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Roverized
Jason Spittel

(10 posts)

Registered:
07/01/2011 02:17AM

Main British Car:


Cast pistons for Rover
Posted by: Roverized
Date: July 04, 2011 02:42AM

Hi everyone,

There is a Silvolite cast piston (Ford 250) that may fit the Rover 3.7 inch bore with 300 crank and Chev 5.7 inch rods. It has a 1.529 comp height. Does anyone know the limitations of a cast piston? Am looking at around 11.5 to 1 comp and 6000 max rpm.
Thanks


roverman
Art Gertz
Winchester, CA.
(3188 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Cast pistons for Rover
Posted by: roverman
Date: July 04, 2011 02:17PM

Jason, You might be better-off with the oem.4L. Rover piston for more compression. You'll need to verify comp. height vs stroke and rod length. I suspect the Rover piston is are hypoeutectic,(some silicon),as they lasted with 24 lbs of turbo boost, for a while. If you want forged, you might compare Ford modular V8, with 3.7" bore. Good Luck, roverman.


Roverized
Jason Spittel

(10 posts)

Registered:
07/01/2011 02:17AM

Main British Car:


Re: Cast pistons for Rover
Posted by: Roverized
Date: July 05, 2011 01:20AM

Thanks Art,
I've run a few numbers with the 4.0 pistons but with the 5.7 inch rod its over 150 thou down the bore. With a 5.85 inch rod its 20 thou above the deck. I guess its just a question of if the Ford cast piston will stand up to a bit of abuse. The Silvolite number for it is 3147. I've calculated these figures with a 3.4 inch stroke for the crank but some say its a 3.36 inch stroke. Which is correct?

I've only had experience with Holden V8 and Chev V8 and I know cast pistons are strong for mst of these applications but when it comes to Rovers, my knowledge is limited.

Thanks again Art.


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Cast pistons for Rover
Posted by: castlesid
Date: July 23, 2011 07:07PM

Jason,

The Rover has 8.96" centreline of crank to deck with a 3.4" stroke and 5.7" chevy rods you have 1.560 left for compression height.

The Keith black hypereutectic chevy 305 3.736" bore. D cup piston will work as it has compression height of 1.561" ie only 1 thou above the deck, they may also do a forged version.

The bowl size is 12 cc. and with composite gaskets approx 8cc. it will yield a static CR of approx 12.5/1 and the dynamic CR could be in the right range if using a cam with a fair bit of overlap.

[www.kb-silvolite.com]

Hope thats a help.

Kevin,


Roverized
Jason Spittel

(10 posts)

Registered:
07/01/2011 02:17AM

Main British Car:


Re: Cast pistons for Rover
Posted by: Roverized
Date: July 25, 2011 03:39AM

Thanks Kevin,
I was trying to get a piston with a bore size of 3.720 as if I'm not mistaken, if I use the 305 piston that will be the last overbore before I need either another block or new liners. Call me tight, I know I am but 3.9, 4.0 and 4.6 blocks aren't exactly in every wrecking yard you walk into here in Australia and if you go to a Rover specialist you sell the car, your house and give an arm and a leg to afford just a bare block.
As a last rebore I would definitely use the 305 piston so thanks for letting me know.
Regards
Jason


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Cast pistons for Rover
Posted by: castlesid
Date: July 25, 2011 04:52AM

Jason,

The rover liners are very hard wearing and you can expect 100.000 + miles from the bores with regular oil changing regime, how many miles are you going to do?

Do I take it you don't have any of the proposed engine parts as yet and are starting with a clean sheet, and what is the car going to be used for, ie fast road use ar some type of competition?

With the Rover there are plusses and minuses in using the various blocks, the 3.9 blocks are normally reliable as far as liner slip is concerned, but limited to two bolt mains but are fine for an engine that is not going to rev beyond 6000 RPM which, with a long stroke crank is as far as you would wan't to go.

The 4.0 blocks are to be avoided at all costs as those engines were built from the worst quality blocks with a high degree of core shift, the 4.6 grade blocks are a little better but still suffer from line slippage from cracking behind the bores.

As you are talking long stroke, high torque engine have you considered a Buick 340 bottom end, I know it's cast iron and around 60 lb heavier but with Buick 300 alloy heads with some decent head work and a mild street cam would offer some serious street performance for sensible money, have a look at Jim Blackwoods 340 build thread if you haven't already.

The problem with stroking an engine is the mix and match and it tends to get expensive to make it all work.

One alternative is to find a sound 4.6 and use the oversize 3.7" Ford modular forged piston
[cgi.ebay.com]
which will fit with a bushing for the Rover small end, these are dirt cheap at around $480.00 without any additional machining work,alternatively the 4.0 piston will swap in and give approx 11/1 CR. I realize you would be approx 300cc less than with the 3.4" crank but that needs a bit of work to fit the rover and the 4.6 (4552cc.) would be a bit free'r reving wih some decent heads.

Kevin.



Edited 1 time(s). Last edit at 07/25/2011 04:59AM by castlesid.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Cast pistons for Rover
Posted by: BlownMGB-V8
Date: July 26, 2011 01:47PM

The 340 crank can be used in the 300 block, and a .050 overbore gives a 5.7L displacement in the 300 sized package. This will most likely require a hood bulge or scoop of some type, check out Jim Stuart's yellow GT or Mike Moore's roadster. No issues with liner shift or threads pulling out. The extra weight is more than offset by the added torque and horsepower, and so far as I know, nobody so far has had anything negative to say about the effects on handling. The 340 is a taller and wider block. Usable but not quite as easy a fit. The 350 is dirt cheap and available everywhere. Just need to build headers. The 455 can also be used, and if the steering has been modded for the 340/350 it only requires a few firewall mods, motor mounts, and exhaust. Plus a big radiator of course.

JB



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