Hi guys.
I have my type 4 turbo stripped down to lower the comp.
That's now done.
While its in bits I could fit some dual valve springs
Do I even need dual valve springs.
I have type 1 hi rev singles at the moment. (CB).
I'm hoping I can get up to 20psi in to this motor.
Are the singles strong enough.
what happens if there not strong enough.(Symptoms).
Thanks for any input.
Dual valve springs on a turbo motor
- craigvwdude
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Re: Dual valve springs on a turbo motor
all depends on open/closed spring pressures. What kind of rpm's do you plan on spinning?
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Re: Dual valve springs on a turbo motor
Hi Craig. I'm gunna rev up to 5.5k . Can the boost actually open a closed valve.
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Re: Dual valve springs on a turbo motor
whats the spring preasure recomended for the cam you have
- Marc
- Moderator
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- Joined: Thu May 23, 2002 12:01 am
Re: Dual valve springs on a turbo motor
Good to see that you're thinking ahead, but unless your valvespring pressures are borderline already it's doubtful that the added boost pressure will necessitate taking them higher. Now, if you find that you're revving higher with the new combination it's possible that higher spring pressure may be needed, but I'd blame that on the RPM, not the boost pressure. Rather than delve into all of the considerations here, I'd ask you to first read this thread which debates the subject: http://www.eng-tips.com/viewthread.cfm?qid=379250GARRICK.CLARK wrote:Can the boost actually open a closed valve.
Simply put, the area of a circle is π × r squared...so even a 2" intake valve presents less than 3 square inches of surface area to the incoming charge - at 20 psi that might justify an increase in seat pressure of ~50 lbs, but it's not going to blow the valve open.
Personally I'm a proponent of using dual springs rather than singles just because of their inherent self-dampening properties and their resistance to harmonic effects - typically you can actually run lighter seat pressures with duals for the same max RPM capability - but if you've been happy with the performance of your singles it'd be hard to justify the expense of machining the heads for duals compared to simply adding ~.020" shims for a little "insurance"...DO check that you aren't close to coil bind first, though, with those Type I singles.
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Re: Dual valve springs on a turbo motor
Ok. been reading up on duals with turbo use and I think while engines apart I'll get the heads cut for the duals. I'm planning on just doing the inlets. the question is once the guide boss has been cut for duals is the spring seat area/guide boss still strong. I have just had new inlet guides fitted so they wont need doing for a while.
Just worried it might weaken them to a point they end up junk.
Just worried it might weaken them to a point they end up junk.
- Wally
- Posts: 4562
- Joined: Mon Oct 28, 2002 12:01 am
Re: Dual valve springs on a turbo motor
Do both. Springs weaken with heat...GARRICK.CLARK wrote:. I'm planning on just doing the inlets. the question is once the guide boss has been cut for duals is the spring seat area/guide boss still strong. I have just had new inlet guides fitted so they wont need doing for a while.
Just worried it might weaken them to a point they end up junk.
Guide boss will be strong enough, thousands have done it before you. Single springs will kill your engine, long before the smaller guide boss ever will.
T4T: 2,4ltr Type 4 Turbo engine, 10.58 1/4 mi
www.apfelbeck.nl
"Mine isn't turbo'd to make a slow engine fast, but to make a fast engine insane" - Chip Birks
www.apfelbeck.nl
"Mine isn't turbo'd to make a slow engine fast, but to make a fast engine insane" - Chip Birks
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- Joined: Fri Aug 26, 2011 10:01 am
Re: Dual valve springs on a turbo motor
Nice one Wally. I'll do both. hope fully after re shaping the bus chambers to a kidney shape, lowering the static comp, going back to flat tops and pressurising the float bowls I'll have this motor ripping tarmac.
- typ4
- Posts: 551
- Joined: Sat Mar 01, 2008 9:46 pm
Re: Dual valve springs on a turbo motor
What Wally said.
Also My turbo engine with 48x38, will float the valves at 10 lbs boost with a single spring. Bugpack I think. I bought GB duals and that was 200 hours ago , no issues.
Also My turbo engine with 48x38, will float the valves at 10 lbs boost with a single spring. Bugpack I think. I bought GB duals and that was 200 hours ago , no issues.