maximumvelocity

I have a set of well flowing heads with stock valves (1.94 and 1.5) on them. The seats have been enlarged to accommodate the larger 2.02 and 1.6 valves. The shop said they sealed just fine, but they were seating right at the edge of the valves, with a little bit of the seat visible around each valve head. He's now trying to sell me 2.02s and 1.55s. Anyone have experience with valves being pushed through their seats because they were too small for their seats?
The person running these heads before me apparently had no issues with them. I'm on a slightly tight budget here and was thinking about just leaving them as is.

What kind of power increases if any would I get from bumping these up to 2.02/1.55? Also, 2.00/1.55 is coming to mind, any better? I'm more interested in better throttle response than maximum top end performance. I've heard some talk about losing power and throttle response by going larger. I'm not building a race engine, but I am expecting to have a 400rwhp n/a daily driver. Stock valves up to this kind of load?
Perhaps a little happy juice and turbo boost in the future, not for sure though.

bkpliskin

Yes, stock heads P&P'd with stock valves should be good enough to get you to 400rwhp. You stated you are not building a racing engine so upgrading to bigger valves would not be worth your money IMO.

reamo04

dont upgrade to bigger valves anyways. mdacton was running 10.80s on motor with a solid roller and small valves....

MachinistOne

If I understand your post correctly, the seats were machined for a 2.02"/1.60" valve combo, but now there are 1.94"/1.50" valves there?

If that's the case, the "seat width" or contact patch where the seat touches the valve is way off, and could be to the point where the valve is only sealing on it's very edge. This is very bad and could lead to burnt or tuliped valves. It also means that the spring and stem installed heights are going to be deeper, making your spring pressure less and valve train geometry off. You should confirm what I have said with your machine shop and put in the bigger valves if needed.

You need to have a seat width of .040" intake and .060" exhaust or wider to have any life expectancy of the valve job in a street motor. Race motors we can run thinner but they get torn down every 20-40 hours.

In this picture you can see that the problem is with a smaller diameter valve it would drop down further and maybe not even seal against the matching 45* angle on the seat...



What is the valve stem installed height now compared to the specification?

maximumvelocity

Yes you did understand my posting correctly. I went over to inspect myself after he told me the seats were for 2.02/1.6's. He lapped the stock valves in there and showed me the contact area on the valve.
The red line shows where the current contact area is on the stock valve.

When he mocked up and lapped a 2.02/1.55 for comparison the contact area shifted towards the center on the same surface angle of the valve. If I recall correctly, the contact width did look wider on the 2.02 than the 1.94.

I'll ask him if he'll measure the contact width and valve stem installed height. I did ask about the springs after I had him check for warping and he said they were seating at roughly 130#.
From what you said (typed), I might be better off going up from stock size valves to avoid tuliping and burnt valves. Still thinking about a 2.00/1.55 combo instead of the 2.02/1.6 though.

NightTrain66

yea, the 2.00/1.56 valves will work best unless changing to larger valve seats. You want the valves to be sealing almost at the VERY edge of the valve and leave maybe .010 that is not touching the sealing surface.

I would question what is going on if he says that you can run 1.94 or a 2.00 (or 2.02) on the same valve job . . . . . ? ? ? ? ?

that must be one WIDE 45 for it to even seal much less it would have to flow like crap for either valve size. Measure the throat diameter and it should be about 90% of valve size (I use 91% on my valve jobs). This means you chould be able to use some calipers and place it in the bowl through valve job as far as you can and measure 1.800" for a 2.00" valve.

Lots of areas in the port are BASED on the valve size. You have to KNOW the valve size before you set the venturi diameter and ever think about doing the portwork or opening up other areas of the port.

The top cut needs to be right at the edge of the valve to suck air around it and you can't have the top cut in the right location for a 1.94" AND a 2.02" valve. it just can't happen. It has to be for one valve or the other. If it is in the middle and "supposed to work for both valve sizes", it will actually work for neither.

Same with the bottom cut. It needs to be right up to 45 degree sealing angle of the valve. A 1.94" and 2.00 or 2.02" valve will want this in different locations.

I guess the only way to make these heads as good as they are gonna be would be to measure the venturi diameter first and then pick the valve size that ends up @ 88-90%. Then do a valve job that locates the 45 correctly and has as many bottom cuts as posible (85, 75, 60) and a real wide top cut (.100 or so) with a steep angle (37 to 39) and radiuses into the chamber.

If he is just using a 30/45/60 cutter or using stones to do the valve job, I would seriously consider calling around and find a local shop hat can handle the work properly for you.

Throttle response will be cam selection, compression, tuning, etc as well as not shooting yourself in the foot with problems (bad O2's, exhaust leaks, dirty MAF, leaks between MAF and TB, bad plug wires, cam not degreed, etc) or something wrong with the heads (crummy flowing valve job, mis shaped or ripped out shortside, wrong venturi diameter, etc).

As long as the heads have the proper measurements for the valve size ran, correctly shaped port areas, correct cross sections, etc, you will have good velocity at every RPM. The things mentioned in the above paragraphs will be the problems and not the heads.

Lloyd

Bersaglieri

This, and I also recommend this:

Lloyd Elliott
972-617-5671
Elliottsportworks.com

This site has seen alot of folks getting hosed by people who have no clue what they are doing.

-Dustin-

MachinistOne

Really, if your machine shop cannot explain what has been said here and tell you exactly what you need to do to make the heads work properly you need to take them somewhere else. If the seat width that they showed you with a 2.02" valve was in the middle of the valve face then like Lloyd said - it was a crappy valve job to begin with and you need to start over either way.

maximumvelocity

Well the guy isn't even familiar with a 2.00 valve, only 1.94 and 2.02. He gave me 2 reasons for running 2.02" over 1.94": on the 2.02" the valve seat contact area was more towards the center of the 45* angle on the valve (maybe he is able to eyeball .01"?), whereas the 1.94's was right on the outer edge, and when looking straight down at the combustion chamber with the 1.94" the outer perimeter of the valve seat was visible around the valve head. He didn't seem comfortable at all about leaving the 1.94s in there. I didn't know if that was his way of trying to sell me 2.02" valves, valve job and cleaning which he quoted me $350ish if I remember correctly.
Regardless, I'll be stopping by the shop with a caliper to find out the venturi diameter. I'm assuming to look for the narrowest part of the venturi for measuring (when looking at the pictures above, just below the bottom gray bar that shows the location for the 75* cut. Is that what I'm looking to measure)?
I'll query him on his valve cutting methods to see what he has to say. I just might remove the heads from that shop. What does a reasonably good valve job go for, so that I know I'm not getting worked over.

Thanks for that great wealth of info you posted Lloyd.

NightTrain66

should be $250 or so for a good 4-5 angle valve job, milling, cleaning seals and assembly if you supply the parts.

The FIRST setp is to pick a valve size and set the venturi.

The NEXT step is to machine a 90 degree angle through the vlave job at the desired venturi.

The next step is to locate the 45 on the valve seat so it contacts the valve in the corrcet location.

Just place the other angles around it so there is a transition from the 90 to the 85-75-60-45 and 37 to 39 degree top cut.

Do the portwork to the 90 degree angle and blend the top cut into the chamber.