 dual valve springs, max. RPM? |
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| SirAndy |
  Oct 4 2005, 11:22 AM
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#1
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Resident German  Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California  |
ok, i'd like to get an educated guess as to what my approx. max. RPM would be with a 2056 with heavy duty dual valve springs, solid rocker spacers, 911 swivels, slightly bigger valves, 9:1 compression ...
as far as i can tell, the components used are good quality. i had the rev. limiter set to 6000 rpm which seemed to be on the safe side. only hit the limiter 2 or 3 times during a AX. always ran plenty of oil, got a tuna can on the motor. no lean running ... the motor always felt like it wanted to pull past 6000 and wasn't done with it's peak power yet so i'm thinking there has to be more ... anyone who can give me a hint as to where the redline could be? ballpark? (IMG:http://www.914world.com/bbs2/html/emoticons/idea.gif) Andy |
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Replies(1 - 19)
| nebreitling |
Oct 4 2005, 11:54 AM
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#2
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Member Emeritus Group: Members Posts: 3,314 Joined: 26-March 03 From: San Francisco Member No.: 478 |
cam, rods, pushrods?
i've heard mixed things about the dual valve springs -- one engine builder mentioned to me that they are too much for anything but the most built engine... in anycase, they wouldn't be weakest link, i've heard of them going to 7500+. for my engine (pumped up 2056), i try to keep it at or under 6000 also. but 6200 isn't too uncommon. it sure wants to pull past that... my uneducated guess would be that 6k on that engine would be quite conservative. did something happen, andy? |
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| SirAndy |
Oct 4 2005, 12:08 PM
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#3
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
yeah, some stuff came apart that wasn't supposed to. no details yet, but i do know the head is cracked ... engine was supposed to come out yesterday, but that didn't happen so i'm hoping for today. as soon as the heads are off, i'll know more ... (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif) Andy |
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| nebreitling |
Oct 4 2005, 12:17 PM
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#4
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Member Emeritus Group: Members Posts: 3,314 Joined: 26-March 03 From: San Francisco Member No.: 478 |
oh, i'm really sorry to hear that. do let me know if i can help drop the engine or something -- i'm just across the bay now.
do you think this could have been a lurking problem developed from the timing issues you had early on? (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/drunk.gif) |
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| SirAndy |
Oct 4 2005, 12:57 PM
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#5
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
everything is possible at this point. i'm actually kind of surprised the engine lasted that long (5000 miles, wooohoooo) ... after all the crap that was wrong with it from the get-go... (IMG:http://www.914world.com/bbs2/html/emoticons/sad2.gif) Andy |
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| Brad Roberts |
Oct 4 2005, 01:17 PM
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#6
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914 Freak! Group: Members Posts: 19,148 Joined: 23-December 02 Member No.: 8 Region Association: None |
I'm yelling this across the shop: FUCK!!!!!!!!!
What a GD pain in the ass.. Let me know if you need another set of heads. I have a set of 2.0's out right now that will be done by end of next week. Double springs: 7500+ typically. The whole idea with them is: keep the valves from floating at high RPM. The issue is: the cam. If the cam isnt designed to make power that high... they are worthless. B |
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| SirAndy |
Oct 4 2005, 01:24 PM
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#7
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
euro "H" race cam ... thanks for the offer, i might take you up on it! i just hope the bottom end is still ok ... (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif) Andy |
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| Tom Perso |
Oct 4 2005, 02:10 PM
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#8
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Crazy from the Cold... Group: Members Posts: 647 Joined: 8-August 03 From: Kalamazoo, MI Member No.: 1,003 |
Duals should be OK up to 7500rpm... Not much more though.
I'd say, for you... no past 6500 - is it still a stock, non-counterweighted crank? Stock rods? Sorry to hear about your luck though. No good. Tom |
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| SirAndy |
Oct 4 2005, 02:16 PM
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#9
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
haha, yeah, i hear you ... no idea on the internals, it's Zeke's old race motor that was freshly rebuilt. i guess i just tear it down to be sure once and for all ... (IMG:http://www.914world.com/bbs2/html/emoticons/rolleyes.gif) Andy |
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| URY914 |
Oct 4 2005, 02:19 PM
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#10
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I built the lightest 914 in the history of mankind. Group: Members Posts: 121,116 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
What about the push rods?
Stock or CoMo? |
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| Brando |
Oct 4 2005, 02:30 PM
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#11
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BUY MY SPARE KIDNEY!!! Group: Members Posts: 3,935 Joined: 29-August 04 From: Santa Ana, CA Member No.: 2,648 Region Association: Southern California |
One thing I've seen is bent pushrods (old stock) when people used too-strong of springs with their double-spring setup. I think there's a way you can calculate how much pressure the springs need to exert onto the valve to keep it closed or keep it from floating with your cam.
For instance, I called FAT Performance (they'll be doing my double-spring job) and they were able to crunch some numbers with my cam stats (Webcam 86b +5ยบ exhaust duration) also what pair of springs I needed to prevent valve float at 7500rpms. Only big problem I see is... bent pushrods! Does someone make beefier, properly machined ones? |
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| URY914 |
Oct 4 2005, 02:33 PM
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#12
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I built the lightest 914 in the history of mankind. Group: Members Posts: 121,116 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
Jake sells Chrome Moly push rods blanks.
You'll need to determine the correct length. (As a matter of fact, I think I'll be doing this tonight!) Paul |
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| Jake Raby |
Oct 4 2005, 02:44 PM
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#13
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
It is absolutely impossible to crunch the numbers relating to the point one will attain valve float without considering the weight of the reciprocating valvetrain mass!
Lightweight components need less valve spring tension.. I run dual springs anytime we are running .485 lift+ We get further and further away from heavy springs every time we build another R&D engine.... Len and I are now running 8500 RPM with our featherwight valve train and a SINGLE valve spring... granted its not an off the shelf single spring and its retainer weighs less than 5 grams! BTW- The biggest mistake made is running a dual spring or any performance spring with a stock retainer- the stock retainer absolutely sucks! I have all the trick valvetrain stuff on my site except the featherweight arrangement, those are only available on full RAT engines. |
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| Joe Ricard |
Oct 4 2005, 03:57 PM
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#14
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CUMONIWANNARACEU Group: Members Posts: 6,811 Joined: 5-January 03 From: Gautier, MS Member No.: 92 |
Dang Jake, That's about one ______ Avatar!!!! (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)
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| Jake Raby |
Oct 4 2005, 05:51 PM
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#15
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
.And thats not even my war face......
People have been pissing me off lately. |
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| Aaron Cox |
Oct 4 2005, 05:55 PM
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#16
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
brando.. cromo pushrods
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| cha914 |
Oct 4 2005, 05:58 PM
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#17
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MUSR 8 - 5lug conversion done wed - drive 500miles thrus Group: Members Posts: 739 Joined: 31-December 02 From: Austin, TX Member No.: 63 |
My Raby 2056, was tested on the dyno up to 7300, by the man himself (Hi Jake (IMG:http://www.914world.com/bbs2/html/emoticons/wavey.gif)) - ... peak power is at 6300 though.
I have hit 7k in second gear on an autox course, and it woulda kept on spinning if I hadn't noticed, I try to keep my shifts at 6K when I am having fun though. Motor has Cromo pushrods and dual valve springs, and stock rockers with swivel feet. Tony |
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| Aaron Cox |
Oct 4 2005, 06:02 PM
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#18
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
andy - what do you think happened? can you describe it? at what rpm etc...
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| SirAndy |
Oct 4 2005, 06:07 PM
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#19
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Resident German Group: Admin Posts: 41,688 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
just cruising down the freeway on my way back from work. wasn't pushing it at all. all the sudden i lost 2 cylinders (both on drivers side), car didn't idle and died. turned up the idle and limped home ... i'll know more soon but you can see the head is cracked and one sparkplug is toast ... (IMG:http://www.914world.com/bbs2/html/emoticons/huh.gif) Andy |
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| Jake Raby |
Oct 4 2005, 06:22 PM
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#20
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
I bet you didn't have a CHT gauge....
BUY FRIGGIN GAUGES!!!!!!!!!!! Heads don't crack without getting overheated! Andy, sounds like it's time to do some trading- you know what I need. |
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