Funky Valve Seat- WTF? Options

[tornik550]

A long time ago, I purchased some heads online. They were bus heads that were supposedly ported to accept 38mm exhaust valves. I got the heads and they were total crap. When I took the springs and valves off, I found that the exhaust ports were completely stock. The valve seat was odd- the base was as narrow as the stock port and it angled out to 38mm so that it could accept a larger valve. Why? Correct me if I am wrong but it seems like if the port is the stock size- a 33mm or 38mm valve would have about the same flow if not less with the larger valve.

Is there something that I am missing or is this as dumb of a head job as Clinton/Lewinski?

(I am posting this for educational purposes- I have several usable heads. These are trash as far as I am concerned)

[HAM Inc]

You were sold a bill of goods!
Used 2.0 bus heads are almost always junk to begin with.

Someone installed new seats, but sized the seat I.D. such that they wouldn't have to do port work to blend to the appropriate seat I.D. (~33mm) for a 38mm valve.

It's not as big a rip off as a Madoff scheme, but it is a rip off, unless it was done in ignorance.

Another popular rip off is 48mm valves installed into T4 heads, but no welding is done to the ports to accomodate the big valves. The port can't be enlarged enough to accomodate a 48mm valve to it's full potential. Flow actually suffers from the giant valve. Big valves in ports sized appropriately for smaller valves is counterproductive.

My 44 valved port outflows one popular shops 48mm valved, unwelded port head.

A LOT of head work is like fishing tackle... designed to catch fisherman, not fish!

[stugray]

This is sort of on topic...(sry if im jacking)

I was just talking to a machine shop today about work for my stock 2.0L heads.
I was going to do the valve stems, new seats, and a flycut.

The machinist said that over-sizing will not cost any more since the work is the same.

So how much SHOULD I enlarge the valves if any?
Where do I get oversized valves?

This a stock 2.0L with dual webers & a raby cam (9700 super).

Any help would be appreciated.

Stu

[Jake Raby]

Why enlarge the valves when the ports won't support a valve any larger??

These are the least performing of all TIV heads. The 9700 cam will not like these heads very much. We can talk about this when we do your consult.

What you should do is find a set of good 2.0 / 914 heads or at least 1.8s..

This post has been edited by Jake Raby: Mar 2 2011, 06:25 PM

[stugray]

Oh, sorry. Mine are the 914 2.0L heads.

I forgot the OP has bus heads.

I also asked this Q on your forum as well.

Stu

[Jake Raby]

Oh.. no problem.
If you have the 2.0/914 heads just keep the stock valve sizes as they balance with the ports exactly. Bigger valves are heavier and harder to control and are not necessary at all on smaller bores.

Whether they cost the same or not, I can count the times on one hand when "bigger has been better" here in my world.

[HAM Inc]

So how much SHOULD I enlarge the valves if any?

This a stock 2.0L with dual webers & a raby cam (9700 super).

Jake is right, you do not need to up the valve sizes at all with that displacement and cam. That cam has a lot of area under the curve and larger valves will make the car more sluggish at lower revs. With the smaller valves you will be much happier with the drivability.

[r_towle]

So how much SHOULD I enlarge the valves if any?

This a stock 2.0L with dual webers & a raby cam (9700 super).

Jake is right, you do not need to up the valve sizes at all with that displacement and cam. That cam has a lot of area under the curve and larger valves will make the car more sluggish at lower revs. With the smaller valves you will be much happier with the drivability.

Given a set of heads already setup with seats, can you inspect them and suggest the right thing to do?

i have a set with large valve seats, ported and bored out for larger cylinders.
The porting looks very well done, but I have no idea if they were built up correctly.

do you have a simple looksee price...
I believe these may have been extrude honed and I know they produced roughly 200hp on a 2.4...till a valve broke.
I have all the dyno charts, but not sure if these are worth taking to the next level, which would be slightly smaller valves and a different cam to reduce the rpm range of the HP..

I did not like driving at that rpm range...and I did not build this motor...just bought it with a car...

Interesting heads though...from about 20 years ago (winning SCCA car)
It sucked to drive this motor...4k to get it moving..
Clearly setup for 6800-7500 rpm range...anything else sucked.
Good race motor...sucky autox motor..
At least for me and how I like to drive....I like it a little lower down...and a little quieter...

Rich

[HAM Inc]

Rich I will be glad to take a look at photos at no charge. You can go through the trouble to box them up and ship them to me if you like. I have a minimal charge for inspection. I don't post prices here, but you can e-mail me directly if you like Len@haminc.us

I have to say though that typically heads that have been prepped for large valves and raced are usually not the best candidates for something street oriented. As a matter of fact they usually aren't good candidates for much of anything if they were raced hard, regardless of valve size. Racing is just hard on these castings.

The fact that these heads have been ported and had a lot of work done indicates to me that they likely have work that I will feel needs to be undone. Since they have already had oversize seats installed the valve seat counterbores will probably need to be welded shut so new seats can be installed without going up to a seat that is larger than I like to use on these heads.

Rich I have had a LOT of ported big valve T4 heads in my shop over the years for an assesment, and typically I have advised people to start with a fresh pair of heads. As a matter of fact I have a pair of very large valve 2.0 914 heads in the shop now that were abandoned some time ago when I told the customer they were useless for his engine. Some work is just tough to undo.

[r_towle]

Lost my long response.
Bottom line is while I agree with you, I am itching to try them just to see the results...may only run them for a few days as is,....different cam...

the port job is cool.
I will take some pics at some point, to cold and to busy lately to bother with my toys.
Rich

[Jake Raby]

Based on my previous experience those would sell real well to someone who still gets an erection from big parts.. Members of the "Bigger is better" crowd are easy to find, they are everywhere and have deep pockets. (more like credit cards)

Use that money to buy something that will actually perform and last.

Keep in mind we make over 200HP from only a 96mm bore and only 44X36 valves. I've made over 260 HP with 46X38 valves and 250 HP from 48X38 valves, the difference was those engines were 3 liters and Len had DOZENS of hours of welding to create a port that would adequately support that valve size.

Valves have a point where their size can create diminishing returns. Large valves decrease the valve deck and increase piston/valve interference. They weigh more and require more spring to control which increases friction and drastically increases oil temperatures. More spring also means more load on lifters which means more force is exerted on lifter bores and cam lobes, increasing wear.

Bigger is far from better in my personal experience, thats why my own cars have 2056 and 2270 engines and not 3 liters. I have all the parts on the shelf for any size of engine, keep that in mind. When I reconstructed the engine in my 912E I could have oput a set of LE 200 heads on it, instead I orded a set of RS+ heads from Len with smaller valves, because thats what I needed. Knowing that what you want is seldom exactly what you "need" is the first key to attaining a true performance mindset.

[HAM Inc]

I'm not going to break my arm patting myself on the back, but I'm very pleased with the RS heads.

I developed an intake port shape that flows as much at .400" valve lift as the 2.0 914 intake port does at .500" lift. And the really great part is that it does it with the same size valve but a much smaller throat diameter! The end result is much higher port velocity than the venerable 2.0 914, and greatly improved low end response with zero sacrifice of top end.

Shape trumps size every time! I don't care if it's N.A. or forced induction.