I eventually got round to putting a pair of reconditioned Vitesse heads (chemically cleaned, new valves, 3 angle cut, very slight skim to surface heads) on my late P6 engine (9.25 - 1 with fast road cam), and got it fired up today (put of for ages due to extreme hassle taking off/on headers in confined engine bay). Unfortunately it has now got a bit of a rattle from the centre of engine. It didn't happen right away, but after a short warm up, and the sound appears to move around. At the worst it is like a loose nut is rattling around somewhere (isn't), and at best a knocking noise.
I inspected the cam for wear when heads off, and it seemed fine, likewise the lifters and pushrods. I had a new set of rocker assemblies from years ago that I also put on to complete the overhaul (oiled and cleaned before assembly)
I started the engine without the valvecovers on to check that oil was getting to them, and before starting I poured oil over the top.
There doesn't appear to be much oil actually getting to the rockers - how much is normal? (can rev engine and not get even slightly splashed), and is there a cure to improve flow?
This may teach me to play with a perfectly good running engine
I took the new shafts I had to bits and reassembled them correctly (had my doubts about them) and noise disappeared. I've not touched car for about a month (decorating), and decided to give it a run today. It didn't start very well, seemed to be running on 7 cylinders, but all plugs were firing (magnecor leads, petronix ignition, new dizi cap etc). I also noticed a lot of backpressure from breathers. I left car running for about 30 minutes, to fully warm it up, and it seemed a bit better, but when I revved it, the loud rattle started again, and it cut out. It restarted ok, but rattled on tickover, which was by now hard to maintain, and loads of smoke from breathers.
It didn't exhibit any of these probs with the old heads (p6), but on reflection, I wonder if a valve or valves are being held open or I have lifter problems. The head gaskets I removed were the composite type, and I replaced them with tin, The heads were from a Vitesse, but of unknown history, but I had new valves fitted, and a 3 angle valve job, and a very light surface. The cam is of unknown origin, but is meant to be a fast road/long duration one from around 1991. I checked the cam when heads were off, and it seemed fine, as did a visual inspection of the lifters.
I am thinking of fitting shims (difference between tin and composite gasket thickness) to the rocker pedestals to see if this sorts it - does anyone have other suggestions?
I think the difference in thickness between composite and tin gaskets is quite alot and certainly enough to mess up your preload setting. (I would have stuck with composites and skimmed the heads to get the compression right if required but thats JMHO).
Also a believe that you can't just subtract the gasket thickness difference to obtain the shim thickness due to the rocker arm ratio. I don't know the formula off the top of my head but someone will!.
I reckon that you are going to have to empty the lifters of oil and spend a few hours setting the pre-load up. I found that you can carefully compress the lifter enough in a vice in conjunction with a small bolt enough to release the spring clip, you can then pour out enough oil to set the pre-load....takes ages to do all 16 though!
I didn't know that composite gaskets were fitted until I removed heads, and by that time I'd had the tin gaskets for a while, so just used them.
I too think it is lifter pre load related, so if anyone can hazard a guess for shim thickness i'd be grateful.
I understand that shims only come in 3 sizes - 16, 32 and 48 thou. You can buy these as a set with all three sizes in.
My 3.5L RV8 with composite heads and a light block decking required 16 thou shimming, but I wouldn't guess the preload, I'd advise draining the lifters and setting it up properly - it's simple to set up as I'm sure you know, but just requires a little patience. - warming the lifters up first would help get the oil out quicker.
I got a shim kit today, and fitted the mid size - engine still ran rough and rattled a bit. I tried to turn the pushrods by hand, and couldn't. I then fitted the biggest shims and engine refuses to start, but pushrods are just moveable by hand, so obviously a step in the right direction.
It looks like the heads I got must have had a bit of skimming prior to me getting them, or indeed the block - who knows. Only way to go now is to fit new lifters and start from scratch with pre load etc - shouldn't have touched it, was running fine with the old p6 heads.
