Are these original Rover P6 Cylinder Heads?

ziptie_engineer · Post by **ziptie_engineer** » Tue Jun 30, 2015 6:25 pm

I'm in the process of refurbing my Triumph Stag's RV8. The block itself in an early P6 block, but the cylinder heads have SD1 rocker covers and 19mm spark plugs fitted. I think that my cylinder heads are the original Rover P6 ones, which means it actually needs much shorter plugs fitted. I've checked for the casting numbers mentioned in the sticky thread in this forum but can't see any of them (just a serial number between two of the rockers). Can anyone confirm which heads these are and which sparks they should use? Many thanks!

Baracus · Post by **Baracus** » Tue Jun 30, 2015 9:22 pm

I've seen the Birmal casting mark on both early and later (slightly) bigger valve heads but from the looks of those valve caps you've got a set of early small valve P6 heads there.

To double check, measure the valve spring diameter, if they're 1.3" you've got early small valve heads, if 1.225-1.25" they're the later heads.

The early small valve P6 heads aren't great for power so it'd be worth swapping them out for some later heads.

harvey · Post by **harvey** » Tue Jun 30, 2015 9:36 pm

Baracus wrote:I
To double check, measure the valve spring diameter, if they're 1.3" you've got early small valve heads, if 1.225-1.25" they're the later heads.

P5B & P6B heads use double valve springs, SD1 onwards have singles.

bigaldart · Post by **bigaldart** » Tue Jun 30, 2015 9:45 pm

I just check the exhaust port, if there is a radiused bump in the top left corner it's an early head. Easily visible and conclusive.

Alan

ziptie_engineer · Post by **ziptie_engineer** » Wed Jul 01, 2015 10:18 am

Thanks guys, I'll measure them on Thursday when I next get some tinkering time. I've ordered a set of short-spark plugs anyhow, the current 19mm ones are fouling with dry carbon, which prompted me to the issue. Hopefully the right length plugs will make a difference.

I doubt I'll bother changing the heads as it's already putting out more power than the cars original TV8 thanks for the Holley carb (as well as being a better engine anyway!). I'm still running the original brakes/gearbox/diff so don't really want to throw to much more power into the mix. There are bigger financial priorities first; an electronic distributor. I'm still running points, so with a P6 engine I assume I need an electronic distributor with a male type gear base? My current distributor is a Lucas 35D8 but has the old style triangular base to the rotor arm. Apparently the drop 'stealth' type conversion kits are a nightmare to fit to this older system, hence why I was thinking a complete new unit might be simpler. Any recommended places to buy from?

DaveEFI · Post by **DaveEFI** » Wed Jul 01, 2015 12:09 pm

I'd be very careful buying one of these new RV8 dizzies at what looks to be a good price. I've read many reports that they are poor quality.

You can convert your existing one to 'electronic' points easily, and for less cost.

Most of the later Lucas electronic ones aren't that reliable either. I had the latest type, the DLM, with amp on the side, on my SD1, and had 3 amp failures. All of which were genuine Lucas parts. I used to carry a spare.

ChrisJC · Post by **ChrisJC** » Wed Jul 01, 2015 4:55 pm

Yet I ran a DLM8(?) with the amp on the side with no problems whatsoever. You do need the correct coil.

But if you have a standard P6 timing cover, then as you say, you have a mismatch at the bottom of the distributor drive shaft.

Is there a reason to ditch the points?

Chris.

DaveEFI · Post by **DaveEFI** » Wed Jul 01, 2015 5:20 pm

Think it's heat that kills the amp - and my SD1 has air-con and gets pretty toasty under the bonnet. I think later Range Rovers moved the amp off the dizzy to somewhere cooler.

sidecar · Post by **sidecar** » Wed Jul 01, 2015 5:42 pm

I used to run the dizzy with an amp on the side, I also went through at least 2 amps. I used to think that the Lucas electronic dizzies were quite good, one of the Rover books bangs on about them being used in a Grand Prix engine. It was only when I went to an MSD system triggered by an MSD pickup inside a Lucas dizzy that I realized that the Lucas stuff was not all that good, my engine used to tail off over 5k RPM but now is easily spins to 6k. I reckon that the Lucas stuff was mis-firing at high RPM.

ChrisJC · Post by **ChrisJC** » Wed Jul 01, 2015 7:23 pm

My ignition amp was on the distributor, under the bonnet of a Sherpa Van. It got pretty hot too.

But as you say, there must have been a reason Land Rover moved it away from the engine......

Chris.

mgbv8 · Post by **mgbv8** » Wed Jul 01, 2015 9:15 pm

ziptie_engineer wrote:I'm in the process of refurbing my Triumph Stag's RV8. The block itself in an early P6 block, but the cylinder heads have SD1 rocker covers and 19mm spark plugs fitted. I think that my cylinder heads are the original Rover P6 ones, which means it actually needs much shorter plugs fitted. I've checked for the casting numbers mentioned in the sticky thread in this forum but can't see any of them (just a serial number between two of the rockers). Can anyone confirm which heads these are and which sparks they should use? Many thanks!

To save all the faffing around with head numbers why dont you just remove a spark plug and measure the spark plug thread depth in the heads ? You only need a bit of wire with the end bent to 90 degree's so you can hook it over the end of the plug hole and make a mark at the top of the thread on your wire. To be honest the difference between the long and short plug threads is ovbious when you shine torch down the hole?

ziptie_engineer · Post by **ziptie_engineer** » Thu Jul 02, 2015 9:45 am

Perry; I've already taken the liberty of doing this and I estimate the internal thread to be circa 13mm, this was the thing that originally prompted me to question why I had 19mm plugs. I haven't had a chance to measure the valve-spring yet, but I'm thinking I might just fit the new shorter plugs I've bought as see if they make a difference. I assume it will be very lumpy/won't start if it doesn't like them.

Chris; I was going to ditch the points as the engine has been a little bit underwhelming (especially from idle) and I've systematically tried to eliminate any potential issues. So far I've fitted a facet fuel pump & regulator, completely overhauled the Holley and fitted new HT leads. These fixes have made it significantly smoother, but there is still a slightly stumble from idle. Hence why it was going to be new plugs and some form of electronic distributor.

Dave; any suggestions? I've apparently got the 'old' style points with a triangular-base. The guy from Accuspark told me the kit is a real pig to fit compared to the later SD1-style kit with the 6mm pin.

DaveEFI · Post by **DaveEFI** » Thu Jul 02, 2015 1:26 pm

sidecar wrote:I used to run the dizzy with an amp on the side, I also went through at least 2 amps. I used to think that the Lucas electronic dizzies were quite good, one of the Rover books bangs on about them being used in a Grand Prix engine. It was only when I went to an MSD system triggered by an MSD pickup inside a Lucas dizzy that I realized that the Lucas stuff was not all that good, my engine used to tail off over 5k RPM but now is easily spins to 6k. I reckon that the Lucas stuff was mis-firing at high RPM.

Never had that reported on the SD1 club. Mine certainly span all the way to when the tappets started pumping up happily. Racing SD1 had a much higher rpm limit too, and think used the same basic ignition.

DaveEFI · Post by **DaveEFI** » Thu Jul 02, 2015 2:56 pm

To be honest, if the points system is in perfect condition, there will be no difference whatsoever going electronic on a road engine. The major advantage is the electronic system maintains its performance with no routine servicing, as there is nothing to wear.

The P6 has a clever external adjuster to set the points gap (dwell) So with a dwell meter, it can be set quickly with no fiddling with feeler gauges. The downside is more mechanical bits inside the dizzy to wear and go out of adjustment.

I fitted a Lumenition optical unit to my P6 3500. and transferred it to my P6 3500S. So it was in constant use for about 6 years without problems.

So don't really know what 'electronic points' would fit - they weren't really around then.

ChrisJC · Post by **ChrisJC** » Thu Jul 02, 2015 5:42 pm

I would go for the Holley being a bit poop giving you the stumble from idle, rather than the ignition.

By poop, I really mean not set up properly. I have never set one up, but I believe there are well over 1 thousand adjustments / needles / twiddlers etc. And you need to be some kind of genius to get them right.

I exaggerate.

Chris.

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Are these original Rover P6 Cylinder Heads?

Are these original Rover P6 Cylinder Heads?

Re: Are these original Rover P6 Cylinder Heads?