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Dealing with unleaded fuel?

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dcoplan

dcoplan

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I've recently read that a stock 948 was designed for leaded fuel and by itself is not suitable for today's unleaded fuels. Solutions included using specially hardened valve seals or a fuel additive to deal with this. A discussion with a mechanic lead to him saying, "Don't worry about it - you're fine as you are." and he even suggested that using hardened valve seals could result in other problems.

What do you all think?

Dan
 
I don't believe the A series engine is particularly susceptible to valve seat regression. The BMC B series however is.

Kurt.
 
The cost of hardening a head and the cost of a replacement head is the same - drive it and only replace it if there is a problem.
 
Another option : Drive it and only start using an additive if you find there is a problem (by the exhaust valve lash closing up).

I use Redline Lead Substitute in my TR3. Stopped the recession cold. I'm still using at the recommended rate of 1 oz/tankful, but I may try tapering off as the instructions from Redline suggest.
 
Valve seat recession is a real physical condition in all cylinder heads using unleaded fuel whether original cast iron, hardened cast iron or with valve seat inserts. Leaded fuel doesn't eliminate valve seat recession, just slows it down. The only difference between them is the rate of recession. The hardened valve seats do create more wear on the valve itself. TEL (Tetra-Ethyl-Lead) was added to fuel in the 20's and 30's to increase the performance of refined fuels and hence the auto's that used it. The side benefit was that it also provided increased valve seat life. TEL provides benefits to the valve seats and the exhaust valve stem. Engines that have had a previous life on TEL continue to benefit from the TEL for some time after transition to unleaded fuel. However, after continued use of unleaded fuels, the previous "coatings" of lead are removed.

Valve adjustment plays an essential roll in valve train maintenance. Periodic adjustment of the valves helps to minimize valve seat wear/errosion.

I have disassembled and performed valve jobs on 100's of A-series and B-series heads. All of these are prone to valve seat recession. Especially on the exhaust side. I have seen poorly maintained engines where the exhaust valve face is below the combustion chamber floor, the recession was so bad. The head when cleaned looked like coked iron in the seat area. All the carbon had been burned out of the seat. Pits, crackes and holes were all over the seat.

On your 948, I would use a lead substitute per the recommendations and adjust valves per the workshop manual. If decreased performance of the engine occurs, check the conditions of each cylinder with a leak down test. This will help identify if you are seeing valve seat problems. Monitoring valve lash reduction on the exhaust valve is something that requires keeping a record of how much the valves are tightening up over time.

Valve seat inserts are already "Hard" by the material selected. The steel alloys or exotic materials (Beryllium) are what determines the seat hardness. The term "hardened" seat is a function of the seat insert itself. Most full service machine shops provide valve seat inserts of at least 2 types. Most don't use the Beryllium alloy ones because of the cost and toxicity of the material. Induction or flame hardening of a cast iron valve seat is a cylinder head manufacturing operation, not an aftermarket service process.

HTH,
Mike Miller
 
Mike - thanks for the great explanation. What lead substitute do you like? TR3driver mentioned Redline. Are they all more or less the same or do you have a preference?

Dan
 
Spridget64SC said:
Monitoring valve lash reduction on the exhaust valve is something that requires keeping a record of how much the valves are tightening up over time.
Click to expand...
I agree with everything but that. There is nothing else that can cause the lash to close up; wear at any other point (cam, lifter, rocker, valve stem, adjuster etc) causes the lash to open up. So if you set it right, and it's now too tight, you've got VSR. I've had two heads (on two different TR3 engines) that suffered from it, and in both cases there was no need to keep a record. In just a few thousand miles it would start idling funny because the valve lash was way too tight. Here's what the first one (which I didn't treat) looked like after I finally pulled the head:



FBHVC did a study in the UK a few years back (when they finally switched to unleaded). Most of the products they tested turned out to be useless, IIRC there were only 3 out of 12 that significantly reduced recession. Of the 3, only the Redline is readily available in the US.
https://www.fbhvc.co.uk/legislation-and-fuels/fuel-information/

("Readily available" being relative of course, the corner store probably won't have it. I buy mine through Amazon.)

Of course there are lots of products available here that they didn't test, and they may work fine. But knowing how much snake oil is sold to "improve" your car, I went with the independent study.
 
I rebuild every head, even race heads with hardened exhaust seats, no professional who is trying to do good work would approach it in any other manner. Valve recession is just the most drastic issue of this unleaded fuel issue. Cast iron exhaust valve seats were never designed to run on hotter burning unleaded fuels. One of the biggest culprits is loss of valve seal, much more common than valve recession, which recession is somewhat rare. What is most common is rapid valve seal loss after a valve job, in which hardened exhaust seats are not used, specifically on cylinder #2 and #3, due to them sharing the same exhaust port . On race cylinder heads, that use leaded race fuel and thru extensive leak down testing, we positively proven that leaded fuel, or lead additive is not the cure once the exhaust seat area material has been compromised by unleaded fuel. You can see when this has happen, by pitting of the exhaust seat area, at this point a typical valve job is useless, and will be very short lived, even with leaded fuel or lead additive.

How strong do I feel about using hardened exhaust seats in my cylinder head rebuilds, so much so if someone called me today and ask me to rebuild their cylinder head,and ask ask me to not use hardened exhaust seats, I would decline the job, because I know there will be hard feelings down the road.

That should explain how I feel about this topic.
 
That is some kind of first hand experience! I would agree that the picture represents acute valve seat recession. Keeping a record of your valve lash history would not have contributed anything to that situation. For instances not quite as severe, having a record of where the valves were set and which have opened up versus which are closing up would be helpful in assessing overall valve train condition as well as potential chronic VSR.

As an aside, but pertinent to this discussion regarding valve adjustment is the need to inspect the rocker pads on A-Series engines. These can become "divoted" where the valve stem wears and create a false valve adjustment.

Most all of my experience is converting heads from salvage and donor engines into race engines. They mostly come from east of the Mississippi. These heads show all stages of VSR. Were run on unleaded fuels from a little to a lot. Show all kinds of valve train conditions. On race engines, seats are installed as necessary. On street rebuild projects, hard valve seat inserts are installed in the exhaust as standard practive. Installing seats addresses any existing VSR and takes a step towards minimizing future rates. A second benefit is that inserts gain back valve spring installed height to be able to use stock springs and meet specs with a minimum of adjustment. Even on race engine rebuilds, there is VSR, but due to different factors being a larger contributor.

Redline products consistently perform well. The FBHVC tests indicate acceptable performance of 3 products and the expected acceptable performance of another based upon analysis. O'Reilly's is identified as carrying the Redline product. You might be able to find one of the other FBHVC discussed products through a local distributor or auto parts supplier. I can usually order non-stocked Valvoline products through my local NAPA out of Atlanta if desired. I would look to see if a stocked product used either lead/manganese/sodium/ or phosphorus. Follow the bottle directions and run your own test.

Mike Miller
 
That is some kind of first hand experience! I would agree that the picture represents acute valve seat recession. Keeping a record of your valve lash history would not have contributed anything to that situation. For instances not quite as severe, having a record of where the valves were set and which have opened up versus which are closing up would be helpful in assessing overall valve train condition as well as potential chronic VSR.

As an aside, but pertinent to this discussion regarding valve adjustment is the need to inspect the rocker pads on A-Series engines. These can become "divoted" where the valve stem wears and create a false valve adjustment.

Most all of my experience is converting heads from salvage and donor engines into race engines. They mostly come from east of the Mississippi. These heads show all stages of VSR. Were run on unleaded fuels from a little to a lot. Show all kinds of valve train conditions. On race engines, seats are installed as necessary. On street rebuild projects, hard valve seat inserts are installed in the exhaust as standard practive. Installing seats addresses any existing VSR and takes a step towards minimizing future rates. A second benefit is that inserts gain back valve spring installed height to be able to use stock springs and meet specs with a minimum of adjustment. Even on race engine rebuilds, there is VSR, but due to different factors being a larger contributor.

Redline products consistently perform well. The FBHVC tests indicate acceptable performance of 3 products and the expected acceptable performance of another based upon analysis. O'Reilly's is identified as carrying the Redline product. You might be able to find one of the other FBHVC discussed products through a local distributor or auto parts supplier. I can usually order non-stocked Valvoline products through my local NAPA out of Atlanta if desired. I would look to see if a stocked product used either lead/manganese/sodium/ or phosphorus. Follow the bottle directions and run your own test.

Mike Miller
 
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