Thread: V8 missing under load,

Wouldn't have thought a tick would cause a miss...first off I would never just replace one lead. Even if you can't find a problem with the others I'd just put a whole new set on for piece of mind and I've often found in the past that ignition problems came mainly from bad leads. Fork out for a new set if you've put new plugs on especially, that's the first thing I'd do before I went any further. Good Bosch ones.

Is it on gas?

Not on gas, no. Alway use 95 or 98 fuel. I only replaced the one lead as thats what i had at home. Living 50km out of town makes it a bit hard some times to take a quick run to the shop

I will try and chase up a set of leads today if i can get out of the workshop for 20min. Most places around here sell Top Gun leads (whats on it now) and to be honest i have never has a good run from them.

Think supercheap may have had Bosch leads on the shelf???? Anybody know offhand what lengths are required? Car is 50km away and wont be much good asking anyone at supercheap

Was thinking the tick may have been a sticky valve, but not having any experiance with a stuck valve before i wasn't sure if it would show up as an odd colouration on a plug or not.

Rick

I have always wondered about "sticking valves", never met one. More likely a broken valve spring, broken rings or worn cam lobe in my opinion. For starters, I would see which cylinder is misfiring by shorting each plug lead in turn, then doing a compression test to see if a low compression coincides with the misfire.

I agree with bee utey.

I have tried Top Gun; Gasmaster and Magnecore leads - Magnecore wins hands-down! Use iridum spark plugs as well; NGK BPR6EIX.

If you can't isolate the misfire to one cylinder, it might be the ignition module playing up - beeutey has an el-cheapo modification that sounds very good. I bought a Scorcher distributor from Performance Ignitions in Melbourne, which uses Bosch parts. It works very well but was rather expensive,

Cheers Charlie

I have always wondered about "sticking valves", never met one. More likely a broken valve spring, broken rings or worn cam lobe in my opinion. For starters, I would see which cylinder is misfiring by shorting each plug lead in turn, then doing a compression test to see if a low compression coincides with the misfire.

It is a pretty well known problem with RV8s, and LR even changed the exhaust valve design in about 2000 to include a "carbon break" waist to reduce the problem.
It is reputed to have started when LR changed the guide material and fitted teflon seal to inlet and exhaust to reduce emissions.

It usually occurs in engines which are lightly loaded although when I pulled my heads with about 100KK on them one exhaust valve had a lot of carbon and was sticky in operation, but not enough to overcome valve spring tension. And I drive hard on the highway towing .
These were pre "carbon break" heads and I did not run a seal on the exhaust which is supposed to help.

However the valve problem usually shows as a miss while under heavy load like up a steep hill and not in general running. I would maybe agree to look at the cam also. IMHO, it is hard to pick a cam lobe when they are not completely worn out as in normal running the engine runs smoothly, only no power.
Regards Philip A

Originally Posted by Rick1970

Think supercheap may have had Bosch leads on the shelf???? Anybody know offhand what lengths are required? Car is 50km away and wont be much good asking anyone at supercheap


Rick

Yep I think Supercheap have Bosch leads and they will just sell a set with all correct lengths for your V8 so long as you match up your engine to the list in the Bosch book. From memory when I went to Supercheap they didn't have many Bosch sets but I could get them from Burson no problems. I'm sure other brands are probably just as good as the Bosch ones but I've just heard a lot of good results from the Bosch leads and plugs with these Rover V8s from this forum and I had good experience with them myself so that's what I'll recommend.

The other more complicated stuff sounds like it might be more likely but I know if it was me I'd do the simple stuff first like brand new reliable leads and plugs so at least I could tick those off my list before moving onto more complicated costly things...nothing worse than doing some big job only to find out later down the track that it was just some crap leads

Yeah, will try the leads 1st. Come to think of it the CB get a lot of engine interferance which could be the sign of a crook lead.

Originally Posted by chazza

- beeutey has an el-cheapo modification that sounds very good.
Cheers Charlie

He did it to mine and it is brilliant, for all intents and purposes it is a scorcher (or equal to) and much cheaper too - mind you it doesn't look as pretty