bevans6

Why not take the opportunity to put in some ARP head studs? I did that last rebuild, I thought they were very good. Brian

AS I recall you read the casting info from the front. The easy thing to do is put the caps in with the bearings out, the parting lines should be perfect. One is at the front, which is the water pump end of the engine. Inspect the bearings. It's completely possible you crushed them and ruined them. Inspect the crank. It's completely possible the bearings have harmed the journal surfaces, although not as likely. Make sure you didn't make the same mistake with the rod caps, and have them on backwards as well. You should always rotate the crankshaft after installing each cap and torquing it, that way if the assembly goes tight you know which one is wrong. You should also install the center cap first, torque it, and measure the end float. You should never never never be finding that your crank doesn't rotate by connecting up a bunch of batteries and a high powered starter motor...that is just bad in so many ways.... Brian

One suggestion that I have, coming from 15 years as a CASC (Canadian version of SCCA) scrutineer: Do complete welds all of the way around all frame tubes. You would be amazed at how many times I've reached up behind the tubes on the halo bar, pushed or cut away the carefully placed padding, and found that the back of the joint wasn't welded. If you carefully plan the order of the install of your tubes, you can probably get them all without cutting the body. It's common to have to cut holes in the roof of the car to weld the back of the joints on the halo bar and the front downtubes that are near the windshield pillars. Being a contortionist and a magician really helps sometimes. I wouldn't use Tig on a roll cage without a hand control, btw. Wouldn't dream of using a foot control for a full cage inside of a car. And I've only been Tig welding on cages, roll bars, race cars for ten years... Have Fun! brian

If you weld in a proper multi-point - say 20 or more attachment points - cage, then you will increase the stiffness of the chassis. But it's a non-reversible modification. A four, six or eight point cage with no door bars isn't going to make much difference, particularly if it's bolt in. Your car isn't going to flex the paint off, and the doors are going to work fine - as long as there isn't some unspoken serious issue like the paint is on bondo that's on newspaper, or something like that... Brian

I use one PC 680 in my race car, starts it just fine. I don't have a charging system and it can run the car for a weekend, but i do tend to charge it once a day. Brian

#61 is hooked over #53, which is the actual pump plunger. #61 is an actuating gizmo. It pulls the pump plunger up when the throttle is activated, and the spring pushes it back down again. I have had the pump plunger sieze in it's bore on old disgusting carbs. Resist the urge to yank it out if it's stuck - all you will accomplish is breaking the #61. After you pry off the cover and the spring pops out, all you can do is start to soak it in penetrating oil and wait. I had one I waited 3 weeks for. It eventually came out. This is why I tell people to buy new carbs. The old ones can cost more to rebuild and jet than new ones, if you have to pay for someones time. Brian

I think, aside from American V-8's, the M10 is about the cheapest engine to tart up that I've come across. It has so much right about it to start with that you don't have to correct many factory cost saving measures. I have as much in my race engine total , including Pauter rods and forged pistons, as I expect to spend on a race cylinder head or a race crank and rods for most other engines I work on. As an example, I called Carrillo to get a price on new rod bolts for a 1965 Cooper S engine that I am rebuilding. The 8 rod bolts alone cost over half of what a complete set of Pauter rods costs for the M10, and that's at jobber rates. The head flow really well out of the box, just do some clean-up of casting flash and do the port matching thing. The crank is stout. The rods are good for any sane street applicatiion. The cam chain is good. The rockers and valve train in general is good for any sane street use (up to 7,000 rpm, anyone who makes their engine live for any length of time over 7K on the street isn't particularly sane in my book...) A performance M10 starts with reasonable compression, a bit more cam (it can actually take a lot of cam for street use compared to many engines), better breathing on the intake side of your choice, better exhaust of your choice, and there you go. Put that on a stock rebuild, put a good tuneup on it, and you should be golden. It's only when you try to get over 200 hp that the M10 starts to need work and parts upgrades, and it really can't compete in the 2 litre race engine wars when BDG's can be brought to 300 HP NA as a standard. But that's why they invented the M12, isn't it? Brian

I would start with 135 mains, and go from there. The chokes are way too small, as has been noted elsewhere, but small chokes will tend to make the car more driveable and economical in the around-town scenario - their effect will be at higher rpms and full throttle. Air correctors in the 180 range. Air correctors have more of an effect at higher RPM, as you probably know. Brian

When you deck the block or head surface, you move the cam closer to the crank. Since the chain length doesn't change, the cam is a little retarded compared to where it would have been. The biggest thing that retarding the crank does from a performance point of view is close the intake valve later. This has the effect of moving the peak HP range up in RPM's at the expense of losing a little torque at the bottom end. It also leaves the exhaust valve open later, and you will lose a little clearance to the piston as it chases the exhaust valve up the bore. It's very common for engine builders to vary the cam timing to change the power characteristic of an engine. I wouldn't worry at all about 2 degrees granularity on your pulleys. As soon as you start the engine, drag and friction will move the cam timing about that much anyway, compared to what it is static. As soon as you put about 100 miles on a new chain, you get a degree or two as well. And where the cam is timed in the first place is just where the cam grinder thought it would work well - and he had no idea of what the rest of your combination is so how would he know? When I build a race engine, I time the cam to one degree, usually with a slotted type pulley or with 1 degree offset dowels. But that's just because it's good practice and not hard to do IF you know how to do it. I wouldn't worry at all about 2 degrees on a street engine. I would always, without fail, time in any cam using a degree wheel and a dial indicator, I never trust the marks except to help me with initial setting of the cam before I start to time it. The equipment to do that can be had from Harbour freight for less than $30. Checking piston to valve clearance is about free - get some plumbers solder that is about 1/8" diameter and stick it in the spark plug hole angled so that it is up across the exhaust valve and roll the engine past TDC, then mic the solder. You'll see if you got it right by the valve impression. Brian

Hard to disagree with most of what's been said, but in addition... If you have the 45's, use em. Put in small chokes, small aux. venturi, small pump jets, big bleed-back valve, tune it lean on main jet, etc etc. Pay close attention to the idle and progression circuit. You can get it to be as economical any other carb, or close to it. I would definitely choose dual valve springs for either cam. No downside so why not? They don't cost much in the greater scheme of things. I had a 304 in my race engine, 10.5:1 CR, dual 45's, very small, light flywheel, and it wouldn't idle much below 1500 rpm. I went to a 316with much the same combo, and it idles perfectly happily at 900 rpm once it's well warmed up. Go figure, I have no idea why. Flywheel weight has a lot to do with a smooth idle, the heavier the better as far as idle is concerned. Brian

On an otherwise stock engine, any power increase will be minimal, likewise you will have a small gain in torque. I would certainly recommend ceramic coating inside and out, it will look great and will last a lot longer. If you go to certain simple mods, like a cam upgrade, carb upgrade and increase in compression the header will help those be all they can be. Brian

Pretty much there is always positive pressure in the crank case when the engine is running. Even when on over-run with throttle closed, there is combustion happening since the engine doesn't actually shut off, so there is some degree of positive pressure from combustion pressure bypassing the rings. But always run the cam cover vent to something, to capture the gasses, and in an ideal world to a filtered vent. What happens is when the engine is turned off, the hot gasses inside of the engine cool, contract, and that draws in dust. Brian

I ran my NTM sports racer with BMW M10 race engine very happily at Roebling Road in December, and it did very well. I got to a mid 1:15 in the vintage enduro on Sunday morning, in traffic, and with a little shifter malfunction only using third and fourth gears (4 speed box). The engine is what I think of as a mild race tune. 10.5:1 JE pistons, Total Seal rings, Ireland 316 cam, mildly ported 121 head with the larger intake valve added, good valve job, headers, dual 45 webers, stock crank with Pauter rods, polished rockers with locks, my own dry sump system (which works flawlessly, I am rather pleased with that...). I limit the revs to 7400 or so, max, usually shifting at 7200. I haven't developed the tune on it at all, I just put in the jets that the nice man at Pierce Manifolds suggested, timed it at 34 degrees maximum advance, and since it ran fine with no overheating, misfires, etc, just left it alone. In the interests of safety I've been running it on 110 octane leaded fuel. I wonder what an engine like this really needs, if I can run it on 100 or 104 octane unleaded, etc. Here's a funny thing. I have a very light, small flywheel on this - 9.5" diameter with an aluminium Quartermaster 7.25" clutch. This engine only wants to idle at 800 rpm. If I try to get it to idle higher, it immediately goes to 2000 rpm and is floaty. I find this very odd, most race engines with this much cam like to idle around 1500 rpm. Ideas? Cheers and Merry Christmas! Brian

I'll be at the VDCA event at Roebling Road in two weeks time. We normally share the event with a BMW club. I'll have my M10 engined sports racer, say hi if you're there. 1972 NTM Mk4 B/SR, with a dry-sumped M10, about 200 hp or so they tell me, anyway. Brian

Have you rebuilt or at least checked your distributor? A sticky mechanical or vacuum advance mechanism can cause a floaty idle. Brian

Take out all the spark plugs so that you can turn the engine over easily. Use a probe in #1 cylinder (carefully) to postion #1 piston at the very top of it's stroke. Do not use the starter motor to turn the engine over while there is a probe in the cylinder, use the crank pulley nut or some other method of manually turning the engine. If you are careful you can find TDC actually quite accurately this way. Then look at the valves. Either both valves for #1 cylinder will be open or they will be closed and the valves for #4 will be open just about perfectly equally. If both valves for #1 are closed, then the engine is at TDC on #1 compression stroke, which is what you want - TDC on the firing stroke for #1. If any of the above is not true, the cam is mis-timed. If it is true, then make sure the distibutor is in so that the rotor is pointing at the distributor cap post for the spark plug lead that is going to #1 spark plug. Brian

A combination like that should be a nice running version of a stock engine. In other words, it might make 5 or 10 hp more than stock, no more, and it should be able to get good gas mileage if you drive it gently. The stock cam will like the slightly increased compression ratio, and will make for the good mileage. The small carb likewise, if you keep your foot out of it it will mostly run on the primary venturi. Adding the EFI and the distributorless ignition will only give you a gain if what you have is poorly tuned. Unless you change the air-pump somehow, the basic characteristic of the engine won't change, it will just do what it can a tad better. It should run a lot better in terms of driveability, though. The stock cam is governing the ability of the engine to pump air and will really decide the character of the engine a lot more than external parts that you add on. If you go to a 292 cam you'll lose bottom end and gain top end and lose a lot of economy. That means you have to drive it harder to get back to where you were at, and harder still to reap the benefit of the longer cam. At 9.5:1, you have a reasonable CR for that cam on the street. Your weak link will be the small carb. I really think that the 32/36 carb is good for engines up to 90 - 100 hp only, at a stretch. I replaced twin SU's with a 32/36 on my MGB, probably lost 10 - 15 HP. But gained a ton in being able to actually drive the thing reliably... Brian

Depending on the compression ratio, 160 hp isn't out of line. I would look for 10.5 - 11:1 compression ratio anyway, for a race motor. You may find some other modifications inside, maybe even Pauter or similar rods. To get such a motor built to spec by a good engine builder, for race use, would probably cost about $5k anyway. Used, with no history, look for half that or less. Few things depreciate faster than a used race engine. Brian

Interesting that no one actually read your post or answered your question. A 1972 121 head and a 121 Ti head are exactly the same. No difference. If you can get a 121 Ti head in good shape it will be fine for a replacement for a 121 head circa 1972... I know because I have one of each. Note that there is a 121 Tii head, as noted in another post, so make sure yours is a 121 Ti. Brian

From what I've seen the stock BMW flywheel is made of pretty good cast steel, a lot better than many stock flywheels. As such, in a street application with "normal" power and rpm levels, you could lighten it down to say 12 pounds and have good results. I make aluminium flywheels for race applications and aluminium is actually stronger, pound for pound, than cast steel so if you go under about 12 pounds then look into an aluminium flywheel. If you want to go really light, then you would need to also be looking at a 7.25" or smaller racing clutch as well. the flywheel helps the engine idle. If you have a big cam and a very light flywheel you get the real race engine idle effect. I have a 316 cam, an 8 pound flywheel and a 7.25" aluminium cover Quartermaster clutch, and my engine likes to idle at 1200 - 1500 rpm. Brian

While I can't for the life of me understand why you would need to source your own steel, last time I was doing what you are doing I called Moldex, talked to the man, and ordered a crank. I have ordered custom stroke cranks from them in the past, the price was right ($1500 for just about any 4 cylinder last time I asked), the quality was amazing, the lead time was terrible (4 months) but the result was a happy engine. The reason for the comment is they use a particular grade of specialty steel that might be 4340, but isn't off the shelf - it has special purity requirements, etc. Not that I know that yours isn't the same stuff, but it's kind of like taking a steak to the restaurant, don't you think? Anyway, Moldex, in Detriot. Brian

If you put oil in the cylinders (great idea) be absolutely sure to spin the engine over well on the starter mtor with the spark plugs out to remove most of the oil before you turn the engine over. if you don't you can easily hydraulic lock the engine and that would be bad. When that happens, if you're lucky it just won't turn over, but if one cylinder fires before one locks, you can break rods or crankshafts. Plus spinning it over without the spark plugs is the easiest way to prime the oil system. There are other ways to do it on this engine, but they aren't the work of a few minutes to set up for. Brian

I would get new pistons rather than looking for used ones, unless you know why they aren't in the motor anymore. Cast pistons can easily have collapsed skirts which make them pretty useless, and you don't find that out until you measure them up. I use a 121 head on my race engine, for vintage correctness reasons, and I just spent some time smoothing, shaping, and cleaning up the short side radius, blending around the guide, etc. Used the larger intake, got a race 3 angle valve job, etc. Motor runs good, so far. brian

BTW, I became a machinist about 10 years ago when I bought a house from a friend of mine that had a 2000 square foot race shop in the backyard, with a 16" southbend lathe, circa 1939. Had some fun, built some race cars, added bandsaws, drill presses, horizontal mill, found a good used Bridgeport, started helping out some friends, started a part time business and now I do race parts machining, race car prep, track support, and have some fun making my hobby pay for itself. Self-taught using the internet as a resource. My customers car is a very fast vintage race 1965 Mini Cooper S, btw. 1310 cc Cooper S 5 port engine (.040" over stock bore) and about 150 hp. We'll be at Watkins Glen in September.

Check out this site: http://fsae.com/eve/ubb.x/a/frm/f/125607348 Formula SAE is a great way to learn how to design and build a car, and there is lot's of machining involved. See if the University you plan to go to has a FSAE program. Community colleges and trade schools offer machinist training, obviously. You still have lot's of choices to make, so have fun! Brian