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Old 09-01-2010, 10:14 AM
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Gm L31 880 Block Stroker Question

First of all...I'm a newbie to the forum and there is alot of great info shared on this board....so I have noticed from Google search

I have noticed there's alot of controversy on these L31 "880" blocks with people saying the bores are too short to stroke these out to a 383? I did however find one good post on here where a gentleman said they have stroked a few of these with the traditional 3.75" crank and 6" rods...of course clearancing the block but that's minimal problems.

i noticed the talk about the HT383 blocks using the 880 casting, but using a 3.800" stroke crank?

I'm gonna leave this up to you veterans and see what comes of this here...thanks guys and glad to be here! If there is a deciding factor here, I will do a thorough writeup on my build so maybe it can be used as a reference to many others searching...with part numbers as well!

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Old 09-01-2010, 10:30 AM
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Since I have some 880 blocks and some old flat tappet blocks I looked into this just a little while ago. First block I checked was a 880 casting that came out of a 97 Tahoe, the bores measured 5 9/16. Next I checked a 73 010 block that came out of a van the bores measured 5 7/8, very close to 6 inches. Last I checked a 96 880 casting, it`s bores measured 5 7/8 like the older flat tappet block so it looks like there`s some truth to the bores being shorter. I don`t know if that`s because the blocks were cast at different plants or if it were a new mod to cut down production costs. Both 880 blocks of mine have been decked so I don`t know where they were casted.
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Old 09-01-2010, 10:38 AM
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Thanks for the measurements double! Good stuff..

Now I also have the 97' block as well...so I will measure mine when I get home this evening and post it up. To my knowledge, it has not seen a machine shop before because the guy seemed to have little knowledge of motors (or just played dumb for the sake of making the sale).

If it is a little shorter...wonder how I would remedy this? I heard of using the 3.800" stroke and 5.7" rods...but I wanted to use a 6" rod so....hmmm

Shooting for a streetable 383 with around 450hp with these Vortecs, and potential for more when I purchase aluminum heads.
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Old 09-01-2010, 11:01 AM
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A 3.8" stroke would make the problem worse- if the is one, but there's not. You can run a 3.75" stroke if you wish with no problems.
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Old 09-01-2010, 11:40 AM
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3.75" stroke w/6" rods? I'm hoping...like I said I will clearance all day as long as the motor will be solid. I just sold my 010 4 bolt block about 6 months ago...
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Old 09-01-2010, 11:47 AM
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Quote:
Originally Posted by callmej75
3.75" stroke w/6" rods? I'm hoping...like I said I will clearance all day as long as the motor will be solid. I just sold my 010 4 bolt block about 6 months ago...
Assuming you have a 4 bolt 880 you're better off- easy to run a roller cam and 1pc rear seal.

To figure if its safe add your stroke to your ch and your wrist pin diameter, subtract from your bore length- as you can then see you can run one of the 4" cranks in a 880 block.
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Old 09-01-2010, 11:57 AM
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Gotcha...it is a 2 bolt...but i will probably either run ARP main studs or splayed caps. Not going to run much over 500hp overall once everything is done.
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Old 09-01-2010, 11:59 AM
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Quote:
Originally Posted by turbolover
Assuming you have a 4 bolt 880 you're better off- easy to run a roller cam and 1pc rear seal.

To figure if its safe add your stroke to your ch and your wrist pin diameter, subtract from your bore length- as you can then see you can run one of the 4" cranks in a 880 block.
what do you mean by ch?
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Old 09-01-2010, 12:05 PM
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Ch- compression height of your piston.

Different bolts do nothing for cap walk, if you plan on keeping it below 5500 rpm then a 2bolt should suffice. Otherwise get splayed 4 bolt caps.
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Old 09-01-2010, 12:13 PM
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Splayed for insurance...thanks Turbo for the info man.

Could anyone point me towards a good rotating assembly that is under a grand for this? If I look myself...should be the kits for a 1 piece main seal and that is it, correct?
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Old 09-01-2010, 06:58 PM
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Quote:
Originally Posted by callmej75
Could anyone point me towards a good rotating assembly that is under a grand for this? If I look myself...should be the kits for a 1 piece main seal and that is it, correct?
I don't like 6" rods for a 383 because it puts the pin up into the oil ring, but I will list the 6" stuff for you since that's what you specified. You'll probably find that most kits will use Eagle stuff because it's cheap and you expect a kit to be cheap. Now, while Eagle rods may be ok, Eagle cranks have had issues in the past. You can do a search on this forum and read for yourself. I'll post Scat stuff here. Nobody has had anything bad to say about Scat and David Vizard has published that he has run 383's up to 550 hp for several years now with Scat cast steel cranks in them and not one single failure. You'll note that the crank is CAST STEEL.
http://www.summitracing.com/parts/SCA-935060L/
Here are the rods...
http://www.summitracing.com/parts/SCA-26000P/
Scat's warning about cross-drilling crankshafts...interesting...
http://www.scatcrankshafts.com/scatt...s_Drilling.pdf

Scat rotating assemblies...Click crankshaft, rotating assemblies, Chevy 9000 series crank...
Scroll down to:
CHEVY 350 SMALL-BLOCK 1-PC REAR SEAL 350 MAIN, SERIES 9000 CAST CRANKS, I-BEAM RODS WITH 3/8" CAP SCREWS
then down a little to 383 and 6" rod....Nice little chart shows static compression ratio with 3 different chambers....
http://www.scatcrankshafts.com/Scat_Crank_Anatomy.asp

Personally, I'd give Scat a call and talk to a tech. I'd want to know the piston crown configuration before ordering any parts. A flat-top or d-cup dish will allow the best squish performance. Either way, I would zero deck the block and allow the thickness of the gasket to be my squish dimension (0.035"-0.045").
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Old 09-01-2010, 07:11 PM
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Thanks for the write up...much much appreciated!

I just read a horror story on eagle cast cranks and yes...SCAT will be my point of contact now. I was going to go with the 6" rods because of the angle...but I saw the piston pin in the bottom oil groove and would suspect some blow by here. So a 5.7" rod will more than suffice? Also...just for added insurance...maybe make it forged.

One last thing...I heard the H-beam rods are a little wider than the I-beam and require more clearancing in some circumstances. Does this hold any weight to it?

You guys are a tremendous help here....I will be donating to the special cause soon on here
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Old 09-01-2010, 07:59 PM
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The h beams are wider but I beams should be plenty. 6" is good for racing where you need light weight and every last hp but shorter rods eliminate oiling issues and can provide better low end (only a slight effect though). Before you spend a dollar add up every little part in the short block and compare it to the cost of a pre built short block- sometimes its a better deal to have someone else do the work.
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Old 09-01-2010, 08:02 PM
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Quote:
Originally Posted by turbolover
The h beams are wider but I beams should be plenty. 6" is good for racing where you need light weight and every last hp but shorter rods eliminate oiling issues and can provide better low end (only a slight effect though). Before you spend a dollar add up every little part in the short block and compare it to the cost of a pre built short block- sometimes its a better deal to have someone else do the work.
Gotcha...

But having someone else do it just takes the fun out of it
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Old 09-01-2010, 09:27 PM
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Quote:
Originally Posted by callmej75
Gotcha...

But having someone else do it just takes the fun out of it
Scat I-beams that are clearanced for a stroker crank at the factory is all you need in my opinion.

Not only does allowing someone else to do it take the fun out of it, it adds plenty of worry because there is nobody I trust like I trust ME.

This whole industrial complex that we call the United States is spiraling down to nothingness. High school students graduate if they can read at an 8th grade level. They can't construct or punctuate a paragraph. They can't even make change without an electronic device telling them what to give back to the customer. Most of the manufacturing jobs have moved offshore. I am ashamed of the U.S... At the end of WWII, we were on top of the world. All the other industrial complexes had been destroyed and you had to get it from the U.S. if you were going to get it at all. We have given all that away, decreasing from a 36% manufacturing base to less than 12%.

If the communists retain power in the House and Senate in November, I'm considering leaving the country.
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