Forged Setup Advice

minorv8 · Post by **minorv8** » Tue Aug 18, 2015 5:21 am

Tony, I asked Omega (IIRC) years ago about doing a set of 94 or 94,5 mm pistons for 4,6. I believed the quoted silly number with a minimum batch of 10 or 12 pistons. Thanks but no thanks.

About the critics, I was stopping at a local petrol station for some fuel with my Minor when a guy shows up and started asking questions. That soon changed to ranting about panel gaps, second rate paint job, silicon spots in paint etc. He then continued by bragging how he´s had Porsche this and Porsche that restored blah blah blah. So, I wished him all the best, climbed in the car and started the engine. Well he came running back and asked what engine have you got. I told him it´s just an engine but still the crappy paint job

He tried to be a bit more civilized by saying that now he understand the outside appearance... Kind of a too late.

Post by **Coops** » Tue Aug 18, 2015 10:03 am

Haha nice one mate
Can't remember who I mailed but they would only do a batch of 12 also

Quagmire · Post by **Quagmire** » Tue Aug 18, 2015 12:02 pm

Coops,

This forum has been invaluable to me (and therefore my family) who run 4 RV8 powered vehicles between us. The support and generosity of everyone here has been far above any that I have come across anywhere else.

Threads put up by people like yourself, Perry etc are an inspiration - I love the fact that everyone is constantly pushing as far as they can, building things that are sometimes on paper totally bonkers.

Keep up the good work!

Jamie

stevieturbo · Post by **stevieturbo** » Tue Aug 18, 2015 11:34 pm

Any decent piston maker will be happy to make 8, if you need to go down that road give Dave a shout.

Interesting googling.

It seems you use 94mm pistons ? These have 24mm gudgeon pin ?

Any idea on compression height ?

Certainly the first two dimensions are the same as a 2.0 pinto and some of the V6 Fords.

http://www.burtonpower.com/accralite-fo ... 32-94.html

Likewise same sort of fitment in the US ( just a cast piston, but someone is bound to do forged )

http://www.summitracing.com/int/parts/s ... /overview/

minorv8 · Post by **minorv8** » Wed Aug 19, 2015 5:02 am

Compression height of 4,0/4,6 pistons is 35,9 mm.

Mahle makes a 94 mm flat top piston for aircooled VWs. I visited a local VW shop years ago and they quoted 300 euros for a set of pistons/barrels. Some engine builder adviced against air VW pistons in water cooled engine. Don´t know why because rally people have used VW pistons Ford OHC engines.

sidecar · Post by **sidecar** » Wed Aug 19, 2015 6:34 am

stevieturbo wrote:Any decent piston maker will be happy to make 8, if you need to go down that road give Dave a shout.

Interesting googling.

It seems you use 94mm pistons ? These have 24mm gudgeon pin ?

Any idea on compression height ?

Certainly the first two dimensions are the same as a 2.0 pinto and some of the V6 Fords.

http://www.burtonpower.com/accralite-fo ... 32-94.html

Likewise same sort of fitment in the US ( just a cast piston, but someone is bound to do forged )

http://www.summitracing.com/int/parts/s ... /overview/

The flat top pistons all else being equal will raise the compression ratio of the engine as the Rover pistons are dished. A higher CR is the last thing that this engine needs. Of course there are ways to reduce the CR.

kiwicar · Post by **kiwicar** » Wed Aug 19, 2015 8:06 am

Hi
5 litres, 26 cc heads, 7cc for the gasket, 0 deck and 5cc for valve cut outs you get 17.5:1 Cr, this may be a tad high.
If you want a 9:1 cr with 5 litres and 26cc heads you will need a dished piston, one with a dish of about 40cc, this may give issues with piston cooling as having more than half the chamber volume in the piston is not generally advised. 36cc dish would give about 9.6:1 CR but that still is a lot of dish and you would defiantly need "0" deck height to get some squish band.
best regards
Mike

stevieturbo · Post by **stevieturbo** » Wed Aug 19, 2015 8:20 am

sidecar wrote:
stevieturbo wrote:Any decent piston maker will be happy to make 8, if you need to go down that road give Dave a shout.

Interesting googling.

It seems you use 94mm pistons ? These have 24mm gudgeon pin ?

Any idea on compression height ?

Certainly the first two dimensions are the same as a 2.0 pinto and some of the V6 Fords.

http://www.burtonpower.com/accralite-fo ... 32-94.html

Likewise same sort of fitment in the US ( just a cast piston, but someone is bound to do forged )

http://www.summitracing.com/int/parts/s ... /overview/
The flat top pistons all else being equal will raise the compression ratio of the engine as the Rover pistons are dished. A higher CR is the last thing that this engine needs. Of course there are ways to reduce the CR.

I didnt say to use those pistons, I was just giving an example of piston availability in similar dimensions. And as we dont know compression height, whether flat top or dished is irrelevant at the minute.

If compression height was lower, even the flat top piston could be lower compression that existing dished pistons.

And obviously in a Pinto fitment there will be dished options too.

sidecar · Post by **sidecar** » Wed Aug 19, 2015 10:18 am

stevieturbo wrote:
sidecar wrote:
stevieturbo wrote:Any decent piston maker will be happy to make 8, if you need to go down that road give Dave a shout.

Interesting googling.

It seems you use 94mm pistons ? These have 24mm gudgeon pin ?

Any idea on compression height ?

Certainly the first two dimensions are the same as a 2.0 pinto and some of the V6 Fords.

http://www.burtonpower.com/accralite-fo ... 32-94.html

Likewise same sort of fitment in the US ( just a cast piston, but someone is bound to do forged )

http://www.summitracing.com/int/parts/s ... /overview/
The flat top pistons all else being equal will raise the compression ratio of the engine as the Rover pistons are dished. A higher CR is the last thing that this engine needs. Of course there are ways to reduce the CR.
I didnt say to use those pistons, I was just giving an example of piston availability in similar dimensions. And as we dont know compression height, whether flat top or dished is irrelevant at the minute.

If compression height was lower, even the flat top piston could be lower compression that existing dished pistons.

And obviously in a Pinto fitment there will be dished options too.

I wasn't suggesting that you were suggesting to use those pistons, even though posting up a link to a set of pistons could actually imply that you were saying to use the pistons at the 'end of the link'

I actually said "flat top pistons all else being equal" will increase the CR.

bigaldart · Post by **bigaldart** » Wed Aug 19, 2015 7:12 pm

https://www.uempistons.com/index.php?ma ... ath=8_9_14

Keith Black Icon pistons, next to bottom of this page looks interesting, chevy pin bore and 0.036 overbore, 10 cc dish or flat top. We use a flat top in the dragster with Chevt rods, depends on your stroke what rod length you need. Much more reasonable than a custom piston.

Alan

stevieturbo · Post by **stevieturbo** » Wed Aug 19, 2015 8:46 pm

Closer to the 96mm range...if you do go down that route.

the 5.3 LS engines seem to run around a 3.78" bore which is pretty much 96mm.

http://wiseco.com/Catalogs/Automotive/Chevrolet.pdf

http://texas-speed.com/p-741-wiseco-22c ... gines.aspx

http://www.summitracing.com/int/parts/s ... /overview/

There will be a variety of shapes and sizes as well as a standard 0.944 pin or the more common Chevy SB pin 0.927 depending on which rods.

If you can find a rod/compression height that all matched together those are more off the shelf options.

Finding different rod lengths for the chevy setup shouldnt be hard.

mgbv8 · Post by **mgbv8** » Thu Aug 20, 2015 7:58 pm

Coops wrote:Haha nice one mate
Can't remember who I mailed but they would only do a batch of 12 also

You can get stock 4.6 dished Omega's at 94mm bore ( I think its actually 94.04mm from memory) off the shelf from John Eales Coops! Thats where I buy mine from.

This is the spare set I have in the other Engine I'm stripping to sell. Dished 94mm Omega's on stock 4.6 rods. If I get a day off work soon I'll get the engine apart so you can come and see them.

Pel

Cobratone · Post by **Cobratone** » Sun Aug 23, 2015 8:14 am

mgbv8 wrote:
Coops wrote:Haha nice one mate
Can't remember who I mailed but they would only do a batch of 12 also
You can get stock 4.6 dished Omega's at 94mm bore ( I think its actually 94.04mm from memory) off the shelf from John Eales Coops! Thats where I buy mine from.

This is the spare set I have in the other Engine I'm stripping to sell. Dished 94mm Omega's on stock 4.6 rods. If I get a day off work soon I'll get the engine apart so you can come and see them.

Pel

I got my Rover pistons off the shelf from John Eales too, I've often wondered why you've not mentioned him as a supplier Tony??

minorv8 · Post by **minorv8** » Sun Aug 23, 2015 9:53 am

Are there any suppliers that have forged +20 pistons for 4,6 engine ?

Post by **Coops** » Sun Aug 23, 2015 10:13 am

You mean as in this place???
http://www.johnealesroverv8.co.uk/23.html

If so did as required mailed them never heard back from them so moved on to looking else where. hence why never mentioned them.