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Old July 19th, 2011, 11:35 AM   #1
mudslinger89
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Default 383 Stoker

For all you engine wizards out there i've got a question. A couple years ago, my dad and I bought an 82 CJ-7 with what we believed was a 383 stoker. The only thing we know for sure is that is has had block work done to it. It has camel back/hump heads. It was never run before us, but the builder was a drag mechanic. When we put spark plugs in, the pistons would hit, therefore we believe its stroked with high top pistons? We had to put the short stubby plugs in it. It has about 12:1 compression so it runs on race gas. My question is this, is there any better way of figuring out whats in this motor than ripping it apart. Also, whats the best way to lower compression so we can run premium instead of 7 dollar race gas. I figure its replacing heads and pistons but I was wondering if anybody had any tips or tricks. Its got the power to spin 35 on pavement without doing a breakstand right now, we would just like to drive it a little more cheaper.

Any inputs helps, thanks guys.
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Old July 19th, 2011, 12:41 PM   #2
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Find out exactly what model number heads you have. If they are the 62cc heads then replace them with some with some different heads and thicker head gaskets.
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Old July 19th, 2011, 01:08 PM   #3
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That assumes that the heads are stock, unmilled, and the chambers are not modified. Not necessarily a good assumption on a built motor. You also don't necessarily know the heat gasket thickness.

You need to pull it apart anyway to lower the compression.
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Old July 19th, 2011, 01:14 PM   #4
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Trade me for my 283 and you'll be good to go :)

seriously, pull the plug and feed a single strand of 14 Gage wire when the piston is at bottom dead center - only use copper so will not score the wall. measure the length.
This will give you a close enough estimate on stroke to find out if its running a stroker crank or not. 3.48 is stock 3.75 inch (400 crank) makes a 383

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Old July 19th, 2011, 01:28 PM   #5
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thanks guys, i've heard just putting in a different head gasket wouldn't do enough to get it to 93 octane, so i figured I'd be ripping into it sometime. I'll definately try the wire. It would be nice to be able to tell people whats done to it.
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Old July 19th, 2011, 01:50 PM   #6
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Yeah, if its really at 12:1, you'll need to change something to get down to, say 9 or 9.5:1 or so.

Hard to say the right thing until you see the pistons and CC the chambers.
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Old July 19th, 2011, 01:55 PM   #7
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if they are 62cc heads by chance you could change to a set of heads from like a late 70s early 80s chevy truck which some of them have chambers in the 74cc range. if this is the case you should be able to run premium in the motor with the bigger chamber heads
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Old July 24th, 2011, 05:47 PM   #8
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Buy a different carb and run E85.
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Old July 24th, 2011, 07:00 PM   #9
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+1 on chamber volume, also , check into a different cam.
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Old September 6th, 2011, 08:41 PM   #10
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easiest way to tell if it a 400 crank is look at the harmonic balancer 400s were externaly balanced they are partially cut out you can tell the difference between 350 and 400s 350s are all solid. as for running on pump gas half your power comes from the top end so find a good set of 194s but make sure you boost the valve springs so you dont collapse a lifter. 383 run hard ive built a couple of them hope this helps
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Old September 10th, 2011, 09:32 AM   #11
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Quote:
Originally Posted by chevfreak82 View Post
easiest way to tell if it a 400 crank is look at the harmonic balancer 400s were externaly balanced they are partially cut out you can tell the difference between 350 and 400s 350s are all solid. as for running on pump gas half your power comes from the top end so find a good set of 194s but make sure you boost the valve springs so you dont collapse a lifter. 383 run hard ive built a couple of them hope this helps
Assuming the previous owner didn't put the wrong one on.
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Old September 25th, 2011, 07:24 PM   #12
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if they did pit 350 balancer on it the lower end woundnt last long 400 cranks externally balanced same with flyweel put the wrong balancer and on a stoker dont plan on it runnig long but it is possible suprising what some people do
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Old September 27th, 2011, 05:16 PM   #13
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Quote:
Originally Posted by chevfreak82 View Post
if they did pit 350 balancer on it the lower end woundnt last long 400 cranks externally balanced same with flyweel put the wrong balancer and on a stoker dont plan on it runnig long but it is possible suprising what some people do
unless its an aftermarket stroker crank
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Old November 5th, 2011, 12:42 PM   #14
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Easiest way is to swap out your motor for one with a lower compression.

Unless you know exactly what has been done to the motor trying to modify it is going to be a guessing game. The only way to get a rough understanding what your dealing with is to take a head off at the very least.
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