Max valve size for 4.0/4.6 heads?

[BlownMGB-V8]

Anyone know how large you can go on the valves for these heads without changing the seats?

I've seen valves about .050" larger for both ex and intake. That hardly seems worth the trouble and expense unless the old ones have to be replaced.

Jim

[mgb260]

Rimmer bros and the Wedge Shop sell larger valve for the Rover heads. Pretty close to the Buick 300 sizes. Years ago I changed the seats and used Ford 2.3 SOHC 1.74 IN and 1.5 EX valves in a 300 head. Probably could in the Rover also.

[BlownMGB-V8]

That'd be a substantial increase. The intake is about 1.570 and the exhaust is about 1.350. The alloy 300 heads have a little larger intakes and smaller exhausts, around .040 difference in each case I think. There is slightly over 3/16 between the valves so I expect that'd be about the limit.

Just for reference the TA heads have the valves repositioned and can go bigger, up to 1.6 and 2.0 in although we decided a 1.9 made more sense.
Jim

[mgb260]

Larger Rover valve sizes in this link:

https://thewedgeshopstore.com/tws-performance-rover-v8-heads-3-5-3-9-4-0-4-6/

[roverman]

Ok TWS. lets see the flow $'s for $2,100 ?

[Airwreckc]

In case anyone is interested, here's a slightly less expensive alternative.  Price is 1550 GBF plus 200 GBF (core).  They are CNC ported and the size of the valves is 1.63" intake and 1.4" exhaust.  I've asked for flow numbers.

https://johnealesroverv8.co.uk/product/stage-2-ported-cylinder-heads/

[mgb260]

Eric, Plus shipping back and forth. Wedge Shop (TWS) might be more like their Stage 3 too.

[Airwreckc]

Jim, agreed.

[BlownMGB-V8]

Saw those, not real impressed with the valve sizes. I mean if I'm spending $18 each for valves I'd want to get a little more than that I think. Probably just stick with the originals, they seem to be in good shape.

Jim

[minorv8]

Hi,

1,63" intake and 1,40" exhaust valves are typically available and fit factory seats. That´s what I have fitted in my Rover heads.

One thing to consider: I have not had much luck finding uprated springs (read inexpensive) for Rover heads. Sure there are double springs available but all the additional parts + possible machining start adding up costs. Also quality of rockers and rocker shafts is pretty poor. I have a pair of new rockers shafts that have smaller OD than worn factory shafts. These came from a reputable source in UK.  

Jukka

[minorv8]

Here is a link to a UK magazine article from mid 90´s when P38 type 4,0 / 4,6 litre engines arrived. It has some useful info about component dimensions

https://drive.google.com/file/d/1uqbLrqPhEsE2csIoIGyt8P5T1rZguPS7/view?usp=sharing

[Airwreckc]

Jukka,

That's a very useful article.  I'm curious about one thing.  The article says the 4.6 heads have a combustion chamber of 28 to 31 cc, while I think I've read somewhere else that they are 22 cc.  Am I missing something?  That would make a big difference in my calculations.

[MGBV8]

Never, ever heard 22cc, Eric.  More like 28 to 29cc.

There are few odd remarks in that article.

[Airwreckc]

Carl,

Probably need to get my eyes checked.  Thanks for the confirmation--now have to redo my calculations.

[MGBV8]

"So, in addition to deleting these bolts a new thicker composite head gasket has been introduced, and the deck height has been reduced by a corresponding amount."

Say what?!  In all these years, I have never heard that the deck height was changed.


"...and the production conrods and pistons remained weak."

Do the Rover V8 engines not use a forged connecting rod?  I know that the Buick/Olds 215 does.

[Airwreckc]

Carl,

I did read somewhere else that the later Rover heads used a thicker gasket and that the combustion chamber was accordingly reduced by shaving the head--I *think* that's what the article was trying to say, but it made it sound like it was the block that was reduced, which I don't think was the case.  Still wondering where I saw that 22 cc reference...

Not sure about the Rover rods, though.

[MGBV8]

Yes, Rover shaved the heads to compensate for the thicker composite head gasket.  I think they are wrong about the deck height.

[BlownMGB-V8]

That would explain the change in chamber volume.
The 340 used cast rods, pretty sure the 300 did too. One of the early mods to the 215 was to use small journal SBC rods which were forged. How certain are you that the 215 rods were forged?

That 22cc number may have been my fault, I had mentioned that as a piston dish volume because I had some notes from an old engine build that contained that figure. But apparently I never actually used it so as far as I know it doesn't apply to any build.

22cc would be a VERY small chamber volume.

Jim

[Airwreckc]

Ha, no worries on the chamber volume--my numbers do work a bit better now, though

I have also read that the 215s had forged rods--I think that was from a spec sheet posted on the V8 Buick site.

[MGBV8]

I'd bet on it, Jim.  

[roverman]

Jukka and all, for better springs, I use "beehives". Light/steel retainer, clears fat rockers better. Cheapest from Comp Cams
  are a decent upgrade. "Pacalloy" is top-end $.    Art.

[BlownMGB-V8]

I agree with Art on the Beehive springs. I used a set for a Ford recommended by Jim N., came with retainers at a good price. On extra thing to pay attention to with beehives: They should if possible be set close to coil bind at full lift I think within 1/16" or so. This is because you don't get the full benefit of their characteristic damping ability otherwise.

Jim

[turbodave]

I've not been able to locate a smaller dia retainers for beehive springs that use the 11 degree stock Rover valve grooves / keepers - unless someone else has a solution? ReelSteel used to sell a custom keeper for the more common GM retainers to mate with the Rover Valves, but not available for several years.

As a result, I am planning on using the Comp 712-16 with Comp 980 springs

And as far as the stock 3.9/4.0/4.6 valves (1.568 / 1.356) go vs the 1.63 / 1.40 of the assumed largest size you can get on the stock seat....

The stock valve throat is around 86% of the valve dia, and the seat job is ok, but not great. If you are going to stick with the stock valves, then a performance valve job, using a .050-.060" wide seat, and a back-cut on the valve, would really help. And a blend of the valve job to the throat of course!

That said, if you go for the 1.63", and bore the throat out to a few thou over 1-7/16", it works out to 88.5% of valve area. Just the CSA of the throat is 13% larger, and of course your curtain area is improved with the larger valve. Personally, I also like the larger throat of improving the shortside just a little by giving you just a little more meat.

[turbodave]

In response to the questions on the Head CC's, this is my spreadsheet I use for Static CR.

I have measured six different "10-bolt" heads at 28.5CC.

[minorv8]

I have Comp beehives on Merlin heads as well as Wildcat heads.

But like Dave already mentioned, there are no retainers to suit beehive spring / Rover valve locks. Unless of course Rover valves are changed to others that use GM type 7 (or 10) degree locks.