Pistons

Hi Guys

I am a new 460 owner and am looking for a set of pistons that will give a compression ratio of 8:1 to 8.5:1

Bore 4.40
Stroke 4.5
Rod 6.8
heads 74cc Dove c
zero deck height

Is there a set of pistons off the shelve I can buy or will I need to order a custom set.

Thanks

Kev

To get that low your probably going to need a custom piston, most of the shelf stuff is only about -30cc and will have you in the 10:1 range.

Check Probe and Diamond and see what they have Listed.

Edit : Looking around a little.

Your going to need a 60cc dish, not very pratical and maybe impossible to maintain structural integrity with your 6.800 rods and stroke.

You need to look at using some D3 heads with substantialy larger chambers and use a 45cc custom dish. and maybe think about using a 6.700 rod to give the piston manufacture some room to work with.

Is this for a turbo application?

Yep, i am building a it with a gt55 turbo running on methanol, is it possible to run the 6.605 rod instead of the 6.8.
i figure this would give me more piston choice

its a custom piston no matter what rod you try to use.

If your crank is a Ford Racing Ford Journal Crank, you can use a Ford 6.605 rod, typical most other aftermarket cranks a Big Block Chevy rod Journals. with a typical choice of 6.7 or 6.8 along with other others. but watch with the shorter stuff they will not clear the throws on the crank.

You need to watch wrist pin sizes too, BBC stuff is .990 and BBF stuff is 1.040.

You'd be best using some D3 heads and a 6.7 rod IMO, its a awful big dish to get the compression down with the DOVE heads.

You also need to do some more reasearch with running methanol, it will tolerate higher compression than 8.0-8.5 in forced induction applications.

You can also use a .0120 head gsk.

What is the thickest head gasket you can get and would use on a turbo motor without going to copper or is copper my best choice.

if your building new and dont have a crank,rods or pistons. maybe a smaller ci. engine will do the job you can get alot of hp when put pressure to it ive seen some small ci. make 1000hp easy how much power are u looking for

As much as I can pump out of a GT55 turbo on methanol.

If I use a 6.7 rod with a 1.245 pin height piston this would bring the piston down the bore 100thou, can this be done?

4117kev wrote:As much as I can pump out of a GT55 turbo on methanol.

If I use a 6.7 rod with a 1.245 pin height piston this would bring the piston down the bore 100thou, can this be done?

Not the best way of going about it.

You have to look al the specific piston to make sure it will clear the crank counterweights, It be a hit and miss thing.

4117kev wrote:As much as I can pump out of a GT55 turbo on methanol.

If I use a 6.7 rod with a 1.245 pin height piston this would bring the piston down the bore 100thou, can this be done?

Yes, this is the most practical way to set up a low compression methanol burning engine. A lot of force-fed methanol drag racing engines (and nitro burning engnies) are built this way specifically and for the same reason you are asking (compession ratio). Quench is not critical in a methanol burning engine and much less so in a blown (turbulent A/F mixture) methanol burning engine.

That being said, MeOH can handle more compression ratio than 8.5:1 but there's not necessarily anything wrong with that compression ratio. Frankly, for structural integrity I'd step away from the 4.50 stroke crankshaft and go with a forged 4.30....but if you must stick with a forged 4.50 then turocharged on alcohol is your best bet.

Diamond makes 32cc-36cc dished pistons that would meet your compression ratio needs when run at .100" in the hole. 0.040" overbore is not a common bore size but rings are out there so if you can use that bore then you will be maintaining better cylinder wall thickness than gong to 0.060"overbore.

Paul

4117kev wrote:Yep, i am building a it with a gt55 turbo running on methanol, is it possible to run the 6.605 rod instead of the 6.8.
i figure this would give me more piston choice

X2

With forced induction and high octane fuel such as alcohol ... simply use a 6.700" rod instead of the 6.800" rod and run the piston .100" down the hole.

Thanks Guys

We already had the motor and have been running it in N/a form for the past few years and it was showing 800rwhp at the track, not bad for an old cast iron headed truck motor.

So the plan is we already have the new 4.5 crank sitting to replace the current cast item and now some new rods & pistons and we will see what it does with the turbo attached to the front of it.

Being new to 460's myself I am sure this won't be the last time I come here for advice.

Thanks

Kev

4117kev wrote:Thanks Guys

We already had the motor and have been running it in N/a form for the past few years and it was showing 800rwhp at the track, not bad for an old cast iron headed truck motor.

So the plan is we already have the new 4.5 crank sitting to replace the current cast item and now some new rods & pistons and we will see what it does with the turbo attached to the front of it.

Being new to 460's myself I am sure this won't be the last time I come here for advice.

Thanks

Kev

new and the past few years and 800 rwhp . OK

800 RWHP with Dove c's N/A..................... I'm impressed good job.............

You may want to look at the cheap Pro Comp aluminum heads for what your doing. May fill the bill if your doing it on a tight budget.