SMALL MOTOR MASTERS!!! Please help with my project.

[degreeoff1]

Hello all,
A kind man who is helping me with parts for my new 914-6 conversion engine suggested I ask the board for some help with my project.

Here is what I plan to use it for:


--1st is a fun in the sun (eat American muscle cars for lunch) car
--2nd is an auto X car with my beefed up suspension and 245/40s on all 4 corners.
--3d is a FAT (Friday at the track) and DE car ( Summit point our local track ).
--4th I love the sound of a high rev engine so a power band of 4-7.5k would be AWESOME........but I am but a mere student and ask all the Masters here who have BTDT for guidance??

Here is what I have:


I'm building a 2.4 on a '72 4r case with piston
squirter's, using a 70.4 crank and 2.2 S 84mm pistons and cylinders. The heads are 2.2E, stock, waiting to be done. The cams he has are S+ (that I intend to buy unless someone has a better idea of what would work). I also have a set of weber 40's that I would need to jet and fit venturis to.

Any suggestions as to how to do the case, and what sort of porting, valve springs, and what cams would be appropriate?
Any info on distributor curves and ignition would be good too?
I have a 2.2 E distributor , I am thinking of a Pertronix ignition and I already have an MSD box and coil.
Well that wraps it up from me, and I thank you in advance for your input.
Joshua C.

Here is my lil Pepe' (From Romancing the stone)

[camgrinder]

Find out the specs on the "S+" cams, and/or who made them.

[camgrinder]

Your freind faxed over the s+ specs. These cams are very close to a factory S cam.

Some ideas might be, do a little work to the E cylinder heads, and run a set of Solex cams. I offer what I call a "Mod-Solex" which I make using the Solex lobe profiles on a wide lobe centers (102 degrees). This makes a cam slightly hotter than a factory solex and not as peaky as the S cam.

[Scott Clarke]

I'd port the heads to 36mmI/35mmE. Distributor should be fine (it has the same advance as the S). Use a S rotor to obtain 7300 rpm limiter. As for the case, the oil bypass modification would be a good idea, as well as a SC or later oil pump. It would be wise to have the cylinder spigots squared, and the main bearing webs checked and drag honed or line bored if required. You can't go wrong with case savers, but you might be OK without them since you intend to use Biral cylinders.

-Scott

[degreeoff1]

Interesting info so far, Camgrinder, is a peaky cam not desirable? I thought that was a good thing for high rpms, I can say that I drive like a bat out of hell from zero to 80 (highway) and zero to what ever (intown)

Scott, would that amount of opening up not kill my bottom end? It is a street car with alterior motives after all.....the rev limiter on the dizzy I don't think I'll need as my MSD has the chip in it as well as my getting the adjustable rev limiter.

it was also brought to my attention that I may not have enough valve clearance with the above mentioned (S+) cam? any thoughts?

The "sponge" and 1st time 911 engine builder
Josh

[Scott Clarke]

Josh-
The S+ cam won't work well with E ports. The solex cam would work well with either E or S ports. If you are concerned about bottom end, then the S+ cams might not be the best choice, as noted by Camgrinder. At 2.4, you don't need to be as concerned about the S cam as you would with a smaller motor, but for street and autocross use you might consider a Solex or E cam. As for valve clearances, if you have S pistons you probably will be O.K., but should check at time of assembly.

E or Solex cam doesn't make much power above 6800 RPM (E ports will limit this regeardless of cam). S with bigger ports will get you to 7000+.

If you have an E distributor it likely has a mechanical rev limiter that will not send spartk to your plugs after 7100 RPM, regardless of the rest of your ignition system.

[degreeoff1]

Scott, thank you that makes sense, the bottom end that I refer to is about 4k+(-) rpm or above as I have already become accustomed to that "powerband kickoff point" with my current engine setup. The "rev limiter" rotor in a 911 dizzy is not like the one in my type 4 engine where I can get one without any?

Call me CRAZY, but I really love high RPM's

Thanks
Josh

[Scott Clarke]

Josh-
You can get a rotor without the rev limiter.

You should take a look at the factory power and torque curves for the 2.4S. The motor you are proposing would have a little more bottom end than the 2.4 S due to the higher compression of the 2.2S pistons. It does sound like you want the S cams.

[TimT]

You can get a rotor without the rev limiter.

yes just break the tab off the rotor, or use one of many Bosch rotors that work.... VW Audi BMW Porsche etc...

[camgrinder]

It depends on what type of track you are running on. Lots of tight corners and you will want a wide power band. With the E ports and the solex cams, the engine has a chance to make power from 3000 and up.
If you run the S cams you are giving up some valuable mid range performance. IF you go with a set of S heads, thats a different story. The S+ cams I saw the specs on will fit the factory S pistons without a problem.

[degreeoff1]

Hmmmm, what do you mean S heads? I thought they were all the same valves just different port size....If that is true can I not just have the heads opened up to that size. If I do, what is different about the story? Will the power band widen a bit?
Thanks
Josh

[Scott Clarke]

Yes, the only difference is port size. There has been much debate about port size that you can read about if you do a search. I think, based on what I have learned here, that for a 2.4 or larger motor E port sizes are a little small even for an E cam. Yes, there will likely be some degradation of bottom end with the larger ports, but if you want the thing to breath at 7000 RPM, E ports won't do. I decided that, even though it cost me a bunch of money I didn't have, that my short stroke 2.5 needed S ports even though, at least for the time being, I'll use E cams. I wish I coud tell you how that worked out, but the motor isn't together yet. Careful searches will reveal the experience of those that have used both sizes. Again, inspection of the factory's dyno sheets for 2.4 Es and Ss will tell the tale.

[degreeoff1]

Once again, it seems that many are in agreement that there are gains to be made in porting the heads. However, there is a consensus that it is difficult to achieve. this I do not understand. For example, the 1972/3 2.4S heads had 36mm intake and exhaust ports while the 2.4 E heads had 32mm intake and exhaust ports. Both had the same valves and the 2.4S was a perfectly streetable engine but has ports 26% larger.

Ran across this in a thread.....So I know the port sizes for the S's........ How hard is it to make an "E" head an"S" head? Even wayne's book list's this as a port size to use in my eng's future config..... I am so blind somtimes....

[camgrinder]

Call Ted Robinson at http://www.germanprecisioninc.com/
(408) 747-0728
I know he does this type of work.

[TimT]

I had Ted open up the ports on my '70 T heads. If you have a die drinder, you can save a few bucks by just having the machinist plunge the mill, then you finish cleaning up the heads yourself. The blending of the heads is an hourly fee, the machine work is a flat rate.

[Plavan]

Call me CRAZY, but I really love high RPM's

Thanks
Josh [/B][/QUOTE]

If you like high rev's grab a 66mm crank (CW or non CW), grab 90mm cylinders and 90mm pistons....The non CW crank will be easier to find and will rev up quicker. Some people are scared of them because they are not CW'ed. Us racers can tell you, do not worry about a thing. The bearings look the same on either a CW or non CW crank at teardown. Have you seen the size and number of the bearings in a 911 motor? . You have a beefed up 2.5L that you can zing. You will also need racing valve springs for those occasional "ooopsies"

-Chad

[degreeoff1]

Chad,
I appreciate the input there, I feel that this engine is already set in stone so far as "hard parts" are concerned as I already have the biggie's 2.2S P&C's and the crank rod and case as well as the E heads. I may just enjoy this whole engine building project so much that I may build another for a "pure" racecar and then that 2.5 L "shorty" sounds like the ticket. I would have to agree with you on the NON CW crank bit, my Type 4 VW is not CW'd and I spin the piss out of it with no issues and its on only 3 bearings!!! that 911 with 8 should certainly be able to handle the added stress of a 8k+ load (from a logic standpoint, NOT an exprerienced one)

One question for you though.......do the bigger P&C's not cause a lot more wear and tear due to their size? I know the 103mm P&C's that type 4 guy's use greatly decrease engine life.

BTW you guy's are great, I love the diversity of the responses.
Thanks
Josh

[Plavan]

We do not use those big of pistons so I could not give you a real answer... There really is not a reason to put bigger than 90mm pistons on a 66mm crank. There are so many other choices for better HP when it comes to Porsche (because of the other cranks sizes out there) those type 4 guys are limited... and the bearings are small.
But your right, 8 bearings..... nothing to worry about.

[Scott Clarke]

Josh-
No need to worry about those "big" pistons doing harm to your bottom end. The main journals are the same as those of the Carrera 3.0., 2.7RS, and 3.0 turbo, so your 2.5 poses no threat to them. The rod journals of the 66mm crank are LARGER in diameter than those for the motors mentioned above- no worries. Just make sure the case is properly preped for the head studs (use case savers and steel or ARP head studs).

The non-counterbalanced crank, as has been relayed, works for race engines. For a street engine, the reduction in vibration offered by the counterbalanced crank is appealing.