351 clevo with 302 rods

[slydog 7,873]

No machine work other than inlet valve notch.No it wasn't over heated they can't handle sustained rpm and combustion temps as well as other performance forged pistons.The structure under neath actually looks thicker than my Wiseco units but it doesn't seem to help them for what ever reason.I'm thinking piston material make up is the cause.

 

While it may not look like much this is not a good thing to happen to a forged slug...next step is a hole.

 

 

That said perhaps there clevo slugs are better I don't know ??? and the above are xflow units but if there doing it in 1 form they prob could/would in another ?

[Trev Vaa 1,185]

i've heard of issues with Ross before as well, but then i've seen engine builders who turn SBF & SBCs to 10,000rpm (nascar and SB drag motors) and they won't use anything else.... jasons SBF turns 9600rpm (pro stock) and he's got Ross inside it and it's pretty much all he will use.... go figure right?

[ando76 4,354]

don't use them in a x-flow on the edge and expect them to survive - they will fail exactly like sly has noted.  I used them in my burnout motor and as soon as I pushed it the pistons died before the head gasket - a sure sign that they just can't handle stuff as good as the wiseco units can.

 

If you set them up right and don't push them they will survive - but get things wrong - even by a little bit - and they will fail quicker than an acl cast unit.

 

I have a shelf full of Ross pistons that have sunken in the middle exactly like sly's - all came from x-flows pushed to the limit on timing and comp.  A wiseco piston will take detonation and pre-ignition and just blow the head gasket.  Ross will just burn a hole in the piston and then you are f..ked. 

 

Me - I'd rather change a $100 head gasket than a set of $1400 pistons - especially when the wiseco units are cheaper and better.  I'll be replacing my fucked Ross units with WISECO pistons for sure and I will never use Ross again. 

 

I have Ross units for my roller cam x-flow and I can tell you that I will not be pushing the tune - I got the Ross units cheap second hand - made up out of a couple of sets of fucked units - and that is the only reason that I will be using them.  I am well aware of their limits and I will be very careful. If I had- my time over again I would have gone straight to the wiseco units - .060 over bore - more cubes and a better piston that doesn't fail - gotta be better. 

[Trev Vaa 1,185]

im hanging to get my set from Dandenong, Special Piston Services, paid top dollar but they have a fantastic reputation and its whats inside 1tuf65, car on pump e85 running 8s can't be a shit bit of kit surely.

[PRO250 1,506]

Id be keen to see if in the same situation would a different set of forged slugs do the same thing I bet they would  

[slydog 7,873]

Gavin has gone to Wiseco's and hasn't had it happen since.Mossy has never had it happen in all his years of using em so I'd suggest it is just the Ross slug and it's make up in Xflow form.

[slydog 7,873]

  A wiseco piston will take detonation and pre-ignition and just blow the head gasket. 

 

Who needs to see proof of this LOL

[ando76 4,354]

sps pistons are very very good.  You will not have any problems. 

 

Agree Rob - I think its to do with the way they are made for a x flow and there is just not enough meat in the dead centre of the piston.  When you see lots of pistons from different engines - all doing the same thing - you know there is a problem.  Conversely when you see the wiseco's take an absolute flogging you know they are right.

[PRO250 1,506]

Going by whats been said in here my flat top engine should have died a long time ago the piston tops are thiner then the ross pistons and are cast 

But going by whats been said in here wayne should say a cast piston it will last longer 

  

[slydog 7,873]

Prob has died as no one ever see's it going...Heathcoate is only down the road from you

 

I'd use a cast over a Ross in a xflow for sure and I prob wouldn't use a Ross full stop,but I'd prob look @ Diamond money no object.But for a street everyday type engine I wouldn't use forged pistons at all and for a weekender it would have Wiseco or Probe unit's.There US made and pretty cheap for what you get really

[CHESTNUTXE 7,310]

how does the shorter piston and 6 inch rod affect compression ratio ?

[gerg 10,871]

how does the shorter piston and 6 inch rod affect compression ratio ?

 

If the piston sits at zero deck height tdc on both combos, then there is no difference in compression. Rod length affects piston dwell time at tdc and side thrust on bores. Also affects the way a cam works in conjunction with where the piston sits at x crank degrees.

[CHESTNUTXE 7,310]

ok so why are people saying in many threads that this combo the cr goes up a lot more than usual ?

[gerg 10,871]

I think it's assuming that you're starting with an entire 302 engine (ie with small chamber heads) and just shoving in a 4MA crank and the special ACL pistons. This gives upwards of 11:1 comp on a zero deck. That's if they make the pistons to the same deck height as the std 351 piston.

[CHESTNUTXE 7,310]

i did some checking ,your right the comp doesnt change the figures were off a zero deck thats why,i probly have a good 030 of deck which will come in handy i guess,plus a 070 comectic gasket will drop it to 10.1.1.thats with the 302 heads.

[gerg 10,871]

Wow the pistons are that far down the hole? Never heard of a clevo like that. Have the rods been resized heaps? It might not be a good idea to run that wide a quench gap. 70 + 30 is 100 thou or 2.5mm. Still better than open chamber but you're losing efficiency the wider you go.

[CHESTNUTXE 7,310]

every clevo i have had has heaps of deck ? your saying down the hole is not good ?

[gerg 10,871]

For the quench chamber to work at its best, zero deck is the go. Some even push it to +5 for max effect. Easy compression too as with a closed chamber head, skimming the block needs less meat off than skimming the heads to achieve the same cc.

[CHESTNUTXE 7,310]

but from the factory these motors pistons are down the hole,or is it too much of an machine cost to deck every engine they produced ?

[gerg 10,871]

I think they had a production tolerance to work with, plus had to keep the compression ratio on the safe side. I'd guess that, like advertised horsepower, the advertised compression would often be a tad optimistic (ie a nominal "blueprinted" figure) especially since the chambers are as-cast and will vary by a few cc between each other. Things like carbon build-up, variations in crank throw and rod length would all conspire to the need for such wide tolerances. They are much better these days. Who would have thought 200kW from a family six would be the norm? 20 years ago a gun V8 wasn't making that much.

[CHESTNUTXE 7,310]

ok i see,good info gerg