refresh951

I have been doing research for quite some time now on a high flow, low cost 951 cylinder solution. LR sell a stage III head that flows great but $1,619 with a core was quite a bit more than I wanted to spend. Nize did a custom high flow head a while back but the cost on that was also very high ($2,500). From my days of building Chevy's I just believed there must be a way to get a high flow solution that is much more affordable. So here is where I am at:

Bought a 951 8V head for $50 as all the valves were bent from a broken timing belt.

As I stated in another thread, through A LOT of research I found a company that manufactures SS 951 intake (and exhaust) valves in the OEM size (45mm) but also in +1 (46mm), +2 (47mm), and +3 (48mm) for $26/each! These valves have the OEM 9mm stems, are OEM length, have OEM keeper grooves, and are undercut. As many of you know 2.7L intake valves (47mm) are hard to find and cost about $130/each new. The company that sells the valves is SI Valves:

http://www.sivalves.com/index.html

The valves are not listed on their website but they have them and they have them in stock. I ordered the valves Wednesday and received them today. Here is a few pictures.

Notice the undercut to improve flow. The orginal valve was not undercut.



The original 45mm valve head (left) and the VTM 47mm head (right)



This solution will be significantly cheaper as only the intake seats will need to be replaced. The OEM guides, springs, and retainers can all be used and again the intake valves are only $26/each. If custom or Chevy valves are used custom guides would also be necessarily but in this case that is not required. I originally tried to purchase custom valves from Ferrea but they do not offer custom valves in 9mm stems as they do not have 9mm blanks. Therefore I would have been forced to go with something like 11/32 stems with custom guides which would be A LOT more expensive.

I have been doing a ton of research on porting as my plan is to do the porting on the intake ports myself. A machinist with 30 years experience also gave me a lot of good advice. I was able to purchase the necessary equipment as shown below at Harbor Freight for about $50. I will post final pictures of the porting by Sunday. The porting will be similar to the pictures shown here:

http://www.aftracingheads.com/Project9.html




Lindsey has great info and flow data for different modified heads here:

http://www.lindseyracing.com/LR/Parts/LRHEADS.html

I will be flow testing my design under the same conditions as LR to see how it compares. I should have these flow number in 1-2 weeks and will keep this thread updated.

Zeff

Keep us posted.

Reimu

Definitely looking forward to seeing what it does on a bench. I've got a n/a head laying around full of bent valves.. hmm...

Really been liking the new life that's been breathed into the 944 world over the last year or so, lot of great low cost stuff.

black944 turbo

Keep up the good work. I love how there are so many people now breaking away from all of this high dollar its a "Porsche" stuff. Very cool.

CyCloNe!

sweet keep it coming sir!

V2Rocket

definitely watching this..have a spare head upstairs...maybe you could offer a service

Paulyy

i am so watching this thread!

refresh951

Not really planning any kind of service but I do plan to document everything and will be posting it here. I really would like to contribute something useful back to the community as so many here have helped me.

Thanks. Blown944's Hybrid motor is a pretty impressive demonstration of getting around the "Porsche Tax".

I attribute a lot of the resurgence to Rogue and the M Tune. Affordable True MAF has opened up a lot of possibilities.

Thanks mate!

Paulyy

are you going to do a full write up on this, because if it works out good, my dad might have his machine shop back next year and might be able to do this!

Adonay

Great thread. Will find my self a NA head to hack up and install 48mm valves in :-D

TonyG

Should have used a 8V NA head.

And you'll need more than 2mm larger valves to make it a good flowing head.

I made with stock valve sizes on a 2.5L engine with a ported 8V NA head 400RWHP at "only" 17psi (with the rest of the top end flowing well).

TonyG

refresh951

Thanks for the input. That is impressive power for a 2.5L.

I guess good is a relative term. I want to stick with the ceramic liners. The exhaust port flows better than the intake port on the stock 951 head. I think this modified head intake will flow about 30% more at 28" H2O vacuum. I will be flow testing the head to see how it performs. This is my first attempt of probably several. Anyway, the valves are the key to this thread.

refresh951

Got a few hours in my shop this afternoon and made some progress on the porting.



Here is of picture of the tools I have been using, all from Harbor Freight.



Intake port before pictures.



Intake port after pictures. (note: all valve guides will be replaced)

lart951

are you going to polish those ports to a mirror finish?

refresh951

The intake ports will be close to mirror (EDIT: smooth) but not mirror when completed.