3.5 V8 Rebuild

I'm a bit late to this element of the thread but it's provided me with some amusement for the last 10 minutes!!

Mark - it might be a bit late now but have you seen the recommended mod for this bit? It takes a pipe from one of the pressurised oil galleries in the oil pump and feeds it up to a spray bar in the front cover, fed through a bored hole in the dizzy securing bolt.

However, having done a lot of research I concluded that the holes in the webs were sufficient, certainly for my uses. The bigger problem on these engines is cam walk that you really ought to address by a cam retaining plate or a cam bolt teflon button, depending which engine you have. A lot of the cobra RV8 guys still had problems when they had done the oil mod, but the issue was resolved once cam walk was resolved.

Jonnyt really is the man in the know on this, I'm very glad/grateful you jumped on board my thread Jonny when I was rebuilding my engine, a cam button is something I would fit to all future builds of mine now

I heard about those, a bit more info on the cam button and a how too would help me

Cam buttons are simple things - basically the bolt that holds the cam shaft dizzy gear to the cam has a teflon disc on top of the head. One of the known problems on these engines is that there is no positive mechanical system for preventing the cam from moving forward under load. The lobes have a slight incline which is supposed to do the job but it isn't great. In later engines (I forget when it changed) a cam retaining plate was added which cures the problem. Rover's interim solution was the cam button which ought to be installed to engines on rebuild. The teflon button interfaces with the front cover and prevents the cam moving forward (i.e. walking). The big problem with a walking cam is that it promotes rapid wear of the dizzy drive gear (either on the cam or the dizzy). Some of the cobra guys have lost one, other or both in less than 5000 miles without positive cam retention.

To install you need to first take the cross hatching off the front cover where the button will hit it so its a smooth surface. Then its a case of trial and error to get a clearance of 0.005'', taking a little off the teflon face at a time to get the right clearance - remember to trial fit with the gasket of course.

I detected movement by using a finger DTI (rather than plunger) which rested against one of the cam lobes (secured by a mag base on a large lump of metal in the valley). This allows you to measure the movement back and forth when the front cover is fitted. On a trial fit basis take it to about 0.006'' and then when you torque up on final fit the gasket crush will give you the 0.005'' clearance.

The other way is to fit a cam retaining plate but you need the right cam (with a shoulder machined) to be able to fit that.

HTH

Thanks, I dont suppose you know whether the leyland p76 4.4 rv8 has the same problem and or can have this fitted?

Thanks mate

Any rv8 camshaft will be able to take the button, so the question is whether the p76 cam is the same/very similar to the rover version?



By the way, in my engine build thread from August this year there are many pics about this cam button setup

I took the bodge route and went for some engineers blue to show when I just had contact with the timing cover, then machined a smidge more and allowed gasket crush/bedding in do the rest.

No man needs trouble himself over 5 thou when fitting a part that wears anyway!

I'm not going to agree with Sam's final comment but we've agreed to disagree over tolerances before now ;-)

He is right though that any cam shaft can be fitted with a button and at that age I doubt there would have been a retaining plate fitted - it was much later I think before these were fitted by Rover.

Personally if I were doing it again (and I admit that I bought loads of shiny bits before thinking about a lot of this stuff) I would just buy a camshaft with the shoulder machined for the cam retaining plate and then fit that - it is only two holes tapped either side of the front camshaft bearing journal and is something less of a bodge than the button. On some uses (racing) the buttons have been known to machine themselves through the front cover which is a bit of a pain! It might justify my slightly anal approach to that tolerance of 0.005'' though...!

Jon

Ahh, he's a good lad, he just about "tolerates" me!

Cam retaining plate = solution

Cam button = bodge fix!

Will be interesting to see what's happened to my 5 thou bodge if/when I take the timing cover off again on that engine, can't imagine a coarse piece of nylon rubbing against coarse aluminium with a splash of oil every now and then will last very long!!

Cheers

ok, ill defo look into the cam retaining, questions is.. is there any reason i can put the cam on my lathe to make the a retaining plate fit?

and reguarding the oil feed, im reluctant to tap into the presurised oil feed as its not all that good on these engines as it is, the chain doesnt realy need much.. and waste oil is perfect in my opinion.

It depends on whether the cam has enough meat on it that just hasn't been machined or whether its just not there. I thought about doing the machining - easy enough to do, but there was nothing to machine on mine.

Re oil fix - I agree but the hole size is tiny so you lose very little pressure, and if the pump is right it won't be a problem. As I said though I concluded that it wasn't necessary with the holes in the web which I think at high revs will allow more oil into the front cover than you'd think and cam retention.

ill have to take a look at the new cam, i migh have a practice run on the old cam see how it fits and what not

My rebuilt engine with decent oil pump makes 80psi at high revs cold, 45psi at low revs cold, 60psi at high revs hot, 20psi at low revs hot.

Seems there is plenty of pressure to go around and more importantly a lot of flow available also.

The only guaranteed option is pressure spray, second i think marks directed oil dripper will work well as long as it works, and then the holes in the valley migt work or it might just dribble down the front of the block, onto the cam and then get chucked around generally.

Who knows?

Maybe holes in the front of the sump baffle would be better to increase oil slosh up the front of the timing cover?!

Mr Noisy said:

Ahh, he's a good lad, he just about "tolerates" me!

Cam retaining plate = solution

Cam button = bodge fix!

Will be interesting to see what's happened to my 5 thou bodge if/when I take the timing cover off again on that engine, can't imagine a coarse piece of nylon rubbing against coarse aluminium with a splash of oil every now and then will last very long!!

Cheers

Click to expand...

lol and lol,

But I will look at your thread sam

just had a look at doing the thrust plate, seems simple enough, just need to turn a bit down on cam and tap some holes in the bolck

The only thing you'll need to find out is the exact thickness of the shoulder that the retaining plate locates on. Should be able to find that out though easy enough.

The other day I got the head faces cleaned up, the valves cleaned and ground in, which is a bit of a pain in the ass job!
Turns out its better to use light pressure when grinding the valves so it doesn't push out the grinding paste. (not what I expected)

The new rings on and the cleaned head.



The ring I used (rim dodger)





Then I had a look the camshaft before putting it in with the new bearings and as seen on post 12 there was some rust dotted around the cam surface, so as instructed I had a go at cleaning it up.
Used a bit of WD40 and a rag to get the worse off and left it at that because It was quite bad and no point putting it in the build if it will fail!

Spoke to RealSteel and they were happy to replace it for me, free of charge. They arranged a courier to pick it up from my workplace last Monday, and today they are sending me a new (rust free) cam.
Very happy with there service, no hassle what so ever!

good to know and you are a bit further on than me ya bastid

what did you use to clean up the ally mating faces on the heard/block without damage? mine has composite gasket stuck to it all over and its a pain to get off!

also what are you doing to your bores?

fett said:

good to know and you are a bit further on than me ya bastid

what did you use to clean up the ally mating faces on the heard/block without damage? mine has composite gasket stuck to it all over and its a pain to get off!

also what are you doing to your bores?

Click to expand...

Mine were tin gaskets, Ive been and still are having a basterd of a time trying to remove the paper gasket from my oil pump mind, I used lots of WD40, rags, plastic and a plastic brush wheel on the heads and block. they weren't to bad to be honest.

For the oil pump gasket I got some gasket remover spray, seems to help... a tiny bit, but still a bitch!

and z bores?