MG MGB and MGB GT Tech Talk
I just bought a 1979 MGB in California. Now I read that it has a "smog cam" making it even slower than a 79 I had years ago. Is this correct? What easy things can I do to this California car to speed it up? Thanks in advance.
Slobo.
Quck edit: There is very little difference between the CA 1979 and the Federal one you had. Minor distributor timing changes only. All the late model engines had the same internals.
The "smog cam" was designed to give better drivability. It sacrificed high rev power to give better low end torque.
For normal street driving, (e.g. sub 5,000 rpm) it is a better choice than the earlier cam, since the car is heavier than early cars and can use all the launch torque it can get. Most of us are not wringing out the last scrap of horsepower at valve float revs.
Critical point: The later cars get a very bad rap. The power difference is not as great as the factory published figures show.
The factory went from flywheel HP to the equivalent of rear wheel HP, which showed a huge difference in power. In reality the later cars are a bit pokier, but still move along pretty well. Don't blindly buy into the smog cars are junk camp, without doing some A-B comparisons between early and late cars. The early cars are crisper and have more snap, but the later cars arn't slouches.
Check to make sure your distributor is working correctly. If allowed, changing to the earlier twin SU carbs and exhaust manifold gives you most of what the Feds took away.
I've never heard of a separate cam for California cars. It's pretty standard stuff to pep up a 79. A few searches will turn up lots of ideas.
BTW Welcome aboard and congrats on finding a CA car in the Northeast.
The best thing I did to my 79 was drop in a complete 67 engine, I'm going to disagree with Kelvin and say the difference was huge, the car is MUCH more fun.
Get Peter Burgee's book " How to Power Tune MGB 4-Cylinder Engines". It is the best book I have seen on tuning and building a MG engine for power and reliability.
Welcome to the forum........ Err.......... Slobo (If that is your real name, someone needs to have a conversation with your parents :) ). You're obviously very new (Just joined today!) to MG's; so let's start with the basics.........
1. You have a 1979 MGB
2. You are not satisfied with the speed
3. You want to make it go faster
A little lesson in history:
In 1975, California (One of British Leyland's - the company who then owned MG Cars - biggest export markets) introduced some rather stringent emissions regulations, and the US Government backed this up with some bollocks about how a car's headlights had to be at a certain height, and that all new cars had to have solid rubber bumpers to lesson damage in parking-lot collisions. At the time the MGB - one of Britain's biggest exports to America, and the best selling sportscar of all time - did not meet these 'requirements', so the cash-strapped company had to figure out a way to comply with these standards, so they could continue selling cars in the US....... In simple terms, they put blocks under the suspension to raise the car by 1" so the headlights would be at the correct level, and stuck on a pair of solid-rubber bumpers fore-and-aft....... This screwed up the handling, which was then fixed in 1977 with some geometry changes, and a rear anti-roll bar. This brought the car back to pre-75 handling standards, but damaged the car's reputation permanently. All of the safety and emissions equipment that the company had been forced to add had added quite a lot of cost to a car they were already loosing money on; so to save a little cash they replaced the tried-and-true twin SU carburetors with a single Zenith-Stromberg 175 CD-2, and a really poorly designed single-piece intake/exhaust manifold...... The manifold contributed to reducing the overall power, so to make up for it; they installed a re-profiled cam, and smaller valves to increase the overall torque....... That's why the later cars have less power.......
Now that we've established this, let's ask a couple of questions:
1. What kind of condition is your car in? In most cases poor performance is just a result of lack of maintenance, and it just needs a good tune-up....... If you've done this (Or had this done..... Properly.) already, and are STILL not satisfied with the performance you'll need to take more of an aggressive view on things.
2. What kind of carbs (SU, Zenith Stromberg, or Weber....) and what kind of distributor (Lucas, Pertronix, Crane....) does your car already have? If twin SU and a Pertronix, you're already heading in the right direction......
3. Have you heard the phrase in Hot-Rod circles: "How Much 'Fast' Can You Afford?", well; that applies to MG's too......... When tuning the B-Series (MGB engine), the formula for extra performance is roughly $100 per HP - so a 10 HP increase (From 62-65 HP to 72-75 HP) is going to cost you about $1000 dollars......... Do you have that kind of money lying around with nothing better to do?
4. Do you care if your car is kept in 'Original' condition, if not; go for it......... Many do......... Just realize that 'stock' late model MGB's are getting VERY rare indeed..........
If you have answered 'Yes' (Or No in the case of the last one), you have several options; all of which are determined upon how much skill you or your mechanic posses, and how much money you are willing to spend.
A Pertronix electronic-distributor is worth about 1-2 HP and costs $100-$150 dollars, it also improves reliability so it's money well spent; and it's straightforward to install....
Converting your car over to a set of Twin-SU carburetors, with the associated split intake/exhaust manifold will net you roughly 10 HP, and will most likely cost $600 to $1000 depending upon who you get the parts from. This isn't as easy as the distributor, but the increase is more noticeable.
Adding the larger valves, and a more aggressive camshaft will complete the conversion; and bring your power up from the stock 62.5 HP (From 1979-1980) up to the previous 98 HP enjoyed by the cars made from 1962 to 1974. If you want more, things are going to get VERY complicated and expensive!
From here on you have two options:
'Build' a street/track engine with a high-compression ratio, ported & polished head (Or Crossflow), overbore, Weber DCOE 45 carb, Kent 270 profile semi-race camshaft, roller-rockers, and a forged internals..... About $10,000 to $12,000, but you'll be pumping out 120-150+ Horsepower..... This job, unless you've had years of race engine 'Building' experience; is best left to a professional.
OR
Install a Moss Motors Supercharger, which costs about $4000 but will bring your 98 HP up to a more substantial 130+ HP.... This, is also a conversion you can do yourself; but if you aren't confident in your abilities their are others that will do it for you, AND helped you get it dialed in properly.........
Okay, that's the scoop on power tuning MGB's: if you want more, you can get it, but you're gonna pay for it...... Big time.......... Also, high-power is best left to those with more experience; so I would recommend enjoying the setup you have now. Later on, if you're still so inclined, attend one of John Twist's Tuning For Speed seminars: he'll teach you everything you need to know about making your car go fast....... I hope this has helped, and I expect to see you lurking around the forum in the future.......
Yours Truly,
Sam
there's also the fact that the B wasn't considered a "fast" car even back then. Today I would expect a Kia Rio 3 door stripper to take on a stock B at a stoplight and win...if only by a little.
One thing that I don't think anybody mentioned was the change to camshaft timing that occurred somewhere around 1974 (?) - close to or concurrent with the switch to single carb. From what I understand, that moved the power band downward. This was necessary since the single carb strangled the engine and couldn't pump enough air at the higher RPM. I suspect that had more of an effect than actual changes to the camshaft profile.
Sam summarized many of the options fairly well - but if you just want early 1970s power levels AND your state doesn't do emission testing of vintage cars then:
1) Move to twin SU carbs (used on all MGBs prior to 1975)
2) Switch to a double row camshaft gear setup - I *believe* that the camshaft timing change was accomplished through the single row gear used in later years, not in changes to the camshaft.
3) Change to an older distributor and distributor curve. Note that there are dependencies between the carbs and the type of distributor advance used.
These changes will not cost too much - depends on how much good used gear you can pickup. And they will undo most of the later smog changes.
It is my understanding, as Terry says, that the cam profiles were all the same and that the "difference" is in the cam TIMING.
It would probably be an interesting and educational winter exercise to actually "time the cam". I think that you will find that your later engine has the cam timing retarded by about four degrees. In reality you may find it plus or minus that figure, but to go through the process of setting the cam timing correctly no matter what to the earlier specs would be fun and not cost very much at all.
If the engine has many miles on it you might want to have a new chain and tensioner and perhaps sprockets on hand if you are working within a time budget. In any case buy all of the offset keys that Moss, r anyone else for that matter offers, and have a go at it. If you have a fat wallet you might even spring for a vernier cam sprocket but that would not be nearly as economical. If you use a new offset key you can always mail the unused ones back, attention to Kelvin :-), and get a refund.
My take is that the awful carb/manifold configuration required the retardation (is that really a word) because there just wasn't going to be a useful mix charge showing up in the combustion cambers with the strangled intake.
Jack
Which 79 did you scoop up, I've been watching a couple....
Thanks for all the thoughtful messages. All appreciated. The car I bought is EBay # 170394312466. The auction ended October 17. Let me know what you think. Thanks, Slobo (Whats wrong with my name?)
Hi check out EBay # 170394312466. It's the MGB that I bought. The seller accepted $5,000.00. I didn't get it yet but it seems a fair deal to me. What do you think? Slobo
It looks like a reasonably sound and sorted car. The engine room is pretty clean, that tends to say something about how the POs treated the car. I'm always a tad leary when I see yellow butt splices but for $5k it looks like a decent car.
