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4mm crank questions


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ok im trying to look at everry possible direction for my banshee that blew up....looking at a 4mm hot rod crank. trued and welded but have a few questiosn....if i got the 4mm stroker crank, could i use a 4mm cylinder spacer, and get away with it? i mean it sounds pretty simple put the stroker in, space a set of stock cylinders the extra 4mm the crank puts out and put in a set of stock pistons and it should work right? or is there more to the puzzle, like possibly needing a adjustable stator platte and other items??? im a new guy to the banshees so dont be too harsh. im just looking for information is all, as i wanna build a strong banshee and not have to worry about it

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You would only need a 2mm spacer plate. The crank pin is moved out 2mm. So the piston goes up 2mm more and 2mm farther down the bore for a total increase of +4mm. When you space the cylinders 2mm off the case you automatically advance all port timings 2mm. That is why it is better to not use a spacer plate and have the head cut 2mm. That way your not affecting the port timings. Then have the cylinders ported for a 4mill crank. Using a cut head you have a less chance of having an air leak.

 

 

If your getting a Hot Rods crank chances are it will also be a long rod crank. These have conecting rods that are 5mm longer than stock. So you need to run a piston that has the wrist pin moved up 5mm closer to the piston crown. Wiseco 795 series pistons are for long rod cranks, both stock stroke, and +4 mill.

 

A 4mill long rod crank requires both 795 series pistons, and a 2mm spacer plate or 2mm cut head (cool head with stroker domes or moddifed stock head).

Edited by jbooker82
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You would only need a 2mm spacer plate. The crank pin is moved out 2mm. So the piston goes up 2mm more and 2mm farther down the bore for a total increase of +4mm. When you space the cylinders 2mm off the case you automatically advance all port timings 2mm. That is why it is better to not use a spacer plate and have the head cut 2mm. That way your not affecting the port timings. Then have the cylinders ported for a 4mill crank. Using a cut head you have a less chance of having an air leak.

 

 

If your getting a Hot Rods crank chances are it will also be a long rod crank. These have conecting rods that are 5mm longer than stock. So you need to run a piston that has the wrist pin moved up 5mm closer to the piston crown. Wiseco 795 series pistons are for long rod cranks, both stock stroke, and +4 mill.

 

A 4mill long rod crank requires both 795 series pistons, and a 2mm spacer plate or 2mm cut head (cool head with stroker domes or moddifed stock head).

 

thank you for the very useful information. now here is where im confused. cutting the stock head down. if i cut it 2mm, wouldnt it make it to the where the head is 2mm closer to the cylinders,a nd end up causing piston to head slamming into each other?

 

the 4mm crank im looking at is a hot rods crank with a number of hr 204 on the crank and the rods say ck 158. so i would need to cut my head down 2mm and install stroker pistons??? also if i were to go the cool head route, what exactly would i be looking for? will it say stroker domes? or is there a certain sized dome that will allow the 2mm of extra travel?

Edited by SteveCZ28
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thank you for the very useful information. now here is where im confused. cutting the stock head down. if i cut it 2mm, wouldnt it make it to the where the head is 2mm closer to the cylinders,a nd end up causing piston to head slamming into each other?

 

the 4mm crank im looking at is a hot rods crank with a number of hr 204 on the crank and the rods say ck 158. so i would need to cut my head down 2mm and install stroker pistons??? also if i were to go the cool head route, what exactly would i be looking for? will it say stroker domes? or is there a certain sized dome that will allow the 2mm of extra travel?

 

they cut the inside of the dome not the sealing surface

 

I would send my cylinders out to FAST racing and get them ported for the 4mil crank and he will set you up with the correct pistons and domes, and it will rip

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they cut the inside of the dome not the sealing surface

 

I would send my cylinders out to FAST racing and get them ported for the 4mil crank and he will set you up with the correct pistons and domes, and it will rip

oh ok. now i ran into a 2mm headgasket also....could that also work for this application, or am i still running a high risk of getting a bad air leak? im currently in the market for cylinders as mine were at 66.5 mm and the left cylinder detonated and scored it all to death so i cannot use these cylinders anymore. unless i were to sleeve. so i will just be on the look out for a nice set of stock cylinders, or maybe a fresh pair of 4mm cylinders that are already ported

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your last senario describes my son's set-up. Unported 4mil with 2mil solid copper head gasket/spacer, stock head. Obviously porting for 4mil and stroker domes can achieve highest output. Cyl spacers would probably be closer to or advanced timing over stock, but the pistons travel 4mm below bottom of port. 2mil head spacer ports would be delayed from stock and pistons travel 2mm below bottom of port. It was like this when he purchased it. It runs good with FMF Gold pipes, has tons of tourque. :headbang:

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If I were you I would get cut domes for your coolhead, if your running stock head then I would get it milled instead of using the spacer. Not only can you get the compression right were you want it but the spacer is just a extra gasket to that can leak. I believe its pretty close to the same price either way, most charge about 65 for standard domes and 85 for cut ones.

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If I were you I would get cut domes for your coolhead, if your running stock head then I would get it milled instead of using the spacer. Not only can you get the compression right were you want it but the spacer is just a extra gasket to that can leak. I believe its pretty close to the same price either way, most charge about 65 for standard domes and 85 for cut ones.

well im currently head-less, as my stock head got destroyed when my motor went lean and grenaded. so i can technically look at all sides to this project, and build it once, the right way

Edited by SteveCZ28
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well im currently head-less, as my stock head got destroyed when my motor went lean and grenaded. so i can technically look at all sides to this project, and build it once, the right way

 

Go with a Noss style cool head then, you can change the domes with ease, make the engine a little cooler and you dont have to swap out the studs like Pro Designs. A couple months ago I ordered one from Chariot Performance for around 165 give or take (You will still have to buy domes) and it works perfect and is less expensive than most aftermarket heads. Look him up on Ebay.

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