Wiseco 75mm piston to cylinder wall clearence

Gilly2006

Gilly2006

Member +
im building a new engine with forged 75mm wiseco pistons, the engine that they came out the bottom end had gone and no1 bore is ovaled as well.
we have decided to use a spare block and bore it out but i can't get hold of the piston to wall clearance. iv searched everywhere and not found a right lot.

any help would be great!
 
S

Skalabala

Member +
I would go with 70 microns :) Wiseco is old school and expands more than Ross, Arias etc.
However I have heard that new Wisecos do not expand a lot.
 
Tim@TBDevelopments

Tim@TBDevelopments

Lifer
other wiseco's i've used in the past are around the 0.030" range, so common with most forged pistons. ross i've found with there high clearance is just a rubbish product, doesn't nothing but increase bore wear and oil consumption
 
A

AdamB

Member +
The piston - wall clearence for 74.5mm Wiseco's = 0.0035 inches. Will most likely be the same for the 75mm piston as well as they are going to be of the same material composition :)
 
Tim@TBDevelopments

Tim@TBDevelopments

Lifer
that does sound about right mate as its a similar material to the CP pistons i use and they are also 0.0035"

well had an email back from wiseco today and this was there response "we don't make a 75mm piston for the 4efte engine, its either not ours or custom made" and then when i replied saying you make loads and sent a link to ones online, got the reply "sorry can't help i'm afraid" useless

This is why i hate dealing with wiseco

only using them for this market, once i get my CP pistons all sorted for this engine i'll be dropping the my dealership with them as i've had nothing but poor aftersales service.

Tim
 
Tim@TBDevelopments

Tim@TBDevelopments

Lifer
I've used wiseco and wossner in the 3sgte engines and never been a fan, had a few fail from skirt failures and similar, were the cp just seem a much better quality item, there after-sales is very good and they will work with me on items. Been building 3sgte's for over 10 years now, one over 950bhp and last time i worked it out done more than anyone else in Europe, arguably the world and i've never had an engine fail using CP pistons.

just sticking with what i know and products that have gave me good success in the past.

yes i can get those but there more expensive than pauter :(

Tim
 
G

GP82

Member +
For the CP pistons, there are many options you can have on the piston, you can opt for what you require or go for all the bells and whistles. What's really great about these pistons is the precisley machined ring grooves which will net you perfect ring seal in the cylinder. Another thing i noticed is the skirt finish, comparing to other pistons, the surface finish is very smooth and has very low roughness average. Also the CP piston is heavily reinforced around the piston pin housing. The Carillo rods are a work of art, but the real jewels in these rods were the sps multiphase rod bolts, much more tensile strength then any ARP fastner apart from there exotic L19 fastners.

The Piston to wall clearance on the spec sheet is only a reccommendation, you need to work out how much hp + boost pressure you are planning to run on the motor. I would personally go looser like 4 thou. if you plan to run any sort of decent boost pressure, this clearance is important, it will help to fight heat build up as opposed to a tighter clearance, which in my experience makes a turbo motor survive when running at it's peak.
 
A

AdamB

Member +
Tim@TBDevelopments said:
I've used wiseco and wossner in the 3sgte engines and never been a fan, had a few fail from skirt failures and similar, were the cp just seem a much better quality item, there after-sales is very good and they will work with me on items. Been building 3sgte's for over 10 years now, one over 950bhp and last time i worked it out done more than anyone else in Europe, arguably the world and i've never had an engine fail using CP pistons.

just sticking with what i know and products that have gave me good success in the past.

yes i can get those but there more expensive than pauter :(

Tim
Click to expand...


Wish you had told me sooner bud :( May be back in touch soon then lol.
 
Tim@TBDevelopments

Tim@TBDevelopments

Lifer
GP82 said:
For the CP pistons, there are many options you can have on the piston, you can opt for what you require or go for all the bells and whistles. What's really great about these pistons is the precisley machined ring grooves which will net you perfect ring seal in the cylinder. Another thing i noticed is the skirt finish, comparing to other pistons, the surface finish is very smooth and has very low roughness average. Also the CP piston is heavily reinforced around the piston pin housing. The Carillo rods are a work of art, but the real jewels in these rods were the sps multiphase rod bolts, much more tensile strength then any ARP fastner apart from there exotic L19 fastners.

The Piston to wall clearance on the spec sheet is only a reccommendation, you need to work out how much hp + boost pressure you are planning to run on the motor. I would personally go looser like 4 thou. if you plan to run any sort of decent boost pressure, this clearance is important, it will help to fight heat build up as opposed to a tighter clearance, which in my experience makes a turbo motor survive when running at it's peak.
Click to expand...

see with the cp pistons we run the same 0.0035" clearance on a stock going road engine to the 950bhp drag car we built before, all works out perfectly, just some different specs in ring gapping that changes. But i do agree the spec sheet is just for reference. Cylinders should be bored after mearusing each piston, add the clearance and then bore to that size, then numbered so #1 piston is sized for #1 cylinder.

All my engines are also done using a torque plate and also mains torqued to spec to simulate block stresses but also bored at a 85 degree heat temperature to give running conditions on expansion of the cast. I Know 99% of people don't bother to do this but this is what sets my engines apart from the competition. :)
 
Tim@TBDevelopments

Tim@TBDevelopments

Lifer
there are many ways to do it, some go overly complicated by pumping hot water through while boring which is aright pain with all the engine water chambers open and everything.

We just do it a simple way and bore the engine as soon as its come out of its 85 degree chemical bath. Its still very warm and only drops a few degrees through the entire boring process. The final tiny amount is honed when cold anyway as you sometimes find if you don't do it that way despite replicating the working conditions the hone generates alot more heat in the centre of the cylinders (the unsupported bits) so can bow inwards in the middle, so if you do it all in one go you get a barrel effect. So the very last tiny amount is done cold when its all perfectly straight.

Bit of a process but this ensures we get perfect bores and hone conditions for our engines.

I don't know of anyone else in the Toyota field that goes to these lengths, I'd be surprised if most engine builds even use a torque block and that makes a huge difference

Tim
 
H

haydn28

Member +
on the wiseco 74.5mm direction sheet ,I've read that u need to measure clearence 0.0035" at the bottom of the piston skirt (they say this is the widest part of the piston) ,does this mean then that blocks need to be bored and honed 'conically' ie the bottom of the cylinder more than the top? or straight bore

I've never done this before , bear with me please lol
 
Tim@TBDevelopments

Tim@TBDevelopments

Lifer
lol ok i won't make fun for that comment.

No what it means is that the clearance from the piston needs to be 0.0035" to the cylinder walls.

Don't take for granted that each piston is "exactly" the same size, there are sometimes slight differences no matter how small. So label the pistons 1 to 4 so that #1 piston always goes into #1 bore.

Measure the diameter of the piston at the bottom of the piston skirt, this will give you a number around 2.9330 give or take any manufacturing differences, Then add 0.0035" ontop. This is what you bore your cylinders to. Some cowboy places will just look at the spec sheet and add the clearance and bore them all to that, but my way is the correct way of building an engine.

This ensures that disspite any tiny changes between the piston diameter there expansion clearance is always a perfect 0.0035"

Also make sure you have your engine bored and honed with a torque plate onto of the head surface, and with the main bearing caps torqued down to correct value.

Tim
 
H

haydn28

Member +
thanks for the reply , I'm not much of an engine builder , this is my first attempt (with some help ) lol

I'm going to bore to within 0.004" of the 0.020" bore , then hone using 220 and 280 grit , then finish with 400 grit to reach the 0.0035 clearance

and as u said use pistons 1-4 and measure clearance on each piston to cylinder
 
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