TheSamba.com :: View topic - 550 Spyder "4 cam"-like engine build up **NEW UPDA

Thu Dec 20, 2007 6:29 pm

I just looked on CB performance's website and that looks like the best solution. With a little extra thought I can see how you would get a two stage scavage pump and a single stage pressure pump with that set-up and it's not a budget breaker

Turk did you get a chance to measure the Type 4 cam bearing journal? When I get home I want to start machining my layshaft. I can order some stock from Mcmaster-Carr and it will be waiting there when I arrive home for Christmas.

Thu Dec 20, 2007 6:54 pm

Mark-

I don't have exact dimensions other than what I measured with a caliper. I imagine that that particular dimension is published somewhere, or someone migh know it off hand. Do you need the diameter of the journal that the bearing fits in or what diameter the layshaft should be?

I don't know how you plan to make it, but I would order stock which is approx. the size of the small/long portion of the shaft, mill a hole in 1/4in flat bar for the flange for the gear, weld it to the shaft and finish machine it from there.

Thu Dec 20, 2007 7:10 pm

I am looking for the Layshaft diameter, I think it's 25mm but I can't remember. I should carry a pocket notebook, I am not that young anymore . I was thinking I was going to machine the Camgear timing flange, slip the layshaft in and then weld it and remachine. I think we are saying the same thing.

Thu Dec 20, 2007 9:11 pm

OK, just checking. That's my real job.
It is tight thou.....

Sat Dec 22, 2007 6:45 am

Turk, why not modify the porsche oil pump? Comnnect to the rear of the layshaft ?

Sat Dec 22, 2007 1:59 pm

Mark-

I think I'm just going to stick with an oil pump in the stock location driven from the layshaft at the front as this will lessen the already extensive amount of re-working I'll have to do.

Btw, here are pictures of the cylinders that I purchased today. They are 911 84mm biral cylinders that will be bored to 85mm:

Sat Dec 22, 2007 6:38 pm

They look pretty good, after you bore them you might want to consider getting them Nikasal Coated anyway, you will find that it will still run cooler and allow for tighter clearances between the piston and cylinder. It looks like your moving along, by the way your heads are leaving the day after christmas I don't think they should take that long for you to recieve. I will send you an email about the postage.

Sun Dec 23, 2007 11:50 am

Mark-

Thanks, I look forward to receiving them. Let me know on postage. I may or may not get the cylinders coated, it looks like it would be about a $700 addition to the budget. We'll see. I am looking at 911 cylinder heads right now and I have a few questions to anyone that might know: I am looking at different 2.4L heads, the ones that will fit my cylinders, and while all the valves are the same at 46/40, the ports are different. Given that I am shooting for 115hp, should I go with the larger ports at 32/32 or will the smaller ports at 30/33 be adequate? Any suggestions would be helpful

Also, what is the RPM limit of most of the 911 valve springs?

Sun Dec 23, 2007 12:29 pm

I have the 32/32 just because that's what I bought on Ebay, I have opened my intake side up to 35mm and at some point I am going to increase the exhaust side but no big as exhaust velocity can't be diminished to much. I think it's not going to matter much both heads have plenty of room to open up. Even at 115 HP the better your engine breathes the better it's fuel economy and emissions.

The dual valve spring in the 2.4 should be good to 9k but you better get other opinions on that. I have had my 2.4 up to 9.9k before and it survived

Sun Dec 23, 2007 4:18 pm

Well I purchased my heads: 2.4L fuel injected 911 heads. This concludes the first round of "investment" in my engine.

Question: Does anyone know of an application for a full-circle engine bearing were the I.D. is around 1"? I am trying to find bearings to use for the camshafts in the heads. Let me know.

Happy holidays!

Sat Dec 29, 2007 3:01 pm

Can anyone think of a reason why I shouldn't use ball bearings for the camshafts in the heads? I know that motorcycles use them (modern ones) exclusively. I would still have to devise an oiling system for the cam lobes, but it would be a lot less work to not have to worry about camshaft bearings. Furthermore, hoe does oil get to the head in a 4 cam engine (Jake?)

Sat Dec 29, 2007 6:55 pm

Hey Turk, I thought most Motorcycles used needle bearings with cages. Take a look at the post Frallen just placed on Shoptalkforums.com it's pretty interesting

Sat Dec 29, 2007 8:58 pm

What post are you referring to? Also, I am incorrect in beleiving that you wouldn't have to have an oil system for needle bearings?

Sat Dec 29, 2007 9:35 pm

Turk u must have a lot of money and time on you hands for this venture. Good luck I would love to see it work.... :D

Sun Dec 30, 2007 8:16 am

I will attempt again to find and post a link
http://www.shoptalkforums.com/viewtopic.php?t=59308&postdays=0&postorder=asc&start=75

Sun Dec 30, 2007 9:58 am

Thanks Mark, btw-I still need to get the money to you for postage, I apologize for delaying that.

Sun Dec 30, 2007 12:01 pm

it's alright it's the holiday season, we can deal with during the week

Sat Jan 05, 2008 7:15 pm

Here's a post-holiday update for everyone:

I received my cylinder heads a few days ago. They are 911 2.4T units. The valves are 46/40 and the ports are 30/33 I believe. They should flow more than enough for my applications. I believe they flow somewhere around 150cfm?

Here is a picture of a quick "mock-up" of one half of the case just to size things up. Engine width will not be an issue using the shorter 911 cylinders. I will have to have custom pistons made with a higher pin height to accomadate what I believe will be stock length connecting rods.

One of the next big steps in this process is to design the camshaft retainers that will bolt to the top of the heads here. One issue I was worried about was the spacing between the valves and how that would effect the length of the camshaft. If it was too long, given the forces of the valve springs, it would be hard to have a smooth running camshaft. Fortunately, and intrestingly, the spacing between the 4 cam valves and the spacing of the valves for my engine will end up nearly identical. While this doesn't assure I smooth running camshaft, it quiets a few of my concerns.

These are pictures of original bevel/pinnion gears and an original camshaft from the 4 cam engine. Suprisingly, the gears are not that large. The bevel is about 2.5" in diameter and the pinnion is about 1" in diameter. These will be reversed engineerd in the next couple of days and then I'll have them quoted by a few gear manufacturers. The shafts are nearly the exact same diameter of a stock camshaft. I'll simply use type 1 thrust cam bearings in the cam retainers in the heads.

This last picture is out of focus but gives you a sense of the more than addequte clearance below the cetner main journal so thats nice!

Mon Jan 07, 2008 12:14 pm

Will the crank clear the gear? it looks tight

Mon Jan 07, 2008 3:38 pm

Yes, the counterweights won't hit as the gears will sit right below the center main. How is your project going Mark? Post some pictures! I will being machining the spacers for the case and my cylinders. Does anyone know the alloy used in the tye 4 case??