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Old 06-19-2013, 02:45 PM
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383 crank clearance

hi am starting to build my 385 stroker build but have a couple of questions that concern me. list of what i have right now:
  1. 350 sbc 4 bolt main 2 piece rear main seal
  2. eagle cast 3.75 stroke crank to fit 350 sbc summitracing part #: ESP-103503750
  3. stock 5.7 rods
  4. 383 speed pro hypereutectic pistons summit part #: SLP-H859CP40

Question is do i have to do machine work to get the required clrearances? or it should just bolt on ready to go? thanks in advance...

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Old 06-19-2013, 03:39 PM
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Quote:
Originally Posted by Jkingof956 View Post
hi am starting to build my 385 stroker build but have a couple of questions that concern me. list of what i have right now:
  1. 350 sbc 4 bolt main 2 piece rear main seal
  2. eagle cast 3.75 stroke crank to fit 350 sbc summitracing part #: ESP-103503750
  3. stock 5.7 rods
  4. 383 speed pro hypereutectic pistons summit part #: SLP-H859CP40

Question is do i have to do machine work to get the required clrearances? or it should just bolt on ready to go? thanks in advance...
Piston compression height is 1.425". Rod is 5.700". Crank radius is 1.875". Add these values together and find a "stack" of 9.000".
Have your machinist inspect the main bearing bores for being round and parallel with each other. Correct by align-honing or align-boring as necessary. Register the block on the main saddle and cut the block decks to 9.000" block deck height. This will give you a "zero" deck block, meaning that with the piston at top dead center, the crown of the piston will be exactly flush with the block deck. Use a 0.039", 0.040" or 0.041" composition gasket to set the squish. It is very important to understand that after cutting the block for zero deck, the block decks at cylinders 1,2,7 and 8 (the corners of the block) will all be the same distance from the centerline of the crankshaft and the heads will sit on the block squarely, allowing the intake manifold to sit squarely and seal up.

You will need to relieve the rods for clearance at the cam, or you could use Scat Pro Stock rods that are ready to bolt in and will clear the cam with no problem.

Spend some time carefully measuring the journals on the Eagle crank. They have not been known for producing accurate numbers in the past. For all you other guys doing this same thing, the Scat cast steel crank and Pro Stock rods are bulletproof parts to use in building a 383/388.
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Old 06-19-2013, 03:55 PM
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Quote:
Originally Posted by Jkingof956 View Post
hi am starting to build my 385 stroker build but have a couple of questions that concern me. list of what i have right now:
  1. 350 sbc 4 bolt main 2 piece rear main seal
  2. eagle cast 3.75 stroke crank to fit 350 sbc summitracing part #: ESP-103503750
  3. stock 5.7 rods
  4. 383 speed pro hypereutectic pistons summit part #: SLP-H859CP40

Question is do i have to do machine work to get the required clrearances? or it should just bolt on ready to go? thanks in advance...
This will not bolt together and go. The typical problems will, especially with stock rods, be rod bolt heads past some cam lobes and cylinder bore extensions into the crankcase often called spigots and the nut end at the pan rail. This takes grinding on the rod bolts and outer shank, the spigots on the pan rail to gain clearance which is generally considered acceptable at .050 inch. And you don't want to go further than absolutly necessary as it is possible to compromise rod strenght and/or get wet by opening into a coolant jacket.

Much of this clearancing and grinding on the rods can be avoided by using an aftermarket rod that closes the rod cap with cap screws that thread into the rod shank. There are Eagle and SCAT rods that are 5140 forgings which are inexpensive that are stronger than GMs 1040 mild steel forgings for little more than a set of rebuit GM pinks. This is a much better way to go, these rods are usually clearanced and if they do need some touching up you're not grinding on the head of a highly stressed bolt. If you use a 12 point headed cap screw that often come with these it usually eliminates having to grind on the pan rail and cylinder spigots as well. You still have to check as the casting process doesn't always result in consistant dimensions, but rods like these solve a lot of problems <<< Small Block Chevy 5140 Steel I-Beam Rods, 5.7 Inch, Press Pin - Speedway Motors, America's Oldest Speed Shop >>>.

Since your pistons will take a floating pin which is a much better way to go than pressed (cheap for the OEM to make and assemble) look at this bushed rod which is the same as above except for the small end bushing <<< Small Block Chevy 5140 Steel I-Beam Rods, 5.7 Inch, Bushed Pin - Speedway Motors, America's Oldest Speed Shop >>>.

You can get these same design of rods in 4340 for about a hundred buck more.

Bogie
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Old 06-19-2013, 04:04 PM
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also i forgot to mention the block has been machined and put together with a stock 350 crank and pistons, but decided to go 385 stroker so i bought everything that is needed like bearings, pistons, and crank all to make it a 383 stroker
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Old 06-19-2013, 04:13 PM
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Originally Posted by oldbogie View Post
This will not bolt together and go. The typical problems will, especially with stock rods, be rod bolt heads past some cam lobes and cylinder bore extensions into the crankcase often called spigots and the nut end at the pan rail. This takes grinding on the rod bolts and outer shank, the spigots on the pan rail to gain clearance which is generally considered acceptable at .050 inch. And you don't want to go further than absolutly necessary as it is possible to compromise rod strenght and/or get wet by opening into a coolant jacket.

Much of this clearancing and grinding on the rods can be avoided by using an aftermarket rod that closes the rod cap with cap screws that thread into the rod shank. There are Eagle and SCAT rods that are 5140 forgings which are inexpensive that are stronger than GMs 1040 mild steel forgings for little more than a set of rebuit GM pinks. This is a much better way to go, these rods are usually clearanced and if they do need some touching up you're not grinding on the head of a highly stressed bolt. If you use a 12 point headed cap screw that often come with these it usually eliminates having to grind on the pan rail and cylinder spigots as well. You still have to check as the casting process doesn't always result in consistant dimensions, but rods like these solve a lot of problems <<< Small Block Chevy 5140 Steel I-Beam Rods, 5.7 Inch, Press Pin - Speedway Motors, America's Oldest Speed Shop >>>.

Since your pistons will take a floating pin which is a much better way to go than pressed (cheap for the OEM to make and assemble) look at this bushed rod which is the same as above except for the small end bushing <<< Small Block Chevy 5140 Steel I-Beam Rods, 5.7 Inch, Bushed Pin - Speedway Motors, America's Oldest Speed Shop >>>.

You can get these same design of rods in 4340 for about a hundred buck more.

Bogie
ok so buying a set of one of these rods will have enough clearance and no machine work required like grinding on top and bottom of each bore?
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Old 06-19-2013, 04:54 PM
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We have found the thickness of a standard paper clip wire is just about right for the pan rail clearances.If you measure that,it is what you will find.
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Old 06-20-2013, 10:34 AM
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ok so buying a set of one of these rods will have enough clearance and no machine work required like grinding on top and bottom of each bore?
They are helpful and usually will clear but you've got to check to be sure. The advantage is if clearance grinding is needed you're not doing it on the head of a highly stressed rod bolt nor the adjacent and supporting structure of the rod. The 12 point headed cap screw will usually clear the cylinder extensions and pan rail also.

Keep in mind these are 5140 rods not 4340, these are better than stock rod materials and are often used in "claimer" competition engines, but this is not top notch super duper racing hardware. They do have several structural advantages over stock rods, the SBC rod wants to deform the cap at high power and RPM settings, this bends the rod bolt which allows the cap to deform which then pinches the rod bearing into the journal wiping out the oil film and welding these parts together. The 5140 rod I aimed you at with cap screws uses a better quality ARP fastener which is more resistive to bending moments, it also uses locating dowels which not only resist the same bending moment but minimize the force from getting into the fasteners and lastly these rods put a larger platform outboard of the fasteners which provides more support area to resolve these bending moments into the larger rod structure. Of course the 5140 material is also stronger and more resistant to these forces. So all this comes together to add a lot of reliabilty to these rods.

Bogie
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Old 06-20-2013, 01:44 PM
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Originally Posted by oldbogie View Post
They are helpful and usually will clear but you've got to check to be sure. The advantage is if clearance grinding is needed you're not doing it on the head of a highly stressed rod bolt nor the adjacent and supporting structure of the rod. The 12 point headed cap screw will usually clear the cylinder extensions and pan rail also.

Keep in mind these are 5140 rods not 4340, these are better than stock rod materials and are often used in "claimer" competition engines, but this is not top notch super duper racing hardware. They do have several structural advantages over stock rods, the SBC rod wants to deform the cap at high power and RPM settings, this bends the rod bolt which allows the cap to deform which then pinches the rod bearing into the journal wiping out the oil film and welding these parts together. The 5140 rod I aimed you at with cap screws uses a better quality ARP fastener which is more resistive to bending moments, it also uses locating dowels which not only resist the same bending moment but minimize the force from getting into the fasteners and lastly these rods put a larger platform outboard of the fasteners which provides more support area to resolve these bending moments into the larger rod structure. Of course the 5140 material is also stronger and more resistant to these forces. So all this comes together to add a lot of reliabilty to these rods.

Bogie
oh ok, so getting one set of rods you mention helps in clearance issues and are more stronger than the stock ones... ok from the 2 sets you posted i can use either one? great info btw
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Old 06-20-2013, 02:44 PM
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Don't forget to get everything balanced after the machine work is done !!''
dave
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Old 06-20-2013, 02:49 PM
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I believe the difference in the 2 sets of con-rods posted above is the ability to use a 'bushed' wristpin which connects the piston and small end of the con-rod; compared to the early factory style pressed fit wristpin. The choice between the 2 types is usually dependent on your piston choice. USUALLY you want to use a 'floating' or bushed pin - type piston if possible.

Last edited by AutoGear; 06-20-2013 at 02:58 PM.
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Old 06-20-2013, 03:53 PM
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Quote:
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ok so buying a set of one of these rods will have enough clearance and no machine work required like grinding on top and bottom of each bore?
You'll still want to verify the main bearing bore on each hole, making certain that each hole is round and parallel with the other holes. Then, you will want to cut the block decks in a mill that registers off the main bearing saddle, so that each corner of each cylinder head ends up the same distance from the centerline of the main bearing bore. If the block decks are not equi-distant from the centerline of the mains, then the heads can sit askew on the block (sitting either uphill or downhill, depending on how you view the whole mess) and the intake manifold will have trouble sealing with the heads. Get everything cut true in the first place and life will be way easier.
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