Sbc new cam and heads won’t start!

I put perfectly fine running double hump heads and a fresh solid lifter 30-30 cam with a Edelbrock performer intake and a Holley 650 double pumper. I’ve taken it apart and back together a few times now and still no luck. Timing is dead on I’ve triple checked installing the timing gear and can’t keep from back firing out of the carb to save my life. Put on a stock 2 barrel intake and carb and was able to run but not idle due to bad carb. My guess is my intake is warped.

 

It’s a Sbc 327 with flat top pistons .40 over. Not a fresh rebuild but ran decent when I decided to upgrade. Hei distributor

 

You need to do an intro post first.

 

Timing, firing order , blown power valve. wrong valve lash.

 

Intake valve holding open, tight guide.

 

I agree. Check the valve lash. You may have the rocker arms too tight.

 

For people to help with any sense of accurateness, the requester NEEDS to get the details correct and complete..!

Camp64 -
You do NOT have .40 pistons, as you note..! No such thing.
You may have .040" pistons though..!

"Timing is dead on".
What does this mean ? "Dead on" what ? The distributor is set to...one degree, five degrees, 12 degrees ? And where, at the crank or total ?
Or...are you talking the timing gears ?
How are we to know what you are talking about ?

Mike

 

Timing was set using the finger over the number one cylinder method. Adjusted while cranking the car and got it where the car was to fire but would just back fire out of the carb even if adjusted further.i have the valve lash adjusted .030 and .030 as what the cam card says and it being a 30-30 cam. The timing marks on the crank pulley and the cam pulley were dot to dot and then turn the motor over so that Both cam and crank dots were pointed at 12 o clock when at TDC. It was a new running power valve in the carburetor a week before this is taking placing.

 

And you dropped the distributor at that location? I think you are 180 out. But on the good side it means you are half right.

 

180 out was my first thought as well. Also valve lash. I had an inline six that I adjusted the valves too tight and it would never fire. Made some good explosions in the muffler until I figured it out though.

 

I will third the 180 out. I speak from experience...

 

When it is at tdc on the compression stroke(finger blown out of number 1 cylinder) I drop the distributor pointed at number one cylinder and adjust timing when cranking.

 

It was also able to run pretty decent with just a stock 2 barrel intake with a Rochester on it but when I switched it back over to this carburetor and intake it back fires through the carb again with out firing for more than a few seconds

 

Did it by chance have a crank timing gear with more than one key way in it?

 

Are you certain that the plug wires are in the correct order? 5 and 7 often get crossed.

 

What method did you use to adjust valves ?

 

Yeah I've checked the spark plug wires for an hei distributor on google image diagrams many time. The crank pulley had 3 key ways and I set it to 0 with the other options being Advanced or retarded I like 4 degrees. When setting valve pash I used the method at tdc on number 1 cylinder and tdc on number 6 cylinder.

 

Do you have someone you trust who could take a look , fresh eyes , you've obviously made an error along the way and now you're missing it ..... Get away from it for a couple days , read through all the procedures , you can guess or speculate till you're purple , it's still a guess.!

My guess is dist. A tooth off ..

 

"Both cam and crank dots were pointed at 12 o'clock when at TDC"

I thought the dots were supposed to be opposite each other on a SBC......crank at 12, cam at 6. Your cam is off by 180 degrees.

 

Cam at 6or 12 , crank at 12 is the same , it's just #1 or#6 firing position , generally , with the cam & crank at 12 , that's #1 firing position

 

Alright thanks everybody one last thing do you think that a bad intake leak could cause this problem. Fires for a second or two and then back fires out of the carb if everything is possibly correct

 

I think "Fresh Eyes" a couple posts up is a very good way to reboot this.

 

Just to clarify, after you felt compression, you continued to roll the engine over until the piston was at the top of the stroke, right?

 

Yeah and the mark on the crank was at 0

 

No,

 

No, bad intake leak won't do that. It does sound like 180 out is a possibility, but again, how did you adjust the valves?
Pull the valve covers, do a search on google for EOIC valve adjustment and do that. When your done with the valve adjustment, go back to #1, watch the intake valve open and close, continue to turn to TDC then do your dist install.

 

As a rough check for valve adjustment , run a compression. check ...

 

Pull the number 6 plug and do the finger test until it blows your finger off the plug hole, where is the rotor pointing ?

 

I set number one to tdc and adjusted exhaust 1,3,4,8 and intake 1,2,5,7 and then number 6 tdc adjusted exhaust 2,567 and intake 3,4,6,8

 

A novice came to my shop, explained much of the same. He said he 'pointed the rotor to #1 after determining engine was TDC, #1.
I asked, "Are you sure it pointed to #1 contact in the cap?"
He said, "No, pointed it to the #1 plug, at the drivers side front of engine!"
More than once I have heard of this...