Speed Pro Hyper Pistons

[str8-6]

Looking at Summit for some parts to rebuild my stroker the next winther; I think I did read here that the newer pistons with mm. rings is OK to use in an older block if so what comp.ratio will I get with the 258 rods and a 7120 head,and probably a Lunati Vodoo 268 deg camshaft (been looking at a Howard also 221@ 0.050 and 0.501 lift), and what happens to compression ratio if I deck the block .020?

Anyone on here that has used the Speed Pro Hyper pistons,on the website they state that they can be used for street/strip engines and even moderate boosted engines,I would like to know if they will survive a 75-100 hp nitrous-shot,can't find that info anywhere...

And finally: ARP rod bolts: Is it the same rodbolts for the 4.0 rods and 258 rods?
/Hans

[FlyinRyan]

I never understood why everyone here uses forged pistons (most everyone, anyways). I've made upwards of 500whp on 360s with speedpros (turbo application). Biggest thing is that the gap will need to be loose to accommodate for sweilling due to heat found in hyper pistons.

You'll be fine.

[jsawduste]

Best to study metallurgical properties of each material for an answer.

Then add in the availability factor for those whom wish to buy off the shelf.

Not a slam but factual information and reasoning behind choices.

[Cheromaniac]

Looking at Summit for some parts to rebuild my stroker the next winher; I think I did read here that the newer pistons with mm. rings is OK to use in an older block if so what comp.ratio will I get with the 258 rods and a 7120 head

Assuming 57cc chamber heads, a 0.043" thick head gasket, and no milling of the block/head, the CR with either the H802CP or H825CP pistons on 258 rods will come in at around 9.8:1 in a 4.6 stroker. By smoothening the piston dishes/chambers and polishing them to a near mirror-like finish, you'll be able to lower the CR some.
You could use either piston type in any 4.0 block. The only difference is that the H802CP pistons require metric size rings so just make sure you get the correct ones.

,and probably a Lunati Vodoo 268 deg camshaft (been looking at a Howard also 221@ 0.050 and 0.501 lift), and what happens to compression ratio if I deck the block .020?

If you deck the block by that amount the CR will be over 10:1. You'll need to choose a cam that keeps the dynamic CR not higher than 8.5:1 so you can still run pump gas without detonation issues.


Anyone on here that has used the Speed Pro Hyper pistons,on the website they state that they can be used for street/strip engines and even moderate boosted engines,I would like to know if they will survive a 75-100 hp nitrous-shot,can't find that info anywhere...

They'll survive up to 8psi of boost from a super/turbocharger or a 100 shot of nitrous without any problem. Just ensure the engine doesn't run lean and that there's enough boost timing retard.

And finally: ARP rod bolts: Is it the same rod bolts for the 4.0 rods and 258 rods?

Yes and it's part no. ARP112-6001.

[SilverXJ]

Best to study metallurgical properties of each material for an answer.

Then add in the availability factor for those whom wish to buy off the shelf.

Not a slam but factual information and reasoning behind choices.

This x100

[str8-6]

Assuming 57cc chamber heads, a 0.043" thick head gasket, and no milling of the block/head, the CR with either the H802CP or H825CP pistons on 258 rods will come in at around 9.8:1 in a 4.6 stroker. By smoothening the piston dishes/chambers and polishing them to a near mirror-like finish, you'll be able to lower the CR some.
You could use either piston type in any 4.0 block. The only difference is that the H802CP pistons require metric size rings so just make sure you get the correct ones.

As it is now I have a Renix 4.0 with the heavy 258 crankshaft,258 rods and nothing done to lower compression,runs great with a Crane 272/284 deg. and .484/.512 lift Econopower camshaft ignition at 37 degrees/5500 rpm 24 deg. at a 1000 rpms,no pingin when it's on 95 octane (RON???) gas,with 98 oct. (RON) it has no ping "that I heard" even at 40 deg.(yup I know, made a minor mistake when setting ignition... melted the sparkplugs "but just a little bit")

This engine is a piece of crap built from leftover stuff in the garage:used stock pistons, new bearings and rings,every bolt and nut is the ones that been there since the engine left the factory,only the crankshaft,rods, cam and lifters are changed internally,I even use a old tired 258 stock watwerpump,but the Melling oilpump was new "20 years ago",258 distributor with a Ignitor 2 and to roundit all out with the the old crap : a 35 year old Offenhauser intake with a 600 vacum Holley that came from a 58 Ford according to the numbers on it...

The engine was thrown together to last over the summer,that was 5 years ago and it still runs but with some rattle and other funny noices,shifts it at around 5600-5700 rpms and it still havent expirenced how it feels to loose against a Gambia Motors SB,did run the 1/4-mile 12.94 @ 100 mph in 2012,valve float at 1000 feets stopped me from going at full throttle all the way to the finishline so it could've gone faster "damn those stock Renix valvesprings..." That was with a stock exhaust hedders,got a real one now... (+30???? hp)

If you deck the block by that amount the CR will be over 10:1. You'll need to choose a cam that keeps the dynamic CR not higher than 8.5:1 so you can still run pump gas without detonation issues.


I'm not affraid of some compression,my buddy runs a Ford SB stroker 347 cu.in. at a 10.6 CR with no pinging,(on Swedish pump gas 95 oct.) some does run their engines with domed pistons at 12.5 CR on 98 oct. pump gas,works too...And if that isn't enough we do have the Shell V-power fuel thats a pump gas with 100 oct. very expensive but all gasoline is expensive here in Sweden... 1.5-2 usd/liter (about a 1/4 Us gallon) fuel how that sound for You guys in the US or elsewhere?



They'll survive up to 8psi of boost from a super/turbocharger or a 100 shot of nitrous without any problem. Just ensure the engine doesn't run lean and that there's enough boost timing retard.

I've got a Holley Red pump for the engine and a Blue for the nitrous when the time comes to use the "laughing gas", retarding will be just like myself "the oldschool way" Nitrous-time= adjust the ignition by hand...-2 degr./50 hp nitrous,I like it simple...Computers should sit on a desk not in an enginebay...



Yes and it's part no. ARP112-6001.Thats good to know,I think I saw some ARP rodbolts with another part no so I had to ask to be sure,will be ARP-bolts in every bolthole they got something that fits after the rebuild...

Thanks Dino "You are a rock"

[str8-6]

Oooh by the way : It will be bored 0.060,nothing to save on that part,it's a short driving season in Sweden "think South Alaska" so it will survive as long as I still can climb in to that thing...

/ Hans...

[str8-6]

I never understood why everyone here uses forged pistons (most everyone, anyways). I've made upwards of 500whp on 360s with speedpros (turbo application). Biggest thing is that the gap will need to be loose to accommodate for sweilling due to heat found in hyper pistons.

You'll be fine.

On the website they state that a Hypreeutectic piston can run a tighter gap,is that without boost/nitrous and when going boosted You will have to open it up a bit?

"Don't mind the order of the words,in sweden we have totally different grammatics so what I write is to be considered to be Swenglish... Doing the best I can..."

[Cheromaniac]

On the website they state that a Hypreeutectic piston can run a tighter gap,is that without boost/nitrous and when going boosted You will have to open it up a bit?

Yes on both counts.
From reading your previous posts, it sounds like you'd already built a high compression motor and had a Crane cam that was appropriate for the task. With 98 RON octane (equivalent to US 93 octane) fuel being widely available in Europe that isn't a problem.
If I understood you correctly, you're planning to replace the original stock pistons and do a +0.060" overbore, thereby increasing displacement from 4516cc to 4657cc. A set of H825CP pistons will lower the compression by ~0.4:1 compared to the stock pistons so you could deck the block 0.020" to bring it back to where it was.

[FlyinRyan]

PS DCR does not need to be held to 8.5:1.

[str8-6]

On the website they state that a Hypreeutectic piston can run a tighter gap,is that without boost/nitrous and when going boosted You will have to open it up a bit?

Yes on both counts.
From reading your previous posts, it sounds like you'd already built a high compression motor and had a Crane cam that was appropriate for the task. With 98 RON octane (equivalent to US 93 octane) fuel being widely available in Europe that isn't a problem.
If I understood you correctly, you're planning to replace the original stock pistons and do a +0.060" overbore, thereby increasing displacement from 4516cc to 4657cc. A set of H825CP pistons will lower the compression by ~0.4:1 compared to the stock pistons so you could deck the block 0.020" to bring it back to where it was.

And if I understand the thing with squish I will get that back to a more favorble number by decking the block "right?"
As I wrote here a long time ago I'm a cheap bastard so heres a tought about save some money: If I deck the block 0.020 can I use stock 258 pushrods since they are shorter than the 4.0 pushrods "I'm learning by doing...WRONG" ,took the 258 pushrods by mistake when I first put this engine together so thats the way I know they are shorter,made a really loud ticking since it had a millimeter play and no preload with those...

[Cheromaniac]

And if I understand the thing with squish I will get that back to a more favourable number by decking the block "right?"

Right.

As I wrote here a long time ago I'm a cheap bastard so here,s a thought about save some money: If I deck the block 0.020 can I use stock 258 pushrods since they are shorter than the 4.0 pushrods "I'm learning by doing...WRONG" ,took the 258 pushrods by mistake when I first put this engine together so that's the way I know they are shorter, made a really loud ticking since it had a millimetre play and no preload with those...

You'll definitely need pushrods that are ~0.025" shorter than stock i.e. 9.600". I don't know if the 258 pushrods are that length though.