Thickest head gasket for Rover V8

dnb · Post by **dnb** » Wed Mar 12, 2014 7:29 pm

Is there a 1.5mm head gasket available for the Rover v8? It would make life considerably easier for me if such a thing existed...

(Considered stacking 3 tin gaskets, but am not all that keen on the idea.)

Thanks

badger · Post by **badger** » Wed Mar 12, 2014 9:02 pm

Thickest gaskets I know of personally are about 0.9mm compressed (composites). The problem if you stack tin gaskets is that they must be stacked with their corrugations the opposite way - they will seal around the chambers ok but you will often get bad oil leaks at the feed holes up to the heads. (they don't compress correctly if stacked the same way).
I have done this once myself with composites, to get round a set of over-skimmed heads! They stacked quite successfully - look at the fire rings around the bores, first gasket goes on with the wider ring to the block, second gasket the same way, use ARP head studs, use plenty of the correct moly lube on the nut threads and washer faces (NOT the block threads!) and torque initially to 20lbft then increase in 10lbft increments to 60lbft, then a final torque to 65lbft.

r2d2hp · Post by **r2d2hp** » Wed Mar 12, 2014 9:14 pm

Topcat was doing 1.2mm in copper a while back

dnb · Post by **dnb** » Wed Mar 12, 2014 9:21 pm

Thanks.

The 94mm standard comp gaskets claim to be 1.2mm compressed

The problems I am trying to work around are similar to your description - that the block and heads have had to be skimmed more than I budgeted for and I am left with a very slight positive piston to deck height - so with a standard gasket I end up with very little piston to head clearance (just about acceptable at 0.85mm, but more would be better) and a compression ratio of more than 11:1.

I could get the pistons machined, but that only fixes the clearance. It makes the compression higher... I doubt there's enough material in the heads to open them up to drop the compression - it would be a lot of metal to remove!

Stacking would seem the easiest answer.

SimpleSimon · Post by **SimpleSimon** » Wed Mar 12, 2014 10:23 pm

Decking/machining the pistons lowers CR

agree the Elring composites compress to 1.2mm

.85 piston to head clearance IMO is def a bit tight

dnb · Post by **dnb** » Wed Mar 12, 2014 10:50 pm

Yes, I mistyped. It does indeed lower the compression - in my case from 11.1 to 10.99. They're dished pistons, so not much volume increase.

It's insignificant compared to an additional 0.3mm of gasket thickness.

I could live with 11:1, but would prefer a bit less - it's more than the last build had, and that was very much det limited for power at the top end on standard fuel, and more compression will only make that worse.

I ran considerably less than 0.8mm clearance last time

Robrover · Post by **Robrover** » Thu Mar 13, 2014 7:22 am

Could use Buick 300 heads, they have a chamber capactiy of 56 cc as stock and will bolt straight on. Plus they will flow a lot better than Rover heads and will take bigger valves too.

kokkolanpoika · Post by **kokkolanpoika** » Thu Mar 13, 2014 7:03 pm

http://www.shopengineparts.com/parts.as ... D+V8+94-Up

0.06" available.. Quite pricey..

ps: my engine is running 0.8mm piston/head clearance without issues.. And 11.8:CR

sidecar · Post by **sidecar** » Thu Mar 13, 2014 7:59 pm

I worked on an engine a while ago where the head skim was cocked up and this would have caused the CR to be way too high, in the end Muscle Manta and I spend a good few hours with a windy tool taking a couple of CC out of each chamber, we finished the chambers off with some fine abrasive pads again with a windy tool It took a hell of a long time to do the work and then buretting the chambers but it worked out OK in the end.

Personally I'd for for a CR of 10:1 assuming that you are not running a massive cam. I don't think that the chamber design is all that good on the RV8 (assuming that's what you are building).

dnb · Post by **dnb** » Thu Mar 13, 2014 9:13 pm

I knew there would be a solution out there.

I can get away with 0.051" gaskets - leaves me with 1mm quench and 10.9:1 compression, so "only" $100 per gasket

It's only money after all.

Yes, it's a Rover v8 with a wild cam. 10:1 is a bit too low - based on running 10.5:1 on the last build and getting good power (for a Rover) Looking at the dynamic compression, 10.8 looks to be sensible.

I'm aware of the limits of the Rover heads. Mine have matched chambers and decent size valves - (TVR 500 heads with my own quality control applied

). Not keen to change them since they seem to work OK.

badger · Post by **badger** » Sun Mar 16, 2014 12:31 pm

1mm (0.040") should be fine for clearance, as a minimum, although I have built hot RV8 engines in the past with only 0.75mm (and 2-stroke KH engines with 0.2mm!!).
Personally, I would machine the pistons by 0.25mm / 0.010" in preference to using two gaskets any day, as it is another potential leak source for the future. You will not weaken the pistons - I have used 3.9 pistons with 2.75mm machined off the tops in the past, in a hillrally racer with no problems whatsoever.
As has been said, this will lower your c.r. slightly as well, but I wouldn't get too upset about theoretical (static) c.r. - if you are running a fairly hot camshaft then the dynamic (running) c.r. will be a lot lower than a standard cam would give you due to valve timing, even when your static c.r. has been raised above standard. I built a 5.2 RV8 for a TVR a few years back, it used the TVR "fast road" cam and even with a static c.r. of 11.5:1 it ran just fine, popping out an easy 300+bhp on the dyno with an extremely strong torque curve. The bloke I built it for put the dyno sheets up on Pistonheads, they may still be there.

dnb · Post by **dnb** » Sun Mar 16, 2014 8:47 pm

I'm not using Rover (or even TVR) standard pistons. It would be an unknown quantity to machine them by that much so I'm not keen. It would probably be fine, but the thicker Cometic MLS gasket gets around everything, gives me the 1mm of clearance and it isn't a 2 gasket bodge - not keen on that either! (And it's cheaper than piston machining)

I've never been worried about static CR. I'm aiming to keep the dynamic compression in the range of 8.05 to 8.1. (This equates to approx 10.8:1 static for my components). The previous build made well over 300bhp, and this one ought to be good for 350+. I have to be a bit careful not to limit my fuel choices - high (>97) octane fuel is not easily available here.

kiwicar · Post by **kiwicar** » Sun Mar 16, 2014 9:04 pm

Hi
I run .03" gaskets with pistons 2 thou out the block, I did run for a while .025" with the pistons decked flat without issues, my red line is 8K at the moment. Perry thinks I have buzzed it beyond that. I would not be keen on running a squish band wider that 45 thou as there is very little squish on a rover head as it is. If you do open it out beyond 45 thou you probably should drop the compression another 1 on the CR to avoid detonation. And that will cost you about 4% on power.
best regards
Mike

dnb · Post by **dnb** » Sun Mar 16, 2014 9:38 pm

I am awfully tempted to try it with a standard gasket and 34 thou clearance... (Red line will be 6.5k)

I know I shouldn't but what's the worst that can happen?

kiwicar · Post by **kiwicar** » Sun Mar 16, 2014 10:04 pm

I know I shouldn't but what's the worst that can happen? Wink

You could make a few more BHP and have it not pink

34 thou is not tight for a squish band, my 25 to 28 is safe provided your machine shop is up to the mark, I read an article in carcraft a couple of years ago where a chap was running down to 15 thou squish band on a 302 ford and making quite a bit of extra power over running 35 thou but on flat top pistons.
best regards
Mike