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  #1  
Old Apr 17th, 20, 04:42 PM
valknova71 valknova71 is offline
 
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Default Bottom end

I am working on building a 383 Stroker from my 350. What is a good brand of rotating assembly parts? This is just a street and show build, may take to a couple test and tunes.


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  #2  
Old Apr 17th, 20, 08:49 PM
Big Dave Big Dave is offline
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Default Re: Bottom end

Ok start over again. My typing finger is getting hard to aim and I keep closing the app or hitting the control key instead of the shift key with all kinds of strange results.

I have used both SCAT and Eagle Products with great success. Like wise I have used Lunati's "Dragon Slayer" rotating kits. All three of these products are forged in China out of 4340 or tougher steel alloy. 4340 is hard to machine with standard tooling because it galls requiring extra polishing to get rid of the tool marks.

Seconds sold by some of the less expensive car part companies, and unfortunately your cheaper engine builders have gouges in the crank that didn't buff out and they didn't want to turn the crank down from standard. As far as that goes I have seen seconds that have different diameter crank journal sizes that are off by 0.003 to 0.006 thousandths of an inch. That can be fixed by regrinding under sized but if you didn't check the machine work ahead of assembly you get a blown up bottom end.

Which brings me back to the companies above. All of them remachine the parts they receive from China because hey have seen the same horror stories that I have. Once I get one of these rotating assemblies the first thing I do is take it to my award winning machinist and have him set up every part and inspect it dimensionally and to rebalance every thing to four grams of weight. When I get it to my shop I check his work with my own micrometers and bore gauge. I also check all weights except the crank on a digital scale (crank is too heavy for my little four pound scale). I will admit I haven't figured out how to measure the rod weight with exact repeatable accuracy, but if I keep trying I hope to one day figure out how to do it.

The first thing you need to do is find a good machinist. They do not advertise because they have more work than they can handle (so ignore the shops with neon signs advertising specials). My machinist displays on his office counter five Wally's won by his customers in national competition (wasn't one of mine). He also has a back wall with all of the trophies on display from circle track racers who win constantly.

Another good sign is his equipment. He has a five axis CNC machine big enough to make a billet block, an engine dynometer, a flow bench and every kind of mill you can think of; all CNC controlled. His shop is spotless and he uses high temp ovens to get blocks clean rather than chemical solvents. Luckily I retired before he had (so far as I know he is still in business).

You will find a good machinist by word of mouth from engine builders in your area.

Big Dave
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Old Apr 17th, 20, 09:11 PM
ramportin1 ramportin1 is offline
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Default Re: Bottom end

a wealth of knowledge

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  #4  
Old Apr 20th, 20, 08:35 PM
62 NovaWagon 62 NovaWagon is offline
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Default Re: Bottom end

Scat is a very good choice for the money, all machine work is professionally done in house, I've built several from daily drivers to high end and never any issues with any of their stuff.... Just my experience with them..
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  #5  
Old Apr 29th, 20, 12:21 AM
valknova71 valknova71 is offline
 
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Default Re: Bottom end

Thank you for the responses and information.

I have another question. People have been telling me that I need to watch what I do and how much power the engine puts out because my block is a two bolt main. Is this true. If so, what am I able to do that wonít cause me problems down the road. Again this isnít a daily driver, I am not going to take it to the track every weekend.


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Old Apr 29th, 20, 08:57 AM
Big Dave Big Dave is offline
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Default Re: Bottom end

Two bolt and four bolt blocks are the sane (assumes it had a four bolt version). Newer blocks out of 1983 and up, and particularly 1987 and up factory blocks can only handle "reliably" 350 horsepower. Keep in mind the rated horsepower of these blocks was rated at 240 horsepower at 4,000 RPM, and 345 pound-feet of torque at 3,200 RPM. So from the factory's point of view it is plenty strong. These blocks were wreaked to reduce their weight for better CAFE numbers.

Older 1968-'82 blocks can "handle "450 horsepower all day long. Get around 500 horse and reliability becomes suspect. If you are building a 500 horse motor or better, consider a Dart Little "M" Sportsman block. They are rated at 650 horsepower continuous use. They also weigh 17 pounds more than a stock block due to the added cast iron in the main webbing (bottom end) of the block. By the time you pay to convert a stock block to 4 bolt mains, and over bore it deck it line hone it and clean and magnflux it your machine work bill is a sizeable portion of a Dart blocks cost.

Additionally you are not limited to a 383 with an aftermarket block. They offer a standard bore of 4.125 inches that nets you 400 cubes with a 3.75 inch stroke. Bigger is better to a point with a SBC (you run out of head flow capacity very quickly above 415 cubes).

Big Dave
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Old Apr 29th, 20, 12:33 PM
valknova71 valknova71 is offline
 
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Default Re: Bottom end

I am not sure when my block was built. It came with the car when I bought it 6 years ago. It is a jasper 350. So are you saying that I will be safe with 400 hp?


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  #8  
Old Apr 29th, 20, 11:17 PM
62 NovaWagon 62 NovaWagon is offline
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Default Re: Bottom end

No problem with 400HP as long as you don't rpm it to the moon, add studs extra strength.
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Last edited by 62 NovaWagon; May 7th, 20 at 07:42 AM.
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  #9  
Old May 7th, 20, 12:16 AM
valknova71 valknova71 is offline
 
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Default Re: Bottom end

Add studs?


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  #10  
Old May 7th, 20, 07:44 AM
62 NovaWagon 62 NovaWagon is offline
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Default Re: Bottom end

Quote:
Originally Posted by valknova71 View Post
Add studs?
On the main caps instead of bolts.
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  #11  
Old May 7th, 20, 08:27 AM
Big Dave Big Dave is offline
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Default Re: Bottom end

Adding studs requires a line boring of your bare block. If it is together now it has to be blown back apart and remachined.

This is because studs clamp differently than bolts. Both impart the same clamping force but bolts twist the caps and studs don't so the fit of the bearings (crush) is different.

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Old May 8th, 20, 05:34 AM
cottonwood green cottonwood green is offline
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Default Re: Bottom end

Both Scat and Eagle offer kits in 5140 cast or 4340 forgings as Dave said. 5140 will reliably support 400 horsepower with 2 bolt main bearing blocks. Quality machine work is key. A jasper has already been rebuilt, so it depends on far how it's been bored is key. At a minimum, the block probably has a .030 overbore. Newer blocks (86 and newer), are light weight thin wall castings and .040 is about max. If the car is going to be driven as you said, you would be better off going with a good cast rotating assembly and using your money for better heads and a hydraulic roller cam. I see far too many people overbuilding a bottom end and going cheap where the power is made. Keeping the motor out of detonation and cylinder washdown is probably the biggest factor to keeping longevity.
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