm very sure we were OK there, but will check again. Never hurts.
Tks for reply.

TXCR13
1966 Chevelle 300 2dr Sedan
385, Flat Top Hypers, Performer RPM, S.M.I. 750 Q-Jet, 72cc Dart Platinum 200cc runners, U.D. Harold 223/233 112 LSA Cam, 700-R4, PS, Manual Disc Brakes, AC, Hedman headers with 2-1/2" exhaust.

1946 Studebaker Coupe- street gasser finally underway!
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post #13 of 14 (permalink) Old Dec 11th, 19, 3:21 PM
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Dave
 
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Re: 406 new build SBC wont start

I would think it would have at least popped even with only 40 lbs.
After all, gas fumes will explode with no compression at all.
You might have multiple issues.
A cam installed incorrectly, firing order incorrect etc.

good luck
sorry you gotta pull it back apart.

Dave

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post #14 of 14 (permalink) Old Dec 20th, 19, 12:07 AM
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Re: 406 new build SBC wont start

Any further updates on this one??

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