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Offline clbarclay

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Changing pistons
« on: July 07, 2007, 09:38:27 »
I'm looking at getting a another 3.5 engnie and either rebuilding it to go in mine or replacing mine and rebuilding the orgional latter.

As far as I can tell the only significant differance between an 9.35 and 8.13 compression ratio block is the pistons. Does this mean if I buy an 8.13 block I can just fit new pistons to get 9.35 compression again?


Secondly, if I do change the pistons could I fit and run 9.75 compression vitesse pistons withough too much difficulty or would I need items like a Vitesse ECU?
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Chris

Various range rovers from 1986 to 1988 in various states
Locost sports car based on mk2 escort - currently working on brakes, fuel and wiring

Offline Range Rover Blues

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Changing pistons
« Reply #1 on: July 13, 2007, 17:13:17 »
I don't think the EFi is clver enough to worry about the CR too much, it's the dizzy you will need to match whatever pistons you fit.

As for a higher CR, might be cheaper to find a high CR short engine in good nich and fit that, perhaps with a new cam (3.9) and followers/rockers and crank shells if you feel that way inclined.
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Blue,  1988  Range Rover 3.5 EFi with plenty of toys bolted on
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Offline clbarclay

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Changing pistons
« Reply #2 on: July 13, 2007, 18:17:45 »
I don't feel very inclined at all (the wallets evan less inclided at the moment). I'm just mulling over ideas having seen a complete 3.5 v8 rebuild kit for sale that included new 9.75:1 pistons.
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Chris

Various range rovers from 1986 to 1988 in various states
Locost sports car based on mk2 escort - currently working on brakes, fuel and wiring

Offline Range Rover Blues

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Changing pistons
« Reply #3 on: July 14, 2007, 00:48:43 »
Depends what it costs.  Would you fit new pistons without any machining on the bores though :?
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Blue,  1988  Range Rover 3.5 EFi with plenty of toys bolted on
Chuggaboom, 1995 Range Rover Classic
1995 Range Rover Classic Vogue LSE with 5 big sticks of Blackpool rock under the bonnet.

Offline clbarclay

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Changing pistons
« Reply #4 on: July 14, 2007, 08:47:32 »
Fear not, have already bear that in mind along with skimming heads.
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Chris

Various range rovers from 1986 to 1988 in various states
Locost sports car based on mk2 escort - currently working on brakes, fuel and wiring

Offline Range Rover Blues

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Changing pistons
« Reply #5 on: July 15, 2007, 00:40:04 »
Skimming heada a good idea, if you fit the composite pitons rather than the ali plate ones they compress to 1.2mm rather than 0.5mm respectively, so you can machine 0.7mm away without effecting the CR at all.  There is a witness mark on the front of the head if you know where to look so that you can judge how much has already been skimmed.
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Blue,  1988  Range Rover 3.5 EFi with plenty of toys bolted on
Chuggaboom, 1995 Range Rover Classic
1995 Range Rover Classic Vogue LSE with 5 big sticks of Blackpool rock under the bonnet.
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