Rebuild it or Run it?

Hi, I am a newB by the way. Thanks for the great place to learn. I just finished the car history this morning in my journal.

After following Gary's post I just have to ask. I have the "78 with single carb and all the junk, being in Canada I can scrap all this stuff.

I have purchased Dual SU, OD gearbox, and the cast manifold to do an upgrade. The engine runs great, no noticeable smoke, oil pressure above 50 running, around 25 at idle (900 rpm) somewhere north of 92,000 KM / 55,000m

Leak down is 115, 125, 125, 125. I am going to pull the engine to install the transmission, and tidy up the compartment. I have been quoted around $4000.00 for a full rebuild.

Here is the question, if the engine is in reasonable shape, which it seems like it is, how much difference in performance will I get by rebuilding with the higher compression pistons vs putting on the duals and the original style cast manifold.

I am not really cheap, but hate to spend the money for not a big difference.

Thanks Hal

If my experience is typical, you will notice a big difference if you change over to the dual SU's. I'd do that and leave the rebuild until later. YMMV.

Yeah, keep it simple. Just put on the dual SUs and have fun with it. Rebuild later when the engine needs it (if ever).

Welcome!

Agreed. Just do the other bits. No need to have potential problems as I outlined.

[quote=NASpecMGB]

Yeah, keep it simple. Just put on the dual SUs and have fun with it. Rebuild later when the engine needs it (if ever).

Welcome![/quote]

Yep. The quote for the rebuild doesn't seem all that out of line either.

Hal,

welcome to the MG madness, you made a good decission to head this way:thumbsup:

Without all the emission stuff the engine should show about 72 FWHP on a dyno. Fitting the twin SU's and an adequate dizzy, you will have the power up to 80 - 82 BHP at the fly with the LC pistons.

When increasing the CR moderate (GCR 9.25:1), you will be close to 90 BHP.

If you want to alter the CR on an engine having done 90K+ Km, you should also change the bearings for new ones!

Ralph

Keep it simple. Leave the engine alone for right now. In fact, I'd suggest just de-smogging the engine and changing the carbs for now and leave the OD for a later date. Pulling the engine isn't horribly difficult, but it is an extra step on the way to restoration (it's been in boxes for 5 years) doom.

Get the de-smog job done and the engine running correctly in tune. Then when you want to install the OD, there is so much less to worry about when putting it back together. The OD is a nicety, but is not essential for MGB enjoyment.

kelvin

I'm with the rest...engine has several miles left. Invest the 4K in gold and by the time you are ready you'll be a millionaire....:thumbsup:

Unless you are like me and enjoy the project more than the driving, just do the carbs, enjoy the car and then do the tranny and engine compartment when you see some down time.

You will appreciate the OD more once you have driven the non-od for a while. If I were you, I would also keep an eye out for a cheap engine core. They are not worth much and you can have a fresh bullet ready to chamber when you decide to do the swap.

Not sure why you want to do anythng to the engine in the first place. Sounds pretty healthy to me.

Peter

I have mixed feelings on this.

One on hand, if you weren't going to yank the motor for other reasons I would agree that you should just hang all of stuff on the side of the engine and run it until it gets tired.

On the other hand having the engine out might be just too much for me to ignore the opportunity to do some house cleaning. With it out some things will be infinitely easier on the body and the wallet.

If I had the thing hanging from a chain or sitting on a stand I would do the following. Not too much in parts and, like I said, with the engine out a whole lot easier.

Pull the head and the pan.

Replace the rod and main bearings

Take the oil pump apart and check it out. If it is scored badly replace it. No matter what, new or reused, pack it full of petroleum jelly before sticking it back in.

Pull the relief valve, replace the spring and lap the piston back into its seat.

With the head off, push the pistons/rods out, hone the cylinders and replace the rings with a set of Deves. If there is a noticeable ridge at the top, use a ridge reamer to remove it. It is important to note that these later engines are prone to heating thereby collapsing the OEM rings and that by doing this single effort you will add lots of life to your engine.

Pull the rocker assembly and check the wear of the bushings and shaft. Pop the valves out, check the guide clearances, and at the very least, hand lap them back into their seats and stick in a set of new seals, your call on the seal flavor.

Send the radiator out and have it boiled and rodded.

Oh yea, take the clutch off the back of the flywheel and check the disc for loose damper springs and wear of the friction material.

Messing with these things is like going out and looking for "might as wells" and I am not advocating spending a ton on all of this, but I do think that it is only prudent to do a little more leg work if the path is not too long and not too steep.

Chances are that you are going to only need gaskets, bottom end and head sets, rod and main bearings and a set of exhaust valves. You might need a clutch disc or an oil pump or a few other things but if you are doing this yourself the rest is going to be just time and sweat.

Jack

If it were me, I'd drive the hell out of it and enjoy it.

I'll have to agree with Jack on this one. If you are going to go to the trouble of pulling the engine and trans, you might as well spruce it up. The additional outlay in parts is minimal in contrast to the reliability gained. RAY

i've always viewed the mg's as a cheap convertible touring car, jump in and drive leisurely from point A to B. I know a lot of ppl here like to mod the engine for "higher" performance and if that floats your boat to do then go for it. Others like to bling it up with wheels and detailing. it all boils down to a matter of what you're looking for and what you're looking to get out of any $ you spend on these puppies. for me I wouldn't spend the $ to soup these engines up, because at the end of the day, a hybrid will still kick your butt off the line bec, you start with a low hp engine, spend $4K and still have a low hp engine. I'd take the $4k and buy high hp car to satisfy the need for speed and when you're in your mg, just wave at those guys when they go by you....drive it!

Thank you all for sharing your experience and know how on my engine question. I think I will do the freshen up as Jack suggested. The real driving season is pretty short up here so I don't want to be broke down in the summer, when I could be driving. So I will follow the "as long as I have gone this far" theory and do the preventive work and reseal.

Hal

This is great info! WOW you guys know these cars! My engine is 99,000 tired and will someday need a rebuild but for now I just need my "B" to get me to work taking the back roads of course. I do have a concern right now. I am scared to drive it fear of breaking down because it is hard starting suddenly. It needs a manifold. QUESTIONS: The manifold is leaking is there a product I can buy to seal it for now? What should I be paying for a new manifold and installed by a good shop? What are the symptoms of a leaky manifold is hard starting one of them? Help please? It was starting fine after its tune, new battery, and new carb; but now 75 miles later it is not wanting to start.

I want to get to know my new "B" purchase before deciding to restore this particular model. I have an indear'ing soft spot for a "GT." I owned a 1972 MGB GT and restored it in 1987. An uninsured motorist crashed into it totaling it two months later. It went to parts. I lost over $6000 dollars in that car. But had I been on this site! I would have gotten advise to repair and a different result would've been had. So now I am a new buyer of a "B."

Off topic I have noticed that there is no respect for my old car on the roads of the Bay Area, CA. People try to push me to go faster by riding my bumper and I mean on it! Tailgaters and angry if I don't (and cannot) move faster. I don't want to go faster I like my vintage 1979 and want to savor driving not get to just go! I'm getting pissed at people heart rate goes up! Do any of you experience this? This doesn't happen in my Jeep or on my Harley!

Sorry if I am not using this forum correctly? new to it all!

Tyler,

welcome to MG madness!

The easiest way to show others the tail pipe of your B is a drop in swap to a 215 Buick V8 with a T5 tranny:thumbsup:

The 1977 on shells are prepared for this engine and conversion kits are readily available.

Before you start to check out your hammers and spanners, just do a valve stetting job and check the timing of your dizzy.

A new fuel filter might also be a good investment and, as long as the old air cleaners had not been changed so far, have new ones intalled. Then tune the carb or have it done at a workshop that is trained to the setup installed to your engine.

Long time Volvo workshops should be able to help as these cars made use of the same carbs that came from Zenith Stromberg or SU, if your car has been converted to SU dual carbs already.

Ralph

Hi:

I think we all find the same thing,SUV's and pickups with automatic transmissions are especially intimidating. I also drive a jeep with a stick and unless u are in to the gas,they accelerate faster without shifting and they are on to u before they realize it,the good ones back off and understand it by the next light,but there isn't many good ones.Wave them by or pull over,lot easier on the stress.

John

Mine has 60K on rebuild, (the 79) and the PO, (Sid Olson) here in Oregon was regarded as a solid mechanic and racer of these cars. I know he replaced the Rod Bearings, rings, pistons, valve job and that's about it. My engine on the 79 revs very high - and has great power - and rockets from A to B (pun) quite well and the added Pertronix for the dizzy and coil - she purrs with my pair of 68 HS 4's. Zero emissions and all I do is turn the key - and she runs so strong.

When I fit the OD to her in about a month - I'm going to of course, replace the clutch and maybe a new pan gasket. Then get'r back in and running again.

Alot of work ahead but I have 6 months to do the job (swapping Gearboxes) with the 77.