rpi stage 3 valves

mgrv8 · Post by **mgrv8** » Wed Oct 28, 2009 8:43 am

Hi , Im after a bit of advise... i got a set of rpi stage 3 valves from ebay.{slightly bigger than std valves} but have been told by a rover v8 engine specialist that these are not a good choice.. and dont flow any more than std size valves.. what do you think? i dont want to cut the valve seats untill im sure im doing the right thing... Steve

kiwicar · Post by **kiwicar** » Wed Oct 28, 2009 10:10 am

Hi
a picture would help alot as "stage 3 valves" means very little to me (especially when RPI are concerned.
Do they have waisted stems?
What is the back cut angle? (have they been back cut?) what is the seat angle job like?
They may increase shrouding being larger, but they may improve flow more in other ways and you may be able to use off set guides to move the valve away fron the cylinder wall.
Mike

Post by **katanaman** » Wed Oct 28, 2009 5:01 pm

it all depends on what you do with the seats when you cut them. If you just open out the seats to fit the valve then you will get little from it. If you reshape the throat and ports then you will flow loads more. As ever its not whats done but how its done. Your next step up will be ultra big valves which need new seats so cost a fair bit £££ to do but again unless you match the rest of the ports to the valves your not going to gain much.

CastleMGBV8 · Post by **CastleMGBV8** » Wed Oct 28, 2009 5:53 pm

Steve,

I assume that from your log in you have 3.9 engine, don't know which rover V8 specialist you talked to but most Rover V8 engines respond well to head mods if done properly,especially the larger capacity versions.

Is this something you are intending on doing yourself as it really is speciallist work unless you have the tools and skills required.

Firstly what valves have you got, the usual big valve sizes are Inlet 1.63" and exhaust 1.4" and they should have waisted stems ie the stems that are exposed in the port area is thinner than the part thats in the valve guide.

The seats require cuttng for the bigger valves and then the surplus seat material that is inside of the actual valve seat area must to be removed and the area below needs to be opened up to the new seat size and then blended into the bowl area right down to the valve guide area, you can also grind away the valve guides to approx 1/4" above the guide support in the roof of the port.
For a road engine the rest of the ports can be left as cast.

Whilst the heads are stripped it would be worth having the tops of the valve guides machined down 100thou. to enable fitment of a high lift cam at a later date, if you have this in mind it would also be worth fitting the one coil less valve springs which are available from Real Steel or V8 Tuner.

The above mods should give an increase of 35+ BHP without a change of cam, a fast road cam should give you another 20+ BHP

Kevin.

mgrv8 · Post by **mgrv8** » Wed Oct 28, 2009 6:27 pm

Thanks for the info on this so far, Im sure that the valves are waisted and 1.63 / 1.4 size.. i was going to fit shorter 'sports' guides and cut the seats to match these valves , 'also blend in' below the seat area and match the ports to the inlet gasket...
my engine is a 5.0lt rebuilt short and i have 4.6 heads to go with it..
I also have a KCR285 cam that i was planning to use but unsure if its a good choice??...
When its built up it will go in my mgrv8 replica with a t5 box that ive had for years but havent got round to using.., relacing the 3.5 sd1 efi low mileage engine/lt77gearbox....{ebay that i suppose?}

Thanks Steve

kiwicar · Post by **kiwicar** » Wed Oct 28, 2009 7:49 pm

Hi
basically sound mods, but don't take the ports out to the gasket, mark up the ports on the inletmanifold onto some card (cerial packet) by placing the card over the inlet ports and rubbing a the round end of a ball peen hammer over the card (don't hit it

) open the up the pushrod pinch area as far as you can without breaking through and use this as a guide for the rest of the port aiming at a very even slight taper out as you go away from the bole area. alot of heads are ruined by taking the port face out too far. try and get a copy of "how to build, modify and power tune cylinder heads2 from speed pro isbn 1-901295-45-1 it has what to do on the rover, (I have a spare copy without a cover I can let you have for £5 +p&p, funny that

but it does covers all the theory in some detal and has pictures of what to do on these heads, coupled with what is described above will get you there)
Mike

CastleMGBV8 · Post by **CastleMGBV8** » Wed Oct 28, 2009 11:16 pm

Steve,

Well obviously a 5.0 can cope with a bit more flow potential, it all depends on your intended use and whether good on road drivability is important.

What sort of induction system are you intending to use as this will have a bearing on what camshaft you can use?

As your building a RV8 replica I can point you at a couple of similar projects, one road car and one full race

Links.

http://forum.britishv8.org/read.php?9,1582

http://forum.britishv8.org/read.php?2,9223

Kevin

mgrv8 · Post by **mgrv8** » Wed Oct 28, 2009 11:43 pm

It has hotwire injection on at the moment , im thought i might stick with that.. im waiting to see if Dimitri still has a 500 tvr eprom chip for sale..
Failing that will have to consider saving up for mark adams chip?,or might go with weber 500cfm if one comes along.... but would rather keep hotwire on if poss... {ive had my replica on the road for 4years now,but its about time i fitted the engine & t5 that i always promised myself!!} Steve

CastleMGBV8 · Post by **CastleMGBV8** » Thu Oct 29, 2009 1:11 am

Steve,

If your going to use a fairly hairy cam with less than a 112 deg. lobe centre angle you would be better off converting the Hotwire to Megasquirt or similar and then you have the option of getting rid of the distributor.

Kevin.

spend · Post by **spend** » Thu Oct 29, 2009 12:36 pm

mgrv8 wrote:.. a 500 tvr eprom chip for sale..

The TVR chip is very closely matched to 43/37mm valves and TVR porting, personally I wouldn't rely on the chip giving the right fuelling just because your bottom end is a 5.0. We have plenty of TVR chips laying around in the TVR community after installing different ecus.

There is one 500 owner I know of that has V8d 1.63/1.4" heads, v8d stealth cam, but I can't recall if he had MA set it up.

mgrv8 · Post by **mgrv8** » Thu Oct 29, 2009 11:43 pm

If a griff 500 eprom comes up fot sale i would be interested,as the alternative might be quite£££ ?. i was hopping that Dimitri was going to get in touch and sell me the one that he had on pistonheads,
Im quite confident on doing the valve upgrade and cylinder head mods. i will give it a good go anyway.. im not to sure about cam choice... i have a 285 cam that i could use ? and a adjustable cam wheel but not to sure how to set it up yet? i have rebuilt a few standard rv8 engines before but not any thing like this before....
Another question if i may....i have got a new set of stretch bolts for the heads. but im wondering if this is wise? should i buy the old type of head bolts or splash out on ARP studs? thanks for now Steve

kiwicar · Post by **kiwicar** » Fri Oct 30, 2009 6:46 am

a 285 cam is OK in a light car, you will have to check for valve clearance on the pistons and that the valve springs do not bind (mod mentioned above) timing in the cam is not a problem, comp cams and isky have descriptions on their web sites.
Mike