MGB Roadmaster

[flitner]

Could have been the contacts in the solenoid stuck closed as well from the hot starts kicking the amperage up softening the copper.

[BlownMGB-V8]

Dan said the key stuck in the on position and he drove it without noticing that. Little doubt that with the engine driving the starter, failure is imminent, such things as shredded reduction gears and thrown windings come to mind. It would have been turning about 10-20 times normal operating speed. And it could have broken the nose cone again as well. Maybe Dan can give us a post-mortum on the starter.

But we don't need this to recur. Whether cleaning/lubricating the switch/lock assembly or replacement is required we need to make certain this particular problem goes away.

Jim

[lawnvett]

Dan,

I think I must have dodged a bullet and it hit you.

Hope it is a simple repair, let us know.

PJ

[MGBV8]

Gotta love those lifetime warranties! Midas has been furnishing my dad mufflers for his MGB since the 60s & J.C. Penny's (warranty now handled by Firestone) has been doing the same with batteries since the 70s.

[Dan B]

Carquest replaced it, no questions asked, no receipt.  I couldn't get the bolt into Rob's brace though.  Hopefully tomorrow afternoon I can get it on a lift and have better access.

[mowog1]

What do we need to do to the RH exhaust/header to keep it from coming apart?

I understand you made yet another roadside repair last week.

[Dan B]

I think I can modify the connector some, maybe put a screw or two in it.  Right now it has an Arizona Tea can wedged in there to hold it.

[madmax]

Exhaust header?  I gave both downpipes a tach weld!   I'd be VERY surprised if it just "dropped off" again!  

M

[BlownMGB-V8]

Apparently it did. Two things going on there I guess. One is the stainless band clamp is thin material so while a spot weld might work a tack weld will probably just tear away. Secondly and maybe the biggest thing, I think the downpipe is against the  bottom of the body (castle rail?) so engine movement, even though slight will tend to pull it apart. We may have to take that into account. Dan said he was going to  either slice the spacer on the band clamp or remove it to get heavier clamping force. One way or another we'll get this sorted out.

Jim

[rficalora]

Be careful if you remove or make the spacer smaller.  I have a similar problem on mine where the right side gets pulled loose over time & did something similar.  The stainless doesn't give so if you tighten it too much, you'll collapse the header & exhaust pipe & have an even bigger leak (DAMHIKT).  If you do that, harbor freight sells a cheap little pipe expander that works well with a body hammer to get the pipe back in shape.  The best answer is to get a V-clamp for it.

[BlownMGB-V8]

V clamps would be much better. Kind of a pain to install though I expect.

Jim

[BlownMGB-V8]

I drove the car around the "block" last night (about a 3 mile loop including the hospital road) and I was pretty impressed with the improvements. The car drives straight and true, is quiet, and seems pretty responsive. I think mainly what Max was complaining about is a huge bog when you mat the throttle, and it does do that. I don't see it as a serious problem, since it has really good power as long as you open the throttle a little slower. This was a really common problem with big four barrel carb engines and is often linked to an inadequate accelerator pump shot. It resulted in the development of the Holley double pumper and even the high capacity 50cc pumps. These were found helpful for engines with a lot of cam overlap, which we may have. Regardless we do have and have always had a serious bog with this engine. We can either live with it, (the car is quite driveable in spite of it) or try to fix it. I rather doubt the carb we have has the capacity to cover up the bog so Carl's recommendation that we put a "real" carb on it has some merit. A Holley double pumper should do the trick and if it does not the big pumps surely will.

I didn't have the chance to look at anything else, but it was a nice drive last night.

Rob, Dan was unable to get the bolt in your starter brace. Do you have any recommendations about that?

Jim

[ex-tyke]

What size double pumper would work best?....650?....750?....850?
Here's a 750 on ebay that might go reasonably....
http://www.ebay.com/itm/HOLLEY-750-CFM-DOUBLE-PUMPER-CARBURETOR-LIST-8156-/271211601697?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f25789f21&vxp=mtr#ht_118wt_997

[DiDueColpi]

The roadmaster is still running a quadrajet I think.
If that's the case and it pulls ok at full throttle once it gets settled, then probably you just need to set up the air door spring.
The air door is used as an alternative for the accelerator pump on the secondaries and also controls the metering rod lift. The carb should have a vacuum brake on the air door. Most "tuners" throw them away and that's a huge mistake. As far as the air door spring,  it is likely too loose. Tighten it up a full turn at a time until the hesitation is gone. Then back it off 1/2 a turn at a time until the transition gets lazy. crank it back up 1/2 a turn and you are going to be very close to perfect.
When set up properly the quadrajet is very hard to improve on. It has massive airflow, 750 cfm for the small ones and 850 for the bigger units. Excellent fuel atomization and small primaries for good throttle response and superior mileage. And a central fuel bowl that is cooled by all for throttle bores.
It's main short coming is a small fuel reserve which makes sizing of the inlet needle and seat critical. Which makes all the drag racers grab a Holley because you can tune them with a hammer.
The inlet jet is likely the cause of your shut down/ start up problems. Pop the carb top and make sure that the inlet valve has a solid body. The "high performance" aftermarket ones have scalopes cut out on the sides to increase fuel flow because they don't use the relived inlet needles. The problem is that the inlet valve mounts to the fuel bowl floor. When you shut the car down and the fuel level drops, the valve opens and the bowel drains back into the tank through the cutouts in the valve. When you restart the car it's severely lean and backfires or bucks the starter.  The stock high top needle/seat assys. don't do this. Most guys think that the carb is leaking through the main jet wells but I have never seen one actually do that.The other issues have to do with the float and the fuel bowel stuffing block. The float needs to be new  or brass. The older "foam" floats can't deal with todays fuels and make carb tuning impossible. The stuffing block must be installed. Without it the carb randomly spills fuel into the throttle bores and makes the engine want to run on during shut down.
Hope that helps some.
Cheers
Fred

[BlownMGB-V8]

I won't have much of a chance to look at it before Omaha, I'm headed back home today. And I doubt Dan will get the chance either. Fred is there any chance you will be at Omaha? It'd be great to meet you in person and maybe we could take a look at the carb there.

Jim

[DiDueColpi]

I would love to meet up at an event or two.
Omaha won't work as I'll be in Portugal from the 6th until the 28th. The lovely Lynne is doing another chef school over there now.
Hopefully I can catch up to her before she realizes her dream of a Latin lover!
I'm certain that we'll all run into one another along the way.
Cheers
Fred

[BlownMGB-V8]

OK, well I did verify that it is a quadrajet. I'm positive Steve DeGroat bought a rebuilt one from CarQuest and installed it. So I'm guessing that it should have come with the stock float valve but otherwise I can't make any guesses. Maybe we could tighten up the spring on the flapper valve.

Jim

[DiDueColpi]

Re the chipping of the fibreglass fenders.
I've got a buddies Freeman RA in the shop today. It's got the inside of the fenders lined with astro turf.
He glued it in place and sprayed it black. It looks cool, noise dampens and stopped the rock chipping in it's tracks.
Pretty clever solution I thought.
Cheers
Fred

[MGBV8]

We should have Rhino-linered the 'glass fender wells. We could do the auto store spray bomb version.

[madmax]

Jim:

RE:  Carb.   I actually "lightened" the spring on the flapper valve and this helped the response!  (However, it increased the pinging.)   Smoothed the transition noticeably.   The "Q-Jet Guru" here (Joey @ HRT Performance) made this suggestion.   He also agreed with Fred re: size of fuel bowls.   The car is stronger once it gets going full throttle, but I would NOT say it was smooth!   Still feels like it's struggling/surging, to Me.  

I know you love manifold vacuum, but I'd like to try tuning it with ported:  less chance of the pinging and probably a smoother overall response. (And,it's how the distributor is curved.)   What I'm sure will be the problem, however, is we'll have idling problems losing all that massive idle timing and we might then get into carb problems not having enough bypass idle air to keep it running (without getting into the progression/main circuit).     I think we have a decent "compromise" setting at the moment so that the car could run and get shaken down.   Something that pings this much, however, just isn't right.  (Esp., as everyone likes to point out, it's a "low" compression motor.   I never got around to doing a compression check to actually Prove this...  Anyone else?)  

It can't run with that pinging forever.   And we need to decide what IS it's next purpose in life-- if it's just going to cruise the countryside, we should focus on reliability and gas mileage.   IF we want to be able to have some FUN with it and take it on The Track, etc., then we need to make it a much crisper revving motor (as well as lighten up the steering effort!)  

I would NOT "buy" another carb!    Any carb will need to be set up properly for it's working environment.   We will NOT find an "off the shelf" carb that will work!   (Might be one that doesn't ping as much-- okay-- but then it probably would have worse gas mileage, etc.)   It is NOT an off-the shelf car or motor.  

I'd rather spend some funds doing a full-range of tuning (timing sets, carb sets and changes) then just trying carbs hilly nilly...   The "hard starts" are just another symptom that basic things aren't quite right.    (though I like Fred's idea of checking the needle valve and float construction.)

I think we should tune the car to a) get rid of the pinging  b) get rid of the hard starts and c) improve gas mileage where we can.    Hopefully, after those issues are resolved, we'll also have a better responding car as well that will be more fun to drive.   It certainly will last longer and should be more reliable as well.  

$.02

M

[MGBV8]

Didn't ping when I had it in March '12. That was with the original carb, though.

[madmax]

Carl, et al:

Yeah, I read through the logbook and there wasn't much recorded re:  pinging.   Since that time, however, I believe PJ changed a fuel pump.    And we also changed carb.  (Was it a 750 before and is now the 850?)

It has also been dynoed since then, and they made some changes (timing, I believe, is what was reported).     I does seem, however, from what Steve reported and I experienced, that the pinging might be a "new" thing.     (Wasn't there a spark retard box during the Power Tour that was ultimately disconnected?)

Fishing for clues....

M

[Dan B]

I haven't really noticed pinging.... I drove it Saturday to our club picnic, but just cruising really.

[Citron]

Carb is a 750 from summit.
No electronics has been disconnected.  If there was a retard box, there still is.
I did not notice ping while I had it.  If it runs on when shutting down, it has a clutch, kill it.
High test will take care of most of that.
If it ping, retard the timing some.

steve

[rficalora]

It didn't ping when I had it and that was after both the synopsis timing changes and the power tour.  I did run it on premium gas - 93 octane around here but also up to 10% ethanol.  Timing box is a timing control box - designed to manage timing with distributor advance locked out.  I still don't understand why we have it and a distributor with advance.  If pinging is new and isn't gas related (octane, pump, etc.) maybe the knobs on the timing box got inadvertently adjusted.  It's mounted in the cabin above the passenger foot well.