TR4/4A What size valves in TR4?

[Alan_Myers]

Hi all,

What size valves are you using in four cylinder TRs?

I've got on hand a set of 1.65" intake/1.42" exhaust, but am thinking these are too large. I know for certain they won't fit, along with valve seat inserts (for unleaded fuel) on the exhaust side. (There's just not a lot of room to play with valve sizes in the 4-cyl. head's squish area.)

Stock sizes are 1.56"/1.30" (39.5mm/33mm).

In oversize, I've found:
- Inlet:
1.61" (40.89mm)
1.65" (41.95mm)
1.66" (42.18mm)
1.67" (42.42mm)

- Exhaust:
1.40" (35.56mm)
1.42" (36.07mm)

Car needs to be "streetable", but is getting "improved" in a lot of little ways. It will have a 182 degree duration/high lift cam. I'm still undecided whether to use 87mm or 89mm pistons/liners (the former, which I have on hand, will qualify for most production class autocross, while the latter usually bumps the car into modified classes). Carburetion is a pair of Weber 40DCOE, most likely with 34mm primaries. Head is skimmed to give about 10:1 compression ratio and has been ported and gas flowed (but will probably still get some more improvements).

All the above O/S valves are stainless steel/improved gas flow design. Of course, a larger size valve can always be custom reduced and reshaped into a smaller size.

Seems to me the stock TR exhaust valve size, in particular, is a little skimpy. The rule of thumb I've always heard is that exhaust valves should be at least 85% of the size of intake valves, to allow for proper scavanging. TR stock exhaust valves are 83.333% of the stock intake valves.

Decisions! Decisions!

Anyone have any magic words of wisdom to share or complicated formulas to apply?

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[trfourtune]

alan,
better talk to BFE Ken. i have the same valves as you and will go 89mm per DKU. you want a PORT flow of 85% of intake port flow with valves in. the Exhaust is the restriction in our motors. let me know what you find out.
rob

 

[Simon TR4a]

Hi Alan, I have the same size valves as you with 86mm pistons.
The first cylinder head I had built used stock size valves, and I could not notice a benefit from changing to the larger valves. Both sets, by the way, were the Triumphtune gas-flowed stainless steel valves.

I noticed a chart from Burgess, the MG engine guru, which listed 1.625 inch inlet valves for some years of the MGB, so on the basis of displacement and power output I would guess the TR engine would benefit from larger than stock valves.

My head has had the shrouding removed from the inlet valve as much as is possible on an 86mm bore; you will be able to do a little better with a larger bore.

Another interesting bit of information I found from David Vizard (I am spending too much time on the internet, obviously), was a statement that if the lift of the camshaft multiplied by the rocker ratio is less than 40% of the inlet valve diameter you will get more benefit from increasing lift than from enlarging the valve, and vice-versa. This formula was given in the context of race engines so I suppose a smaller percentrage would be appropriate for a street motor, maybe 35%? Perhaps some experts can offer an opinion on this point.

I suppose the bottom line is, why not use the valves you already have, and the pistons and liners, it seems extravagant to buy this stuff again.
Simon.

 

[Alan_Myers]

Hi Simon & Rob,

Simon, good to hear you've got those valves installed, particularly if you aren't noticing any negative effects and didn't have any fitting problems. One of my concerns is that too large valves can reduce low- to mid-rpm performance (and it's not easy to put material back once the head has been modified for the larger valves!)

Yes, Simon, I think the valves I've got originally came from Triumphtune/Moss. They are well made and definitely stainless steel. My question to you would be if you also have unleaded seat inserts installed on the exhaust side? If so, how does it all fit in the head? /ubbthreads/images/graemlins/confused.gif

Rob, my concern about valve sizes actually comes from a discussion with Ken G. at BF&E. My understanding from talking with him was that the 1.65"/42mm (actually 41.91mm) intake valve is physically too large to fit in combination with the large exhaust valve *if* exhaust valve seat inserts are also used, for unleaded fuel. Reportedly, the exhaust valve seat insert intrudes upon the enlarged intake valve seat.

I've pretty much settled on using the 1.42/36mm exhaust valves, since I think they will give the most benefit and address the main issue when trying to improve the TR 4-cyl.'s breathing (i.e., improving exhaust flow, as you mention Rob).

So that leaves the intake valve size to be determined.

Something else I've looked at is what Greg Solow is using. He's a very well-respected TR/Morgan engine builder and seems to know the tricks getting the best out of the old "TRactor" engine, in fact probably has invented more than a few new tricks! Greg uses 1.61"/40.894mm intake and 1.40"/35.56mm exhaust valves. Unfortunately, his valves are custom made with longer stems because he also drops the ceiling of the combustion chamber to boost radically compression ratio to 11.7:1 or more (full race engines and certainly not practical for street use). So Greg's valves can't just be bought and used without also doing the ceiling modification.

If needed, one alternative might be to have a machine shop modify the valves I've got to a slightly smaller size.
And, since writing my original question, I've also found 1.614"/41mm inlet valves at BP Northwest. Used with the 1.42"/36mm exhaust valves I've got, the exahust size would be over 87% of the inlet size, which appears to be a good number to shoot for.

Simon, you bring up one key reason I'm considering using 89mm pistons/liners instead of the 87mm ones I've got: unshrouding the intake valve. The larger bore does a better job of than the 87mm (or 86mm, of course). Yes, there are alternatives such as relieving the liner a little next to the intake valve, as you did, or even shifting the head a little to the side (see below).

Rob, yes, I agree that the port flow is what's important, with valve size only being one factor. I intend to do some work on porting to insure it's as good as possible. (Head is still on the car. I know it had some porting done 25 years ago, just not sure how much more will be needed.) I am thinking about welding up some of the intake side to form a more constant venturi effect and eliminate the *dead end* wall that's in the stock head (opposite the intake manifold), i.e. form a more gentle curve, more like the exhaust port. The exhaust port is easier, just a matter of removing a little material to make the curve as gentle as possible and being sure the manifold matches well. (BTW, these mods are well illustrated in Kas Kastner's latest book.)

And, I find it interesting what Kingston Sports Cars in England was doing in terms of intake porting and re-aligning the head slightly (some info also in the Kastner book.) Intake porting is quite different from most approaches, doesn't try to match the intake manifold at all. Instead, it creates even more of a mismatch when the port is opened up a lot at the manifold end, and then tapered down toward the valve. This is said to do wonders on both the 4-cyl. and 6-cyl. TR engines. It appears the intake port venturi effect is enhanced quite a bit, and fuel/air mixture might even be improved when the gas flow sort of "tumbles" from the smaller diameter intake manifold into the larger diameter port in the head. I just wish I knew more about the specific dimensions being used.

Another trick Kingston uses on the 4-cyl. is simply elongating the cyl. head holes to shift the head about 1/8" toward the pushrod side of the block. That helps centralize the valves better and unshroud the larger intake, in particular. Doing this, a concern is that the oil and coolant passages in the head need to be reworked to make sure they match and aren't blocked at all by the slight offset and head gasket.

Some neat tricks to consider, but I can just imagine the cost of shipping a heavy cyl. head to England for work, so ruled that out! Hoping to email them and ask some questions, I tried to track down the company and owner (Tony Lindsey-Dean) on the Internet, but have only found some comments here and there that lead me to believe they are no longer doing this work and the company may be be out of business. Anyone have any info? I might ask Kastner if he can give more details.

Simon, thanks for the Vizard formula, too. I've got a downloaded pdf of his Triumph tuning book and will take another look at that too. My only concern is that some of the tricks Vizard lists might be a bit out of date. A few things have changed in the years since that was published (unleaded fuel being one major difference). Of course, there are also a lot of "tried and true" tricks in there, too, as applicable today as they were then. BTW, I have recently found a local gas station that sells "racing fuel"... just in case I get really radical with the car! But, I haven't asked about the cost yet! /ubbthreads/images/graemlins/shocked.gif

Whoops. Just noticed a mistake in my first post: make that a 282 degree duration cam, not 182 degree! /ubbthreads/images/graemlins/rolleyes.gif

Thanks for your feedback and ideas!

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[trfourtune]

alan,
i'm a little out of touch in the welding aspect of cast iron. i know you can weld aluminum heads and you can spray weld with special materials to cast iron (the cam grinders do it-not for the average joe). how do you weld to cast iron heads to build up material in them? i don't think you can just grab your mig and go to it. /ubbthreads/images/graemlins/confused.gif
rob

 

[Simon TR4a]

Hi Allan,
The valves I have are definitely 1.65 intake and 1.42 exhaust, and have been in use for 3 summers, about 8-10,000 miles. I assume I have unleaded inserts, but will have to check with the shop that built the cylinder head; certainly did on the old head with the stock size valves.
The rims of the inlet and exhaust valves are very close together, but do not touch. I have heard of cocerns about the "bridge" of metal between the valves being too weak and cracling but have had no problems myself. (I have a spare head and my set of very low mileage stock size Triumphtune valves so I guess I will build up yet another head if I have to!)

I believe Greg Solow and other racers are constrained from using larger valves by the "point in time" section of the rules governing vintage racing; the car must comply with the SCCA rules for a specific year, usually 1972, and the bigger valves were either not yet available or not allowed at that time.

I must have misquoted the rule of thumb from Vizard as it gives ridiculous camshaft lifts for a 2 inch valve as would be used on a V8; I'll have to see if I can find the info again. Interesting about the offset head but it sounds like a lot of engineering, and potentially a lot of things to go wrong. I think for reliability I would be inclined to keep it simple.
Let us know what you decide, and how it works out!
Simon.

 

[Alan_Myers]

[ QUOTE ]
alan,
i'm a little out of touch in the welding aspect of cast iron. ...how do you weld to cast iron heads to build up material in them? i don't think you can just grab your mig and go to it. /ubbthreads/images/graemlins/confused.gif
rob

[/ QUOTE ]

Hi Rob,

There are various methods to weld and braze cast iron. Actually, there are cast iron welding products for stick, oxy/acetylene and TIG. Might be for MIG too, but I'm unaware of any.

For head work, I'd expect methods with the least spatter and that provide a workable fill material would be the best choice. If welding (not brazing) I think that would be a high nickel content rod. Often cast iron is pre-heated before welding, and then cooled slowly afterward. That's to prevent any stress cracking.

Inside intake ports, which are relatively cool compared to other areas of the head, brazing might work well too. Probably oxy/acetylene would be used. Brazing might be easier and less expensive than welding (high nickel content rods are expensive), although pre-cleaning and using the correct flux would be very important.

Anyway, for a job like this, I don't think I'd try it at home. I'd look for a shop with experience, to avoid any problems. I would do the porting work, after they have done the welding or brazing.

In the TR 4-cyl. head, the valve guide holes would need to be redrilled. But that's not too big a deal.

Yes, aluminum is easier. Wish I had an alu head for the TR. (Way expensive! Maybe some day, right after I win the lottery).

A lot of people don't know that oxy/acetylene can be used with several aluminum welding and brazing processes. It's mostly a matter of selecting the right rod for the particular alloy and usually a flux is used. Flux might be applied separately, or come pre-coated onto the rod, or the rod might be flux-cored. Gas welding alu is sometimes better than MIG or TIG, such as when the aluminum needs to be shaped and worked afterward. Gas welded alu remains soft and ductile.

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[Simon TR4a]

Alan, the intake port modifications you describe as used by Kingston sound very interesting because the head currently on my car has had a typical amateur porting job doe, i.e. hog out the port for the first couple of inches where you can get to it easily!

I have been using a long branch inlet manifold opened up to match and with the internal divider slimmed down and polished as per Kastner. But I also have a spare long branch manifold which is stock, so I could try this out when I get the car back on the road.
In theory it sounds as if it would help an engine with a lot of camshaft overlap to run more smoothly and make more power at lower revs.
Simon.

 

[Alan_Myers]

Hi Simon,

Hey, I got the link you emailed and thought I'd copy and post it here for anyone else who might be interested in that article by David Vizard on Hot Rod's website. It certainly applies. I've printed it out to read over more carefully and digest.

[ QUOTE ]
I found an article from Hot Rod reprinted on the internet, try looking at www.hotrod.com/techarticles/18218 by David Vizard.
He is discussing race engines, not street, but maintains all 2 valve engines are "undervalved" for their displacement, especially narrow bore, long stroke motors like ours.

[/ QUOTE ]

I need to find out more about the Kingston porting technique before I start removing metal! But, it sounds like you may have nothing to lose on that head of yours. According to Kastner's writeup about it, the idea of this porting technique was to build torque and not worry too much about HP, which will take care of itself when torque is improved. It reportedly works well on either the 4- or 6-cylinder TR motors.

In your email you also mention exhaust pressure, and yes that's another important consideration. On the TR race engines, I think they went to 2.5" OD pipe about 45" long. Besides the noise level, a problem with that is that it will really gut the lower and mid rpms of torque, puts all the emphasis on high rpm work. I had been running a full "custom" exhaust system with 2.5" pipe, but 2.25" pipe is about the largest I'd run on a TR street engine now. In fact, my car has 2.125" on it right now, i.e. just slightly larger than stock. We'll see how it works with the new headers when I get it back on the street. Different header design, too, 4-into-2-into-1 instead of 4-into-1 I'd been running. Reportedly, the 4-into-1 is best for top rpm, while the new style I'll be using preserves more lower to mid rpm torque.

I can't comment much about the stock manifolds because I've been running Webers for the past 25 years. I have only heard that the later HS6 (short) SUs combined with the longer manifold are the best performing of the various possible combinations. I do have one of the long OEM manifolds, but it's fitted with Hitachi SUs off a Datsun 240Z, of all things! That's what came on the car when I first bought it, and what it had been raced with. It's been way too many years since for me to recall what improvement I saw when I swapped to the Weber 40DCOE! (BTW, for street use I'm also running slightly undersize DCOE, compared to full race engines. The 40DCOE will be fitted with and jetted around 34mm primary venturis - aka chokes - just slightly larger than the 32mm spec in 42DCOE for stock 86mm TRactor motor, but not the 38-40mm chokes in 45DCOE often used for full race.)

What it all comes down to is that all the intake and exhaust "engine breathing" factors need to play well together, to be balanced and well-matched with each other, to really get the best out of the engine. I was concerned about too much intake valve, but it sounds like I don't have to worry... just can go ahead and fit all the valve I can get in there after the exhaust valves have been enlarged as much as possible (35.5-36mm)and unleaded exhaust seat inserts have been installed. Some careful porting, unshrouding and combustion chamber shaping will be the icing on the cake.

Now I gotta decide if I want to use roller rockers or original type! Rollers would be quieter, put less strain on the valve train and would be a true 1.5:1 ratio (OEM rockers are actually about 1.43:1).

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[Simon TR4a]

Alan and Rob,
I found another article relevant to this discussion this weekend, in a magazine.
The author quotes a formula relating primary pipe diameter to the rev range at peak torque. So assuming you have a cam intended to produce peak torque at, say 4000 rpm, you can choose a header which will match.
The formula is cross sectional area of header pipe x 88,200 divided by displacement of one cylinder in cubic inches = peak torque rpm.

In my case the header primaries are 1.5 inch outside diameter, so 1.38 inches id approximately, and with 86mm pistons I have about 130/4 = 32.5 cu. inches per cylinder.

Cross sectional area is .69x.69 x 22/7= 1.49 sq. inches, multiply by 88,200 = 131,418 divide by 32.5 = 4,043.

That sounds pretty high, and I have no way of verifying the formula is correct, but its an interesting idea. It also shows you don't need primaries more than 1.5 inches, and bigger engines will make torque at lower revs, as we might have guessed.

Simon.

 

[trfourtune]

simon & alan,
i saw that article also, classic motorsports i think, which also agreed with the numbers i came up with from "headerdesign.com". i sent off a package of information to "headers by ed" to get an "expert sizing design" done. costs a few bucks but i hope to build only one set of headers. i will post it when i get it.
alan, i bought the harland sharp roller tip rockers because i have thin stem valves (5/16") and want to reduce the thrust on the stem. these have a "plain" bearings on the shaft so they wont wear out as fast as roller bearing ones. the roller bearing ones are good for race engines were you replace those every year and need every little bit to be competitive. also the shaft and rockers when i bought this project were completely shot! they are also best price. i got mine on e-bay for $280 but they aren't that price any more, more like 340. "goodparts" has roller bearing roller rockers for 400 something dollars. british suppliers much more $$$$$. if you have stiffer valve springs then roller tip rockers make even more sense.
cheers /ubbthreads/images/graemlins/cheers.gif
rob