Z24 w/ KA24E rods and pistons

[Lockleaf]

From the research I have been doing it looks like this combo should put me up at about 9.5 compression ratio and appears to just bolt in. Since I am pulling my Z24 apart again anyway to see what I screwed up the first time, I thought this might be a cool new thing for me to screw up. I have a KA24E 240sx long block just chilling in my garage anyways, so why not?

 

Are there any valve clearance issues you guys think I should be careful of? Anything at all that would make it more than bolt and go compression upgrade? Any reasons you engine experts know of as to why this would be a bad idea, i.e. blowing my z head clean off the block, or something?

[Wide14u]

you should talk to hrh he can tell you what way to go

[datzenmike]

The KA rods are thinner/lighter than the Z24s. Not sure how this will affect the crank balance, if at all.

 

 

KA pistons are almost flattops. Don't forget that the valves are never fully open at TDC exhaust stroke. The intake only starts to open at 16 degrees BTDC. The exhaust is still open but closing and fully closed at 14 degrees ATDC. The exhaust valve is smaller diameter so less chance of it's lower edge meeting the upward traveling piston than the larger intake.

 

I calculate 9.52 not bad. Not sure how this will affect pre ignition. The Z head is practically a HEMI shape and dual plugs need less initial advance. We'll see.

 

.

[Lockleaf]

I apologize if the following question seems inane. And if the answer is "try it and tell us what breaks" feel free to say so. With regard to the crank balance issue, catastrophic crank wobble or "my truck is really vibratey"? And if I do go for this I will definately spin the motor a number of times by hand just to be sure that I have no valve clearance issues. thanks for the help datzenmike. and I will have to try pm-ing hrh, thanks for idea.

[HRH]

PM replied, and spinning the engine by hand is only part of the problem. Spinning the engine at 4500 rpm when the valves are nice and loose is the problem. Then click, bang!

[Lockleaf]

Thanks for the PM, HRH. I appreciate it. I also went ahead and read through your whole build. Between your pm and your thread there is definately some stuff I will have to look it. Not even sure I have the extra money for another set of new piston rings, so I suppose I will see what the future holds. There is another member named something like "medengines" has a post in here that alludes to him having run this build, but does not say it out right. I sent him a pm so we shall see what happens. thanks guys.

[medengines]

We are using this combo in about 3 truck motors we race..Z24's with the flat tops and the rods with no balancing problems at all..My brothers is spinning at 7500 to 8000 grand easy!! His races every weekend and doesn't miss a race. All run on pump gas. Don't have any overheating or pinging issues at all either. I even welded the chambers closed on my sons for more compression with out problems.

My sons does consistant 15.5's on motor with street tires burning out with an automatic trans, it's all original ST model 720 truck no weight reducing, has gone 13.9 on juice. My brothers has gone 13.6's on motor no juice but it is a lightened Hardbody race only set-up. Other one is a chopped less lightened!! does low 14's(14.2s) motor.

Alot of people here are using this set-up, it works and it is Proven and best of all its cheap!!

Not a forged piston though! So limit the nitrous if using it.

Vince

[medengines]

Forgot to mention that you do NEED to clearance your pistons for the valves!!! Sorry for not mentioning that..Dont forget this part..you will have interference if you don't cut them. BENT VALVES

Get a machine shop to do it, Or use valves made into cutters and do it yourself, we use flycutters for this purpose. We are charging $150 bucks at our shop here, likely cheaper out there.

hope this helps, Vince