111 replies to this topic

[nwr31]

excuse my ignorance, but why didnt they have offset pins?

[BMGTZ]

excuse my ignorance, but why didnt they have offset pins?

no idea.....they are special order from wiseco. {no part number on box} I got them from euroexport

I thought it strange when I looked at them when they arrived. I discovered the nil offset when measuring the bottom of the piston for bore clearance....just happened to measure the pin offset because they arent marked with a front of engine mark/ arrow like a lot of pistons are.

[MOAN]

can I hijack a little?

so it is in and running now.....but sounds like a tractor. I thought at first it was piston slap or the lifters needing more bleeding but the lifters settled down after 30kms. it has done 330k now and still has a very annoying rattle when you accelerate. it isnt knock ...but sounds similar to lifters.

it isnt so serious that there is any danger of damage .....just pissed off that it there at all. I have had a few guys listen and we all think it is top-end related. strange as the head was just done !!

my GUESS is a bad valve guide.....so head comes off i want to kill the machinist that "serviced the head"

Did you end up resolving this?

I just built my 4G93t as well and it had severe lifter rattle. Just had it back with the builder to replace the lifters and they put little shims in to compensate for the gap that shouldn't be there and they're quietened down a fair bit but they're still noisy as hell.

I'm starting to think it isnt the lifters now though because there is no gap whatsoever to allow for any ticking. Oil has been dropped twice in the past 10 days to thicker to see if it helped to no avail. Builder and machinist are at a loss.. and I'm not cluey enough with this shit to suggest other options. Anyone I ask seems to just suggest additives which I am very very reluctant to do when the engine only has 1200ks on it.

I guess I'm looking at things to suggest to the builder and see what he thinks?

[BMGTZ]

I had some issues with lifters and replaced the whole set at the start of the build. then for some reason the guy at the head shop didnt do the tip heights on the new valves properly and several lifters shat themselves and went solid. Not his fault he says.....just like the cracked and worn guides he left in the head weren't his fault.! the head casting was changed to a new one as I thought is noise caused be the lifter bore being oval or the loose guides. that quietened the top end a little but the main noise was still there.

the head castings are available through Nason Parts and come as a bare head.....just needs a face and all your stuff assembling into it. it was only 365.00 so was actually cheaper than changing the guides

[lozza]

there is a lot of visual piston movement at the top of the bore but it is withing spec when using a feeler gauge to check.....11 thou

hey brian, that seems like alot to me, even when you account for the difference in thickness between the skirt and piston top. i can't remember even having half of that PTW clearance with wiseco's.
i think you have piston slap - sorry!

[nwr31]

yep, definate piston slap, due to not having any offset.

pistons need to be thrown in the bin

[BMGTZ]

piston to bore has been checked at build and then re-checked when it was apart......{with the head off it doesn't take much to drop out the bottom end} the measurements were all ok.

even std clearances at the piston skirt give slop at the top of the bore....I have the engine she over heated with the head off and measured that. it was close to 20thou

strangely when some of my old mates from rallying heard it...the first thing they said was..."you got forged pistons in that? we discussed the old days and how noisy the pistons were.

whilst it is going well now....I don't expect will do very many miles before it it needs rebuild again.

question is what pistons to get then.....

[nwr31]

get pistons with offset, & dont drive it to save your bores.

[BMGTZ]

get pistons with offset, & dont drive it to save your bores.

pistons for these in any form are specially made.....not off the shelf. But I will be asking the question next time that is for sure.

as to the block.....lets say...I have a couple. I wont be pulling this one out to change the pistons because it will probably need a re-bore at a larger size anyway. So I can get pistons and have a bottom end waiting..

But she will probably sell it anyway.

[nwr31]

specially made or not I would be asking why they didnt have offset (and maybe asking for a replacement set) - its fundamental to any piston after all.

[Smutt]

Brian.... my engine is nice n quiet... top and bottom end...

You may recall where i got my pistons from

Keep it in mind..

[BMGTZ]

having thought about it...........if it dies. i will put a 2 liter in.

I have plenty of those and they are cheaper to build!

[Smutt]

Cant blame you with the troubles you have had with this one..

[BMGTZ]

yeah sam ...it has been a challenge.

[nwr31]

feel sorry for you for being let down so many times & i was looking forward to seeing the build done.

so getting well made forged pistons for a 93 is a real mission is it? cause doing them (& rods) is in my long term plan.

[caged]

How much power are you hoping to make? If it makes good power and doesnt use oil who cares if it rattles like a truck.

specially made or not I would be asking why they didnt have offset (and maybe asking for a replacement set) - its fundamental to any piston after all.

Lots of forged pistons dont run offset gudgens to reduce friction, an offset pin is only used to reduce piston slap. Cp's dont run offset pins and with their recommended p-b clearances they are very quiet for forgies.

[nwr31]

offset pin is also used to reduce stress in the rod/reciprocating mass - (it means the piston & rod dont hit TDC at the same time)

for a street motor i would sacrifice a slight difference in friction for no piston slap anyday.

[BMGTZ]

"BIG"power wasnt the real reason to forge the engine. just a bit more with safety for turning up the boost

as to getting pistons NWR31....they pretty much are special order with all the companies. As with a lot of 4G93 stuff......not much of an aftermarket following and what there is, is way dearer than the 4G63.

[mymidlifecrisis]

well after doing some work with replacing lifters....16 new ones to rule them out as the culprit of the noise.



I ended up taking the head off and inspecting very closely the the " JUST RECONDITIONED HEAD"

valve tip heights wrong! 11 stuff lifters that did 300 kms.......and yes they were bled before install.

5 valve guides with excess wear and to top it all off.....one cracked guide.

so I have purchase a new casting from nasons.....


MESSAGE TO ALL.....do not use alltorque heads in bibra lake.....you dont get quality work

Buggers me why they left the guides as is. I mean, they're in the game to make money so, R&R all valve guides equals more money. Defies my logic.

[caged]

"BIG"power wasnt the real reason to forge the engine. just a bit more with safety for turning up the boost

as to getting pistons NWR31....they pretty much are special order with all the companies. As with a lot of 4G93 stuff......not much of an aftermarket following and what there is, is way dearer than the 4G63.

Why not just go 4AGZE pistons then, mine were cost me 100$ and teamed up with a set of eagle copy rods was a bullet proof set up.