Low compression engine

Post by **fsk658** » Thu Oct 08, 2009 8:28 pm

What is the difference between the low compression engines fitted to some LCV's and the normal 1098cc engine's. I assume it's the piston's can anyone please advise. If so, are the piston's marked in some way. Thank's John

Post by **PSL184** » Thu Oct 08, 2009 9:04 pm

I know for sure there were low compresson 948's and the post office continued to use these even after the 1098 was introduced. As for a LC 1098, I'm not sure. It is the pistons that are different though in the 948's and I also believe they are no longer available new although I hear Imp pistons can be used.

Post by **mike.perry** » Thu Oct 08, 2009 9:20 pm

Sorry to have to correct you but the post office never used the 948 engine, they went straight from the 803 to 1098 in 1963/4. I know, I had a 1963 ex GPO driving instructors van with 803 engine and box, 8in front brakes and large back windows.
The low compression engines have a deeper dish in the pistons.

Post by **PSL184** » Thu Oct 08, 2009 10:18 pm

Yes you are correct Mike - I was confusing myself as I am looking into rebuilding a low comp 948 myself at the moment and forgot it was the 948 the PO skipped....
So to correct my original post - Yes there were LC 803 & 948 engines but still not sure about 1098's

Didn't PO vans have an additional restrictor plate in the carb also ??

Post by **mike.perry** » Thu Oct 08, 2009 11:04 pm

The Workshop Manual only lists 7.2:1 comp ratio for 803 engine, which is pretty low. For the 948 it lists 8.3:1 or 7.2:1 and for the 1098 it lists 8.5:1 and 7.5:1. I believe that LCVs were normally low compression.
Yes GPO did use restrictor plates but I don't know whether it was the PO vans or the Telephone vans or both. Russell Harvey would know the answers to any LCV questions.

Post by **bmcecosse** » Thu Oct 08, 2009 11:24 pm

Whatever you do - don't rebuild as 'Low Compression' - you want all the compression you can get!

Post by **rayofleamington** » Fri Oct 09, 2009 7:41 am

They really did / do exist.
I rebuilt an LCV engine from my van - 15 years ago now.
At the time I got a good deal on the crank, shells and +20 pistons.

The pistons are more 'bucketed' than dished! The engine ran great and was very happy with the modern (2 star) unleaded. I needed an engine for my saloon so that's where the engine ended up, long after the rotten van was scrapped.

Post by **millerman** » Fri Oct 09, 2009 9:48 pm

If have a set of low compression pistons; if anyone wants them let me know

Post by **bmcecosse** » Fri Oct 09, 2009 9:51 pm

Could be very handy for a supercharger/turbo installation!

Post by **fsk658** » Sat Oct 10, 2009 3:20 pm

Thanks for the info. This engine was rebuilt by the previouse owner of a two door I bought for spares. I put it in my car tempory as I was rebuilding my own engine. No matter what I did or changed it never had any go in it, and the only thing I could put it down to was a low comp. Pitty I did'nt do a comp check before I changed it back to my engine, which pulls so much better. I will take it apart one day.

Post by **RobThomas** » Sat Oct 10, 2009 4:20 pm

Millerman. Do you know the oversize for those low comp pistons? I have a 1098 Shorrocks kit and some late 1098 Midget blocks.

)

Rob
Llantwit Major, Vale of Glamorgan

Post by **rayofleamington** » Sun Oct 11, 2009 4:05 pm

Thanks for the info. This engine was rebuilt by the previouse owner of a two door I bought for spares. I put it in my car tempory as I was rebuilding my own engine. No matter what I did or changed it never had any go in it, and the only thing I could put it down to was a low comp. Pitty I did'nt do a comp check before I changed it back to my engine, which pulls so much better. I will take it apart one day.

Was the donor car a trafalgar blue 1965 2 door??

Post by **fsk658** » Tue Oct 13, 2009 9:29 pm

No it was white when I got it but it was a two door.