Valve Train Geometry with Cam., Beating a dead horse. |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Valve Train Geometry with Cam., Beating a dead horse. |
jaredmcginness |
Sep 8 2020, 01:14 PM
Post
#1
|
... Group: Members Posts: 502 Joined: 12-June 19 From: Baltimore Member No.: 23,209 Region Association: MidAtlantic Region |
Hey guys,
Making headway on my 1911 build (no pun intended). I have a few valve train questions. I've researched this a good bit the last few days and read a couple informative threads on here with some info (including one by @nditiz1 that went through a very similar issue) I am trying to not over complicate this, so my tiny brain can make sense. I was having an issue with my rockers, posted a photo of my heads on the 914world facebook group and got a great response from J. Raby with a lot of helpful info. It seems I bit off a bit more than I can chew with valve train geometry. (I understand he wrote a dissertation about Valve Geometry a number of years ago, but I cannot seem to find it.) It does not surprise me that the fella/shop who built my bottom end didn't go into too much detail about this. He basically laid the numbers out and said "If I have X amount of cam lift, we need to machine the heads for dual springs to achieve X amount of clearance. All there is too it." Maybe there is a bit more involved than that. (IMG:style_emoticons/default/smile.gif) Specs: -1911 (96x66mm) -51cc heads - fresh. -Scat c35 .495 Lift -Scat solid lifters -Scat dual HD springs, head machined. Recommended additional purchases by Jake: All available at Type4Store -911 Swivel Foot / Machine rockers .060 -Solid Spacer and shims. Byebye rocker spring. -8mm HD studs for strength. Question: With all of this added, it seems like the heads will be much more sound, and be able to handle the possibly over-sized lift on the cam. -I have seemingly completed a proper valve adjustment using the "Lobe per lobe" technique. (I.E. Intake 3 fully open, adjust opposite rockers on 1) I cannot find a lot of info on the right way to do an adjustment with a large cam. Thoughts? My TDC mark on the flywheel doesn't match up with the valves due to the ramp of this cam. (I think I understand that right) -Does this geometry affect my pushrods? They SEEM to be working fine at their length. Do I need "chromoly"? Is this for strength and + cut to size? I read all these threads on the Samba of guys running large cams with stock rods. (probably my engine builder posting that stuff (IMG:style_emoticons/default/biggrin.gif)) I would just like to do this right the first time. (IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-23209-1599592477.1.jpg) (IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-23209-1599592477.2.jpg) Sounds like this motor is going to run like scat if I don't wrap my head around this and study a bit more. I'm really proud of what I have learned so far building this 914. But I am just at the tip of the iceberg. Feel free to just tell me to use the search function. (IMG:style_emoticons/default/beerchug.gif) |
Lo-Fi Version | Time is now: 1st May 2024 - 06:35 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |