as title standard everything bar some let turbo pistons what kind of CR will it see?

 

depends on head gasket but around 7.5.1 i think

 

st170 has smaller combustion chamber so more likely to be around the 8.0-1... but get it properly cc,ed

 

I'd say approx. 8.2:1, based on the 47cc chamber coming in at 7.6:1 typically.. (ST being 40cc chamber)..

 

quite a drop from a standard st 170 then!

would i still need to get it cc's its a standard engine thats never been apart. Head will be checked when its off etc.

I don't want to silly silly power hence maybe using standard st170 rods and let pistons. Arent the st rods better than zetec ones as standard. What kind of power limits are they?

Cheers

 

You cant use the ST170 rods with C20LET pistons.. you need early silvertop rods (shorter and larger small end, which still needs modifying)

 

ah settle's that one then pmsl

i knew they needed modding but didn't know you coudlnt use the st170 items

i was trying to avoid buying steel rods etc to be honest!

so either track some early zetec rods or use steel rods i guess!?

whats are the limits of a standard zetec rod seams daft to go backwards with them?

 

I've never seen one break when used properly... Someone on here has a set of rods and pistons for sale for Ł500? CR would be a tad high for anything high power on a ST170 head.. there is no cheap way to do all this to be honest.

 

yea i have seen them from the states but as you say its 8.5 for a zetec which i presume would be more like 9 in an st170 head?

 

Yeah something like that. Turbocharging the ST170 isn't as straight forward as a normal zetec as you have the VVT to worry about etc.

 

i would perhaps like to retain the vvt one day but certainly to get going i believe parts can be blocked etc to stop it doing anything. The idea is to get it up and running and then work from there realy.

 

the st170 uses the same rods as the US SVT, so it has a 20mm small end. JE will do custom pistons for $175 each with a lead time of about 4 weeks

don't be a cheapskate though, Eagle rods at the moment cost Ł160 a set! they come with arp bolts which cost about half of that, so the rods are only costing you about Ł80!!

 

oh, the CR of those pistons you're looking at turns out more like 9.5:1 on a standard zetec and 10.5:1 on an st170 (by the figures they give for the dish in the piston

 

no it doesnt st170 with them eagle rods and je pistons and 1.6mm head gasket comes out at 9.2.1 i run them in mine built by jamsport.

 

Eagle rods for Ł160 !! where do I get these for a 2.0 zetec bottom end? can they be used with XE pistons?

 

i make it 9.8:1:

1.6mm head gasket 9.3cc
+
head 40cc
+
piston 7.2cc
=
56.5cc

cylinder capacity = 499.55cc

499.55 + 56.5 = 556.05 / 56.5 = 9.84:1

JE pistons are 40 thou taller than standard too, so would probably be higher than that in reality.

 

from the states on ebay! and no, you can't use XE pistons with them as they're 21mm on the small end as opposed to 20mm on the ford. i wouldn't like to take the bush out another mm

 

JE rate them at 9:1 on a 47cc head with a OE head gasket..

The yank rods and pistons have a 19.00 small end, not 20mm.. You could re-bush the eagle rods but it quickly becomes not the bargain you first thought.

 

The yanks use a 19.95mm pin, .787 in old english. Trying to fit the xe or let pistons is pointless though, as the compression height is all wrong for the rod length.

 

Actually it almost corrects the compression height 'problem' you get with the GM pistons - unfortunately this completely voids the usefulness of them in this application!

 

well now your all talking in riddle's! lol

the eagle rods and custom pistons seam to be the best plan? so i can choose the CR?

Is it worth having and of the heads cr lowered or just get the correct pistons.

Any views on a "good" cr am going for a chat with rusty this week "peter kenedy" for anyone that knows him to see what his views are

 

How much power do you want?

Personally I think you should approach one of the few big tuners who build this kind of thing a lot rather than letting the internet spec you an engine.

 

as everyone seams to say "i am not chassing power" pmsl !

but on the other hand i would like to future proof the engine to an extent! dont want to have to change all the internals at a later date?

as above i am going to speak to Rusty he builds very good cars he does he was the one who built the capri who raced clarksons brabus merc many years ago. Lives down the road fromm me which is handy!

Just wanted people views i guess really before hand.

 

Careful with secondhand LET pistons, most of them have done 150K+ by now, and are really starting to show it.

If you need advice on where to get new ones, drop me a PM

 

cheers chip, as above though looks to be a no go with the st170. A chap called beardy who i think you may know of? was going to supply, so yea they were probably fooked lol

 

There are different CR pistons available for the let anyway though mate.

 

ah yea suppose there is!

was only going to go let if it meant i could get away with leaving most of the engine intact. As above though rods seam very cheap for these it would be daft not to change them anyway!

 

ok i picked the engine up yesterday, comes with both manifolds which i dont need so should be able to claim some money back from them!

Anyway i have decided to go the proper route with the custom pistons and rods. Now i want to be aiming for 7.9:1 ish as a comp ratio can anyone help with the piston spec? i have spoken to the chap from the usa but just making sure i dont end up with zetec spec 7.9 and not the st170 7.9:1

Cheers

 

I'm sure Ian Howell could sort you out a piston+rod package.

 

i've bought je's from the states for the build i'm doing... i've worked out with the cometic 1.5mm gasket and a normal head, i'll get about 8.7:1, if i can take 6cc from somewhere, i get 8.1:1

should be able to take that off of the pistons and out of the chamber without any problems!