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914World.com _ 914World Garage _ dual valve springs, max. RPM?

Posted by: SirAndy Oct 4 2005, 11:22 AM

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?
Andy

Posted by: nebreitling Oct 4 2005, 11:54 AM

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?

Posted by: SirAndy Oct 4 2005, 12:08 PM

QUOTE (nebreitling @ Oct 4 2005, 10:54 AM)
did something happen, andy?

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 ...

Andy

Posted by: nebreitling Oct 4 2005, 12:17 PM

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?

Posted by: SirAndy Oct 4 2005, 12:57 PM

QUOTE (nebreitling @ Oct 4 2005, 11:17 AM)
do you think this could have been a lurking problem developed from the timing issues you had early on?

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...
Andy

Posted by: Brad Roberts Oct 4 2005, 01:17 PM

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

Posted by: SirAndy Oct 4 2005, 01:24 PM

QUOTE (Brad Roberts @ Oct 4 2005, 12:17 PM)
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.

euro "H" race cam ...

thanks for the offer, i might take you up on it!

i just hope the bottom end is still ok ...
Andy

Posted by: Tom Perso Oct 4 2005, 02:10 PM

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

Posted by: SirAndy Oct 4 2005, 02:16 PM

QUOTE (Tom Perso @ Oct 4 2005, 01:10 PM)
I'd say, for you... no past 6500 - is it still a stock, non-counterweighted crank? Stock rods?

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 ...
Andy

Posted by: URY914 Oct 4 2005, 02:19 PM

What about the push rods?

Stock or CoMo?

Posted by: Brando Oct 4 2005, 02:30 PM

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 +5º 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?

Posted by: URY914 Oct 4 2005, 02:33 PM

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

Posted by: Jake Raby Oct 4 2005, 02:44 PM

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.

Posted by: Joe Ricard Oct 4 2005, 03:57 PM

Dang Jake, That's about one ______ Avatar!!!!

Posted by: Jake Raby Oct 4 2005, 05:51 PM

.And thats not even my war face......

People have been pissing me off lately.

Posted by: Aaron Cox Oct 4 2005, 05:55 PM

brando.. cromo pushrods

Posted by: cha914 Oct 4 2005, 05:58 PM

My Raby 2056, was tested on the dyno up to 7300, by the man himself (Hi Jake ) - ... 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

Posted by: Aaron Cox Oct 4 2005, 06:02 PM

andy - what do you think happened? can you describe it? at what rpm etc...

Posted by: SirAndy Oct 4 2005, 06:07 PM

QUOTE (Aaron Cox @ Oct 4 2005, 05:02 PM)
andy - what do you think happened? can you describe it? at what rpm etc...

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 ...
Andy

Posted by: Jake Raby Oct 4 2005, 06:22 PM

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.

Posted by: Aaron Cox Oct 4 2005, 06:24 PM

QUOTE (Jake Raby @ Oct 4 2005, 05:22 PM)
Andy, sounds like it's time to do some trading- you know what I need.

The Plot: Raby blew up your motor to get you to trade something.

Posted by: Jake Raby Oct 4 2005, 06:29 PM

If I were that powerful I'd blow up a certain persons entire garage!

Posted by: Aaron Cox Oct 4 2005, 06:30 PM

QUOTE (Jake Raby @ Oct 4 2005, 05:29 PM)
If I were that powerful I'd blow up a certain persons entire garage!

Posted by: DNHunt Oct 4 2005, 06:49 PM

I smell . My money's on Jake in that one.

Posted by: SirAndy Oct 4 2005, 07:48 PM

QUOTE (Jake Raby @ Oct 4 2005, 05:22 PM)
Andy, sounds like it's time to do some trading- you know what I need.

i certainly keep that in mind. i thought you had dropped the ball after you didn't get back to me ...

Andy

Posted by: Jake Raby Oct 4 2005, 07:52 PM

No, been really busy...

And the $$ I sent to you ended up going out with no postage (damn stamp came off) and was sent back to me...

I still need the help.