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Old 05-02-2012, 08:51 AM
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Mystery 383 in a truck I just bought, need some advice

Just picked up a '74 3/4 ton chevy truck with a 383 in it. The prev owner seems trustworthy so lets assume it is actually a 383. According to what i've been able to find out and what he's told me here are some specs:

383 with keith black pistons, AFR heads (unknown runner and chamber size), unknown non-factory aluminum dual plane intake (no identifying marks), quadrajet carb, MSD distributor. This is all i know about it.

The way it is set up as i got it, I can get it to pull about 12" vacuum at idle with 12 degrees base timing with vac advance hooked up to a manifold source (the way it came to me). 34 deg total mechanical timing all in fairly quickly.

My question is how do i go about some detective work without pulling it completely down? Mainly interested in what cam it has in it and any way externally to tell if it actually is a 383. Down the road I would like to put a good cam in it and an rpm air gap manifold, but for now i'd just like to know what i've got so i am not blindly spending money on parts i might not need.

Any detective work advice or future cam selection advice would be much appreciated. Truck has a 4 speed manual and will be used as a work truck/dirt bike hauler/sleeper sort of a thing. Needs to have some grunt off idle but also needs to pull hard up top to mess with my friends in their diesel trucks

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Old 05-02-2012, 08:57 AM
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Well, what I would do is take it to a dragstrip, get a couple timeslips, take the MPH and weight of the truck and that should get you close to the horsepower the engine is producing, then take it from there.
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Old 05-02-2012, 08:58 AM
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Quote:
Originally Posted by lgndvs88
Just picked up a '74 3/4 ton chevy truck with a 383 in it. The prev owner seems trustworthy so lets assume it is actually a 383. According to what i've been able to find out and what he's told me here are some specs:

383 with keith black pistons, AFR heads (unknown runner and chamber size), unknown non-factory aluminum dual plane intake (no identifying marks), quadrajet carb, MSD distributor. This is all i know about it.

The way it is set up as i got it, I can get it to pull about 12" vacuum at idle with 12 degrees base timing with vac advance hooked up to a manifold source (the way it came to me). 34 deg total mechanical timing all in fairly quickly.

My question is how do i go about some detective work without pulling it completely down? Mainly interested in what cam it has in it and any way externally to tell if it actually is a 383. Down the road I would like to put a good cam in it and an rpm air gap manifold, but for now i'd just like to know what i've got so i am not blindly spending money on parts i might not need.

Any detective work advice or future cam selection advice would be much appreciated. Truck has a 4 speed manual and will be used as a work truck/dirt bike hauler/sleeper sort of a thing. Needs to have some grunt off idle but also needs to pull hard up top to mess with my friends in their diesel trucks
To find out what cam you have you would need to degree the cam to get the timing and lift figures and then you still don't know what brand just the timing figures.
If you take some pictures of any numbers you see under the valve covers, block, intake, carb and such we can help you out to identify what you got. Any AFR head I have seen has their logo right on the end of it where the accessories bolt to so a pic there would be helpful too.
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Old 05-02-2012, 09:29 AM
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Tear it down tgo a short block and get all the part numbers. Then reassemble.
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Old 05-02-2012, 09:45 AM
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Quote:
Originally Posted by lgndvs88
Just picked up a '74 3/4 ton chevy truck with a 383 in it. The prev owner seems trustworthy so lets assume it is actually a 383. According to what i've been able to find out and what he's told me here are some specs:

383 with keith black pistons, AFR heads (unknown runner and chamber size), unknown non-factory aluminum dual plane intake (no identifying marks), quadrajet carb, MSD distributor. This is all i know about it.

The way it is set up as i got it, I can get it to pull about 12" vacuum at idle with 12 degrees base timing with vac advance hooked up to a manifold source (the way it came to me). 34 deg total mechanical timing all in fairly quickly.

My question is how do i go about some detective work without pulling it completely down? Mainly interested in what cam it has in it and any way externally to tell if it actually is a 383. Down the road I would like to put a good cam in it and an rpm air gap manifold, but for now i'd just like to know what i've got so i am not blindly spending money on parts i might not need.

Any detective work advice or future cam selection advice would be much appreciated. Truck has a 4 speed manual and will be used as a work truck/dirt bike hauler/sleeper sort of a thing. Needs to have some grunt off idle but also needs to pull hard up top to mess with my friends in their diesel trucks
First thing I would do is check the casting number to be sure it's a 4" bore block.

Not all, but most 383 SBC stroker engines are externally balanced. So look to see if the damper is scalloped and if the flexplate/flywheel is counterbalanced.


SBC 400 DAMPER

You can always use a piece of wire down the plug hole to estimate the stroke.

If it's possible, it's always a good idea to disassemble a 'new' engine to be sure the oil clearances are as they should be, ring end gaps correct, oil pump/pick up all up to par, timing set same thing, degree the cam, etc. Then reassemble after it's been checked out w/fresh seals and gaskets.
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Old 05-03-2012, 08:41 AM
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Thanks for the replies so far, much appreciated.

Found some free time last night and pulled the valve covers/accessories. Heads are stamped "180 ST" so i'm assuming they are AFR's 180cc street heads. There is no other AFR markings on the heads other than the guide plates- maybe an old set of their heads? Also some numbers/letters that someone engraved by hand on the heads by the accessory holes that i couldnt make out with the light i was working with. Has a set of Comp 1.6 roller rockers too. I'll try to remember to look for a block number and take a look at the balancer tonight.
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Old 05-03-2012, 09:03 AM
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Quote:
Originally Posted by lgndvs88
Thanks for the replies so far, much appreciated.

Found some free time last night and pulled the valve covers/accessories. Heads are stamped "180 ST" so i'm assuming they are AFR's 180cc street heads. There is no other AFR markings on the heads other than the guide plates- maybe an old set of their heads? Also some numbers/letters that someone engraved by hand on the heads by the accessory holes that i couldnt make out with the light i was working with. Has a set of Comp 1.6 roller rockers too. I'll try to remember to look for a block number and take a look at the balancer tonight.
AFR's have their logo on the ends of the heads. Their guideplates may be used on other heads than AFR...
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Old 05-03-2012, 09:07 AM
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Quote:
Originally Posted by cobalt327
AFR's have their logo on the ends of the heads. Their guideplates may be used on other heads than AFR...
Figured you'd catch my drift. Now i have to figure out what heads these are..
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Old 05-03-2012, 05:18 PM
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Yeah. If you get some photos up, someone will ID them.
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Old 05-03-2012, 05:28 PM
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Here's 3 i took last night. Probably not much help. Any guess as to what intake this is? No markings or anything on it whatsoever.



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Old 05-03-2012, 06:07 PM
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Intake looks like a Professional Products p/n 52013.

Heads might be one of the offshore heads like Procomp, etc.
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Old 05-03-2012, 10:09 PM
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you need around 15 degrees of timing at idle without the vacuum advance connected, then plug it in and run about 30 at idle. You may need to buy a 20 dollar adjustable vacuum advance canister.(summit racing)
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