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oversize valves?

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tomshobby

tomshobby

Yoda
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Reading Paul's posts about the work he is doing has gotten me fired up to finally rebuild my engine. Among other things I am going to do some work on the head and replace the valves and install seats.

I have read about installing oversize valves in a TR6 head.

Has anyone done this? Is is only for the early TR6 heads? What would be the best source and what size?

Most of all, were you happy with the result?

Thanks,
Tom
 
I am in the process of working on a TR6 head for my fast street engine. In my readings, they pretty much say that for street use, you don't need larger valves. Just open things up to allow them to breathe better.
Kas Kasner's book is very good for what you want to do. I strongly recommend you buying it. The original is $10.00 or less...a lot cheaper than a new head.
 
Hi Tom,
You can get oversize valves for the TR6 head from the UK.
A company called Chris Witor does them off the shelf.

He does performance inlet valve 34mms, 36.6mm, 37.75mm, 214 N stainless, and performance exhaust valves, 30.3 mm, 31.25mm 214N stainless,


I have no association with Chris Witor, just suggesting where you might get some valves from.

Steve
 
Steve,
now that we have you online, what is the true story about the difference between the horsepower of the British TR6 and the U.S. version?

Ive heard 50%, 20%??

Terry
 
Terry,
The TR6 is not my forte but, in the UK the TR6 was fitted as standard with Lucas mechanical fuel injection which on the CP series of engines was rated at 150bhp @ 5500rpm and with the CR series, the engine was rated at 125bhp @ 5000rpm

Due to emission requirements at the time I guess all the TR6's which came your way were fitted with twin Stromberg 175CD carbs, with the CC series engine it was rated at 104bhp @ 4500rpm and with the CF series engine it was rated at 106bhp @ 4900rpm

So I guess that would put the greatest difference at about 30%

Steve
 
Compression on the US engines was lower. The TR5 had a pretty radical cam. I'm not sure if the early TR6's ran the same cam.

Chris Witor has an interesting article on the best flowing head. For some reason I cannot get the article to come up right now. It's the 219016 from a sedan. The late model US heads are 219019 which is the low compression version of this head. Including the EGR port.

Although I've never seen any comments about this. I wonder about the longevity of heads with larger valves. My '71 TR6 had a crack between the intake and exhaust valves on one combustion chamber. Maybe it was a fluke, but I've been curious about decreasing the amount of material between the valve seats ever since.
Anyone know about this?
BOBH
 
Hi Tom,

As suggested, definitely research this modification carefully before you make any mods (although valve seats can be installed to reduce the size again, if that becomes necessary in the future).

Enlarging valve diameter would need to be done in conjunction with other mods to really get much benefit.

I can't say for certain if the same is true on the 6-cyl. motor, but in the 4-cyl. TR enlarging the exhaust valves tends to be more beneificial than the intakes. This is because the exhaust side is a bit undersized to begin with. There is precious little room to increase valve diameter in the 4-cyl. though.

Of course, the whole idea is to improve flow in and out of the head. So even leaving valve diameter the same a lot can be done. Start by refining the flow characteristics of the intake and exhaust manifolds and the ports in the head. Use valves with thinner seats and back cut to sort of a "tulip" shape, to increase volume flowing in and out. And, of course, a high performance cam will open the valves farther for greater flow.

Have fun!
 
Hi Alan,

A side note you might find interesting. I installed an 87mm piston and liner kit in my 64 TR4 in 1965. I bought them from the JC Whitney catalog. I wish I could remember the price. Oh, I am still the same age and only slightly more mature.

Back to the valve issue. The reason I brought it up here is that I was not sure if the benefit vs risk made it reasonable for a streetable motor. I have complete confidence in the shop I go to that the job would be done right. I am going to have valve seats installed anyway and so it would be almost no more work or time to do it.

The biggest drawback I see is that if id turns out to be the wrong thing it would be a pain to reverse it. I know all I have to do is pull the head and take it back to the shop and wait while the weather is warm and I want to drive the car.

I am tending to agree with your suggestion that there are a lot of other things I can do that might even be more help.

Thanks,
Tom
 
The Chris Witor article I mentioned earlier is available today. He has some interesting comments on the 6 cylinder heads. In particular the statement that the 219016 head is virtually a gas flowed head. His markup of the cross section on an inlet port indicates there is very little material that needs to be removed for additional improvement. This is pretty much inline with what Kastner said in his Competition Prep Manual.

https://www.tr6.org/cylheads/index.html
 
Bob,

I very much appreciate the information you sent by pm and here. It certainly establishes that my money and time spent on improvements would be better spent in other places. Especially since I want a quick street car and not an all out race car.

Might be a good thing I did not have this information when I had my GT6. Got in enough trouble as it was! /bcforum/images/%%GRAEMLIN_URL%%/smirk.gif
 
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