what`s minimum space between piston and head?

E10-2001-CT9

E10-2001-CT9

Member +
hi, got my 4efte rebuild (wössner pistons), block and head skimmed. so my pistons are 0.10mm higher than the block. I want to use 0.6mm TRD head gasket because want better response with OEM CT9. I would only have 0.5mm from the piston to the head if all is fitted. Can there be an contact between both? all bearings are new.
thx,Jan
 
E10-2001-CT9

E10-2001-CT9

Member +
these are 6.2ccm dished. CR is no problem. will give me around 8,5
but i am not sure if the 0.5mm are enough space between piston and head
 
Texx

Texx

Super Moderator
I'd doubt 0.5mm would be enough clearance, 1.1mm is about the minimum but it really depends on the materials the rods and pistons are made from. Personally I would aim for a clearance of 1.2mm to be on the safe side. Taking into account the expansion rates of both the rods and pistons as they heat up and also the 'stretch' of the rods at high RPM's, only having 0.5mm clearance allows a good chance for the crown of the pistons to hit the head. I'd suggest using a 1.2mm or even a 1.4mm MLS gasket instead of the 0.6mm.
 
Texx

Texx

Super Moderator
Piston to valve clearance is not really an issue due to the fact that the piston will be half way down the cylinder when any of the valves are at full lift. Piston protrusion is the issue here, in this case the head gasket is essentially a shim that spaces the cylinder head away from either piston crown at TDC. If the shim is not thick enough the pistons will come in contact with the head when they reach TDC.
 
E10-2001-CT9

E10-2001-CT9

Member +
i dont think that valves will hit the pistons. I use 4efte cams. if cam belt broke, the valves hit the piston with 0.6mm trd HG.
rods are scat. i dont know how much the rods and pistons grow, but pistons got little more clearance because the grow while heating up the engine. but i dont realy think the grow 0.1mm or more. I dont have any experience and dont want to do an supid mistake. 0.6trd is solt for 4e engines, so i believe its enought clearance left for street using (ho higher RPM,oem cams...)
 
S

Skalabala

Member +
0.5mm is the bare minimum, good forged rods are needed.
And do not rev past the 8k mark.
You might actually gain a few hp. Your quench might be more effective.
You have the right idea of the 0.6mm gasket. It is being made as standard and cope for a freshly skimmed head and block as this is needed when installing a MLS.
And you can still get better cams. Even high lift race cams will work.
 
E10-2001-CT9

E10-2001-CT9

Member +
@skalabala : REV is OEM set, and if i later use different turbo i´ll also change HG. so you also believe this will work fine?
 
S

Skalabala

Member +
Yes it should be fine with the 0.6mm gasket. You are going to have a nice build! But a very good stand alone and tuner is needed also.
Just saw now that you want to use a CT9. You are going to torture the poor thing :D
 
E10-2001-CT9

E10-2001-CT9

Member +
i hope the ct9 can handle it some time,will use little less boost. now with my 4efe turbo i run 0,7bar but the CR is much to low believe under 8... i think i got an calculate mistake in the past when i builded the first engine :)
actually i have not the money für bigger turbo and other ECU. possibly later. but i think an EMU will be a "must have" to make the engine correct running
 
S

Skalabala

Member +
4efe under 8 CR, what pistons are in there?
And yes a good management and tuner is important.
0.7bar is safe. Keep it like that :)
 
E10-2001-CT9

E10-2001-CT9

Member +
th e first engine was OEM 4efe form Ep91 with cr 9.6, i skimmed 0.7 from head, uses 2 OEM Headgaskets and an 1mm metal plate between the gaskets. but the oem rods are very thin and i dont wantet to kill these engine. but i dont know the accurate CR.
 
wildchild

wildchild

Member +
ahem.. errr ur running wossner pistons and still using a CT9? you could have utilised that money to go TD04 and have a better response with stock 4efte pistons at 1 bar! the power is amazing. i ran 250bhp on stock 4efte pistons at 1.2 bar
anyway for you current setup i wouldnt advice you to run high boost with high compression pistons or if the piston to head clearance is very low...
 
E10-2001-CT9

E10-2001-CT9

Member +
@wildchild.
i have only an broken 4efte from ebay. engine isnt available in germany. so i decited to build an new forged engine instead of making all OEM and this would cost nearly same.
but i dont have money fpr bigger turbo and emu an all these other little things is will need. I only can make small steps forward.

because of this, i want little more CR for the next time with my oem CT9. but the head-piston-clearance is low i think, but i dont realy know
 
S

Skalabala

Member +
There are hight performance engines out there using 0.6 TRD gaskets, you will not have any problems!
And I can promise you that all of them have skimmed head and maybe block also. Ive seen engines with 0.3mm..
 
weeJohn

weeJohn

Lifer
Skalabala said:
There are hight performance engines out there using 0.6 TRD gaskets, you will not have any problems!
And I can promise you that all of them have skimmed head and maybe block also. Ive seen engines with 0.3mm..
Click to expand...

I would say 90% of the TRD gaskets in 4EFTE engines are being used with dished pistons, from 6 to 10cc as this was a proven and then popular way to go from many years a few years ago.

To be honest I dont know of anyone using flat top pistons and a TRD gasket. Spuddys car has the highest CR I have heard off in a GT, he runs dished pistons and a TRD gasket with high duration and high lift cams, but there has been quite a few passes with the mill over his block and I am sure that head will have been done at least once.
 
E10-2001-CT9

E10-2001-CT9

Member +
so 0.6mm trd gasket is good thing with dished pistons to reach little higher CR for small turbos. And there are no problems known. this gives me a little certainty i will not kill my engine
 
S

Skalabala

Member +
If the piston is dished or not is completely irrelevant...
It is the crown that we are focusing on, the CH of the piston.
If you are worried then you can machine the pistons down by 0.1mm
 
wildchild

wildchild

Member +
dished or not does make a difference mate. btw though its dished the outer width is the std size. i mean the piston height on the sides. only the center (crown) has a hollow square shaped depression. these factors hav an effect on CR. i have wossner pistons on mine but its not dished. its flat top.
 
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