Importance of Valve Job

[BlackKnight]

Gentelmen, I am new to the form and have a question for head porters. If there's some sort of initiation I'm sure to fail, so I hope I can get a response. Questions; How important is a valve job to a race engine? Moreover, are there any head porters that doesn't do there own valve jobs?

[JoePorting]

It's very important. If you're doing a intake 45 degree valve job, use the Sunnen #17258 bit. For the exhaust, use the #17536 bit. They're both on page 17 of the below Sunnen catalog.

http://www.sunnen.com/graphics/assets/d ... 3b0d7d.pdf

[justahoby]

I am no expert, but by my experience valves and piston ring seal are never to be ignored..
Some people find the need to use a roundout gage to less than .0001"
A poorer yet sufficient crappy job on the valves can show fluttering on a vacuum gage.
If a valve dont seal, it can burn over time, and loose even more compression.
A good sealing valve is power..

[BlackKnight]

thanks guys. the reason I asked is because i had a set of heads ported and the valve job sucks (putting it mildly) and they are leaking air everywhere. it's obvious that there is no valve job at all. no little rings around the seats as i've seen on the web, nothing but light shining through and air flowing past the valve. in the end it was a learning process and i will never spend another dime with the guy, but i'm having them fixed now. i will direct my local guy to the site posted here. thanks again

[Zebedeehall]

thanks guys. the reason I asked is because i had a set of heads ported and the valve job sucks (putting it mildly) and they are leaking air everywhere. it's obvious that there is no valve job at all. no little rings around the seats as i've seen on the web, nothing but light shining through and air flowing past the valve. in the end it was a learning process and i will never spend another dime with the guy, but i'm having them fixed now. i will direct my local guy to the site posted here. thanks again

Wow, that's amazing! What's really amazing is that I had a similar situation. Probable not as bad but still jacked up. I read your other post on another forum and we seem to have some things in common. Good luck in getting your heads fixed.

[Cubic_Cleveland]

As has been said, the valve job is extremely important. Not only for sealing and valve life, but the right valve job can help get more airflow, and the wrong valve job can hurt considerably.

To answer your second question. No, the head porter doesn't have to do the valve job, but should know what he wants in the valve job. I see it written here a lot that a good porter must do his own seats and if they don't the porter can't be good. This is rubbish. I cut the seats for my own port work as well as others (quite good porters at that too). Just because you don't cut seats doesn't mean you can't port. If you have the seats cut to your specs, and work closely with the guy doing them, what's the difference?

[ProPower engines]

Just as an example. Back in the 80's when we used the Busch type V6 in our tour car when the valves started leaking and they did that often till I tightened the guide clearance from what AFR supplied the engine would loose 50-60HP and in track time that was 2-3 10th's.
That was not a real bad leak either maybe 1% but still a leaks of any kind from the valves is just plain bad news.

[Abbottracingheads]

The valve job is one of the most critical parts of reworking heads for performance. The valve job sets the basis for what you are going to do with heads. One valve job cutter does not fit all scenarios. Also if the valves do not seal all is wasted.

[MaxFlow]

Looks means virtually nothing to me. Will it vacuum test? That tells the story.

[saleen385]

I'm on a 2 sets of heads a week development program for NASCAR cup & nationwide/truck engines. So I play a lot with the VJ. I widened the seat the other day .040 and lost 40hp.
You can make or break a good head with just the VJ.

Jim

[wil8115]

I'm on a 2 sets of heads a week development program for NASCAR cup & nationwide/truck engines. So I play a lot with the VJ. I widened the seat the other day .040 and lost 40hp.
You can make or break a good head with just the VJ.

Jim

I'm curious, from what to what?

[BlackKnight]

Looks means virtually nothing to me. Will it vacuum test? That tells the story.

no! they would not pass a vacuum test. i'm having the valve job re-done by someone else. thanks guys.

[BlackKnight]

I'm on a 2 sets of heads a week development program for NASCAR cup & nationwide/truck engines. So I play a lot with the VJ. I widened the seat the other day .040 and lost 40hp.
You can make or break a good head with just the VJ.

Jim

i'm hoping the heads pick up after they are fixed. i have been looking on line at back-cut valves and valve jobs that have three rings/cuts around the seat area. my heads don't have single ring/cut around the seat area. is there ever a reason not to cut the rings around the seat area, which is what i thought was a valve job, on a race prepped head?

[user-9274568]

Your saying it has a radius seat on the intake? It doesn't have sharp edges.

Does the intake seat look like the exhaust seat?

This is a sharp edge, both seats.

[TMSJoe]

I'm guessing he is not seeing the 3 defined angles from a typical 3 angle valve job.