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Klatka
06-09-03, 02:53 AM
This is my first post to this forum, and it appears to be the best place to ask questions about the RV8. There are not very many experts on Rovers in the States.
I am in the process of building a stroked engine. I have aquired a 1996 4.0 engine, had it bore aligned ~.022 to accept the Buick 300 crank and bearings. Cylinders have been honed .010 over for the use of Ford 255 pistons with standard 3.5 connecting rods. Heads are p/p Buick 300 with 54cc combustion chambers. Calculated compression will be ~10.00 to 10.8 with a metal gasket. What will the compression be if a composite gasket is used. (looking for 9.0 to 9.5) Second, is there a list of breakers who are willing to ship to the States for those hard to find bits?


No Cobra yet, but looking at a Hawk 1.8 for the RV8

Klatka

TINKA
06-09-03, 11:03 AM
Hi Klatka, Russ is the expert on RV8 so hopefully he will pick up on this thread. As far as using the composite gasket goes I read on a previous post by Russ that it will cost 0.75 ie, 10.8 - 10.05. I think I am right in saying that if you go this route you should also use the later stretch head bolt fitted to later engines.
If you are having problems getting spares over there, there is a company which will supply you new parts, and ship them anywhere called Rimmer Bros WWW.rimmerbros.co.uk got most of my bits from there and they are quite reasonably priced.

Best of luck and I hope this is of some help.

Martin :tu :tu :tu :tu

osgood
08-09-03, 10:45 AM
Contrary Mary

As Martin says Russell is your man on this subject, I think 3/4 of a ratio is about right. I tryed metal gasket on my 3.9 which was 10.5 CR and it blew every one I fitted Eric.

russell_ram
08-09-03, 04:43 PM
Klatka,

Been doing a few sums on your question - so here goes.

Buick 300 crank has a stroke of 3.4inch.
Std 3.9/4.0/4.6 bore is 3.7 + your .010 over bore. = 3.710 inch.

Engine capacity 4818cc.

Buick 300 heads have 54cc combustion volume (as you say) compared to 36cc for std Rover heads.

Tin gasket compressed volume (94mm bore) = 3.524cc
Composite gasket compressed volume (94mm bore) = 8.105cc

Comprssion ratio is governed on most RV8 engines by piston bowl volume typically 15 to 25cc dependant on derivative. I assume your Ford pistons are however, flat top which with your heads, engine volume and tin gasket gives 11.47:1. With composite gasket, the same sum gives 10.7:1. To get down to your desired 9.5 you either need the pistons not to reach the top of the bores or a bowl/dish in the piston to increase compressed combustion volume. You need approximately a piston bowl volume of 8.5cc to get 9.5:1 or 13.5cc to get 9.0:1. Alternatively, with flat top pistons they need to be 'down the bore' at TDC by 48 thou to get 9.5CR or 76thou to get 9.0CR.

Hope that helps.

Russ

r0lex
08-09-03, 07:37 PM
Well you took the words right out of my mouth.;-)

I feel like a dumbo now.......how on earth do you manage to work all that out. Took me long enough to work out how much petrol to put in the tank.

Paul

russell_ram
08-09-03, 08:10 PM
Paul,

Sorry I didn't let you answer first then!!!

Perhaps I is gud at sums? :)

Russ

ps When it says E, then that is the time to put some in. :) :) .Quite often in a Cob actually.

Klatka
09-09-03, 02:44 PM
Russ,
Thanks for the sums, this will give some direction when I go shopping for pistons. If needs be I can get them machined down to achieve the proper C/R.

Thanks to all for their responses.


Klatka