1800 head ports and valve shim question

HawaiianSpider · Post by **HawaiianSpider** » Fri Aug 25, 2006 1:39 am

Hello everyone,

I'm replacing the head on my '79 Fiat Spider with a rebuilt 1800 head. I have a few questions that I hope you all could answer.

1) There are ports on the 1800 head that do not exist on the 2000 head. In the picture below they are represented as red circles. Are these emmission ports and is it ok to block these off?

2) From what I have read I was expecting to see valve shims between the tappets and the keepers. That does not seem to be the case. All I see are tappets (see picture below). However, the head of the tappet comes off. Do the valve shims slide between the head of the tappet and the tappet itself? Or do they fit underneath the tappet?

3) When comparing the rebuilt 1800 head to my old 2000 head, I noticed rings or bands of metal surround the cylinders in the 2000 head that are not apparent in the 1800 head. In the picture below one band is highlighted in red. I was just curious to know the purpose of the bands? Are they just products of the way the head was cast?

Thanks for having patience with my questions,
Mike

fiater · Post by **fiater** » Fri Aug 25, 2006 8:13 am

Those ports go to the air pump. If you're not going to use your air pump, you'll need to block off those ports. What you're calling the "head of the tappet" is the shim.

So Cal Mark · Post by **So Cal Mark** » Fri Aug 25, 2006 10:19 am

the "band" around the combustion chamber on your head is from the fire ring on the head gasket. It's a metal ring that prevents the flame in the cyl from burning through the gasket. If you suspect a head gasket failure, inspecting it closely will reveal spots where the gasket was leaking; either between cyls or from a water jacket into a cyl
The shim sits in the tappet, they come in various thicknesses

HawaiianSpider · Post by **HawaiianSpider** » Fri Aug 25, 2006 1:18 pm

Thanks for the answers fiater and Mark! Mark, I thought that "band" was a part of the head itself - hence the question. What you are saying about the metal ring in the head gasket, however, makes sense.

racydave · Post by **racydave** » Fri Aug 25, 2006 5:38 pm

I am going to replace my shims per a article I read,increasing valve overlap slightly. .17 intake, .19 exhaust Stock is .18 and .20

So Cal Mark · Post by **So Cal Mark** » Fri Aug 25, 2006 6:01 pm

that's quite alot of work to close the gap .001. You'll find that there is a range of clearances, since it's near-impossible to get each valve clearance exactly the same as the others

Jim DeShon · Post by **Jim DeShon** » Sat Aug 26, 2006 1:12 pm

As for valve clearances, I would stick with what the factory recommends. Decreasing the valve lash doesn't get you enough to notice the difference and increases wear on the cam and shims. If you want more duration and lift [overlap is not what you are after] change out the cams, don't decrease the valve lash. That clearence is recommended by the cam grinder because he knows what clearence is needed with the ramp angle on that particular cam grind. I have see this done some in drag racing [closing up the valve clearences] but it is only minutely effective. ...J.D.