Heads and gaskets

[bencorkill]

tin or composite gasket? and i think i heard some where you need to have the heads shaved for composite ? is this right. And on look out for a set of heads so can get all cleaned and new valves in so its a straight swop if any one has a set they want to sell (its a 3.9) thanks

 

[Mr Noisy]

Yep, heads are skimmed down for comp gaskets.

4.2 LSE heads were 3.9 heads skimmed down.

You could fit a set of 4.0/4.6 heads that were the new casting, all skimmed for composite and have wasted stems as standard. Also they're 10 bolt and have the best stem seals.

 

[bencorkill]

So if i went for a 4.0/4.6 head composite gasket would be the one, and wouldn't have to change anything else, it may be a stupid question but im clueless on rebuilding , once i know whats what will be okay i hope ha

 

[Mr Noisy]

4.0/4.6 heads are the best, not by much but they are better in more ways than one, and yes they are skimmed for composite which are also the better gasket!

You can fit composite to standard 3.9 heads but will lower your compression ratio

I think there is a bolt hole different on the front of the NS head but I don't know if it affects 3.9 cos alternator is on other side to 3.5

The 4.0/4/6 heads are your best option, but there's also nothing wrong with your current heads if you get my meaning!

 

[bencorkill]

Yeah man understood , you think best thing to do test compression and decided wether to do a top end or fullish rebuild?

 

[Mr Noisy]

If I was doing one I wouldn't hesitate to do a full rebuild but do a compression test to get the idea first.

If the crank is in good nick it can go back in with new shells, it needs a new cam and followers anyway, piston rings definitely, rebore and 20thou pistons if you're feeling flush, inspect rocker gear and oil pump (both will hopefully be acceptable) and timing gear and chain set have a few options depending on budget but you need to fit one of them!!

Generally RTFM but its so simple once you get into it you won't be able to resist taking the bottom end apart aswell!

 

[Mr Noisy]

By the way take your time, and you need to invest in proper measuring equipment (I prefer a dial vernier for most stuff, a dial test indicator for runouts and tdc, and a micrometer for crank journals)

Cheers!

 

[bencorkill]

yeah, i mean according to paper work she had a new cam in like 19k ago, no receipt for tappets and push rods so defiantly want to change them out, but i still cant work out where its making its horrible tapping, hopping its not a slipped liner! The engine is on 164k

 

[Mr Noisy]

Can't see it having a cam without followers?!

My 3.5 was tapping all the time, will have been dodgy stuck follower

Get it stripped and be happy, or buy a donor engine and take your time, but better the devil you know??

 

[bencorkill]

I would like to get a donor , only problem is family lol (im 19) dad doesn't want garden and drive turning into a scrap yard, i think i could bring him round haha ! in a ideal world would do that i will keep an eye out 4 any rotted discos near me

 

[Mr Noisy]

Yeah my old man uses the same 'scrap yard' quote!

Come on dad, it's not scrap, it's SPARES!!

I didn't mean a donor car, just the engine! Sorry if I was misleading, yeah just get hold of a cheap 3.9 and rebuild it as and when you can! The problem is that becuase of the inherent problems the 94mm blocks have you might be better off rebuilding your motor.

The only option is to pull yours out, break it down, find out if the block is ok and then proceed.

I was in the same position as you, enthusiastic but never opened an engine before, but once I was inside the RV8 i was relieved how easy it was.

Firstly once it's clean it's a nice stand up job, and there really isn't anything complex. The only thing is you do have to take care to measure and measure again.

Let us know how you get on, but I'm afraid with any 3.9 it's a guessing game until you get it out and inspect the block!

 

[bencorkill]

thanks mate, not to sure which way to go, if i could find a 3.9 i would be tempted to buy it as disco is my daily runner , and dont wanna be wheel less for weeks ! what about just swoping it for a RR 4.6

 

[Mr Noisy]

stick a 4.6 in it, no problems at all, get a cross bolted block if poss but i think they tend to be ££££ because they are what the racer boys are after!

 

[bencorkill]

Or just do the real steal crank and up mine to 5.0

 

[jonnyt]

There may be one or two other things beyond the crank to look at if you're taking your block to 5.0....!

 

[bencorkill]

There may be one or two other things beyond the crank to look at if you're taking your block to 5.0....!

I know dot think my insurance company would ever look at me again, theres a cam and new pistons needed for that

 

[Hybrid From Hell]

Tin gaskets compressed thickness 0.45mm /18 thou + Composite compressed thickness 1.0mm / 40 thou.

Frankly, if you're running a standard engine you won't notice any difference, even more if its done loads of miles and not in the 1st flush of youth,

Peeps argue about the huge loss of power due to reduced compression - but you wouldn't be able to tell if the gaskets were switched without your knowing
and you drove it - you wouldn't see any difference in the real world - except on a low compression motor then you will !

And use ELRING ones

Nige

 

[bencorkill]

Found a engine pretty close to me , they want £350 for just engine, its on 150,000 miles , and regarding new piston rings why is a standard set on rimmer bros like £220 and oversized are like £40? :s

 

[Mr Noisy]

I can't see the economy in paying £350 for a 150k engine unless its had some kind of rebuild in which case it's cheap.

Not sure on your rings but I thought they were like £8 per piston?!?!

 

[jamesmartin]

some of rimmers stuff genuine stuff is dealer priced