Twin Cam Fuel/Exhaust Valve Modification

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Hi Guys,

My Big Valve, Twin Cam engine is at the machine shop and will shortly begin to have work done to it.  Best we can tell, there is only 22,000 miles on it and it spun freely before it was taken out by the previous owner.  He did not try to start it but tells me the starter motor spun it freely after about 40 plus years in storage. My intentions are not to rebuild it but go through it and clean up any areas that might need attention.  I can find no mention of modern day fuels to use as leaded gasoline is no longer available.  I was thinking I could use what is called recreational fuel and add a lead additive to it rather than regular grade ethanol laced .
I also know that I could have the exhaust valves redone to accommodate ethanol fuel, taking advantage of the motor being out.  That would make 93 Octane ethanol fuel available to me.
The only fuel recommendation I can find is in the Twin Cam Owners Manual and it states 101 octane.  So I have two questions.

The first one is what type of fuel, here in the US, does everyone use in their motors?

The second one is what recommendations are there for modifying the exhaust valves to accept ethanol laced fuels rather than leaving them in their original state, while using an lead additive to the fuel?

Now that I'm thinking about this, I'd also like to hear any recommendations as to the appropriate engine oil you're using and why.  Lotus recommended a number of oils at the time of manufacture, one of them being Castrol GTX, which is still available.
I haven't researched the others to see about their availability.

Making some progress on the car but it is slow.  I don't have a heated work space so I take things off and bring them inside.  Both door cards needed some minor repair and since those were off, I removed the seats too.  Everything has been thoroughly cleaned and treated with conditioner and the upholstery vinyl looks almost as good as new.  That part is really pleasing since I'd like to keep things as original as possible.  Next on my list is to take the front rotors off and clean them up since their heavily rusted.  Don't know if I can clean up the rust or just have them given a skim pass on the resurfacing machine.  Along with this I planned on new front bearings.

Thanks for your help!

Bob

[BDA]

Premium gasoline should work fine. The valves have steel seats so lead isn't a problem. I would make sure your hoses and fittings will stand up to alcohol. I doubt you still have the original plastic (was it nylon?) fuel tubing so as long as you have a metal 'T' between your carbs, you are probably ok.

Because the cam and tappets are bathed in oil (as JB reminded us a while ago) it's not critical to to have high ZDDP levels in your oil. Still, I use Red Line 10W40 partly because of its ZDDP.

How about some pictures of your baby and your progress, Bob?

[surfguitar58]

I proposed using avgas (aviation fuel ) in another thread and was told there is a very good reason (which I forget) NOT to use avgas. I’ve been using 91 octane premium pump gas with ethanol with zero problems for 2 years now. FYI, I have all new fuel lines, electric fuel pump, in-line filter and a solenoid cut-off valve now.

wrt oil, I use Mobil One 15W50 which has some, but not a lot of ZDDP. I was told by someone at Mobil that Mobil V-Twin (Harley oil) would be a good high-zinc choice, but as BDA and others have pointed out, our flooded tappet design makes zinc less important.
Tom

[BDA]

Because avgas is designed for use at higher altitudes, it is less volatile than ordinary gasoline and so no ideal. Some racers use it because of its higher octane rating without problems, but racing gas is pretty available so I suspect their numbers are fewer than in the past. It's very expensive and the higher octane rating is wasted on a stock or even a modified street motor. Regular premium gasoline is all you need and it's readily available.

There are other high ZDDP oils that cater to the classic car market if you are of a mind. r.d. enterprises sells some and I would expect places like Moss Motors do too. They can be as expensive as synthetic oils. I would stay away from "modern" oils because they are generally much thinner than what the engine is expecting. I don't know enough about oil to say definitively that that assessment is accurate but it does no harm to use heavier weight oils and be safe.

[Certified Lotus]

Glad to hear your steadily moving along with your restoration. My garage is also un-heated but I bought a fan forced propane heater from Loews that connects to a regular grill size propane tank. I can get two full days of heating out of one tank in a 1000 sq ft garage. A tank refill is $20 so $10 a day isn’t unreasonable. I turn it on about an hour before I go into the garage to work. Gets so toasty I can work in a long sleeve t-shirt.

If you have the engine apart and have a machine shop looking at it, I might suggest new bearings, piston rings and valve guides.  Test all the valve springs. A light refresh is the best approach. Although 22,000 miles doesn’t seem like a lot, the engine has been sitting for a long time and that is worse than a higher mileage engine that has been regularly used.

I’ve had a number of TC engines built by Quicksilver Racing and they make the following recommendations for engine operation at peak performance and life:

* always use the highest octane fuel you can buy on the street (no racing fuel or av gas) 93 octane pump gas
* Mobil One synthetic oil 10W30
* Driven carb defender in each tank or gas
* MOA engine oil supplement in every oil change

Considering they build a huge amount of engines and have been around for a long time I take their word as gospel.
TC engines are very expensive to rebuild. Take good care of them.

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Wow, lots of good information and I appreciate every bit of it.

Thanks BDA for your comments.  After my first post I found some good info in the Dave Bean catalog that mirrors your comments concerning the valve seats.  It was buried in the fine print in the "Engine" section.  I intend to replace all of the fuel lines with suitable upgrades from the original stuff.  Haven't decided on rubber tubing or braided yet.  I'm not familiar with Red Line oil but surely I could find some.

Thanks Surfguitar54/Tom, I had not considered av gas but only because it didn't cross my mind.  I can readily get 93 octane here and will probably go with that.  I assume the solenoid cut-off valve  is precautionary in the event of a fire.  Since it's electrically activated, what happens if you lose electricity to it?  Does it stay open/closed or does it automatically revert to the closed position.  Fire prevention has been in the back of my mind but I'm a ways from that at this point.  I haven't considered the cost of the various proposed oils yet.  I like the mobil one and use it in my 2015 Porsche.  But since I think I'll only put 2 or 3 thousand miles on the Lotus each year, it might get costly.  Regardless of the miles, I'm in the habit of an oil change at the start of each new driving season.

Thanks Certified Lotus, I read all of your posts, retroactively and am thoroughly impressed with your approach.  The Europa came out magnificent and I would love to see it some time as a measuring stick.We intended to replace all of the seals and gaskets along with piston rings after the cylinders have been honed.  I have limited knowledge about these things but if we use new bearings, does that necessitate "align boring"?  The Driven carb defender and oil supplement are new to me so I can spend some time researching all of these things while awaiting the motor.  I just spoke with them on Friday and he thought he could have it back to me by April, maybe May, which would fit in my schedule very well.  Seperately, I sent my Strombergs out to Joe  Curto in New York for a rebuild.  He ought he could have them back to me be mid March.  I originally thought I would do that myself, but after looking at the exploded print of the carbs I decided I would be in over my head.

These pictures may have been posted before.  I have not had the opportunity to get it out in the sunlight for some good shots.

Again, thanks for all the help.  I have not had the opportunity to drive any Europa and am anxiously awaiting my chance.

[BDA]

Dave Bean's catalog is a wealth of information. I should review it again. The Red Line oil website is www.redlineoil.com. It's available, along with everything else at Amazon. I would also pay attention to Quicksilver's recommendations.

You can align bore the mains or not. On some engines, align boring moves the center line of the crankshaft which can cause problems but bearings for Kent blocks come in different ODs so that isn't a problem (if it is a problem on a TC). I would do it because it eliminates any difference in the concentricity of the mains.

Changing the oil at least every year is a good idea.

[jbcollier]

Nothing wrong with using SS braid lines but be careful how they are routed.  A loose line can act like a buzz saw cutting a surprising array of materials.

You line bore a block only if it is required.  While common practice in air cooled VW engines, it is relatively rare in cast iron blocks.  It does not change the crank centre if done correctly.  Similar to resizing rods, on TC blocks, you remove a small amount of metal from the bearing caps only and then line bore them to size again. 

[Kendo]

Regarding the owner's manual saying we need 101 octane, isn't octane measured differently in Europe and America?

Answered my own question: https://en.wikipedia.org/wiki/Octane_rating

From that Wikipedia article:

"Because of the 8 to 12 octane number difference between RON and MON noted above, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel."

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Thanks for that Kendo, the octane rating never crossed my mind.
If I understand this correctly, then 101 rating in Europe would convert to 97 or 95 here.  Nowadays, our 93 rated fuel could be considered to be 97 to 99 rated in Europe.  Correct me if I'm wrong.

Thanks for the info.

[brucelotus26r]

I would replace the valve guides with silicone bronze guides as Lotus guides are short & have no stem seals.
Check the cam followers for wear & fit as these are area that can lead to oil consumption.
I use Valvoline VR1 oil it is a high zinc oil but I work on a lot of A H & Triumph & I can get it at the local auto parts store for $7/$8 a qt.
I use 93 octane & no additives with no problems as I do a lot of long distance drives and don't want to deal with carrying & using them?