DIY Valve Reliefs? :)

[caffeine]

I have a big cam in my Fiero, and I pulled the heads for what I thought was a head gasket issue, but turned out to be something else.

I was getting air in the coolant every time I would run the engine but couldn't figure out where it was coming from, so I decided to do a compression test. Compression test revealed 175 psi everywhere except cyl #3 at 80 psi. So I figured it was the head gasket.



Turns out that the exhaust valves had been hitting the pistons. One exhaust valve had managed to bend more than the others causing the loss in compression. Coolant issue is most likely a cracked head, according to the machine shop down the road.

Not wanting to give up on this cam, I decided to try making valve reliefs myself using the methods outlined here:
http://www.mifbody.com/vbulletin/sho...free!-(almost)

and here:

http://www.fordmuscleforums.com/engi...-notching.html

I finished one side of the block today:





Plan is to finish the other side, throw on a new set of heads, and see how it goes . If it all works out then maybe others will be brave enough to try it.

[Superdave]

Welcome to the club! haha


My compression test was still good after, no damage to the valves so i just left mine alone.

[3400-95-Modified]

Yeah mine was very minimal... I'm surprised this is happening so often... I think it's time we start doing a interference check before running the engine... I have no idea what my pistons look like right now after I had the DRTC stretch as bad as it did... I'm kinda afraid to take it apart. LOL.

Should probably do a compression check on it first then I would know if it's worth the time and effort.

[caffeine]

Well even though 5 cylinders had decent compression, all of the exhaust valves were bent. Just the one in cylinder #3 had bent more than the others enough to cause a huge loss in compression.

What compression test results are you guys getting with your cammed motors?

[Superdave]

I think mine were lower than yours, like 140-150 but i'd have to look. It's been a while though.. lol

[ForcedFirebird]

That's an interesting way to do it. I have always seen using old valves with notches cut in them to act as a cutter, or have seen people use a carbide lathe insert rigged into a valve. This is the first time seeing sandpaper. That must have taken a while to cut?

[caffeine]

It cut VERY easily. Like seconds for each cylinder haha.

[ericjon262]

I've seen special carbide cutters for doing this too.

[caffeine]

I used 40 grit. Just like a hot knife through butter.

[ForcedFirebird]

Guess it depends on how deep you have to go. Here's an article where a guy used some flat top DOHC pistons in an M20 single cam head, these are fairly deep, though...

http://www.e30tech.com/forum/showpost.php?p=990948&postcount=180

[caffeine]

Pulled the heads from my Firebird today and interestingly the #1 piston has a nick in it from the exhaust valve. Nothing like the Fiero has and only on the one piston. It's running a street/strip turbo cam.

The Firebird's head gaskets blew in October so I'm just gonna put its old heads on the Fiero for now and replace the engine that's in the Firebird. Head studs this time .

[ericjon262]

so I take it you marked the valve stem so you could see how deep you had gone?

[caffeine]

Just put a feeler gauge set at 0.1" over the valve seal then bottomed out the drill chuck on the gauge. Drilled till I hit the valve seal.

[Mars]

This that gnarly cam you got from me ?

Man I'd love to see how much that would make on a dyno, just kept pulling.

[caffeine]

Yes it's that cam haha. It does pull very strong at high rpm. I plan on dynoing it when all the problems are sorted.