Valve Tolerances Make No Sense after Head Gasket

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Shadoobie
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Valve Tolerances Make No Sense after Head Gasket

Post by Shadoobie » Thu May 09, 2019 1:21 am

Hello everybody,
So I'm running Bayless 245 cams in my '79 Spider and I ended up using a slightly milled cambox and a set of .070" lash caps to be able to get the tolerances in a workable range, though it ended up being very tight. However, I could just barely adjust them to the .014" reccomended by Bayless. Well I just replaced a blown head gasket and naturally had to change cambox gaskets. Now my valve tolerances have gone from normal to zero, and since I'm already running the tightest shims I can't even go lower to find out where they actually are. I decided to throw on one of my old non-milled camboxes to widen up the gap, but it's still zero. I honestly have no clue what's happening right now, so if anybody has any suggestions or tips on how to proceed I would appreciate it. -Josh
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mikehynes
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Re: Valve Tolerances Make No Sense after Head Gasket

Post by mikehynes » Thu May 09, 2019 11:28 am

You could cut the tips of the valves down. I know, that's not a great solution, but it can be done. Or, you can use different, thinner, lash caps. Or, probably the easiest, just double up on the cam box gaskets, or make one out of thicker material.
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bartigue
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Re: Valve Tolerances Make No Sense after Head Gasket

Post by bartigue » Thu May 09, 2019 12:24 pm

You likely have less than zero tolerance in both cases. Zero would indicate that increase in cam tower size would naturally increase the clearance. Thicker gasket should help, known stock spec cam boxes as well.
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Re: Valve Tolerances Make No Sense after Head Gasket

Post by fiatrn » Thu May 09, 2019 12:55 pm

Disassemble and measure the alfa-style shims (lash caps) that you used. Then re-assemble without them at all, measure your gaps, and put in proper sized ones. Odd that something changed with re-assembly, but maybe you have extra thick gaskets or some such. Don't worry too much about what happened, just make sure that you start from scratch and redo the system into a proper state.
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engineerted
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Re: Valve Tolerances Make No Sense after Head Gasket

Post by engineerted » Thu May 09, 2019 3:18 pm

I think there is something that you are not telling us?? Why would you have to change the cam box gaskets when replacing the head gasket. Did you have the head machined and they also re-cut the valve seats??
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Shadoobie
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Re: Valve Tolerances Make No Sense after Head Gasket

Post by Shadoobie » Thu May 09, 2019 6:26 pm

Thanks for the responses everyone, I came back this morning with a level head and checked the thicknesses of the new and old valve cover gaskets after compression. The new one was almost half the thicknesses of the old one! That accounted for my difference in clearances between the two. I put the old gaskets back on for now and the tolerances came our right, but I plan on ordering some new thicker gaskets and losing the lash caps. As for your comment Ted, I always remove the camboxes when I do a head gasket to endure that tourque is evenly distributed on the block. I guess you could do it with the boxes on, but since the head gasket kit comes with new gaskets anyway, I don't see why you wouldn't do it. -Josh
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Re: Valve Tolerances Make No Sense after Head Gasket

Post by fp55scca » Sat May 11, 2019 9:52 am

Shadoobie wrote:
Thu May 09, 2019 6:26 pm
…. I always remove the camboxes when I do a head gasket to endure that tourque is evenly distributed on the block. I guess you could do it with the boxes on, but since the head gasket kit comes with new gaskets anyway, I don't see why you wouldn't do it. -Josh
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--Josh, really no need to do cambox gaskets with a head gasket replacement. If cambox gaskets are 'set' and not leaking, best to just leave them alone. As you experienced, you will only throw off valve lash settings when you do refresh them.

--You might also consider getting some fresh camboxes. There are lots of them out there, if you don't have spares; and, they are fully inter-changeable. If a cambox has ever been milled, and not done to perfection, you might find your timing belt walking.
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Re: Valve Tolerances Make No Sense after Head Gasket

Post by jseabolt » Wed May 15, 2019 4:43 pm

After the exhaust cambox gasket started to shoot oil , I thought I'd be clever and make one out of GorTex material. Since this stuff still seal anything. I did not take into consideration the thickness of this material and it really messed the valve clearances up to the point I had no thinner shims to get any exhaust valves in spec. They do make this GoreTex material thinner but not in the thickness I can get for free!

I installed one of Ricambi's gaskets with the bead of red sealant and it seems to be holding up.

I have heard you can stack two cambox gaskets if the camboxes are warped. But as bad as these cambox gaskets are to leak, I would think that would be asking for trouble (twice the possibility of leaking). Ever notice that the intake cambox gasket never seems to leak? Or at least I have never had one leak on any twin cam.

My cambox wasn't warped. The guy who rebuilt this cylinder head was big on using Permatex aviation gasket dressing on the gaskets and I think over time the stuff hardened up and sprung a leak.

You know who can resurface these camboxes with minimal tools without having to depend on a machine shop to do it for you? Get a large enough piece of glass (say from a picture frame) and tape a piece of 220 grit sandpaper to it, overlapping the ends of the sandpaper to the backside of the glass, tape it in place and lay it onto something rubbery, like that stuff you line kitchen drawers with so the glass won't move.

Take a magic marker and cover the entire surface with the ink. They lay it on the sandpaper and go back and fourth one way a few times, then up and down the other. Or in a circular motion. As the metal is removed, so will the ink and when all the ink is gone, it's flat.

I used this method on a cylinder head from my lawmower after blowing the headgasket and the exhaust housing off my turbo.
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Re: Valve Tolerances Make No Sense after Head Gasket

Post by Jefco » Fri May 17, 2019 8:40 pm

jseabolt wrote:
Wed May 15, 2019 4:43 pm
I used this method on a cylinder head from my lawmower after blowing the headgasket and the exhaust housing off my turbo.
You have a turbocharged lawnmower? You must get done mowing really fast!
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Re: Valve Tolerances Make No Sense after Head Gasket

Post by jseabolt » Fri May 17, 2019 8:53 pm

Jefco wrote:
Fri May 17, 2019 8:40 pm
jseabolt wrote:
Wed May 15, 2019 4:43 pm
I used this method on a cylinder head from my lawmower after blowing the headgasket and the exhaust housing off my turbo.
You have a turbocharged lawnmower? You must get done mowing really fast!
No, it's not turbocharged.

Dumbass me put too much oil my lawnmower engine. Long story. The head gasket blew and was forcing oil into the combustion chamber from the valve chamber. It took longer to scrape all that RTV off the valve cover gasket than it did to replace the head gasket.

Here's some pics. I noticed if I hit the forward button it takes you to a photo on someone else's folder! I've been meaning to migrate my photos to somewhere else. If you are really interested , just right click open in new window for each photo.

https://s222.photobucket.com/user/turbo ... wer?page=1
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