How much to open a 24v piston bowl? Mud truck motor build.

SPEEDSHIFT

SPEEDSHIFT

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I am going to be putting together a P-pump 24v motor for my 87 K5 Blazer. I wanted to open the piston bowl up, but I am not sure how much. Does anyone has any pics, or specs on this being done? This is going to be a cheap build, just using what I already have laying around the shop, so I don't want to buy new pistons. I am not sure which injectors, I will probably just find some used injectors off here in the classifieds, so they wont be any kind of custom spray angle.

The truck is just going to be used for mud racing, on a fast track, no bogs. Just a straight 100ft line of a track that has been disked and watered. Here is a quick build list...

Ported CR head w/runner intake/heavy springs
24v block/pistons/crank
polished 24v rods
215 or 180 pump(barrels turned, 5k GSK, full cuts, rack set)
balanced/studded bottom end
large 70+mm single
TH400 trans/Art Carr conv/ high stall/manual VB
Large 24v inj 250hp+ (whatever I can find)

I might be able to get away with water injection, but I am not sure if I will even need it because the pump wont be very hot.

I do have a set of CR pistons I could use also, but they would take custom nozzles wouldnt they?

TIA, Bodie
 
You want to de-lip the pistons, just make the wall of the bowl straight. I had a local machine shop do mine.
 
If they are SO pistons de-lip them and it will be right around 64mm, if the are HO de-lip them and open them up 2mm to 64mm.
 
So at the tops, should there be a sharp 90* angle or put some kind of curve at the lip?
 
Here is what I have now, even though the one in the pic is a junk piston. 64mm isnt much more of a difference than it already has, if I remove the lip, the bowl will be larger than 64mm. Right now the bowl measures 61.3. Unless I am doing something wrong?
 

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I don't recall off the top of my head what I used on the last set of pistons I did, either a 0.020" or a 0.040" radius? I'd have to check.

You could just measure the radius on the top of the stock bowl and duplicate that...
 
What is the advantage of doing this? Doesn't this lower the compression?
 
GOT-Torque said:
I don't recall off the top of my head what I used on the last set of pistons I did, either a 0.020" or a 0.040" radius? I'd have to check.

You could just measure the radius on the top of the stock bowl and duplicate that...
Click to expand...

Cool, ill just make it close to that, I doubt its a big deal anyway.

On another note, I do want to run one of your billet tappet covers on my 12v, but I will PM you when I'm ready.

Thanks, Jesse
 
I guess while I am at it, I can lower the compression ratio. Something around 14:1? I would prefer it start with the starter though, and it will be plenty hot during the racing season, so what would ya'll recommend taking off the top?

Stock size gasket.
 
don't take any off the top, put valve reliefs in it and run a higher lift cam. I didn't see a cam in your list of parts?

Only running a single 70mm or close to it, I don't see a reason to drop the compression very much.
 
GOT-Torque said:
don't take any off the top, put valve reliefs in it and run a higher lift cam. I didn't see a cam in your list of parts?

Only running a single 70mm or close to it, I don't see a reason to drop the compression very much.
Click to expand...

Yeah sorry about that, a cam will be included, I just haven't decided the size until figure out my piston situation. I really didn't want to mess with valve reliefs because I would have to pay to have it done, plus the cost of the cam going up for them.

Turbo-wise was thinking 71-75mm T4 S400, 90-1.xx housing.
 
SPEEDSHIFT said:
64mm isnt much more of a difference than it already has, if I remove the lip, the bowl will be larger than 64mm.
Click to expand...

It's enough, if the lip is removed it will be just over 64mm. Fly cut them for the cam, your done.
 
Try This.......

SPEEDSHIFT said:
Here is what I have now, even though the one in the pic is a junk piston. 64mm isnt much more of a difference than it already has, if I remove the lip, the bowl will be larger than 64mm. Right now the bowl measures 61.3. Unless I am doing something wrong?
Click to expand...

Turn your caliper over and measure inside the bowl.:Cheer:
 
matty169 said:
Turn your caliper over and measure inside the bowl.:Cheer:
Click to expand...

...I know how to use calipers... Like I said, the bowl right now measures 61.3mm. The pic I posted has the calipers set at about 64mm to show what the difference would be.
 
I wonder if you could open them up yourself at home with the right flush cut router bit? If the bowl has a consistent straight wall to act as a guide for the router bit, I'll bet it could be done at home for FREE.

Worse case scenario, try it on that junk piston and see how it turns out.
 
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