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MG MGB Technical - Modified Head / Cam

Hi,

I have a Marina B series engine which I understand is the later MGB (18V?) which is the "5 bearing" model (suggested by the lack of mechanical tachometer).

Anyway, I'm considering a suitable upgrade in the form of a new/modified Head and Cam to gain suitable power. There is no way I could modify the head myself so would be needed to get a company to do the honours.

Who in the UK should I be speaking to? I've already emailed Peter Burgess who would charge around £400 for the work, is anyone else cheaper whilst offering the same level of respect from the community?

Similary where does everyone pick there Cam's from - I was told a kit is around £100 (includes cam followed et al).

And lastly, is there any websites which sit and list what is needed to be done to do the change? Every time I read an article something else is suggested to be added to my list. I'm contemplating doing it myself but would really need a good list of what actually needs doing.

cheers

stefan
Stefan Carlton 1

Stefan,

This link should help you answering yours questions:
http://www.mgcars.org.uk/peterburgess/
The 18V engine head shared between Marina and MGB are
strictly the same. The bests beeing the cast number#12H2788 equipped with the biggest inlet valves and the most suitable casting for tuning.
Hope that help !
Renou

Miss a part of your request...
Ask too at :
Octarine services whose link appears sometimes on this BBS .
Renou

Renou,

I am not sure I agree with you about the casting number. Isn't the larger inlet 12H2709 ? Perhaps 12H2788 is the desmog version?

David
David Witham

Stefan
Is this engine still in a Marina?
I had a '74 GT. I installed a MGB overdirve unit in mine. Made it into a decent car.
Sound to me like Peter Burgess is the best source.
If I lived on that side of the 'pond'
But do go to an electric fuel pump.
Safety Fast
Dwight
Dwight McCullough

Dwight, the engine and running gear has found it's way into a Marlin Roadster (www.stefancarlton.net has details of my car), the tunnel is too small for a MGB 'box, but you can put a Ford type 9 in quite nicely by all accounts but the conversion seems to run well into the thousands of pounds - a bit high for my budget.

I do plan to put an electric fuel pump in to help solve the fueling problem, but it's another thing on my list of jobs to do.

At the moment this is all speculative as I fear the £400 for the head and £100 for the Cam (+17.5% for VAT) is too much never mind the labour costs as well - hence asking if anyone modifies heads who is respected in the UK :)

thanks for the replies either way :)
Stefan Carlton 1

Expertise does not come cheap. Inexpensive head work is as likely to give you worse results as better. I was given to understand that Peter did customer heads (as opposed to outright sale) for 280 pounds.

The entire system should be approached as a "unit."

If your cylinder wear is not large (you can still see cross-hatching with no "polished" spots), Then you can get away with a "decoking" unless your blow-by and oil consumption were noticeably large. In that case I'd re-ring as well (and you may as well get Total-seal gapless ring set). Get the "file to fit" type to ensure proper gap.

All this presupposes your oil pressure is excellent and no seal leaks at the crankshaft (both indicators of a need to fully rebuild or at least freshen the bearings).

Personally, I'd not bother with just a head and cam (alone) unless the engine was nearly new and I just wanted an upgrade to performance. A decent "freshening" (all new bearings, pump, rings, etc...) would be called for in an engine with many miles on it and a full on rebuild if any major wear indicator was present.

Consult with Peter as to an appropriate cam, level of head-work, and exhaust to suit your needs. You will likely need to use a new needle so ask for recommendations on that as well.

The stock cam (in the MGB) is pretty good so a little head work, exhaust and proper needle selection will really perk it up.

Mike!
mike!

Mike,

Excellent! Thanks for that heads up.

The engine was actually rebuilt a little over 9000 miles ago (but has been running without air-filters for that time). I'm a little concerned that taking the top off will show that the engine needs a little more work than I can afford (the only drawback IMO.

As for the price, excellent news - I didn't realise I was looking at the "brand-new" prices.

I shall be speaking to Mr Burgess in a little more detail now then ;)

Cheers.

Stefan
Stefan Carlton 1

Hello everyone. I'm doing a similar job on my engine. I have e-mailed Peter Burgess but as yet have had no reply. If he doesn't hurry up he will only sell me a head I'll go elsewhere for the other bits. My biggest question is what rings are the best to use with a used bore. I intend to glaze bust it then fit new rings. I'll need ridge dodgers 'cause there's a bit of a step at top ring reversal. Where can I get the rings from. I need to fit cam and followers too, but intend to stick with original profile. Oil pump is knackered too.
Shells were worn but crankpins spotless - not bad for 112,000 miles
Paul Hollingworth

Hi Paul

If you sent an email from the address in your post...I haven't seen it, I cannot find it in search either. Did you put anything in the subject line? I get about 50 emails a day and that narrows down to 3 or 4 'proper' ones when I have got rid of the junk mail. I am afraid this may include some proper emails without subject matter...this also seems to be a way that the spammers use to attract attention so I tend to delete most messages without subject line.

If you re-send your message I will reply asap.

Peter
peter burgess

Paul, with all due respect I feel that 112,000 miles tells its own story. That is a very good mileage for a B series engine and from your comments it looks like it needs a little further work.

I would be surprised if the bores are within useable limits especially as you say "there is a bit of a step" My advice to you would be to put the block and shaft into your boot and take it to your local engine specialist at least to have the bores and shaft journals measured. This way you can be confident that you can deal with any additional work which may be needed and also that the engine will be well up to handling the additional power you will get from the modifications.
Iain MacKintosh

Peter,
No harm done, I'm taking my time anyway. I guess you must of chucked out my mail with the spam by accident.
I'll forward it to you again and I'll double check I've got the address right. Please let me know if you don't recieve anything from me.

Iain,
I haven't got the facilities to take the engine out of the car never mind a bench to strip it on. The bores don't look too bad. The engine was running well before I stripped it, but using a lot of oil, some of it at least down to worn guides. I found broken top rings on Cyls 1&2. Despite this compression readings were respectible 150,145,140,155 psi bearing in mind the age of the engine. I am betting new rings and shells will get me another 30,000 miles. Thats another 10 years worth
Paul Hollingworth

Ian
I pulled down the 1979 motor I'm using in my '67 gt. It had 140,000 miles with no perceptible ridge. Stock bore, original pistons, etc. The valves were recessed more than 3/8" from use of unleaded gas and the cam was flat on some lobes. The crank main and rod journals were within specs and I rebuilt the engine with standard size bearings. I did rebore to .040 over to gain a couple cubic inches and some compression. The last 25,000 miles or so were with a second owner who didn't appear to do much to keep the car up. The records indicated regular oil changes with synthetic oil for most of the engine's life. The records stopped at 113,000 miles.
Barry
Barry Parkinson

Paul;

No facilities to pull the motor or a bench to strip it on, yet you've already done most of the stripping???

Talk about dog gone cussedness! Certainly you can rent/beg/borrow a suitable hoist and get it out so you can get to it easier? Plop it on a packing crate with another to cover it and a tarp for the moisture and you'll save yourself a lot of skinned knuckles and sore backs!

Don't get me wrong, I admire your persistance, but...

Since you are taking your time, find a set of internal micrometers in the 3-4" range and measure the bore at several points around the cylinder and at several levels. Scrape off the carbon at the top first with steel wool so you can measure the "new" diameter there. Hose down with WD-40 or the like so it doesn't instantly rust.

If the pistons weren't burnt (broken rings... perhaps you were a little wild on disassembly?) they can be cleaned and re-used. Check the skirt clearance in the bore too. If broken rings were run for long the ring lands in the pistons are likely shot and you will need new pistons anyway (or at least a good used replacement).

Cannot recall the exact factory wear limits off-hand but if you have a difference in diameter of more than 0.008" at any single "elevation" in the bore then you have excessive ovality and new rings will have difficulty seating. You can't hone out ovality with hand-tools.

My test is "do I see hone x-hatching." If not, it is re-bore time no matter what everything else looks like. OTOH I've "resurrected" ALMOST gone cylinders by careful hand honing and fitting the next oversize rings and hand-fitting to the bore. This was on engines that had no other damage whatsoever (just "normal" wear).

Oh, if there are ANY vertical scratches in the bore... re-bore. They don't hone out worth a darn either and tend to catch the stones causing nasty chatter and a poor job.

Mike!
mike!

Stefan-
Peter Burgess is the Master when it comes to headwork on B Series engines. As for a choice of camshaft, the Piper 270 will give a broad spread of power, a smooth idle, and about 8 extra horsepower. The Piper 285 camshaft will not idle as smoothly and decreases performance below 3,000 RPM, but produces strong mid-range and top-end power, about 18 hp more. Driving in heavy traffic will be a bit of a nuisance.

Paul-
You couldn't get compression readings like yours with broken compression rings. The ridges at the top of the bore are probably what broke your rings as you extracted the pistons. The cylinders will need to be rebored and new oversize pistons installed.
Steve S.

This thread was discussed between 13/01/2005 and 22/01/2005

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