^^^^^^^^ Well said.

^^^^^100% Agree.

Uhh...I didn't read a single post suggesting that the Tuthill heads did not flow enough. Nor did I read a post criticizing them for what they flow. I only read posts that say Xtreme heads flow as much. Also, if you noted my post where I did comment that my Xtreme head flow more, I also commented that there was nothing that could be done with 2 valve heads to reduce the mass of the individual valves, springs, and retainers like is possible with the 4 valve heads.

The only cynicism I see in the thread is regarding the price and the overall lack of power. The cost is really high and the power numbers are puzzling. Both points of cynicism are indeed valid.

Well there is that one post on the porting which I don't really don't get.

Otherwise the vast majority of the thread is praising the redline and overall coolness of the product....

Neil. you're taking my comment too seriously. It's a bit of humor. No, I won't be a customer, but not because the ports aren't ported; but rather because the price makes gaining power that way extremely uneconomical compared to other ways to build power, such as turbocharging or supercharging.

I hope Swindon is successful at selling these heads--with or with out porting--because that might bring the price down. But right now, It looks to me like a very small market.

As for my car, have you checked out the prices of early '70's longhood cars in good condition?

And if you're thinking I'm just a cheap bastard, well, my other daily driver is a Ford GT.;)

Well said.


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Hello Neil - I was actually thinking of you when I saw the Swindon 4 valve kit - would like your review/opinion of it.

And if this kit was used on a 4 liter (assume a 102mm bore x 80mm stoke) what advantages would it provide over 'extreme' style heads with similar levels of flow. I'm thinking you would not rev a relatively long stroke engine like this to 11-12k.

Regards,
Steve

I have a lot of admiration and respect for those that do make something for these engines. Whether its a small part or a large complex part like these heads, thought and effort has gone into designing and making it.

I have not seen these parts other than the photos. From what I have read, it appears that the required performance was meet with the heads as presented. I'm sure the design includes the ability to go larger in the ports, valve sizes etc.

To answer your question, typically the upper rev limit is dictated by component weight, the engines ability to pump air and rotational forces. I do not think you would build an engine with a long stroke and rev it in the rev ranges discussed here. Typically these engines have smaller cylinder volumes, requiring them to rev higher to gain the HP, but have lower torque numbers.

You should out flow any 2V head with a 4V head, given the same build criteria. I think the largest Intake Valve that can be fitted to late heads is in the 53.00- 54.00mm diameter. Those have an area of approx 2200 sq mm. The biggest valve we currently fit to a 4V head Porsche head is 42.00mm. That would net you upwards of approx 2800 sq mm.

Better shaped ports, smaller stems and guides both would help the flow. I know the flow numbers for the best 2V heads and I know what our 4V heads flow. The 4V heads out flow the 2V heads by a lot. To be expected.

No disrespect to any 2V head sold. Its just simple physics. A small valved 4V head may not flow as much as a big valve 2V head, but I am suggesting that max sizes are included in this point.

Cost will be the limiting factor here. There is no way you can produce parts like this without expecting the costs to be high. Investment monies have to be recovered and profits made to stay in business. For what you get, 36K UK pounds is not bad at all. I know how much some high end 2V V8 heads go for.

Not sure who is really behind the heads, but I'm guessing Tuthill are the man with the plan and Swindon that has the means to execute it.
He says a couple of interesting things in the Chris Harris video:
* They over delivered on torque and under delivered on power, how that goes together with that revlimit I have no idea...
* The point of it all was to rev it to 11... so they could call it the 911k

Its a cool thing, if its reliable its a great engineering feat, but in his own words, its kind of a gimmick.

http://forums.pelicanparts.com/uploa...1699305761.jpg

A 911 that revs to 11k (or 12k actually) is a cool gimmick!

It goes to 11 though.

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Cooling is going to become an issue, it's air-cooled remember, with no intercooler. I think to get 350hp from a 3.1 and have it idle like a vw lupo they chose friendly cams.

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Hah, Hah!

Funny how things happen when you don't expect. Also, always good never to dish on another product.

I have 2 customer who have asked us to build an engine for them using this product.

I'm currently in the UK on business and the other day visited with Swindon PT. Got to see, feel and touch a system and go over all of my concerns etc. Came away prepared to use two on these two new projects.

Had a long visit with the owner of Swindon Power Trains and discussed many issues etc that I can see with this system. I had all of my concerns answered and are happy to move forward.

I look forward to reading about your results.

I totally agree. Builder of the first 912 Super powered by a 2.4 POLO.
I have been in emails back and forth about the potential of a modern day air cooled 4 CAM 4. Most POLO's are based on 993 and 964 parts. Maybe a long stroke 100X76.4x4 -2400 like my engine to 8k ish or the short stroke 100X66X4- 2073 to 85 to 9K. My engine has Ti valves and currently spins to 7200 without issues. 28K on the engine. Others with my spec twist them to 7500. I just think a contemporary air cooled 4 cam 4 would be cool. I have a friend with a 2.5 POLO with extreme heads making 250hp. The 4 cam 4 isn't about hp it's about trying something I've never seen before. I constantly reSee my car. I think of it as a 912 tub with endless possibilitys. It's on it's 3rd new spec configureation in 12 years.
I've really enjoyed reading this thread.

Has anyone seen the new Chris Harris video with the 993 with these heads? 4.0l. He mentions power anywhere between 360-380hp. That’s far less than I had expected, I was expecting in the 480-500 range

Thats less than normal 4.0 engines… Whats going on?

Don't get lost in quoted HP. AT the crank (calculated) or at the wheels (subject to different dynos and different opperators who can skew numbers)....

Baseline vs new engine is the only thing that matters. Measured on the same dyno......


Cheers

It's not crazy hp, granted. But is that build optimized for highest hp, or drivability, or ... ? I didn't listen to the whole video. Were more specific build details shared?

I did notice that it "only" revs to 8000. Quite a bit lower than the 11k RPM 3.0.

Isn’t the 911k 3.5l not 4.0…??