i have a early model 383 short block and i want to put it in my 96 yukon and use my l31 heads and injection. what do i do about crank sensor, cam and lift options and what do i need to know to finish it up and do it right. please help me out guys i am lost and i need to finish it quick.......
at this time i have....
:383 shortblock
:400 balencer and fly wheel
:l31 heads and intake
and im lost....lol, please tell me what i need to know guys, i just got back from iraq and i need to get the truck going..... thanks

 

This is Jon Goodman of Lawton Oklahoma and I have already done what u are attemting to do with your Tahoe. I have a 97 chevy truck with 383 and I know everything it takes to make it all work together. I am not much with typing so if you are interested you call me at 580 678 1765 or email me at Jongoodmanmechanic1@yahoo.com. I can help you with cam,heads, and my own personal fuel injection retrofit kit for the factory L31 CPU and motor.


Need help,I've been there and done that and its not that hard.
Trust a custom fabricator and mechanic. Lincoln Tech Trained
Jon Goodman

 

You need to fit the plastic front timing chain cover from teh Vortec 350 onto the older 383 block. This plastic cover houses the crank postion sensor. This plastic cover has 8 bolt holes vs. the older blocks 12 bolts. Everytime you loosen the bolts on these plastic covers you are supposed to buy a new cover. GM says to use RTV on the covers to prevent leaks. The older block 383 will not work without teh crank position sensor.

The Vortec heads need to be installed onto the 383. They should just bolt on, then install the GM intake gaskets and torque the intake down in 3 steps with a final torque of 11 lb/ft.

The Vortec heads do NOT use guide plates, because of this you will need to use rocker arms that are self aligning. The self aligning rockers have 2 little nubs that keep them centred on te valve when running. You shoul dbe able to use the ones off of your Yukon.

The early 383 block is not equipped for rollercam, the stock 350 has .414"/.429" of lift and 191/197 degrees of diration (roughly) on a 111 LSA. You are going to need a cam that uses flat hydraulic tappets. Because the Vortec used roller lifters which are longer than the flat tappets, you will need to purchase a set of longer pushrods.

You must stay under 0.475" of lift on the Vortec heads with the stock vortec springs and retainers. If you use comp cams 918 Beehive springs and accompanying retainers and locks, you can run up to .550" of lift and still have lots of safety clearnce. The 918 springs are around $180 but are well worth it.

You will need to use the 400 balancer if your 383 is externally balanced, the problem is that there is a reluctor ring that must be used to trigger the Crank position sensor in the Plastic front cover mentioned above. You will also have to use the 400 flexplate, which may or may noy require a different starter.
I am not sure if the balancer will fit at the front of the block or not, yiou will have to take the reluctor ring off the Vortec balancer/crank and install it onthe older 383.

It would have been easier to use the Vortec block, and make an internal balance 383, then you can use rollercams, the front crank sensor stuff would be easier.

if you have any more quetsions, feel free to ask.

peace
hog