You have to realize that 4032 does not expand like 2618 but having said that, with clearances that tight good machining is a must! Cylinders must be straight and round! It doesn't hurt to add a half a thou but you really have no reason to NOT trust the manufacturer. I think you will also read in the instructions that "some builds may require more clearance" like when using power adders but if you're building a power adder engine then 4032 is the wrong choice of piston. For your build you should be fine.

 

Well said

 

Hi Frank, set them at .041" and don't look back, you'll be fine. Make sure the gaps are OK. This is a much "harder" material than the 2618's, therefore less (tighter) recommended clearances.

Thanks, Gary in N.Y.

P.S. Years ago when TRW was one of the largest players using the 4032 material, we built many units using as much as .008" P/W and had some very fast record-holding rides. Not recommending this, just a fact from years ago. Mahle use's much of it today in their line.

 

My Racetech/Autotech 4032 BBC 4.600" bore pistons call for .004" in their written instructions.

 

Hello,

I have ordered the following pistons
- SRP 351c 4.04
- Partnumber: 231320

The clearence the pistons must have according the instrution manual is .0020" to 0.0025". I have also emailed JE pistons and they confirmed that the clearence build in the piston is perfect for my engine setup. This means i can have a bore finish of 4.0400

I have still some doubt....
Here in the Netherlands some say that i give it some extra. I have hear that some have damaged/jammed pistons with this cleanrance. On the other hand i don't know what's the quality of the machine shop was. Many machine shops don't use torque plates and are not very accurate. I have now found a machine shop which seems to accurate and uses torque plates.

Can somebody confim with his experience that the clearance is OK? or must i give it some more like .0025 to .0030 (4.0405 bore finish).


The engine has the following setup:
- 4 bolt block
- closed chamber 4V heads
- stock crank
- stock rods with ARP nuts & bolts
- pistons SRP forged 0.040 over
- Comp cam 290HR (LSA 110, IC 106, lift 0.588, 230 @.050)
- 1,73 rockers
- Holley 750cfm
- Holley strip dominator, 1/2 inch spacer
- 1 7/8 headers
- toploader & gears 3.50
- ratio 10.53:1
- DCR ratio 7.86 :1
- RON95 fuel
- rev limit 6500 rpm
- approx. 425hp

Greetings Frank (Netherlands)

Another 20 degrees at .050, and another .050 lift on that cam and you'll be 500+ at the flywheel.

 

Skirt design has far more effect on running clearance than material does.

 

Thanks for the info!! I really appreciate it.

Tuesday I get the piston, I gonna measure the pistons and look what the build in clearance is of those pistons.

Greetings

 

I run those Pistons at .0040 and have no issues they don't rattle and they don't scuff

.0025 gives you no room for error

 

I see a lot of 4032 pistons and to date I have always seen they are fit tighter then 2618. The clearance is built into the skirt.

In a perfect world .4040 is great but its best to add .0005 to .001 If you are going to be using power adders its best to add clearance.

 

Hello,

Shall i tell the machine shop that de bore finish must be between the 4.0405 and 4.041?

Greetings

Frank

 

Machine shop should have piston in their hand and set the clearance using the actual piston. You set the dial bore gauge with the micrometer used to measure the piston so you dont have to account for any variance in gauges being off standard. Loose is fast

 

OK i understand...

I gonna give the machine shop the piston and let them set the clearance at .0030?? ( .0025 min clearance + .0005 extra)

 

:smt023

 

Hello,

I have the SRP pistons (partnumber 338200). This are 4.020 pistons. (i gonna use another block)

Anyway,

I have measure the pistons and the build-in clearance is app. .0033-.0035. The instruction manual says:
- SB (4.000-4.200) minimum clearance .0020 to .0025
- BB (4.200-4.600) minimum clearance .0030 to .0035

I seems the build-in clearance is for a big block application. I'am a little confused here!!.

I have emailed SRP. And they had a short answer. "The build-in clearance is perfect for your application".

With another words....finished bore of 4.0200 is perfect!
Miss a something?? Can safely bore and hone the block to 4.0200???


Greetings

Frank

 

can you explain what you mean??
My english is not that good...sorry

Greetings

 

If you have confidence in your machine shop, take the pistons to them for fitting. Be sure to provide them with the instruction sheet from JE. The shop will be able to sort it all out for you.

 

Our day job is several sets a week at 4.060 bore.
We hone the 4032 CP pistons in at .0026 to .0028