mjones31 Posted November 17, 2008 Posted November 17, 2008 Had a engine problem start suddenly.Engine is 1850 cvh. Sierra cvh block overbored with 1600 head ported double valve springs,race cam and twin 45,s. Reversed car off the drive and had a big backfire from the exhaust. Car now runs on 3 with 1 plug really oiled up. Changed the plugs and the engine ran fine for about 20 seconds then back to 3 again.Changed the leads..no change. Rotor arm seems ok. Done compression test dry and the dodgy cylinder is lower than the others but not by much.Say 10 % ?Did the test wet and no real change. So...is it time for the head off ?? Car will have to go in somewhere to be fixed but should i take the head off myself first and have an investigation?Dont want to pay a garage to do a job i could do myself but if i find nothing wrong i cant put the head back on as ive no idea how to set timing etc. What are your thoughts chaps? Mark Quote
perksy Posted November 17, 2008 Posted November 17, 2008 Don't start stripping it to bits just yet Mate Compression test with wot (wide open throttle) ? Can you post up the Dry and Wet readings ? The plug is definetly oil fouled and not wet with fuel ? Tested for a decent spark on the problem cylinder ? Quote
DavidR Posted November 17, 2008 Posted November 17, 2008 If the engine ran OK for 20 secs then the problem doesn't seem to be inside the engine so taking the head off may not help. Also you will need new head bolts as AFAIU they are one time use due to stretching. Try checking the sensor assy inside the distributor under the rotor arm. They have a habit of coming loose and give all sorts of strange symptoms. The sensor is instead of points and works on the lobed part of the distributor shaft. It should not touch the lobes nor be loose. David Quote
ChrisF Posted November 17, 2008 Posted November 17, 2008 As Perksy says don't panic yet It could be a fuel problem, the aux venture retaining screws have a habit of vibrating loose, causing the venture to spin and so the car runs on 3 cyclinders. This wont explain an oiled up plug but would expalin a wet one....it's worth checking Does it appear to have raised pressure from the crank case I cant remember if the cvh has a crank case breather, but raised crank case pressure would indicate a compression issue. Hope this helps... Quote
mjones31 Posted November 17, 2008 Author Posted November 17, 2008 Had the problem with the venturi,s before so not that this time. All now wired in. Getting a good spark on the dodgy cylinder. Its almost as if with a new spark plug it takes a few seconds to get covered in oil then wont fire any more.The compression test was with wide open throttle. I,ll post the results when i can find them.No noticeable crank case pressure issue.I was going to get a new distributor any way for the sake of 40 quid so i will check the sensor cheers. Perksy..its definately oil on the plug. Results to follow... Mark Quote
perksy Posted November 17, 2008 Posted November 17, 2008 When starting it up after it's been standing, are you getting a puff of Blue smoke out of the Exhaust Quote
mjones31 Posted November 17, 2008 Author Posted November 17, 2008 No visible smoke at all from the exhaust and non from the rocker cover cap either. Had the rocker cover off and all seems well. No sign of any damaged valves . Everything seems to be in order.?? Quote
perksy Posted November 17, 2008 Posted November 17, 2008 Was thinking Valve stem oil seal or Worn valve guide Quote
mjones31 Posted November 17, 2008 Author Posted November 17, 2008 Its strange because on the last run about 2 weeks before it ran the best it ever has. Had it rolling roaded about 3 months ago and was pleased with the results. Gave gooders zetec a run for its money all day. Then after starting it up to reverse of the drive and sitting for 2 weeks it seemed fine then the backfire then the problem started. As if something had broke. Local engine builder said could be a ring as they tend to crack on the cvh or a holed piston?? Could be a zvh conversion on the cards Quote
perksy Posted November 17, 2008 Posted November 17, 2008 *If* there was a Hole in the Piston Mate the Compression figures would have shown it... Quote
Jenko Posted November 18, 2008 Posted November 18, 2008 Would second Perksy's comment....Check valve guides, and also make sure valve is not sticking.... Is it oil on the plug?....Or could it be fuel mixing with the carbon deposits?.... Quote
John Fisher Posted November 18, 2008 Posted November 18, 2008 Where abouts are you in the West Mids? I can lay my hands on a boroscope to look down the plug hole to see if anything is a miss Fish Quote
mjones31 Posted November 18, 2008 Author Posted November 18, 2008 Thanks for the offer John...in Wednesbury which is just off junction 9 of the m6 right by were it joins the m5...you know that massive carpark of a road. About 20 mins from the factory Quote
mjones31 Posted November 21, 2008 Author Posted November 21, 2008 Right ...the compression test results. Must say before we start that i dont have alot of faith in the gauge but here goes. From the bulk head dry they were 170,168,150,190 And wet they were 160,150,100,180. The third cylinder from the bulk head is the oilly plug which is the lowest readings both wet and dry ? Thanks to Fish were having a root around with the boroscope on sunday so will find out more then. Once again top top club. Quote
perksy Posted November 21, 2008 Posted November 21, 2008 Those results aren't the other way around are they Mate *if* there's a ring problem, with the wet test they ought to be higher figures not lower Might be worth borrowing another Compression tester to compare readings If Big John Fish is coming to have a look You are in Good hands Quote
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