Hi
I had my engine rebuilt about 2000 miles ago, and I never found out at the time what the compression ratio was, so yesterday I decided to do a compression test to give me some indication as to what it might be. The psi readings were #1 265, #2 185, #3 260, #4 180. I did it twice, engine hot, all the plugs out, wide open throttle and the figures were the same. what might cause the huge variation in figures? Its a completely recon'd engine (recon'd head - new valves, new pistons, rings, bearings, cam, lifters, oil pump, etc). I really wouldn't want to pull the engine back out after it took me 9 months to get it going. Its a 1330 S motor, 12g940 head with 1.4 in's and 1.2 ex's and a few other mods. Any suggestions? Is it possible that the readings on 1 & 3 are too high? could that have caused a problem with the other two?
TIA

Geoff

Make sure your valve clearances are all set the same.
Could also just be the valves are not seating properly- but to check you would need to pull the head..

265 does sound a bit high, but I can't see how that would affect the other 2 cylinders.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

just did a leakdown test today on this... seems the 80psi drop on 2&4 is due to a leaky exh valve on 2 and leaky inlet on 4. so the head's coming off in a coupla weeks. will work out comp ratio this time. Is the leaking valves likely to affect performance much?

I believe so, yes. And the leaky ex valve is likely to burn it in one place. Have a good look at them all before you refit them, any cracks or burns- replace them..

Maybe the reco shop did the usual thing- grind valves, grind seats, throw together, beauty!
I always finally lap them in by hand, to check.

If you have bronze guides in it, check the exhausts are not sticking. I find these guides tend to close up once run for a bit, can grab the valve.
If you have these, run a 9/32" solid reamer thru, just to be safe. (The running clearance is built into the valve stem size- it's a few thou' under 9/32")
BTW, cast iron guides are less problem, but are not good with plain (shiny) SS valves and straight unleaded fuel- they wear the valve stems.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Further developments:
My mate called me today to say that he's pulled the head off to check it out, and found that the the exh valve guides are chewed out, one of them (the low comp one) very much so - 5mm play at the top apparently. As far as i know they're steel guides not bronze. He reckons the wear may be due to lack of upper cylinder lubricant but I've always used an additive with bp ultimate. i was using valvemaster (just because that's what bp had) but lately (past 3 or 4 fills) i've been using flashlube. could a lubrication problem cause that much damage in only 2000 miles? Instead of putting the additive in first then the fuel, i've been getting it when i pay for the fuel and adding it to the full tank - would that make too much difference to how well it mixes? Any suggestions how or why this can happen?

Geoff

never put it in after u fill the tank!!

the feul at the bottom that will go to your engine first will always have very minute, if any traces of the flashlube in it.

if u put it in first, all the petrol going in splashes around and mixes it all up at the same time.

how many times did u do this? ie first petrol then lube?

dont know if it could cause too much damage though if you havent done it much but ur prettymuch running the first 5-10kms on unleaded petrol without the lube....until the car goes over a few bumps and corners and mixes the lube with the petrol.

If they are plain S/S valves running in iron guides (no, these are NOT steel) they will wear fast, particularly with unleaded.
I run these same valves in bronze guides and have had no trouble, since I reamed them to size.
S/S valves for use with unleaded fuel are tufftrided- they have a black surface on the stems.

As b_m says, always put the Flashlube or other additive in first. Just like you do with the old 2 stroke oil for the Victa.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Maybe that explains my 'reconditioned' unleaded head blowing a sh*t load of smoke after 3000 kms.. well come to think of it it blew smoke at 1000kms. I am still not convinced it was recoed properly. The ironic thing is the 295 i pulled off a car that was driven into the ground (front bearings were worn so much the rotors had grooves in them on both sides from rubbing on the steering arms) hydro was down on one side completely and the other barely up anyway. It even had a genuine dried eucalyptus stick shoved in the vacuum hose for the servo on the inlet side anyway enough of getting carried away about the poor condition- I cleaned up the 295, lapped the valves put new stem seals on and it runs beautifly and with no smoke.

I've done 8 or 9 tanks since the rebuild. one of those i had a bottle of flashlube in the car already, the rest were petrol first.



We've apparently got half a set (4) bronze guides to throw in for the exh valves. I think the inlet guides are ok. Is there any reason to change to using the Redline additive instead of flashlube?

yep, sound like a nicer name...LOL

nah, dont know the difference but flashlube seems to work for everyone else...

unfortunately, maybe not in ur case? i think even if u kept using the redline additive, u wouldve had the same problem, either way.

Redline is supposed to be bast according to UK tests, but I've never seen it here.

OTOH the Flashlube is pretty easy to get. I've used it for about 5 years now.

My 1293 A+ motor which is about to hit the road has new valves with chrome plated stems and iron guides, with unleaded valve seats. I'll run it without additives.
Will be interesting to see how it lasts.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.