875 or 930cc

Date: Mon, 17 Aug 1998 16:53:17 +0100 (WET DST)
From: Dave Edge
Subject: 875 or 930cc

Quickie question what is the bore difference between the 930 cc unit and safe enlarging of the 875 cc bores in terms of shear capacity, how much can an 875 cc unit be enlarged.

do I need a different head gasket if fitting a 930cc block and can I reuse my reconditioned cylinder head. How much power should it produce with Janspeed small bore and 150 Strombergs and would this increase with a hotter cam. Dave Edge


Date: Mon, 17 Aug 1998 22:08:38 +0100 (WET DST)
From: Nickcleak@aol.com
Subject: Re: 875 or 930cc

> what is the bore difference between the 930 cc unit and
> safe enlarging of the 875 cc bores in terms of shear capacity, how much
> can an 875 cc unit be enlarged.

The 930 is 70mm bore size , the 875 can go to + 0.060" usually . although the factory maximum was 0.030"
so with a max overbore the 875 becomes about 915cc

> do I need a different head gasket if fitting a 930cc block

Yes you need a 930 gasket , but the 930 gasket will fit the 875 .. not the other way around!

> and can I reuse my reconditioned cylinder head.

yes no problem

>How much power should it produce
> with Janspeed small bore and 150 Strombergs and would this increase with
> a hotter cam.

a 930 Imp Sport spec will be about 60 bhp .
the 998 imp sport was 65 bhp

the 930 unit goes well and is very economical if the 875 ( high compression ratio ) head is used .

I am running a 930 Sport motor at the moment ..

nick ...


Date: Tue, 18 Aug 1998 15:57:05 +0100 (WET DST)
From: Dave Edge
Subject: 930 it is then

Yes I have just given my card details over and for #145 I will have a new 930cc block tomorrow morning.

The cost of reconditioning my existing block got silly, #15 rings, #25 bearings, #120 pistons (If available) plus #55 rebore, so yet again it is cheaper to buy new. The man in the engineering place sucked so much air through his teeth I thought he was going to pass out when I suggested overboring the 875cc lump to 915cc but was entirely confident that he could machine my crank for a few quid.

60 bhp here we come (and no stalling, no smoke, less oil, less lethal emissions - oh yes they were, idling that doesn't shake your teeth out)

I am going to remachine the crank but what else do I have to do?


Date: Wed, 19 Aug 1998 00:09:00 +0100 (WET DST)
From: Nickcleak@aol.com
Subject: Re: 930 it is then

> 60 bhp here we come (and no stalling, no smoke, less oil, less lethal
> emissions - oh yes they were, idling that doesn't shake your teeth out)

Excellent !

well i assume you are going to use the IMP crankshaft in which case you need to machine the scroll oil seal off the Imp crank to a dimension of 3" dia (check that ! )
get them to leave the lip behind the seal as it will act as an oil thrower ...
fit the crank , try to fit the flywheel , it won't fit !
A few webbs behind need grinding off , a disc cutter will do fine , they are angled outwards and need to be machined ( ground ) parrallel . the crank fits now ...

Which front cover are you using?
The Imp one will be fine if it is the same height as the block , you can use the sunbeam 930 one and make a bracket to mount the engine as the 930 has the imp mounting lug removed on the new mould .

use the 930 oil drain pipe and special unions to connect it to the head and block , they are both the same ..

The starter motor holes will need re drilling , fit your motor and use the mounting holes as a template , there is plenty of metal in the right place as the imp block mould has been extended slighty to suit the new type lucas starters and the original metal is still there , just needs driling .

Sealing the main bearing cap ... assemble dry and make up a suitable adapter tube to a cartridge of silicon sealant , inject it into the channels down each side of the rear main bearing cap until it emerges inside and outside the block . you will need a good seal where you apply the nozzle at the outside edge ..

That's about it ...

On the Strombergs you can get the co down to 2% on idle but it won't go , needs to be about 5% ... static timing about 5° you wil probably need to reduce the max advance by putting a piece of brake pipe over the distributor end stop .
arrange it to be about 36 - 38° max advance , don't forget to disconnect the vacuum advance whilst checking the timing ..

grease the rubbing surface of the rear crank seal !
but not the outside edge which requires friction to hold it in !

mine is a beautiful motor as i said before ..

good luck .

nick ...


Date: Wed, 19 Aug 1998 10:32:44 +0100 (WET DST)
From: Dave Edge
Subject: Re: 930 it is then

Hi Nick,

I have had some conflicting advice recently, esp that I should not use the old crank on principle alone and it would be a safer option to machine a flywheel to fit an imp clutch but a few problems arise from this.

Can I still use my starter motor

Does the imp clutch housing bolt on or does it have to be centralised on the flywheel and new holes drilled and tapped.

How tough is the original imp crank to machine/grind

Which have you done.
Dave


Date: Wed, 19 Aug 1998 13:39:39 +0100 (WET DST)
From: Russell Maddock
Subject: Re: 930 it is then

I used my old starter motor, but new holes have to be drilled in the block because the 930 Sunbeam takes a pre-engaged type. I just lined the block up with the transaxle and drilled holes to match those in the transaxle.

Can't help with your other questions because Graham Cashmore did a lot of the hard work on mine.

Russ Maddock


Date: Wed, 19 Aug 1998 15:03:45 +0100 (WET DST)
From: Simon Trickett
Subject: RE: 930 it is then

I also Have a 930 Sunbeam Blocked imp Engine.
Mine has been converted to a Wet Liner 950cc using Peugeot 205 cylinder Liners (see Franka Site, I should hopefully be having my details page added)
I have always used an Imp Crank for these conversions.
I think this is a quicker cheaper way to go.
If you are getting the crank ground etc this is a good time to get the Oil Scroll Turned and ground to the 3.000" Dia size as Nick said leave the Lip on.
The large Red Oil seal is available from any Pug Garage:
Part Number : PT 75221391 3.40 plus VAT !!

Make sure that this seal is seated properly and oil the sealing lip before assembling to the crank.
My method of assembly for this seal (after all the flywheel clearance work has been done + a dummy build) is to fit the crankshaft, then fit the Oils seal over the machined down scroll. It should fit easily with the smear of Oil you can use a thin bit of smooth plastic to help.
Then run a bead of Silicone sealant in the places the manual suggests as well as filling the 'Club Foot' recess on the bearing cap. Assemble the bearing cap trying not to get goo every where whilst ensuring that the seal is properly seating in the bearing cap And in the Block.
Nip the Bolts up then push some more Goo down the club foot gaps to fill.
The goo should stand proud of the sump gasket face, tighten the cap bolts to the correct torque figure then trim the goo with a sharp knife when it has dried.

Give me a call if you want
Simon Trickett


Date: Wed, 19 Aug 1998 19:11:30 +0100 (WET DST)
From: Nickcleak@aol.com
Subject: Re: 930 it is then

Dave ,

> I have had some conflicting advice recently, esp that I should not use
> the old crank on principle alone and it would be a safer option to
> machine a flywheel to fit an imp clutch but a few problems arise from
> this.

Well there are two ways of dealing with the crank problem , i chose the easier.
In both cases the std Imp clutch is used .
I used my Tuftrided Crank which i bought from Hartwell in 1974 ! it has done 220,000 miles , about half of that life is with a turbocharger .
i had it crack tested and balanced at the time .
Just the oil seal scroll was machined down to suit the 930 oil seal ..

I guess a new crank is an unknown factor , unless it is crack tested .. where as your original crankshaft is tried and tested .. best to have std size journals though ...
Using the 930 crank needs a different flywheel , which means the whole lot needs balancing again .
The spigot bearing is different and needs modifying on the 930 crankshaft

I have used the IMP crankshaft on 3 930 engines now and all seems well .

> Can I still use my starter motor

yes , just two new mounting holes need drilling in the 930 starter mounting flange on the block , use the bellhousing as a guide for the drill ...

> Does the imp clutch housing bolt on or does it have to be centralised on
> the flywheel and new holes drilled and tapped.

No it's the same as imp , everything else is the same as Imp ..

> How tough is the original imp crank to machine/grind

Andy Chesman did mine ,although tuftrided he got a mirror finish ...
on the turned-down oil seal end ..

Nick ...


Date: Wed, 19 Aug 1998 19:20:21 +0100 (WET DST)
From: Simon Trickett
Subject: RE: 875 or 930cc

Apparently some people have successfully bored out a standard 875cc block to the 70.00mm 930cc size: I think they were lucky !! it depends how accurate the 875 block was made......... this is NOT a good idea.
Better instead to get a 930 block and get it overbore to 70.75mm (second oversize +0.030") this will give you a 950cc.

bye

Simon Trickett


Date: Fri, 21 Aug 1998 04:47:59 -0400 (EDT)
From: Richard Candler
Subject: Re: 930 it is then

Dave,
lack of emissions sounds good - I am fed up getting gassed every time I go in your car! However, I think the idling is more to do with the Janspeed than the block...

Rich