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Discussion Starter #1
i have just rebuilt the top end in my T16. all went well except i have a slight a miss now and idling is a bit random. but it holds steady at either correct 850rpm(sounds rough though) or 1000 to 1100rpm

the throttle body is all set up correctly (TPS the lot).

The only problem on the engine i know of is cylinder 3 having 20psi lower compression than the rest of the cylinders @ 130psi (rest150-160).

I put a squirt of oil in the cylinder and did the compression test - 155psi
does this test only indicate worn rings or can it create a seal on a leaky valve?

the engine ran pretty smooth before the timing and head rebuild. it was just a bit noisy from the lifters and chain.

once again im relying on you guys experience! certainly after i paid a saab mechanic £60 to find the problem and then have to readjust the TPS and other bits and bobs...and the problems still here lol
 

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So it looks like the top-end rebuild brought up the compression of the other cylinders slightly.
We should have suggested the squirt of oil in the cylinder before you pulled it all apart!
Thats definitely a worn piston ring in that cylinder. However, I'm sure the engine will run fine even with that difference. Replacing the rings leads to a minefield such as - should you replace all the rings, do you need to have that cylinder bore honed, etc, etc. I went for the quickest solution, new rings in all cylinders and did not get the bores honed.
 

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Just found this on my thread about the same subject:

"140 on number 1, down to 110 on number 4. "

I think thats why I decided the rings should be done as well :)
 

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Discussion Starter #4
PhilB! thanks for your help. so you think the worn rings on cylinder 3 wont give me the miss? im tempted to take the head off again and lap in the valves, but when im there i'd be aswell to do the bottem end eh! its just one of those things.

its certainly a good shout to look at the engine in detail before fixing it for one problem. ach, you only live and learn!

whats also annoying me is this damn pinking im getting at WOT, i raised up the ohms on the AMM from 380 to 500 to see if it helped...slightly (i know before the rebuild i was running it rich at 700 odd)....running boost you see

one things for sure im confident in doing the work now and i know once i have the parts its hopefully only 2 days work for me now instead of a week! if i replace the rings i might aswell replace the cranks bearings too. as you say do the bores need honed. probably in my case as there is slight scratching on them. is this an expensive task? DIY'able?

but if you think my miss is not coming from the guts of the engine then i'll concentrate on the visible parts. i have new HT leads coming monday, see if that helps. they were certainly in need of change anyways.

ach!!!!!:roll: never ever ever turn up the boost, i swear this is the cause of all my heartache
 

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Oh right, I thought you were just worried about the low comp. 130 psi is not going to give you a misfire all by itself, none of the cylinders in my engine are much over 130 :)
I'd have to suspect ignition system. There are checks in the bentley for the coil. Presume distributor cap and rotor arm are in decent nick? How does the plug for number 3 look?
 

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Discussion Starter #6
thank f*ok :cheesy: i'll toast to that! the whole dizzy is a replacement from my spares collection. the vacuum is working on it and cap/rotor are good. but im now gonna go out and check again ;)

I'll have a look at the coil too.

All plugs are good, gapped and clean blue spark

i wonder did i plug something back to front when putting the engine back in.

cheers!
 

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Discussion Starter #7
I tested the electronic side of ignition.

sparks ok.
coil reading from :
pin 1 to 15 @ 0.9ohms
pin 1 and centre @ 7500

the dizzy and rotor were actually coated with burn marks. im sure i cleaned them before i put them into the car. this used to happen on the old dizzy a lot too.

i wonder whats causing burning/build up on the contacts so quick, certainly theres no oil getting in there anymore. its bone dry

new leads monday ..so

after cleaning the contacts in the dizzy she ran a bit better, less rough. but still not 100% the engine still wants to vibrate on its mounts a bit, certainly not sitting silky smooth like my mates n/a. its hard to hear whats happening becuase of a nice hole in the centre section :evil:

forgot to mention.

ohms for AMM went up from 500 to 790 on there own. set them at 750 to see if she'd pink and yes still pinking so i stop boosting just into the red. i used to get right to the end of the red and NEVER heard a pink unless just after start up and i got carried away, but that was more of a buck than a pink.
 
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