Last month I talked about some very easy and inexpensive methods of increasing power in your LBC. This month, I will get a little more costly. Before I go there I need to put in my “CYA” warning. Following any of the suggestions or recommendations listed below could cause you to have more fun with your car and therefore drive in a more spirited manor. You may find yourself driving beyond your or your cars ability. This could lead to an accident that may cause bodily injury to yourself or to others. It may lead to property damage belonging to you or to others. Follow these guidelines only if you know, or feel you know, your own personal capabilities when behind the wheel of your LBC.
Now you cannot sue me if something goes wrong. While there were no internal changes last month to gain a few extra ponies, this month we will go inside your engine to make a few upgrades. If you do not feel you have the knowledge to do this, get a good repair manual on your car, either Haynes or Bentley are good choices. Some of our LBCs have specific books on upgrades that can be made and if one is available for your, get it and read. There are several tools you will need and you may already have most. If not, do not fear the great prices of Harbor Freight. I will try to mention the tools as they become needed. I would also suggest a drain pan for oil and water and bottles to put it in. NEVER leave anti-freeze where your pet can get to it. It is poison and sweet to them at the same time. Next, I want to say to make sure your suspension, brakes, and other safety items are in good order. If you have trouble stopping your car as it is, you will have a lot more after gaining extra power. Every LBC has adequate brakes and handling for these upgrades and you need not worry about flying out of control, unless you pretend you are autocrossing while on the streets. Make sure your brakes at all four wheels are in good repair with no leaks, clean pads or shoes and properly bled and adjusted. Your suspension should have good bushings and properly adjusted bearings. Enough crap, now let’s see what we can do. The next best way to get power would be one of the supercharger kits. Or you can go a turbo route. Turbos can give a tremendous boost in power but at a great cost in engine repair either before or right after your first full throttle run. The supercharger kits have less boost and are safer but you still need a very fresh engine before installing one. And these articles are not about full engine rebuilds, yet. If your engine has low oil pressure before beginning any work suggested in either this or last month’s article, STOP now and go no further. Fix that first then continue. The next easiest way to power gains is higher compression. To do this, you will need to pull the cylinder head off and have it surfaced (decked, shaved) at a machine shop. You cannot do it at home with a belt sander.
It can be a little difficult to get the original thickness of the head on your car when it was produced but you can find some close estimates. I found two numbers listed for MGBs in several places. Google it. Then Google how much to remove to get no more than 10.5:1compression. You still want to run the car on pump gas so be conservative with decking. On MGBs there are bigger valves you can get and there will probably be the same available for most of the other LBCs out there. Get them and have your machinist install them. If your valve guides are worn, have them replaced with the stock guides and not the bronze guides for reasons I have talked about before (you have to clearance them so much to not seize that you may as well leave the worn ones in).
Have a three angle valve job done at the same time. Unless your seats are burned, I do not like hardened valve seats, especially when you are increasing the size of the valves. They get very close together and there is risk they can fall out while the engine is running. This is very bad. When you get your head back, make sure it is very clean before putting it back on.
Now, here comes the place where I start saying; “while in there, you might as well as” and this can get expensive. While the head is off, you can look at the lifters easier. Some engines will require removing the side covers but now is the time with stuff out of your way. Unless you have a 1275 Midget/Sprite engine that is, these require the engine removal and disassembly to look at lifters.
Pull one lifter out at a time and look at the bottom. It should be shiny, smooth and have concentric circles on it. If there is a groove across it or any pitting, they should be replaced. Lifters are relatively inexpensive but what they ride on can cost a bunch to replace. If you see any wear on a lifter, get a good light and look at the cam lobe thru the lifter bore. You can rotate the engine by hand and see if there is any sign of wear on the cam. If you see pitting on the high point of the lobe, or it looks like a sharp ridge, you need a cam. Damn, this just got a lot more expensive than you wanted it to be. But we will wait a little before getting into a cam discussion. It the cam has no pitting or at the most very minute (and I mean very minute) pitting, you can get away with a new set of lifters and this will prolong the cam life some. I bet you will quit driving the car from old age before the cam and lifters wear out. I know there will be some out there reading this that are agast that I suggest this, but your only other option would be a cam replacement and some of you may not feel up to the skills required or the costs involved.
Just put new lifters in whether they have any wear or not. New lifters can go on a used cam, not the other way round. Now, you are ready to put the head back on if this is all you want to do. There is a activity called porting and polishing that you can have done and I do not recommend it for the average mechanic to do. It requires special tools and knowledge to do it right. Some machinists can do it but not all. For a street car, it is not worth the extra cost. If you want that tiny bit of extra power you can get, and the ego satisfying ability to say “my head was ported and polished” then get it done. One thing that is easier and cheaper is port matching. This still requires special tools and abilities but takes a lot less time. Using a good intake/exhaust gasket on the head, mark the opening of the ports with a scribe. You can color around the ports first with a magic maker and the scribed line will show up better. With a high speed grinder, either air or electric but a little bigger than a small Dremel, you want to grind the port to match the opening in the gasket as close as possible. On the intakes, you really would like the opening to be just less than 1/16” larger than the gasket opening and on the exhaust, it should be 1/16” smaller than the gasket opening.
Why, you might ask. Okay, I will explain in as few words as possible. I said so. When the intake valves are opening and the air and fuel charge are rushing into the cylinder, there is a column of air/fuel mixture traveling at a fairly quick flow rate. When the intake valve closes, the intake charge hits the closed valves and reverses it route along the outer walls of the port. The tiny little lip you have created with the port matching will block the path back into the manifold and turn the charge around again to join the next bit of fresh air and fuel rushing into the cylinder.
This gives a little boost (I said little) that can improve power. The exhaust works about the same except in reverse. As the exhaust is rushing out and hits a charge of exhaust from another cylinder in the manifold, it can reverse and the little lip keeps it from trying to go back into the port it came out of. This is a very simple explanation.
While you are port matching, do not go much more than an inch or a tad more into the head or manifold. Polished ports are not necessary and add very little power. It is being discovered (some of us have practiced this for a long time) that a pebbly or rough intake port can keep the mixture of air and fuel in a better suspension than a polished port. The exhaust can have a polished port but it really doesn’t matter here. Exhaust comes out under pressure and flows better, that is why the exhaust valve is smaller than the intake.
Putting things back together is as simple as reading your manual and torquing everything to specs. One word of advice, and this comes from Mr. Gasket, the maker of Felpro and Payen gaskets, use Permatex High Tack gasket sealant in spray or brush on on both sides of the head gasket. They have the fewest failures in their “tests to destruction” of head gaskets with this. Add oil and water and see if it runs. If all seems ok, set the idle around 2,000 and let it run 15 minutes past when it reaches normal operating temp.
Follow your book about torquing the head, most say let it cool back to normal and then re-torque to specs. Readjust the valves and set the carburation. You have now gained about 10 to 15 more horsepower and you can get a few more by playing with your carbs, timing and valve adjustments. Next month we will get into more internal engine work. This does cost considerably more and requires more tools and knowledge. If you ever get in too deep, you can always call or email me with questions. You now have the satisfaction of doing something to your car that improves it beyond just looking prettier. You have bragging rights in conversations at your local club events. Brag on, you deserve it. Until next month, see yall somewhere soon. Do not forget about our next tech session at British Car Service on February 15th. We will start at 9:00 as last time and continue on putting an engine together. This time I will be degreeing in the cam and head installation if time permits.