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16valve piston-valve clearance

ZVOLV

<Master Tech>
Joined
Nov 19, 2002
Location
California
OK. So I got my timing belt tensioned on my 16v head on the b230 block. I put play-doh on the top of the pistons and spun the crank around with the timing belt tight. No contact between the valve and the piston. However, it was close.

My question is: do the lifters need to be full of oil for my test to be valid?

EDIT- if you dont feel like reading all the crap below: i measured clearances as little as 1mm between the valve and piston. That was with cold unpressurized lifters. The 16v pistons have 3 and 4mm deep cuts in them. My conclusion is that there is NOT enough clearance to run without cuts. EDIT
 
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Another semi-crude way to test would just be to take the head off and turn it upside down. Turn the camshaft and watch the valves, then measure how much above the head surface they protrude. You'd also need to know the squish clearance of your shortblock.

Just for comparison, Stealthfti told me that on an SOHC head an A-cam would make the valves stick out past the deck about .020". And a compressed headgasket is I think .047".

Good luck figuring this out, it's interesting!

John
 
The Aspirator said:
Another semi-crude way to test would just be to take the head off and turn it upside down. Turn the camshaft and watch the valves, then measure how much above the head surface they protrude. You'd also need to know the squish clearance of your shortblock.

I was going to do that, but i figured in real life the valve will never be fully open when the piston is at TDC. However, it would tell me if I had an interferance engine, but I know that it already is.
 
I could pressurize the oil pump by spinning the aux shaft with a drill, but that would require the timing belt to be removed and then I couldnt do my clearance test.

If I pressurize the lifters, wont they just go flat again when I remove the oil pressure?

Anybody know where to get solid lifters for the b234? The 8v lifters are too fat.
 
I am assuming the b204 also used hydraulics...? Well, they are at least listed as such in that link. I just remember a euro guy say that they cut the crap with the hydrualics and go solid, but i dont know where to get em.
 
ClayTop.jpg

ClayFront.jpg



EngineTensioned.jpg
 
I dont know to many specifics about volvo engones but can probably give some general pointers. I know that you need more than for the valves to just barely clear. The valve stems will expand with heat and strain, probably more than you might think. In the pictures it looked like you had pretty much clearance (~3mm) but this is hard to see just from pics. I did this exact thing on a porsche engine this summer and tried playdoh but found that silly putty is much better because it isnt as soft so you can actually take it of the pistons and measure it. Also I dont know about the lifters in the volvo head but I would think that if they are hydraulic that with no oil press this test doesnt really mean to much (unless you know how much the lifters expand with pressure.). Would it be possible to get pistons with valve cut outs, arent these usually needed on interference type engines?

sorry if you read this and it didnt really help you. I just wanted to share my bit of knowledge.
 
I am sorry that the pics are kinda poor but those are the only pics I have right now. I wanted clay, but i the store only had play-doh.

I have a set of 16v non turbo pistons with valve cuts, but they are 10.0 compression which i dont want to run since I run 91 octane pump gas.

The test revealed that the valves did not hit the pistons, but it is VERY close. That is why I posted the pics so people could critique my tests and give feedback.

I need to know if the valves are going to get closer to the pistons because of reasons like heat expansion, lifters filling with oil, or anything else.

The non turbo pistons have cuts in them, so they are there for a reason....

EDIT- here is a link to my pics that show the NA pistons with the valve cuts in them. Those suckers are deep. EDIT http://forums.turbobricks.com/showthread.php?t=26597

I REALLY cant afford 16 bent valves so I need to be 100% sure those valves arent going to hit.
 
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OK, so i did another test with the playdoh. This time I pulled the playdoh off the piston and cut it in half so I could look at the cross-section. I took pics, but i cant focus in well enough to show you guys. The valve gets within 2 mm of the piston. Is this enough clearance?

EDIT- According to my manual shims for the 8 valve come in a range from 3.30-4.50mm so from this info I would imagine the most a lifter will affect the lift value is about 1mm. Since I have about 2mm to work with I should be in the clear, right? EDIT

clayOnRuler.jpg
 
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Why not get the low comp pistons cut. My shop said $60-$80. You will probably already have them out to re-ring them right? I can give you the specs on mine or just take the 16V piston to the shop so they can compare. The bent valve problem is bigger than an $80 headache. You will probably need more dish anyway because of the chamber size differences. Depending on what compression you are trying to run, of course.
 
Don't assume that because the adjustment shims only come in a range covering 1mm, that the lifter will only affect that same 1mm. It could be lots more.

There's lots of stories of people setting up their hydraulic lifters cold and dry, and then starting the engine to only have it run for about 15 seconds and then when the lifters pump up, it shuts off.

I think the guideline is .050" minimum clearance with solid lifters - I'd go for at least 0.100" with hydraulics. At high RPMs you could still float or bounce the valves, or you could pump up the lifters, or you could miss a shift... Better to be safe than sorry. Cut the pistons, but don't cut so far that the top ring land gets thinner.

And don't assume that 10:1 will be too high for a turbo using that head. People are F+Ting 8 valve heads up in that C/R range, and that combustion chamber and spark plug location should allow much higher cylinder pressures and should have better detonation resistance than the 8 valve heads do. That central spark plug will go a long way towards making things better, and the evenly-shaped chamber will allow quick, unimpeded flame travel. I'd go higher rather than lower C/R when building a turbo 16v Volvo, unless you have the support for lots of boost at high flow, i.e. turbo and IC.

My views, as always.
 
I was going to use the b234, but i need to:

plug the aux shaft holes (gonna plug em and weld em)

make custom motor mount on exhaust side (to fit turbo and oil filter)

make custom oil feed and return lines (well, i have to on the 8v too but i wouldnt have to tap into the block or oil pan for the return like i do on the b234)

run high compression

and swap out crossmember (or make really custom mounts. But I have the b234 X-member)


I would like to run the 8.5 CR if possible. I can already detonate easily with pump gas and my 8v set up. However, the b234 is still an option. In the factory manual it also explains that higher compression can be run with the pent roof chamber with center spark plug.


However, the b234 looks like its in better shape than the b230. The b234 has lots of crosshatcing left on the cyl walls and the b230 has little to none. I am not even going to bother re ringing it yet because I can get another used block for 70$ and this is my prototype engine anyways. I am not putting big power thru it yet.

This is budget build. So I wont run the cuts if i dont need to. However, since a new set of valves is about 300$ i gotta be careful. Looking at my pic with the ruler and the clay it looks like i have plenty more than .1" to work with. I measured it at 2mm which seems very close to .1". I posted the 2mm spec so that people would comment if it is enough. You guys mentioned valve float which was one of my concerns. It doesnt make sense to me why the pistons on the b234 are cut so deep and I would be able to run without them on the b230.

Let me know if you guys think i can get away with running the b230 block with the b234 head with 2mm of measured clearance between the piston and the valves.
 
hey...lets get ours cut together and save ourselves the possibility of screwing stuff up. $50...remember??? Lets do it next week and stop worrying about it and get this 16v monster running!
 
Because if I dont need to do it, why would I waste the time and money to do it and have potentially weaker pistons.
 
Any reason you can't just swap the B234 pistons in? Bore is the same.. and I think the wrist pins should be the same too. At that point though, you could just get your B230 pistons cut for reliefs.. should be less then $100 for all four if you have a B234F piston as a good example.
 
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