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#555
by
Toby
on 18 Nov, 2016 12:10
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How do you know valve is being blown open? Just curious... nice to hear you having fun 
You really wouldn't know for sure until disassembly and saw valve imprints. Some signs would be after a certain boost it would stop raising as fast as it did and not as good of performance as it should have. It really comes down to math and the psi of the boost vs valve diameter vs spring
Ok, What kind of "valve impressions" do you think you will see with the mythical "valves blown open" problem? Try putting 35 psi on the back of the valves and see if you can blow them open. If the valve and seat are in good shape you won't see any leakage. I used to check valve seal this way and never saw any leakage as long as the valve and seat were OK. This was head upside down on the bench with the combustion chamber full of solvent.
Valve float at high RPMs is a much more likely problem. If the valves really were being "blown open" the seats are not going to look any different than if the were not. If they are floating and crashing back down on the seat with solid lifters, that will be visible. With HLAs nothing should be visible since the HLAs will hold the valve off the seat until they bleed down.
Are you using a hydro or mechanical head? Valve float in a head with hydraulic lash adjusters are much more prone to valve float issues. Valve float that would go unnoticed in a solid lifter application will kill performance because the lash adjusters (lifters) take up the slack on even the tiniest amount of valve float and then hold the valve open the HLA bleeds down.
I had this happen on a Paxton blown 340 Mopar in my youth. It would pull like a freight train in first gear until the got into float near redline. It then nosed over in second and ran like a 2 bbl. Let it idle for a minute or two and it was fine until the next time it got close to redline.
I am not saying that pressure on the back of the valve does not lessen the effective valve spring pressure. Just that the effect is unnoticeable until the intake valve is almost completely closed. Once the cylinder pressure comes up slightly the effect will be negated and the valve will close. It would only be held open if the pressure behind the intake valve is significantly higher than on the chamber side, so no leakage out of the CC is possible. It will act like an old atmospheric intake setup in the worst case. The worst thing that could happen would be that overlap would be extended in any situation where the turbo could still cram in more air. So where is the downside?
If you are running wimpy valve springs on a hydro head, a lot of boost will get you into hydraulic valve float at a lower RPM. The solution? Do like we have always done when dealing with valve float: ditch the wimpy springs and the hydraulic lash adjusters.
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#556
by
RabbitJockey
on 21 Nov, 2016 08:30
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if anything it would be the exhaust valves because there is a lot more pressure in the exhaust manifold, i don't think it would blow them open as much as it could it delay them from closing, and if it holds them open too long on a hydraulic head the lifters will adjust and hold the valve open more until they adjust back down, it does happen and a few people have reported it on here.
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#557
by
libbydiesel
on 21 Nov, 2016 11:55
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I'm just trying to imagine with physics... Any time the valve is open, the pressure on either side of the valve will be very close to equal. With the pressure close to equal on either side of the valve, the valve will close if the cam is not pushing it open and it will stay closed until either the cam pushes it open OR there is significantly more pressure on the back of the valve than there is on the front.
Thinking about intake valves if the intake pressure is very high... On the intake stroke, the pressure in the cylinder will be lower, but the valve IS open by the cam. Near the start of the compression stroke, the pressure inside the cylinder will be the same as the pressure in the intake manifold or darn close. Because the pressure is normal, the cam and valve spring will close the valve. The pressure in the cylinder will then rise abruptly and vastly overtake the intake pressure so there is no chance of the intake valve opening during the compression stroke or the power stroke. On the exhaust stroke, the cylinder pressure will be higher than the exhaust manifold pressure and definitely higher than the intake manifold pressure so no chance of the intake valve opening during the exhaust stroke. Ok... intake valves cannot be blown open.
Thinking about the exhaust valves when the exhaust manifold pressure is high. During the power stroke, obviously cylinder pressure is much higher than EMP - exhaust valves will not be able to open. On the exhaust stroke, the cylinder pressure will normalize with the exhaust manifold pressure - exhaust valve is open by design. On the intake stroke, if the exhaust manifold pressure is higher than the intake pressure by enough of a difference to overcome the exhaust valve springs, some exhaust will leak into the cylinders. On the compression stroke, the cylinder pressure will quickly overtake the exhaust manifold pressure and keep the exhaust closed through to the end of the power stroke when it opens by design.
My conclusion... intake valves cannot be 'blown open', exhaust valves could possibly be blown open on the intake stroke if the difference between intake and exhaust manifold pressures is very high, and there is not any situation of valves being blown open that can result in piston/valve contact.
This is just my attempt at a logical assessment based on physics and it could certainly be wrong due to my missing some key factor. At this point, though, I think it's solid thinking.
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#558
by
RabbitJockey
on 22 Nov, 2016 11:32
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i agree libby, definitely not an intake side issue, or a contact issue except maybe in extreme cases, but there is the possibility for hydraulic lifters to pump and cause compressor leakage out the exhaust valves, causing white smoke and a lack of power, which is what a few people have reported, but the cars recovered fine.
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#559
by
theman53
on 20 Feb, 2017 09:48
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I am putting this here as I seem to have lost what specs my turbo has...
Holset HE221W
Cummins ISBe 3.9 and ISF 2.8, Brazilian Ford F-250 (2006-current)
Billet compressor wheel
5cm, 6cm, 7cm and 8.5cm turbine housing options
Identical to the HX27 except for having a billet aluminum compressor wheel
Compressor
Exducer: 60mm
Inducer: 43.5mm
12 blades
52 trim
Turbine
Inducer: 53mm
Exducer: 45.7mm
11 blades
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#560
by
Mr.Captain
on 19 Jan, 2018 15:27
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trying to bolt up my 221 turbo, what manifold setup did u use? I tried looking through the post but the photobucket pics wont load.
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#561
by
Dakotakid
on 19 Jan, 2018 23:24
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You'll need to private message Lucas.
I don't believe he comes around much any more.
This engine proved to be a bit much to have sitting in front of an O2O trans.
This engine is now waiting to go into his Dukes of Hazzard Jeep. Kea kea kea kea..........
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#562
by
theman53
on 28 Jan, 2018 10:10
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I don't get on as much as I used to. There is a T25 flange turbo exhaust manifold on ebay for the 8v vw's, that is what I used. They also make a T3 flange one for the 8v vw. The holset I used is T25, it was approx. 100.00 when I bought it but the last I saw they were about 175.00 now, the T3 were much cheaper. Don't ask me why.
Yes, this engine destroyed my clutchnet red clutch and broke the bolts in the cv of the drivers side 100mm cv which threw the cv into the cryo treated ags trans and knocked a hole in the case...if someone wants over 1,000 dollar cryo treated arp bolt kit trans I would sell it pretty reasonable, just needs a new case or this one welded.
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#563
by
libbydiesel
on 28 Jan, 2018 16:49
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Ugh. I didn't look back and check but did you pass 40,000 miles on it? :-P
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#564
by
theman53
on 12 Feb, 2018 22:10
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Engine is still going strong with about 10,000 miles on it...everything else doesn't like it
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#565
by
theman53
on 29 Aug, 2018 22:15
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so, I blew up the trans last year. I am still tinkering with the Jeep and I might just use this engine for the Jeep project. I haven't been on in months, I might not for a while. This was such a fun engine. If I keep an older VW I will convert it to O2J so the power isn't an issue for the trans