383 Build with 3.8" Stroke Cola Crank
06-06-2008, 10:35 PM
#31
Registered User
Join Date: May 2004
Location: Bay Area, CA
Posts: 2,001
I got your PM - you've got good advice in this thread and you really do have a few options. First being order all your parts as if building a standard 383 w/ 3.750 stroke - deck the block square as minimal as possible and use a gasket that will put your quench in a safe range. If you end up with the pistons out of the hole you can either order thicker gaskets (no problem with this, ala LS motors) or have the piston crowns turned down .025" in the lathe if the block was already decked to the standard 9.0" - any machine shop will have the arbor to hold a piston in the lathe square and can turn them down easily - we do this quite often for custom compression heights.
You can also order up a set of custom pistons from JE, Diamond, CP, etc - in a 1.100" compression height for a 9.0" deck height with your 3.800" crank, only downside to this is putting the piston pin in the oil control ring which some believe causes oil consumption - I've never seen that with correct piston to wall clearances and ring gaps....and piston cost.
My personal preference would be to deck the block and order a gasket from Cometic to put the quench where I want it, using off the shelf pistons. This will be the cheapest and easiest route. Shelf pistons from Wiseco, SRP, Mahle, etc will all handle a 150+ shot of no2 with proper ring gaps.
As for the balancing, I have never used one of those 3.800" cola cranks - so I don't know what they are rod length they are cam cut for, use 6.0" rods and let the machinist take care of it during the balancing process. As for internal vs. external, I personally would want any race type motor to be internal but it will be very expensive, with the goals you have I really wouldn't worry about it - just use a good quality balancer (ATI).
For a motor that will make 400+ NA coupled with a 150-200 shot, you need to be willing to fork over the money for quality connecting rods and a splayed cap conversion.
Let me know if I missed anything...
You can also order up a set of custom pistons from JE, Diamond, CP, etc - in a 1.100" compression height for a 9.0" deck height with your 3.800" crank, only downside to this is putting the piston pin in the oil control ring which some believe causes oil consumption - I've never seen that with correct piston to wall clearances and ring gaps....and piston cost.
My personal preference would be to deck the block and order a gasket from Cometic to put the quench where I want it, using off the shelf pistons. This will be the cheapest and easiest route. Shelf pistons from Wiseco, SRP, Mahle, etc will all handle a 150+ shot of no2 with proper ring gaps.
As for the balancing, I have never used one of those 3.800" cola cranks - so I don't know what they are rod length they are cam cut for, use 6.0" rods and let the machinist take care of it during the balancing process. As for internal vs. external, I personally would want any race type motor to be internal but it will be very expensive, with the goals you have I really wouldn't worry about it - just use a good quality balancer (ATI).
For a motor that will make 400+ NA coupled with a 150-200 shot, you need to be willing to fork over the money for quality connecting rods and a splayed cap conversion.
Let me know if I missed anything...
06-07-2008, 10:34 AM
#32
Registered User
Thread Starter
Join Date: May 2004
Location: Maryland
Posts: 970
This is some very very helpful information! I am pretty busy right now but when i have a minute i have a few more questions for you. Great to have people like you on this board!
Brandon
Brandon
I got your PM - you've got good advice in this thread and you really do have a few options. First being order all your parts as if building a standard 383 w/ 3.750 stroke - deck the block square as minimal as possible and use a gasket that will put your quench in a safe range. If you end up with the pistons out of the hole you can either order thicker gaskets (no problem with this, ala LS motors) or have the piston crowns turned down .025" in the lathe if the block was already decked to the standard 9.0" - any machine shop will have the arbor to hold a piston in the lathe square and can turn them down easily - we do this quite often for custom compression heights.
You can also order up a set of custom pistons from JE, Diamond, CP, etc - in a 1.100" compression height for a 9.0" deck height with your 3.800" crank, only downside to this is putting the piston pin in the oil control ring which some believe causes oil consumption - I've never seen that with correct piston to wall clearances and ring gaps....and piston cost.
My personal preference would be to deck the block and order a gasket from Cometic to put the quench where I want it, using off the shelf pistons. This will be the cheapest and easiest route. Shelf pistons from Wiseco, SRP, Mahle, etc will all handle a 150+ shot of no2 with proper ring gaps.
As for the balancing, I have never used one of those 3.800" cola cranks - so I don't know what they are rod length they are cam cut for, use 6.0" rods and let the machinist take care of it during the balancing process. As for internal vs. external, I personally would want any race type motor to be internal but it will be very expensive, with the goals you have I really wouldn't worry about it - just use a good quality balancer (ATI).
For a motor that will make 400+ NA coupled with a 150-200 shot, you need to be willing to fork over the money for quality connecting rods and a splayed cap conversion.
Let me know if I missed anything...
You can also order up a set of custom pistons from JE, Diamond, CP, etc - in a 1.100" compression height for a 9.0" deck height with your 3.800" crank, only downside to this is putting the piston pin in the oil control ring which some believe causes oil consumption - I've never seen that with correct piston to wall clearances and ring gaps....and piston cost.
My personal preference would be to deck the block and order a gasket from Cometic to put the quench where I want it, using off the shelf pistons. This will be the cheapest and easiest route. Shelf pistons from Wiseco, SRP, Mahle, etc will all handle a 150+ shot of no2 with proper ring gaps.
As for the balancing, I have never used one of those 3.800" cola cranks - so I don't know what they are rod length they are cam cut for, use 6.0" rods and let the machinist take care of it during the balancing process. As for internal vs. external, I personally would want any race type motor to be internal but it will be very expensive, with the goals you have I really wouldn't worry about it - just use a good quality balancer (ATI).
For a motor that will make 400+ NA coupled with a 150-200 shot, you need to be willing to fork over the money for quality connecting rods and a splayed cap conversion.
Let me know if I missed anything...
08-13-2008, 08:24 AM
#33
Registered User
Join Date: Jun 2001
Location: Hinesville, GA
Posts: 1,192
I've built an LT1 with a 3.8" cola crank, so I figured I would offer my input. You may have built with it already, but I think this might be of use to someone later on down the road. These questions might come in handy to someone someday.
First, the 3.8" cola crank for the zz383 is an external balance crank. I had to have 3 slugs of mallory put in mine to balance it, but that was ok, I got mine at a steal (free) because the dealership thought it was junk (zz383 broke a piston, crank was fine). However, it was designed to be used with a 5.7" rod. Everybody I saw so far made some good points, but there are options for people who want to use this crank.
I bought a new piston and rod and sent it away to the machine shop. However, there is a simple formula that will tell you alot when it comes to piecing together rotating assemblies:
deck height-half stoke-rod length-compression height
That will tell you where you are at TDC.
A standard 383 would be 9.025-1.875-5.7=1.45". Use a 1.430" piston (1.45"-1.430") for a 383 and you would have an engine with a piston .020" in the hole at TDC.
For example, you could use the 3.8" stroke with a 6.125" rod and a piston for a 408 sbc and come to zero deck, for 388ci, assuming a stock 9.025" deck height:
9.025-1.9-6.125=1" compression height. If you used a piston for a 4" stroke sbc, which are usually 1", that would be zero, meaning the piston is at zero deck. Then you could use a .040" head gasket and be on your way.
If you took the answer, and added the head gasket thickness, it will tell you the quench. It's ok to have the piston slightly above the deck, but you need to use the right head gasket.
I would start with a 3.8" internally balanced crank, since you wont have major balancing issues. You have to use a minimum 6" rod with an internal balance crank, but with the cola 3.8" crank, you can use 5.7" because it's externally balanced...the counterweights are different so there is more room for the pistons. I understand why you want to use it though...you already have it
I like the long rod 388 because not only do you get the benefits of the 3.8" stroke, but you get a more favorable rod length to stroke ratio, compared to a 5.7 or 6.0 rod 383 (1.61 compared to 1.6 or 1.52, stock is 1.63). Or you can do a 382ci and keep a std bore. It wont have as much clearancing issues (I kept a standard cam core in mine) and very slight clearancing compared to a 396 or 408. Just use good rods if you plan to push it or not go crazy with clearancing or if you want to use a standard cam core.
If you wanted to use a long rod but keep some meat on the deck for future rebuilds, you could go with a 3.75" stroke with the same pistons and rods and have .025" to play with. I'm suprised not that many people do that.
My next one will be a 3.8" 4340 internal balance crank with 6.125" manley rods and '408' 1" compression height mahle pistons for a 388ci LT1. Going to toss on some of those new ported dart pro 1's with my single plane. I'm keeping it a NA motor though, since the 1" compression height starts pushing the rings into the wrist pin and leads into a whole different topic.
Just a bit of friendly advice: advrtisers put the engine size with certain pistons to denote the typical application they are used for. Knowing this formula will keep you from having to get custom order pistons sometimes, and can save you some cash. My $.02
My 382ci LT1 is going into my other camaro. It's running as a tuned port LT1 and I dont feel comfortable with it making lots of power in my '94Z, so I'm switching out the long blocks. The motor likes to twist up alot, and its still running to stock ZZ383 rotating assembly, just internally balanced. Would make a more reliable TPI motor than a single plane LT1.
I like building things by thinking outside the box, so you have to know this if you step out of the mainstream. My next toy will be a tuned port 427 on a late model bowtie block with a first injections TPI intake...going for the stock look.
First, the 3.8" cola crank for the zz383 is an external balance crank. I had to have 3 slugs of mallory put in mine to balance it, but that was ok, I got mine at a steal (free) because the dealership thought it was junk (zz383 broke a piston, crank was fine). However, it was designed to be used with a 5.7" rod. Everybody I saw so far made some good points, but there are options for people who want to use this crank.
I bought a new piston and rod and sent it away to the machine shop. However, there is a simple formula that will tell you alot when it comes to piecing together rotating assemblies:
deck height-half stoke-rod length-compression height
That will tell you where you are at TDC.
A standard 383 would be 9.025-1.875-5.7=1.45". Use a 1.430" piston (1.45"-1.430") for a 383 and you would have an engine with a piston .020" in the hole at TDC.
For example, you could use the 3.8" stroke with a 6.125" rod and a piston for a 408 sbc and come to zero deck, for 388ci, assuming a stock 9.025" deck height:
9.025-1.9-6.125=1" compression height. If you used a piston for a 4" stroke sbc, which are usually 1", that would be zero, meaning the piston is at zero deck. Then you could use a .040" head gasket and be on your way.
If you took the answer, and added the head gasket thickness, it will tell you the quench. It's ok to have the piston slightly above the deck, but you need to use the right head gasket.
I would start with a 3.8" internally balanced crank, since you wont have major balancing issues. You have to use a minimum 6" rod with an internal balance crank, but with the cola 3.8" crank, you can use 5.7" because it's externally balanced...the counterweights are different so there is more room for the pistons. I understand why you want to use it though...you already have it
I like the long rod 388 because not only do you get the benefits of the 3.8" stroke, but you get a more favorable rod length to stroke ratio, compared to a 5.7 or 6.0 rod 383 (1.61 compared to 1.6 or 1.52, stock is 1.63). Or you can do a 382ci and keep a std bore. It wont have as much clearancing issues (I kept a standard cam core in mine) and very slight clearancing compared to a 396 or 408. Just use good rods if you plan to push it or not go crazy with clearancing or if you want to use a standard cam core.
If you wanted to use a long rod but keep some meat on the deck for future rebuilds, you could go with a 3.75" stroke with the same pistons and rods and have .025" to play with. I'm suprised not that many people do that.
My next one will be a 3.8" 4340 internal balance crank with 6.125" manley rods and '408' 1" compression height mahle pistons for a 388ci LT1. Going to toss on some of those new ported dart pro 1's with my single plane. I'm keeping it a NA motor though, since the 1" compression height starts pushing the rings into the wrist pin and leads into a whole different topic.
Just a bit of friendly advice: advrtisers put the engine size with certain pistons to denote the typical application they are used for. Knowing this formula will keep you from having to get custom order pistons sometimes, and can save you some cash. My $.02
My 382ci LT1 is going into my other camaro. It's running as a tuned port LT1 and I dont feel comfortable with it making lots of power in my '94Z, so I'm switching out the long blocks. The motor likes to twist up alot, and its still running to stock ZZ383 rotating assembly, just internally balanced. Would make a more reliable TPI motor than a single plane LT1.
I like building things by thinking outside the box, so you have to know this if you step out of the mainstream. My next toy will be a tuned port 427 on a late model bowtie block with a first injections TPI intake...going for the stock look.
Last edited by dhirocz; 08-13-2008 at 08:32 AM.
Thread
Thread Starter
Forum
Replies
Last Post
dbusch22
Forced Induction
6
10-31-2016 11:09 AM
