johnsjmc

Yes I was talking about 993RS valves as in the Pelican link. Reading something by Steve Weiner last night he says most improvement from upsizing intakes only. He said RS int. valves and RS cams make a solid 290-300 HP. Ollies machine shows a charge of about 300 to perform the update to the cylinders .I am only guessing that would be the gasket groove.

ALEX P

Thanks for the info all.

Looking at the pelican prices for valves, if they need replacing then it makes sense to put the 993 RS ones in if they're cheaper, I can't quite figure out the logic in their pricing on these though - the Porsche supplied exhaust valves come in at an eye watering $264 instead of $37 for the RS jobs, what's all that about, does anyone know about the quality of Intervalves???

I'm also struggling to get my head round the concept of just increasing the size of the inlet valve - surely if you're letting more in then you want/need to be able to let more out or am I not getting it?

johnsjmc

Intervalves are good quality aftermarket valves. The ratio of intake size to exhaust size is not a hard fast rule. Porsche and other manufacturers often play around with int and exhaust flow by altering valve ,port,and cam timing. Some cams will use more exhaust duration and lift than the intake side others the opposite.
The 964 3.6 uses the same size valves as the 3.0 from the SC but ports are larger ,FI flows better and engine is larger.The 993 int was increased and 993 RS incresed both valves. The 993 exhaust side flow is helped by the already free flowing HEs . The bigger valve I am talking about will mimic the effect of a perf cam at mid RPMs with less boost at high RPMs. Both cam and valves together will boost mid and high RPM power. I think big intakes will be a cheaper power upgrade than new cams as long as you are in there anyway and not seeking huge high RPM power gains.

johnsjmc

I would contact Steve Weiner at Rennsport and ask him advice re big valves into a 964.

ALEX P

Thanks for the advice John, maybe I'll contact Steve after Christmas.

Well, I picked up most of my bits from my specialist following their inspection and as always seems to be the way there was good news and bad news!

Good news was that all the pistons and cylinders are fine.

Bad news is that the both the cams have pitted lobes with a similar story on 5 or 6 rockers with the surface hardening worn down and pitted / flaking. You'll have to excuse the poor quality of the photos, really hard to take with a rubbish camera/photographer & the pitting looks worse than it is shown in the photos!!

So it looks like a few replacement rockers which isn't the end of the world and get the cams reground so I'd better start doing my homework about the most suitable place to send them to and what profile to go for.

Yet to disassemble the heads, hopefully do that next week & see the state of the valves & guides etc.

Happy Christmas everyone!

johnsjmc

too bad but you wanted cams anyway. John Doherty operating as "camgrinder" is the man to talk to about 911 cams. He offers the 993RS/SS profile and another one DC21 I,ve heard good things about. Since you have a 964 you will need a profile ground for solid not hydraulic lifters.The rockers should ALL be reground like the cams then both rubbing surfaces are new for the break in. Rebuilding a rocker with a reground pad and new bushing if needed is still much cheaper than new rockers. Last I heard new 911 rockers were something like $150 ea.

ALEX P

Well, I was thinking of reprofiling the cams if they needed doing but didn't really think about the rockers, Pelican prices are $120 for Porsche or $79 for OEM.
http://www.pelicanparts.com/catalog/...pg4.htm#item16

Amazingly, it must be about the only part that's cheaper in the UK than in the US!
http://www.type911shop.co.uk/shop/ar...6aid%3D1688%26

I guess I'll have to find out what it costs to rebuild a rocker & weigh it up againt the cost of the new one.

johnsjmc

All the rocker faces need regrinding if regrinding the cams. Rebuild some and replace as necessary. If this were my engine I would use RS intakes. RS cam profile for manual rockers and ARP rod bolts. All new guides and replace or reuse ex. valves as needed. Anything else as found

Marc Shaw

Get the 9M rockers -highly functional art.

Marc

ALEX P

Speaking to someone today who suggested that maybe the reason to enlarge the inlet valve but not the exhaust valve was due to the possibility of the heads cracking with both valves being overside due to the wall thickness between them being reduced so much??

John, sounds like quite a good plan with the RS intakes, cam profile and ARP rod bolts. Guides do need replacing (especially exhaust) and maybe some stiffer springs etc. Ordered Supertec head studs today

Split the case today and it's had quite a lot of windage/knife edging/boat tailing done to it. Cylinders were not mooned so maybe do this as well.

Marc, 9m rockers do look great but the price tag puts it on the unrealistic wish list!

johnsjmc

The wall thickness isn,t reduced at all. Both valves close against a hardened seat insert. The contact ring when the valve is closed will only move out closer to the edge of the seat with no effect on the metal in between. Perhaps the larger valves will come closer together when fully opened as they are pointed at each other because of the shape of the hemi combustion chamber. Talk to Steve Weiner he has much experience with these engines. I have installed oversize valves in a number of other engines not actually in a 3.6 but I have seen it referenced here and elsewhere.
If the bottom end has been apart before then there might already be aftermarket rod bolts. ARP and raceware can be reused up to 15 times ,factory bolts are one time use and not as strong and about the same money.

mrmoots

Hi Alex

Watching this with interest.

Shop around for Parts. I have found that though the US suppliers do appear cheaper, but when you factor in postage and sometimes import costs the UK suppliers are only pounds apart. Its also easier to return stuff should there be an issue with it. Dont forget your local Porsche Centre, I brought a load of seals the other day which worked out the same including VAT as a well know independent supplier ex VAT!!!!

Interetsing to see what else you find if the case has been apart before and someone has given some thought to modifiing it.

Good luck

Ross

falcor

love the pics, any chance of getting a hi-res of the last image?

ALEX P

Hi Johnsjmc, thanks for that, I'll drop Steve Weiner an email first thing in the new year, we're talking about the Rennsport Steve Weiner right?
The rod bolts were stock but will be replaced with ARP items. Rods also have marks where they have been linished or ground so I'm thinking someone has tried to balance the engine. I'll have to weigh them all with the pistons & see how close they were.

Mrmoots, wahey - a local boy!! Yeah, most parts on my list have a Porsche price, a Porsche specialist price and a Pelican price next to them then do a comparison to see what's worth getting where. Like you say, import tax can add an extra 25% so needs to be significantly cheaper in the US.

Falcor, I thought there were restrictions here for file size - I'll give it a go but if not then PM me your email address & I'll happily send you full size images. If there's anything specific, let me know.

Kuchar

Thank You for hi-res pics.