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Location:
sunny coast, qld
Registered:
October 2002
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1jz valve springs
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Thu, 20 January 2005 08:08
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Does anyone know what the valve springs are rated on in a 1jz?
My gf's dad was having a look at my engine yesterday (who works on drag cars) and said that in his car they were 70lbs stock and he now has 140lb ones. They use 420lb ones in the doorslammers.
So I was just wondering if anyone knew what the 1jz valves are stock as he was explaining to me why they should be very strong. He called it valve bounce. Is this a possiblity in these engines? He works on ford v8's so there is obviously a different setup there.
thanks in advance
Chris
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Location:
Sydney
Registered:
March 2003
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Re: 1jz valve springs
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Thu, 20 January 2005 09:26
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Remember, a JZ motor runs smaller valves than a top fueler and 2 valve big block so it doesn't require the anywhere near the kind of seat pressures.
Valve bounce can/will occur if you rev it hard enough, boost also plays a factor in this too.
I believe the stock 2J valve springs are around 50lbs from memory, I'd be willing to say the 1J's are roughly the same.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: 1jz valve springs
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Thu, 20 January 2005 11:49
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For a stock engine, stocky springs are fine. However, if you go bigger on cams, revs and/or boost, then upsize the springs. They're not actually all that expensive, either, and can sometimes improve an engine that you didn't think had a problem in the first place.
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Location:
Brisbane
Registered:
May 2002
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Re: 1jz valve springs
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Thu, 20 January 2005 12:07
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Old-school dinosaur V8's have OHV drivetrains, which have lots of big heavy components bouncing around at high speed (pushrods, rockers, large valves etc). You need big heavy springs to keep all of this under control, especially if you want to rev it. A modern engine like the JZ series on the other hand has a DOHC multivalve setup, ie small light valves, no pushrods, no rockers, cam directly over the valves - thus they can get away with much lighter springs and still rev like there's no tomorrow.
So as you can see, any comparison between a 1JZ valvespring and a Ford V8 valvespring is pretty silly. Apples and oranges!
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Location:
Montrose, VIC
Registered:
May 2002
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Re: 1jz valve springs
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Thu, 20 January 2005 12:10
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Yes, the rates are a lot lighter, and they cope much better, however when you increase the stress on them, they do still encounter problems.
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Location:
Brisbane
Registered:
May 2002
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Re: 1jz valve springs
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Thu, 20 January 2005 12:27
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Naturally... that applies to anything really!
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: 1jz valve springs
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Thu, 20 January 2005 12:35
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2JZ ones are 42-46 lb/ft at installed height.
Remember that if you intend upping the boost (let's make it a silly number like 30 psi), you will significantly reduce the seated pressure of the valve when at full boost. In this setting, upping the seated valve tension is a must.
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Location:
sunny coast, qld
Registered:
October 2002
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Re: 1jz valve springs
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Thu, 20 January 2005 12:58
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Thanks for that info.
So while using a turbo rated at a maximum of 650hp with stock cams, would it be a good idea to get stronger valve springs. Or shall I wait until I get cams?
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Location:
tallahassee FL usOFa
Registered:
May 2002
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Re: 1jz valve springs
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Thu, 20 January 2005 15:11
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i think he's F'ng with you, and i'd stay away from anyone that reccommends stronger springs for a stock cammed engine, or a modified engine that hasn't experienced valve float, and/or hammered & strange wear marks from bouncing on the down side of the cam.
it needs the weakest spring possible, that will keep the follower/lifter in contact with the cam at redline + 500 to 1000 revs more for missed shifts & safety.
heavy springs = less power if they aren't necessary.
turn your cam over by hand, and then imagine the HP it takes to do that at 7000 rpm!!!
i don't know anything about turbos.
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Location:
sunny coast, qld
Registered:
October 2002
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Re: 1jz valve springs
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Fri, 21 January 2005 03:41
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So if I were to take the cam covers off every now and again and just check that the cams don't have wear marks on them, then the stock ones will suffice?
BTW I don't think he is doing it on purpose, but simply has never worked on newer tech DOHC cars.
thanks
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Location:
tallahassee FL usOFa
Registered:
May 2002
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Re: 1jz valve springs
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Fri, 21 January 2005 06:11
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oops, I'm sorry. he's probably used test springs just a little larger then yours for a dummy setup/dry run to check out valve train geometry & timing. all the extra weight stuff in those big ohv 2 valve things really ups the pressure needed.
also i'm sorry giving the impression about having a cam turning 7,000 rpm when it's only half speed - 3500.
if it's doing much of any bouncing/hopping, it'll be noticable, expecially with a magnifing glass. don't get carried away, it won't look perfect. even when it isn't floating or bouncing, there is still a difference in pressure between the opening & closing side, like comparing your weight going up & down in a fast elevator. every thing that revs has a different wear pattern then a daily driver will have.
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