RebelExtrm02

iTrader: (3)

I picked up some 243 heads and have been shopping around for a shop to check them, clean them, mill them and do a valve job. A full port job isn't in the budget. I've talked with a few shops and each ones opinion on the affect of a valve job on performance has varied. Is there really any variation in what I'm wanting done? It seems they all just use a die to cut the valves and seats and then clean everything up. None seem to do any bowl or seat blending outside of a full port and polish job. Should I just pick the shop that's the cheapest or most convenient for me?

Rise of the Phoenix

iTrader: (27)

Theoretically, any local machine shop SHOULD be able to do what you need done, but sadly you hear horror stories all of the time about machine shops screwing up heads. I would ask around about some of the local machine shops in your area and go from there.

farmington

iTrader: (14)

ask if they use stones or actually machine the valve job.

01ssreda4

iTrader: (96)

A stock valve job will net you zero hp gains. Its a waste of money if your valve seats are in good shape. I personally disassemble the heads, carry them to the shop, and tell them to hot tank them and mill them x amount. Some basic machine shops who focus on stock rebuilds wont be able to mill x amount. They have belt sanders to mill and dont have an accurate way to measure before and after. The local shop said he usually makes two passes and it cuts about 4 off a pass but thats not good enough to say go to 25 or more....meaning its not accurate enough. Then after getting them back I will hand lap the valves in (search youtube for how to vids) and reassemble to my specs (meaning spring height, the kind of valve seals and springs I want etc).

RebelExtrm02

iTrader: (3)

So you're saying if I'm not going to do a full port then I'm better off just having them cleaned, checked, and decked and if all is well to just run em like that?

01ssreda4

iTrader: (96)

Well not exactly. There is a difference between a basic stock valve job and a performance valve job. Not all shops can do a performance valve job. That is possibly worth the cost because you will gain some flow. Ive had good luck with milling stocks heads for free compression. Get em cut 25 or 30 and you will feel the difference from that and it's cheap. Remember pushrods need to be adjusted accordingly

RebelExtrm02

iTrader: (3)

Can you explain the difference between a basic stock valve job and a performance valve job? I did some digging earlier and everyone just talks about 3 vs 5 angle. AI told me multiple angle/radii # of angles has little to do with anything in the end, that it was marketing. I'm not asking because I don't believe you. I'm asking so I can be more educated while talking with shops.

I read a long time ago that most gains can be had in the valve job and immediate areas. However everyone I talk to only includes work beyond a valve and seat cut in their full port. Seems like there is no middle of the road work. Maybe I, or the shops I've talked to, just don't understand the difference.

warriorpluto

iTrader: (2)

I heard the same thing. I had a competition valve job done on my 243 heads. Haven't put then on yet though

01ssreda4

iTrader: (96)

Im not that versed in it that's for sure. I know if you ask for a performance valve job from a stock rebuild type place they are gonna tell you they don't do that, so obviously its a specialized service that not every shop can offer.

zblee

I am interested in this as well as I too will be looking to find a place to get some heads cleaned up and milled. for just milling is there a specific technique or piece of machinery that is used to accurately machine a head for .0XX amount that you can ask the shop if they use this technique/equipment?

vettenuts

iTrader: (4)

Personally, I would disassemble them myself and then take the bare heads for the mill but make sure of the surface finish you will get back. I would simply lap the valves once the machine work is done then clean real well before reassembly. Many have had shops do the valves and ended up with 8 different valve heights per head.

Zmg00camaross

iTrader: (11)

Where in Missouri are you?

01ssreda4

iTrader: (96)

Yep, why create an issue when you don't have to.

RebelExtrm02

iTrader: (3)

*Deleted*

KCS

iTrader: (20)

A "basic stock valve job" is most likely going to be a 3 angle valve job with a 30, 45, and 60 degree profile.

A "competition valve job" could be the same valve job with just a 75 degree bowl cut added underneath the 60. The good shops will have a profile that they like to use that may be much different because they have had good success with it. This is only one reason why the shop that you trust to do the work matters.

MyFirstLS1

iTrader: (8)

I had mine checked to make sure the valves weren't leaking after they were cleaned and milled and when i got them back i lapped the valves/seats myself

drew408

I spoke with Advanced Induction after reading here about most gains from the porting are in a performance valve job....

This is simply not true. Sure there are gains to be had but not a ton.

Most would consider a performance valve job consists of 3-4 angle valve job,back cut valves,and setup spring height. Around here that goes for around $150-$200.

Know It All

Well with respect to Phil, many other experts disagree.

The largest gains are realized by working on the largest restriction in the intake path. For most of the induction cycle, the valve is that restriction. Do the math. Calculate the port cross section and compare it to the curtain area around the valve at each lift point. Throughout most of the cycle, the curtain area is smaller than the minimum area in the port except for a small window after about .400" valve lift, and that's not even where the highest pressure differential is between the cylinder and the port.

Thanks to a guy named Bernoulli, we know that the air will be the fastest at the smallest area in that flow path. Now, velocity is a good thing but too much in the wrong spot is not a good thing either. A bunch of airspeed around the valve isn't really ideal, but its something we have to live with and accommodate as best we can, especially if larger valves are out of the question. Experimenting with different angles and widths in the valve job makes the big gains because it manipulates the air flow around the valve where its most chaotic, but the valve job alone isn't going to be the end of it. Blending in the valve job to the chamber and into the bowl is just as important.

drew408

Phil has the best CNC stock castings,I think I will listen to him....

I know all flow benches are different but I'm sure there is a reason why AI's CNC castings flow 50cfm MORE on the exhaust at .500 lift than any other CNC head I've found.

And I don't think that's "all in the valve job"