View Full Version : Unleaded fuel question

11-01-2006, 05:18 PM
I just acquired a 1962 TR4 Surrey from my neighbor. After a nice restoration, it was parked and has not been driven for 6 years. I got her running and just made large parts order to get her back into top driving shape.

In high school I drove MG's and Triumphs. Unleaded either wasn't an issue, or I didn't care.

I asked about engine mods and unleaded gas, but the guy didn't know anything about it. Obviously, or he would have been driving the car instead of letting it sit in his garage.

Questions are:
1) Any way to tell if engine has been modified for unleaded fuel?

2) What are issues if I drive it without any mods?

3) What mods should be made and any idea on cost? New heads suitable for unleaded are about 3k at the usual sources.

4) Any suggestions short of mods to make unleaded not so hard on the engine? Additives etc.?

Prost! /ubbthreads/images/graemlins/cheers.gif

11-01-2006, 05:24 PM
My understanding is that you have to replace the valve guides not the head. You have to use steel ones rather than the bronze. Thats machine shop work. You need to consider how much you are going to drive it before you make a major ??? decision. I'm sure someone else will give you a more definitive answer but these are my thoughts.
Cheers, Tinkerman

11-01-2006, 05:32 PM
I have always been told you need very little lead to lubricate the valves in a cylinder head. I would bet there's enough lead already on them to do. Besides, whats going to happen. You wear out the head and have it rebuild or replaced? You were going to do that anyway. Drive it and worry about that later. It being an LBC you WILL have other problems to worry about. /ubbthreads/images/graemlins/grin.gif

11-01-2006, 06:32 PM
My understanding is a potential problem with the valve seats. The exhaust valve seats can errode over time. I read a good explanation that said the valve sticks to the seat when it closes. When it opens again the valve pulls a little material away from the seat. All of this happens at a very small level. Maybe even microscopic. Over time enough material can be pulled from the seat to compromise the sealing of the combustion chamber. Hardened valve seats will prevent this gradual errosion. There are mixed opinions on whether this is a critical item. Some say wait until you need to do a valve job. Others have it done whether there is evidence of erosion or not.
The general recommendation for valve guides is to go with one of the newer bronze alloys when replacing the worn guides.

11-01-2006, 07:21 PM

I'd drive it as is until you need to have the valves or valve guides replaced. Then you can have hardened valve seats, stellite faced exhaust valves and manganese-bronze valve guides installed. There is no need to replace the head. Depending how and how much you drive the car it may take a long time before any cylinder head work is needed. If the restoration was done in the last ten years or so the valve work may have been done.

You can always use an over counter fuel additive such as "Relead" to ease any concerns you may have.

Geo Hahn
11-01-2006, 07:22 PM
Yes, it is hardened seats that protect against recession (th e valve kind, not the economy). I had these added to the head when I had it off for other work earlier this year. Prior to that I drove it 20+ years on unleaded fuel w/o a problem.

So... my take was: it's worth doing if you have the head off and doing the valves, otherwise not a big problem.

As for how you can tell -- if you have the head off you should be able to see the seats if they have been inserted.

11-01-2006, 07:45 PM
The seats need to be hardened....the guides should not be a factor in this although I see alot of Brit cars guys seem to think it's important...I don't know one engine builder who does domestic engines that agrees.

That being said...drive the **** out of it and when it needs a valve job/overhaul do it then...I drove my last TR3 for 13 years without any problems at all...plus lotsa old (I mean OLD) American iron and never did any valve work to 'em.

If it ain't broke.....

11-01-2006, 08:01 PM
Hi Kirk,

First off, let me say that if the engine was rebuilt within the past ten or fifteen years, it's pretty likely it was brought up to unleaded specs then. I wouldn't worry too much unless you hear *a lot* of valve tappet noise (there's always some ticking with these old engine designs, especially when not yet fully warmed up) and find you cannot keep the valves adjusted.

For one thing, the metal alloy used in TR4 (and TR2/3) cyl. heads is much more resistant to unleaded fuel than most folks give it credit for, better actually than most other LBCs of the same vintage.

The most likely condition that would cause problems are hard driving at high rpms, working the engine hard and heating it up above normal operating temperatures. Really pushing it.

You might be able to go for many years and tens of thousands of miles with no problem, if the car is driven just a little more oderately and carefully.

In other words, keep it under the redline. ;-)

If you were rebuilding the engine for other reasons, it would make sense to set up the head for unleaded at the same time. However, I'd be very unlikely to tear apart a good running TR4 engine for the sole purose of converting it for unleaded. Nor would I worry at all about driving and enjoying a TR4 (or 3 or 2) just because I knew it hadn't been converted for unleaded. I'd take it out and have fun, would just avoid driving it really hard. Once the valves get noisy and can no longer be adjsuted properly, then it's time to rebuild the head and, most likely, give some attention to other things in the motor, too.

Regarding your more specific questions:

1. No, there really isn't any ideal way to check without removing the cyl. head.

You could try to see the valve guides from above. If they are bronze colored, that would indicate at least they have been changed to unleaded type. But, the guides are a bit hard to see, hidden inside the valve springs (which are probably triple springs on the exhaust side, if the head and engine are original to your car) and are no indication if other work has been done.

You also might be able to tell if the valves are made of stainless steel, if a weak magnet won't attract to the tip that protrudes from the keeper (the valve rocker assembly would need to be removed to check this, but that's just a few nuts and bolts to lift it off).

I'm not totally sure that a valve stem that attracts a magnet would be complete proof it's not unleaded compatible, anyway. I think there are other types of unleaded valves, not stainless steel, and/or some have stainless steel valve faces and mild steel stems. But, I'm not sure of this.

It might also be possible to peek inside the cylinder with one of those fiber optic probes, but I'm not sure if you will be able to see well enough in there to tell if there are valve seat inserts installed. Maybe a local repair shop has one of these and can pull a couple spark plugs, take a look for you. Alternatively, the exhaust manifold could be pulled off and a fiber optic probe used to inspect inside the ports to see the valve seat insert from the back side. Of course, in both cases it would be useful to have someone doing the inspection who knows what to look for!

Unfortunately, even if no sign of a valve seat insert is found, that doesn't necessarily mean that the head hasn't been set up for unleaded fuel. Another process called induction hardening might have been used, in the area right around the original seats in the head, and cannot be visually detected.

2. I think I gave you some ideas above. However, let me add a bit more. If you start to notice frequent need to adjust valves, i.e. they tend to loosen up, that's a symptom of valve seat recession. This is erosion of the seat itself, due to higher temps of the combustion gases. It will mostly show up on the exhaust valves first, since they run hotter.

Another thing is more rapid wear to the valve guides, if the original cast iron type are still in use. This would show up as added valve noise, and lateral play in the valves.

A third possibility is loss of compression if the valves themselves are eroded around the sealing area, where they meet the valve seat. A leak down, compression test performed by a shop could help identify this problem.

In really extreme situations where timing is too advanced, pre-ignition and detonation can occur, which can damage pistons and cylinders, etc. However this is more likely to happen if the cylinder head has been skimmed a lot either to correct for warpage or to raise compression. If the ignition timing is reasonably well adjusted, and premium fuel is used, it's unlikely to happen. I'd avoid regular and mid-grade, lower octane unleaded fuels. (Lead also increased fuel's effective octane rating and these engines were designed to run on fuel that's closer to today's premium grade.) You can get some idea whether or not or how much a TR 4-cyl. head has been skimmed by measuring it. From the bottom face to the top edge it should measure 3.30" if unskimmed, anything less means some has been shaved off it. Unfortunately, it's difficult measure while in place and bolted down. But, you might be able to get some idea.

3. The normal mods to make the engine more compatible with unleaded fuel are:

- Stainless steel valves, especially on the exhaust side.
- Hardened valve seats on at least the exhaust side (usually seat inserts are installed, but sometimes the area is induction hardened instead).
- Phosphor bronze valve guides (which must be honed slightly on the loose side of specifications, since they expand more than the original guides and can seize a valve stem).
- If the head is removed for this work, the rocker assembly should probably be rebuilt. It's usually in need of a new shaft and bushings, at least. It is really hard to assess wear without taking it apart.
- When the head is removed for this work, the pushrods and cam followers will all need to come out. If they are going to be reused (i.e., there isn't a plan to refresh the cam which calls for at least new or freshened up cam followers at the same time) they must be carefully kept in order.
- A replacement head gasket will be needed.
- It's a good idea to check the head studs to see if new are needed, and replace as required.
- A great deal of care must be taken to not disturb the cylinder liners, unless the rest of the engine is going to be rebuilt at the same time.
- Overall, you may also need to retard the ignition timing, due to unleaded fuel the car will be more prone to pinging or knocking, both of which can do damage if left uncorrected. This has probably been done already, in previous tune-ups.

Parts cost of these items you can get from any of the usual catalogs or online sites. Labor is a bigger issue, but that varies a lot from one part of the country to the next, and even from shop to shop.

While it's apart for this work, it often makes sense to renew and refresh a lot more in the engine: valve springs, timing gears and chain, pistons & liners, rings, bearings, camshaft, cam followers, pushrods, oil pump, etc., etc. Of course, cost goes up quite a bit as more is done and more parts or machine work are needed.

Of course, total costs for any of this engine work can be kept down quite a bit if you have the skills and experience to do the work yourself. The TR 4 cyl. engine isn't terribly difficult to work on.

4. Do an Internet search about unleaded additives. There are lots of articles out there that might answer your questions better than we can here.

Congratulations on getting a nice car to enjoy!


Don Elliott
11-01-2006, 09:34 PM
You only need the inserts installed for the exhaust valves. When I did my restoration from 1987 to 1990, I re-did the head as original. Then in 1990 when I was ready to put the car on the road, Canada ruled "no more leaded gas". So I drove 43,000 miles with un-leaded gas, no additives and no steel inserts till I had to change them. The "clue" was that I was losing all the 0.012" valve gap clearance every 1,000 miles. So I pulled the head and had the machine shop put in 8 new valves and 8 new guides that I bought specified as " valves and guides for converting the head to be compatible for un-leaded. The shop told me he had the seat inserts. He preferred to use his own because he had the tooling etc. to put in his own inserts so they would stay in. I've heard of some who had a valve seat insert fall out and "CRASH !!" a head. See attachment. This can happen ifthe job is not done right. The shop did all this at a reasonable price and I've driven 51,000 miles since putting them in and have never yet had to re-gap the valve clearances, even though I check the gaps about every 5,000 miles or so.

11-01-2006, 10:05 PM
Don makes a good point..I have seen "loose" valve seats do big damage.

But I still question having to put in bronze guides.

Factory iron heads from most makes still use iron guides...and I just built a blown Hemi and my engine builder recommended iron guides. Bronze guides wear a little quicker than iron...no big deal, I guess.

Andrew Mace
11-01-2006, 11:11 PM
To my knowledge, nothing has ever been done to my little 1147 since it left the factory in late 1961. I bought it with about 50k on it and have put 26k on it in the last four years. NO PROBLEMS with valves at all. In fact, I checked valve clearances recently and didn't have to reset any of them.

Mind you, I don't baby this car at all, and that little 1147 works a LOT harder at highway speeds than does the average TR wet-liner or six.

Drive it until (if) the head needs other work, then have all that stuff done if you like!

11-02-2006, 08:54 AM
Thanks for your input. I was planning to drive it and worry about it later. This is a really nice car and I practically stole it. It is truly a "garage find". It has 3k miles on it since the resto.

I hope to have her purring and ready to roll in time for the last tailgate of the regular season on the 11th. I've gone through her from bonnet to boot and there doesn't appear to be any one large problem. Mostly just dry rot, corrosion, leaks etc. after sitting for 6 years. I got her fired up last week and it was great to hear the SU's spit, sputter and pop back to life. I'll rebuild them this weekend. The egine ran pretty well and didn't overheat or make any unusual noises. The hydraulic system is shot, so I ordered new master and slave cylinders, new lines and front and rear brakes (rotors, drums pads etc.).

Man, it has been in the mid-70's here in the South Carolina mountains this week, so I was aching to drive her.

Want to see pics?

11-02-2006, 09:13 AM
1962 TR4 (https://static.flickr.com/96/277369294_e8b82bd149.jpg?v=0)

profile (https://static.flickr.com/82/277369297_e97b0ea346.jpg?v=0)

interior (https://static.flickr.com/117/277369307_f95ce0fdeb.jpg?v=0)

dash (https://static.flickr.com/114/277369302_cea68873dd.jpg?v=0)

11-02-2006, 10:00 AM
Nice car. Thanks for the pictures.

11-02-2006, 10:12 AM
Wow! that one RED interior
Nice find.

11-02-2006, 01:09 PM
Hello all,

the reason taht bronze guides are advised is to improv ethe heat transfer from the valves, thus they should run cooler and last longer. A lot does depend on how you drive the car, stay below 3,000 r.p.m. and a standard head will be good for a lot of miles. Mine?, well I use 6,000 r.p.m., non modified head and fuel additive, no real adjustment in 35,000 miles required. When there is serious wear I'll have inserts installed.