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Old 06-16-2011, 07:59 PM
lt1silverhawk's Avatar
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SBC 350 / SBC 383: Verification Tips and Methods

Quote:
hey whats up i have a 350 but has work on it a 383 kit on it the motor is on the truck right im going to take it
out on sunday so if u would like to heird it run before let me know
$600.00
Hi All,


If one comes across a complete, running engine that is being advertised as a SBC 383 stroker, can the buyer check certain things to verify that the motor is indeed a 383 stroker without having to take apart the motor?


Assuming the buyer cannot remove the oil pan to check the crank for one of various reasons (engine still in the vehicle, hear before you buy, will not pull motor until buyer ready to pay, buyer has no idea what to look for), and the seller does not have any documentation or receipts for the build, what else can he or she do to make sure or get some sort of verification that the motor is indeed a 383?


It is understood that a 383 stroker has a higher compression than a 350. Is there a general range of compression in which a run-of-the-mill or a mild 350 operates, vs the compression range of a run-of-the-mill to mild 383 stroker?


For the sake of simplicity, when answering this question, it is safe to assume that the buyer has no idea what he or she is doing and that in the end, ending up with a healthy 350 isn't too much of a loss.

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Old 06-16-2011, 08:13 PM
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It1silverhawk,

At the local race tracks participants had to have his or her engine pass the "blow" test. The officials would take one spark plug out and connect it to this devise that was calibrated to show Cubic Inches. They would crank the engine and the balloon inside would give the cubic inches of the engine. If your engine was bored over too much it would fail. Some people would over-bore 7 cylinders and leave one stock so they would pass this test. So there must be one of these things around someplace.

Good Luck

Scholman
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Old 06-16-2011, 09:55 PM
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Quote:
Originally Posted by lt1silverhawk
It is understood that a 383 stroker has a higher compression than a 350. Is there a general range of compression in which a run-of-the-mill or a mild 350 operates, vs the compression range of a run-of-the-mill to mild 383 stroker?
Compression ratio is a function of the cylinder's largest volume over it's smallest volume. There are dozens of different piston and chamber combinations available for any displacement or bore/stroke combination that makes just the difference in displacement basically a moot point in determining cr.

The first thing to determine is whether the block has a 4" bore. The block casting number, date code and suffix can all be used to determine what the bore was originally.

That leaves the stroke to be determined. Because there is a ~0.250" difference between a SBC 350 and 383 stroker, I am confident that anyone w/a modicum of attention to detail could use a flexible wire to "measure" a cylinder at both BDC and TDC to determine whether the stroke was 3.5" or 3.75".

The reading of the piston depth will not reflect the actual exact stroke because of the angles involved, but if a known 350 engine's cylinder were measured this way, the difference would be obvious if a 383 stroker was measured the same way.
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Old 06-16-2011, 10:06 PM
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Quote:
Originally Posted by scholman
It1silverhawk,
At the local race tracks participants had to have his or her engine pass the "blow" test. The officials would take one spark plug out and connect it to this devise that was calibrated to show Cubic Inches. They would crank the engine and the balloon inside would give the cubic inches of the engine.
It's a P&G checker. Been around for years. I used one to check cubic inches at the Nationals in Pomona one year. They've been used around circle tracks and drag strips for a long time and probably a little searching and calling around would find one that you could borrow or rent from a circle track operation. If I had one I was gonna rent you, I'd want a 500 dollar deposit.
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Old 06-17-2011, 05:03 AM
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Aren't the 350's internally balanced and the 383 externally balanced with a weight on the flexplate? If true that would be an easy check.
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Old 06-17-2011, 06:14 AM
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Weighted flex plate would only be used on an OEM 400 crank or an after market crank that must be externally balanced. There are internally balanced 383 cranks available. What makes this 383 attractive? Is it because of a very low price? If so, I would be become more interested in the real, verifiable thing for a few bucks more.

Trees
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Old 06-17-2011, 06:15 AM
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That depends on which engine kit is used. Some are external balance, some are internal balance. With the 383ci size as popular as it is, it can go either way.

You have to measure.
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Old 06-17-2011, 08:17 AM
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If it has enough power for you....Why would you care which it is ?

There's lots of "350" and "383" engines around that look like they have never been apart.

Buyer Beware !!!


454 RATTLER
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Old 06-17-2011, 12:21 PM
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Hi all,


Quote:
hey whats up i have a 350 but has work on it a 383 kit on it the motor is on the truck right im going to take it
out on sunday so if u would like to heird it run before let me know
$600.00
The above is an actual local Craigslist ad. Lets treat this as a generic ad that all those who browse Craigslist have come across at some point. If it helps, consider how you would approach this potential purchase if you were interested in buying a 383 stroker.



--------------------------------



Quote:
Originally Posted by cobalt327
The first thing to determine is whether the block has a 4" bore. The block casting number, date code and suffix can all be used to determine what the bore was originally.
Research information before hand. Contact buyer and ask for casting number. Use this info to determine if the block has a 4" bore. Or check online on your cellphone or have someone near a computer with internet access who can run the numbers for you while you visit the buyer.




Quote:
Originally Posted by cobalt327
That leaves the stroke to be determined. Because there is a ~0.250" difference between a SBC 350 and 383 stroker, I am confident that anyone w/a modicum of attention to detail could use a flexible wire to "measure" a cylinder at both BDC and TDC to determine whether the stroke was 3.5" or 3.75".

The reading of the piston depth will not reflect the actual exact stroke because of the angles involved, but if a known 350 engine's cylinder were measured this way, the difference would be obvious if a 383 stroker was measured the same way.
A quick, on the fly method for getting some kind of measurement that can be used in conjunction with the info decoded from the casting number. Useful when visiting a yard or a local car parts swap meet.



------------------------------------



Quote:
Originally Posted by scholman
At the local race tracks participants had to have his or her engine pass the "blow" test. The officials would take one spark plug out and connect it to this devise that was calibrated to show Cubic Inches. They would crank the engine and the balloon inside would give the cubic inches of the engine. If your engine was bored over too much it would fail. Some people would over-bore 7 cylinders and leave one stock so they would pass this test. So there must be one of these things around someplace.
Quote:
Originally Posted by techinspector1
It's a P&G checker. Been around for years. I used one to check cubic inches at the Nationals in Pomona one year. They've been used around circle tracks and drag strips for a long time and probably a little searching and calling around would find one that you could borrow or rent from a circle track operation. If I had one I was gonna rent you, I'd want a 500 dollar deposit.
If available, use a P&G or other brand cubic inch tester. They are rather pricey for one time use, ranging from $600 to well over $1000 depending on the model. Renting or borrowing may be an option.



-----------------------------------------



Quote:
Originally Posted by chucksrt
Aren't the 350's internally balanced and the 383 externally balanced with a weight on the flexplate? If true that would be an easy check.
Quote:
Originally Posted by trees
Weighted flex plate would only be used on an OEM 400 crank or an after market crank that must be externally balanced. There are internally balanced 383 cranks available.
Quote:
Originally Posted by cleanspeed1
That depends on which engine kit is used. Some are external balance, some are internal balance. With the 383ci size as popular as it is, it can go either way.

You have to measure.
While keeping in mind that 383 stroker cranks are available internally balanced, check for an externally balanced crankshaft by checking for a weighted flex plate.



------------------------------------------



Quote:
Originally Posted by 454 Rattler
If it has enough power for you....Why would you care which it is ?
If the motor is being pulled from as running vehicle, while keeping an eye things like acceleration, also try the seat-of-the-pants feel or the "butt dyno" to see how strong the motor feels.



-------------------------------------------



Quote:
Originally Posted by trees
What makes this 383 attractive? Is it because of a very low price? If so, I would be become more interested in the real, verifiable thing for a few bucks more.
Quote:
Originally Posted by 454 Rattler
Buyer Beware !!!
Don't get lulled into a bad deal because of an attractive price. Research first. Do the math on what is actually being offered for sale and compare with the cost of having to do it from scratch if the engine turns out to be bad or a 350. Ask the seller questions on the build: receipts, documentation, history. Check the running condition if possible. Then make a decision. It the deal is too good to be true, it probably is.



---------------------------------------



I'll be using myself as guinea pig for some of these tips. If I had the time, money and space, I'd go check out the motor advertised just to learn something.


A couple of years ago, when the "hotrodding bug" took a strong bite, I bought an '84 Camaro T-Top that was advertised as possibly having a 383 stroker motor that needed the carburetor rebuilt. The vehicle also came with a five gallon fuel cell, carbon fibre cowl hood, M/T slicks and skinnies, suspension upgrades for drag racing, a switch panel for turning various things on and off, a start button, wiring redone, no emissions equipment, a huge aluminum radiator, dual electric fans, battery relocated to the truck, no keys for anything and, interestingly, a complete interior.


The seller said he was the first owner and he had bought it and sold it back to his buddies several times. After buying it back one last time from his buddy who was turning the car into a dragster, he decided he wanted it gone as he was tired of seeing it around. He was quite a ways away from me and offered to deliver it for a fee. Long story short, I thought the deal was good, even if the motor didn't turn out to be a 383. He delivered it, and the car has sat in my garage ever since.


The motor turns over but doesn't start. The fuel is shooting from the fuel lines. I bought a used/rebuilt carb for it that I am now 100% certain I never set up properly.


Now, not to make this into a "help me get my motor running" thread, I am going to try using the information that you guys have offered here to see what I can determine before finally pulling the oil pan off or even pulling the motor itself out.


Thank you everyone for your very helpful tips and info!
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