Seized engine - rebuild or not?

Post by **sowden** » Sun Jan 18, 2009 2:57 pm

Hi all,

I have an engine that I bought from a chap on here. It was siezed but was, as suspected, "a tuned engine"; specification given lower down the post.

Despite the sump being full of water (!), I've stripped it down into bits now, because I wanted to find out which bit was stuck. It was the two middle pistons that were gummed up; I suspect it had overheated.

The spec is:

295 head, 70 thou skim.
(looks like high lift rocker gear; the pedestals seem tall?)
+30 pistons
duplex timing chain
big end shells read +30 (does this mean the crank has been reground?)
Dont know if the cam is standard or not, but it's in good nick.

I was toying with the idea of trying to build it back up - any thoughts? Dont want to spend a packet on it but if it would make a nice engine for not too much, might be worth it. I judge that there are a couple of ridges on the bores, but that might be just where the piston travel ends. I'm not sure the pistons will be reusable (the rings are glued into two of them).

As I say: your thoughts would be appreciated.

All the best,

Russ

Post by **bmcecosse** » Sun Jan 18, 2009 3:07 pm

Always worth a go. But you would need to ungum all the piston rings and clean out the ring grooves and check for any piston damage. Then clear away any marks/ridges on the bores - and 'glaze-bust' the bores by hand - rubbing in a 45 degree criss cross pattern with some emery paper. The crank is indeed 30 thou undersize - with 30 thou oversize bearings. Are the journals ok ? You really need to measure them accurately - and ideally - if you have dismantled the bearings you should fit new bearing shells anyway. But -as long as you know where they came from and they are 'perfect' - you could re-use them. Inspect the oil pump - if scored/mangled then new one required. High lift rockers don't have tall pillars! Someone may have fitted spacers under the rocker pillars because the head had been skimmed. This is really not necessary - it makes no sense - but it used to be the 'done thing'.

Post by **sowden** » Sun Jan 18, 2009 4:05 pm

BMC,

the main bearing shells are in place but the con rod ones have all just dropped out. I wasnt being particular as I didnt know if I would ever rebuild the thing.

Could I just sling em back in and change the oil earlier the first time, do you think?

R

PS - how big is the new cc with a +40 cylinder rebore, do you know?

Post by **MarkyB** » Sun Jan 18, 2009 5:00 pm

Some pictures of the pistons would be nice.
Anyone got any thoughts on what would cause the middle pair to seize?

Post by **bmcecosse** » Sun Jan 18, 2009 5:15 pm

Over heating and/or lack of oil! Could be result of running with pinking/detonation although would expect some piston crown damage.
You 'can' just put the b-end shells in 'anyhwere' if everything is in excellent condition but it's obviously not ideal. Pictures of the shells/journals and the centre main would be interesting. +40 on a 1098 is 1132cc. NOT a significant increase in power terms !!

Post by **sowden** » Sun Jan 18, 2009 9:36 pm

will try and get some picks on here. Thanks for your posts guys.

Post by **sowden** » Tue Jan 20, 2009 8:57 pm

Hi gang,

hopefully, below will be a couple of picture of the most gummed up pistons, although I have relieved the more built up deposits. The rings are still nicely glued in though. I have a few questions which you might be able to help with:

How do I unglue the rings?

Will a standard set of +40 rings go onto these (e.g. ex Bullmotif) ?

You may see a little distortion on one of the skirts (this fool tried to drive one out the wrong way). Has this knackered the piston or will it fettle with some emery? It doesnt look cracked. I'm more keen to risk it than to spend on it, as it will be a spare engine only.

Thanks,

Russ

Post by **bmcecosse** » Tue Jan 20, 2009 10:03 pm

Look like dead standard pistons to me - so BM etc rings should fit. Search ebay - you may find rings there very cheaply - or even a set of pistons for less than cost of rings! To free off these rings - try hot water - or perhaps spray with Carb/choke cleaner (it's highly flammable) from Poundland - and allow to soak in. Then tooth brush (but clean it thoroughly before using again on teeth!) or nail brush etc followed by gentle wiggling. If you are buying new rings - don't worry too much about snapping the old ones, although to handy to some spares in case of accidents! How about some pics of the journals and the bearing shells ? Note you MUST keep the big-end caps with the rods they came off - they MUST NOT be swapped about!

Post by **sowden** » Tue Jan 20, 2009 10:54 pm

Here you go BMC. Dont look too bad to me! The bearing shell shown is typical of the condition of all. The basis for a dog-end rebuild, surely!

Post by **bmcecosse** » Wed Jan 21, 2009 2:40 pm

Well - the journals look a bit marked and the shells are starting to show through to the bronze. You would need to put a micrometer on the journals and decide from there - they may well be ok. Ideally new shells should be fitted - but if it's just for a 'spare' you could just re-assemble and hope for the best. I've certainly seen much worse! Make absolutely sure you get the big-end caps back on tyhe rods they came from - and the little 'tabs' go on the same side on rod and cap. When you re-assemble (with lashings of oil) - check each and every journal as you tighten it up to make sure the crank still swings free and easy.

Post by **MarkyB** » Wed Jan 21, 2009 6:15 pm

They don't look like standard split skirt pistons to me.
File off the damaged bit with a fine file and clean them up any way you can without removing any more metal.
If you are going to keep the engine as a spare I'd be worried about rust proofing it now that the rust has "got a start".
Maybe seal it in a large plastic bag with some silicone gel?

Post by **bmcecosse** » Wed Jan 21, 2009 8:41 pm

They are after-market pistons - but still with the extra ring below the gudgeon pin. Years ago when building up my engines - I used to machine off almost all of the piston below the gudgeon pin and never fitted the extra bottom ring. But that was for competition use ! So - you won't have damaged the piston, just tidy it up.