Engine build options...
Turbo Mini Forums

Engine build options... (something a bit different)

My current engine is a standard 1098 with 12G295 head with twin HS2s, with unknown cam (could be standard). This engine was in the car when I bought it 4 years ago. It has served me well, but now its time for a fresh engine...

I would like to do something different, so thinking small bore rather than standard 1275 block. Also much easier to find for a reasonable price!

I currently use the car for weekend fun, but could be interested in track days in the future. The car is a mk1, so i'm not sure it would be suitable for all out competition work (although it is not original enough to worry about keeping it 100% standard)

Option 1)

I have got hold of a pair of Hillman Imp pistons from a friend. I could build these into a 1215cc lump as detailed in Vizard. This would be a period relevant mod, that would create a nice torquey engine for A-road driving.

Option 2)

I have also found a SC12 supercharger as used on a number of kits in Aus. I was thinking of doing a custom 1098 +40 blow through supercharger setup. This would create plenty of torque, and would be great fun, and a challenge to build!!!

Option 3)

Combine both options, but I would be worried about the strength of the block for forced induction give the larger overbore required for the imp pistons. I'm less keen on this option due to potential reliability issues...

Anyone built either of these engines in the past? Or anything similar? Any advice?

Any other opinions appreciated...

Cheers,
Rich

I am not an expert by far, I have no clue on how strong the Imp pistons are.
But there are people here that have gone way over 100hp in a small bore.
So option 3 could be a route after all if the pistons are up to it and the rest of the engine and gearbox are adressed accordingly.

Dazed and Confused....

imo this sounds awesome

id go for number 3 running about half bar boost and high compression to make one bad ass blown road motor !!

i think bore thickness will be key if your going to boost it anything over like 10 psi..

a std bore block (or like 20) that can be off set bored correctly as visard says to maintain equal bore thickness also a thick flange would be nice for the same reson stiffness

bottom end strength (over 170hp?) depending on power out put as said above many people on here run well over 100 bnanas
i know ben runs or was running like 160 ? i think that way it is treated and use/abused has a LOT to do with what can be gotten away with

look at your box including drops as well if using a std gear set make sure its in grate shape and use at least an offset type diff not the 90 degree ones they have been proven not as strong as the offset due to tooth engagement/mesh

Thanks for the replies guys!

I agree that option 3 would be awesome. I cannot find any info/experience about the strength of the imp pistons? This is my main concern with this option, and the obvious think bore wall. Would this flex much? Would this engine 'eat' head gaskets?

I was planning on using standard drops and gearsets. I haven't heard of an offset type diff. Do you have any further info on these?

Has anyone got any experience of imp pistons? Either in a mini, or an imp (surprsingly!)?

Just a note, if running the SC12 charger I have got hold of a HIF44 turbo already. I was planning on running an intercooler and sort out the ignition with megajolt (this should give me more room by loosing the dizzy, plus the obvious improvement in ignition control) Any other 'must have' suggestions?

Cheers,
Rich

When I looked at using Imp pistons I found them to be very rare and expensive. Seeing as you only have access to a "pair", then you are missing a couple.

I would use 1098 +0.060" pistons from Calver:
http://www.calverst.com/shop_open.htm

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Sorry for the confusion. I have a full set (four) imp pistons! Typo

Edited by rich080487 on 22nd Oct, 2013.

If you feel the need to use the imp pistons that is awesome i love 1215 engines, throw a 1275 head on it and it goes like stink! the pistons are old though, have you got rings for them? Graham Russel in Australia has started manufacturing brand new 100+ pistons for 1098's... just an option.

I too love option 3, boost isnt extreme with the SC12, it too is an old blower, would make an amazing torque machine! Long stroke, big OB and a blower... drool... As Josh mentioned, make sure the box is 100%

“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.” - Jeremy Clarkson