Input on '68 MGB engine mod?

Hi. My father is restoring a 1968 MGBGT in Albuquerque, and would appreciate any suggestions that folks might have on what to do with the engine. Here's some background info on the engine and his objectives;

He's looking for the best possible balance between drivability, good torque and mileage mostly in the 3000 to 4500 or 5000rpm range. Primary operation will be in the 6000-7000 ft altitude range. This will just be a street driven car. Cost IS an object.

The carbs were rebuilt by Joe Curto and the distributor by Advanced Distributors given the above performance objectives.

The engine is a de-smogged 1968 18GF presumably with a stock cam. Compression is 135, 135, 140, 139 at 6000ft elevation. Note this is after he retorqued the head, so it appears well within tolerances now. Don't know if it has hardened seats installed or not, but he has discovered one bent push rod. Further investigation is clearly needed.

Does anyone have experience, or know someone or a shop with experience with building engines of this nature? If the head ends up needing work anyway, any input on the tradeoffs (flexible performance / fuel economy / cost) of aftermarket heads (which one?), port work, cams, etc? Again, he's not looking for a race car but rather an engine which will comfortably get up the hills of Albuquerque and be fun on any mountain excursions in NM or CO.

Thanks in advance!

Contact these guys:

http://www.swms.org/

They're in your area and should know some MGB racers who can answer your questions.

I'm pretty sure I used that block in my MGA. I had built an autocross engine for my 'BGT and found a cracked head (common) on the MGA, so the 'B engine went in.

You can mix and match stock parts to get a pretty lively engine. I used an early block and head with late pistons, which results in something like 9.8:1. Basically in stock form, BL paired dished pistons with a shallow head and later shallow pistons with a deep head. In the middle, 72-74, they used larger inlet valves, which offer negligible gains over the other heads. The parts will interchange. Because of the design, there isn't a great deal you can do with a stock head other than port and skim a little. You can go .060 over on the block normally; larger if you want to start spend money.

The stock exhaust manifold is pretty good and anything but a Peco will actually drop the HP. Don't waste your money.

A cam isn't that expensive and will help - mainly because the 7 and 8 lobes on his cam (assuming it's the original) will probably be worn round (check lift on them all). Crane uses billet blanks rather than regrinds. Cam followers from a real Mini will plug right in and they come drilled for improved oiling and are hardness tested.

I also used a stock flywheel that had been lightened. That really makes an engine feel sporty.

Aside from any machining, the rest is just bolt-on. Keep in mind the B-series engine isn't going to make gobs of horsepower or torque. I think the economy/power lines cross at about 120 HP or less, but having tinkered on MGs for 30 odd years, 100 HP feels pretty good and is doable with mostly stock pieces.

For an economy build, I'd have the block bored, magnaflux the head, skim it and do a DIY port job following Vizard et al spec, buy shallow or flat pistons, get a "fast road" cam, and have the flywheel lightened. That will put you over the 100 HP mark easily.

If he's not truly restoring the car, a V6 or V8 swap is easy on these cars, and it might end up cheaper than modifying the MG lump (especially for a V6... those are nearly given away).

www.britishV8.org

If you're considering a swap, for your goals you should consider a modern I4 or V6.

All good advice, particularly the ZDDP/cam wear thing. I'll add that bumping compression can be very beneficial at higher altitudes but carries with it the costs of the original work and needing to always run 92 octane.

The B's combustion chamber shape does not really lend itself to ultra high compression, so stay around 9:5-1 or so. 10:1 is pretty much the upper limit for a streetable motor on pump gas, and even that is pushing the envelope without octane boosters. For comparison, the stock 18GF is somewhere in the low to middle 8's.

I'm assuming that the dizzy has been converted to run electronic ignition. If not, that's an inexpensive and very worthwhile modification.

Something else that might be considered, but it too steps outside of the low budget requirement, is to add fuel injection. Like anything, it's possible to go bonkers with TWM Induction sidedraft throttle bodies etc. but if this is done with a TBI setup and one of those Cannon intakes for a downdraft Weber it can be done with mostly JY parts, the most expensive item would be the Megasquirt controller. The benefit of doing this is better control of air/fuel ratio which equals better performance and gas mileage. The TBI will give away power compared with the more high end systems but like anything it's a tradeoff.

No one mentioned that CMS had a whole series of articles on this car/engine? Most of what has been said, so far, was explored in that project car series. While I'm more of a Triumph fan, I saved most/all? of the articles because they were interesting and "exploded" several "bigger is better" or "if one is good, 2 or more is better" ideas.

Just found the mag in question....issue 133, July '08.

The car used was a '73 B GT. Baseline testing showed it was producing about 64 horsepower at the rear wheels. Cam used was APT's VP11 cam, tho the article states that the stock cam is already on the aggressive side. Chilled iron lifters were installed when the cam was installed. Head work was done on the stock head, which unfortunately can't be summarized here.

Some of the sites used in the write-up included:

www.aptfast.com

www.eclecticmotorworks.com

www.mossmotors.com

There might be other MG project car write-ups "floating around" at CMS...try looking at the website to see what's available.

EDIT: I found an article on headers for the "B" engine in issue 151 July 2011. Several different headers were tried, but the best setup would seem to be the factory/stock header from a late MG a or early (pre-smogged) MG B.

Wasn't there a series of CMS or GRM articles some years back dealing with upgrading a Midget? The engine modifications should apply to the MGB.

I recall the Midget was treated to a Pertec ignition, a new intake with a single Weber carb and a header with a custom exhaust and they made a signifigant power increase over stock.

The stock MGB cast iron dual outlet manifold is a pretty well designed piece. The Peco header bears a strong resemblance, the Pacesetter and others are lighter but that's about all they have going for them.

Stock B exhaust manifold:

PECO header:

Pacesetter header:

The Peco copies the stock manifold's joining of #1 and #4 cylinders pretty close to the same place the stock manifold does, and it seems that's about the best place. The Pacesetter joins all 3 tubes (the center ports are siamesed) at the collector, meaning the exhaust pressure waves do not help evacuate the adjoining cylinders.

Buddy of mine has been polishing his swap over the last year or so. Midget powered by a DOHC 4 valve Duratec 2.0L backed by a T5 and with a narrowed Dana30 rearend w/3.73 gears; Megasquirt'd. All used/ebay pieces. About 150HP with bags of torque down low. Having ridden in it/driven it - makes me realize that I wouldn't even consider sticking with a stock motor if/once I'd decided to start modding/changing things.

mguar - his car was vintage raced prior to the swap - so the 2.0L was replacing a 1275. He didn't weigh before and after - but he's hustled both engines in and out many, many times over the years. Even though physically larger, I gotta think there's not much difference between the all aluminum Duratec and the all cast iron 1275. Hell - the Duratec may be lighter. The blog isn't completely up to date - but you'll get lots of details here -- www.midgetec.com

I'd add - ride height appeared completely unchanged before/after swap.

I think this is a Spitfire motor -- but pretty slick video stop-photo sequence on the rebuild.

http://jalopnik.com/5922349/watch-an-engine-rebuild-itself-in-this-3000+photo-stop+motion-video

It's surprising what can be stuffed in a Midget chassis. I've seen a Toyota DOHC engine in a Midget with no hole in the hood etc, also a couple of rotaries. There was a guy in my hometown who had a SBC in a Bugeye, no hole in the hood but he did have to run side pipes.

A while back CM had an article on a Sprite with a Jag 6 banger in it.

A B will hold a BBC but the clearances for exhaust and steering would be a major PITA.

Back in 2007, my 5.0L Volvo was 'juried' into one of the buildings behind the Velvet ropes for the import car gathering which occurs every May. I was next to the Jag-powered Midget pictured above. That is one nice piece.

brgmcs wrote: Hi. My father is restoring a 1968 MGBGT in Albuquerque, and would appreciate any suggestions that folks might have on what to do with the engine. Here's some background info on the engine and his objectives; He's looking for the best possible balance between drivability, good torque and mileage mostly in the 3000 to 4500 or 5000rpm range. Primary operation will be in the 6000-7000 ft altitude range. This will just be a street driven car. Cost IS an object. The carbs were rebuilt by Joe Curto and the distributor by Advanced Distributors given the above performance objectives. The engine is a de-smogged 1968 18GF presumably with a stock cam. Compression is 135, 135, 140, 139 at 6000ft elevation. Note this is after he retorqued the head, so it appears well within tolerances now. Don't know if it has hardened seats installed or not, but he has discovered one bent push rod. Further investigation is clearly needed. Does anyone have experience, or know someone or a shop with experience with building engines of this nature? If the head ends up needing work anyway, any input on the tradeoffs (flexible performance / fuel economy / cost) of aftermarket heads (which one?), port work, cams, etc? Again, he's not looking for a race car but rather an engine which will comfortably get up the hills of Albuquerque and be fun on any mountain excursions in NM or CO. Thanks in advance!

Not sure why you think you need to do anything to this engine? From what you tell us, it should be operating pretty close to "As New" with the compression and upkeep you have done so far. I have been driving MGs for 36 years, and power to get around has never been an issue.

If you MUST do something with the engine, get Sean Brown head and a mild cam upgrade to go with it. If you don't already have one, the money would be better spent on an overdrive transmission.

MichaelYount wrote: Back in 2007, my 5.0L Volvo was 'juried' into one of the buildings behind the Velvet ropes for the import car gathering which occurs every May. I was next to the Jag-powered Midget pictured above. That is one nice piece.

Oops - at Carlisle......

OD transmissions are nice, but the B motor is going to give away some horsepuppies at higher altitude so it may not be all that great of a benefit. It certainly does not hurt to have it, it made highway trips in mine much more enjoyable.

It's possible that instead of throwing money at N/A parts, he might look into forced induction. That's a real boon at higher altitudes and by the time you add up the cost of bumping the compression, changing cams, etc it could come very close to the cost of one of the Moss supercharger kits. Then he'd have the added 'holy E36 M3!' benefit when the bonnet was popped.

Thanks for the input folks! Some good comments (and some interesting diversions ) which I'll pass along.

I'm positive that my father will want to stick with the same engine, but is open to doing a few period correct mods, or at least appearing along those lines. He's sort of building the car the way he feels that MG should have, but there's absolutely nothing there that anyone not extremely familiar with MGBs and the changes year by year would pick out as non-original.

Its got a functioning OD unit, which is good. As commented on, altitude is an issue as he's more likely to go up from the home altitude of 6000' than he is to go down. For those that haven't been to Albuquerque, many city and suburb streets have long grades since there's nearly a 2000' elevation change from downtown to the eastern outskirts of town. An hour drive will make that a 6000' change upwards. So, a little more grunt wouldn't be objected to. Roughly stock power does get the car around, with the right classic noises, it does take some pretty serious throttle openings to really keep pace with modern traffic on some of the steeper major streets.

This is really a bit of a "fact finding" mission so he has some options as the running restoration progresses. Again, thanks to all for taking the time to comment, and we'll still welcome any and all other input.

Scott