whats the trick for decreasing cid by removing pistons?

[}{ead$hot Zod]

I have a straight 6 diesel and the ECTA record recently got bumped from 120 to 160. And I know I don't have the ca$h to beat that. However I can race in a smaller engine class. I would rather not swap motors. Do you use a custom crank? If I could pull two pistons......

whats the deal?

[sockjohn]

I have a straight 6 diesel and the ECTA record recently got bumped from 120 to 160. And I know I don't have the ca$h to beat that. However I can race in a smaller engine class. I would rather not swap motors. Do you use a custom crank? If I could pull two pistons......

whats the deal?

I would imagine that removing pistons will result in a really rough running engine! 

I'm not sure what the magic word to type into the search is, but half V8's have been discussed before and I'm sure some of what's learned there is applicable.

What class?  Can you do and engine swap to a smaller motor?

Destroking will require new crank and rods, and you will most likely be talking custom for both but should be a smoother running and higher revving solution.

[RichFox]

Some semi successful V7 SBC engines have been run. Make a bob weight to replace the rod and pistons you remove and hang on to your fillings.

[}{ead$hot Zod]

I could go with a 4bt. But no one in the cummins online forum world seems to know where the engine mounts are in relation to the 6bt.  They could actually be the same. The 4bt is basically a 6bt with 2 cylinders cut off (maybe that explains the terrible vibration they all have) and would be almost be a direct bolt in if I could figure out where the mounts were. I was probably reading about the 1/2 V8's somewhere. I could stroke it to the next higher engine/class. As the measurements already exist. The European 6.7l 6bt has the measurements I'm looking for. I'll probably have to go that route.

[JackD]

During the gas crunch of a few tears ago, Crower made a piston kit that was just a piston blank, and it was cut away at the dome to allow the thrust sides to remain but with the same balance weight as the original.
He killed the valve action in those holes and instantly (sorta) had a smaller motor.
It wasn't perfect but it was a waytadoit.

[Sumner]

I have some info on V-8 to 4 cylinder on my site here:

http://purplesagetradingpost.com/sumner/bvilleother/page%205.html

Now for in-line stuff you might want to talk to Rick Y. and see if he is willing to talk about what he has done with his Busa motor in his streamliner.  He is running this year in the 750 cc class by only running 2 cylinders on the 4 cylinder Busa.  He has also been successful in setting new records in this configuration, but I'm not sure the durability question has been answered.  I wanted to talk to Rick about what he did at Speed Week, but didn't get the opportunity.  Anyone know what he did??

Personally almost all of these conversions have run into one problem or another and I decided against that route as there are already engines available in most cases that are the right displacement and better at making HP vs. one that is cut in half.

New motor mounts would be way simpler to make than going this route in my estimation, but....

good luck in what ever course you take,

Sum

[JackD]

The 4 cyl Suzi has a 180 deg crank that makes the reduction down by 2 cyl a snap.

[russ jensen]

The 4bt is basically a 6bt with 2 cylinders cut off (maybe that explains the terrible vibration they all have)

    4 cyl will all vibrate unless there is a balance wt spinning twice crank speed-{this option is becoming a little more common these days} don't member which eng but had a 2x wt running off a gear in ctr of crank- probably doesn't do anything for output but makes the operator feel better..

[JackD]

The ZX series Kawi motors had the separate balance shaft but it is common performance practice to remove it.

[Stainless1]

The ZX series Kawi motors had the separate balance shaft but it is common performance practice to remove it.

Ditto on the new Suzuki motors, just remember to plug the oil supply...   

[Ervin]

I remember seeing a jack -hammer rig with a 318 mopar engine/ compresor. 4 cylinders were engine, the other 4 were compressor. And I don't know the rule on this,,, but could you just disable a couple cylinders,,ie. no injectors, valves, etc.  To make those cylinders inop, but keep the balance, without having to build oddball bob weights and plug oil galleys etc?
  Just something to think about, I don't have a clue on how to go about it myself.

      Ervin

[Jonny Hotnuts]

I have seen a few VW motors split to run 2 cylinders (for small aircraft).

I am a real fan of the idea of destroking larger motors to run is smaller classes. You end up with a smaller displacement motor with valves, bearings, case and fuel delivery of a larger motor in a smaller package.
I have found it is often cheaper then to take a smaller motor and do the head work and all the mods necessary to be safe at higher HP.

Just something to consider.
-JH

[JackD]

I remember seeing a jack -hammer rig with a 318 mopar engine/ compressor. 4 cylinders were engine, the other 4 were compressor. And I don't know the rule on this,,, but could you just disable a couple cylinders,,ie. no injectors, valves, etc.  To make those cylinders inop, but keep the balance, without having to build oddball bob weights and plug oil galleys etc?
  Just something to think about, I don't have a clue on how to go about it myself.

      Ervin

My dad had a Flattie 8 Ford with that compressor conversion head set, the crank turned a generator.
Except for MC production that changed at the wishes of the entrants, the downsize method is available to anybody.
I built 1500cc ant 1997cc 4cyl Fords from what started as 2300 Pinto blocks.
In the case of a MC, imagine all the parts designed to make a screamer that started as a 1000cc and squeeze it down to a 750 .
Many people would die to have that type of breathing and strength, but sadly, most of them are just falling on their sword.
Everybody knows what a Z-1 Kawi is, but how about a Z-2 ?

[mtkawboy]

Wasnt a Z2 a Japan only 750cc Z1 lookalike?

[1212FBGS]

no... a Z2 is a rare horrible old antique 2 valve head motor that made about 50hp... why start there when you can pick up a 130hp gsxr motor off of ebay for 2g
kent