1967 MGB Engine Project

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Larry Kluss
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1967 MGB Engine Project

Post by Larry Kluss »

So for some time my MGB has been oil fouling the #4 spark plug every 1,000 miles or so. It was also producing small puffs of blue smoke. Recently it also fouled the #3 plug. The engine has only 8,000 miles on it.

First a little background: I bought the car in 1981 when I was still in high school. I drove it home and dismantled it with the plan of making it into a fender-flared canyon racer. At the time, the only real “high-performance” parts and information for the MGB were in the factory Works Special Tuning manual. So I rebuilt the engine using that information as a guide. I ended up with about 10:1 compression, reground stage 5 camshaft, and a Weber carb. The original head was cracked, so I had a new one ported and polished.
1981 - Dig those Dune Buggy seats :)
1981 - Dig those Dune Buggy seats :)
scan0014.jpg (148.2 KiB) Viewed 17952 times
After doing numerous modifications and refurbishments to the car, I finally got the engine running in ’85. I had some issues when first firing it up and I found out years later that some of the cam lobes went flat I believe because of those issues.

Fast forward about 20 years: Life got in the way and the project got set aside until 2004. By this time my goals had changed and I decided to finish the car as a tribute to the original factory Works race cars. I already had the Works spec engine. I was glad I hadn’t gotten around to adding the fender flares 20 years earlier :) I decided to completely assemble and sort out the car before painting it. One issue I hadn’t resolved was the engine temp rising under load. So I decided to go through the engine when I had it out during painting.
2005 - Nearing time for paint
2005 - Nearing time for paint
I checked the bearings, installed ARP rod bolts and head studs (they didn’t exist in the early ‘80’s), and re-sealed the engine. The cylinder walls and everything else looked good. But when I checked the cam that’s when I found the flat lobes. So I installed and degreed-in a rally-spec cam that is very close to the original stage 5 Special Tuning specs. The engine’s run great for ten years and no more temp concerns.

Back to the current problem: I checked the compression when I changed the plugs and it was good. I also scoped the bores. #1 and #2 piston tops and plugs looked normal with a light coating of dry carbon. Both #3 and #4 piston tops appeared oily and washed clean around the perimeters.
Cylinder #4 - oil-washed piston
Cylinder #4 - oil-washed piston
Cyl 4a.jpg (137.6 KiB) Viewed 17952 times
With help from Steve and Dean, we did a leak-down test on the cylinders. #1, #2, and #4 were pretty good, but #3 showed a leaky exhaust valve. Given the condition of the #3 plug, we guessed the valve may be carbon fouled. Some research indicated the oil fouled cylinders may be caused by stuck oil rings. So it was apparent the engine needed to come out.
...a little help from my friends
...a little help from my friends
IMG_8202.jpg (143.2 KiB) Viewed 17952 times
More on the tear down later...
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HealeyBN7
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Re: 1967 MGB Engine Project

Post by HealeyBN7 »

Great write up. Love the early photos... If I had anything to do with the orange paint, I'll deny it.

Here is a 2012 press release about your former owner... You can blame him for all your lost mail. Read it carefully and pay close attention to the last sentence. In addition to picking the same sports car, you were both drawn to nearly the same names for your other babies.

Uncanny.

https://about.usps.com/who-we-are/leade ... -ao-vp.htm

Dean
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Re: 1967 MGB Engine Project

Post by Steve Simmons »

Nice to see the early history!
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Larry Kluss
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Re: 1967 MGB Engine Project

Post by Larry Kluss »

HealeyBN7 wrote:If I had anything to do with the orange paint, I'll deny it.
The story I heard was that you were the one who sprayed the color, not the one who chose it...What was he thinking?

That is weird about the kids names. They have the same nicknames.
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Larry Kluss
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Re: 1967 MGB Engine Project

Post by Larry Kluss »

So, Tyson helped me pull the engine the week after Christmas. I know, I know, I’m a bit tardy with the blog posts. No issues to note with the extraction, but never a fun ordeal. The hardest part is not damaging the painted engine bay.
Protect that engine bay
Protect that engine bay
DSCN3287a.jpg (123.39 KiB) Viewed 17913 times
DSCN3291a.jpg
Once out and on the stand, I pulled the head and confirmed what the scope pictures indicated. Combustion chambers #1 & #2 look normal and #3 & 4 oil/carbon fouled. You can see the #3 exhaust valve looks different. It was the one that showed up in the leak down test. I checked the valve seating using lacquer thinner which confirmed the valve leak. All of the remaining valves seemed to hold.
#4 cylinder to the left
#4 cylinder to the left
The piston tops show a similar story with #1 & #2 normal, and #3 & #4 oil washed. Otherwise the cylinder walls look good, still cross-hatched with no ridges. I pulled the pistons expecting to find stuck oil rings, but interestingly, no. So why all of the oil in the two cylinders?
again, #4 cylinder to the left
again, #4 cylinder to the left
Dean came by to help diagnose the issues. With the valves out, we agreed the #3 exhaust valve was carbon fouled. There was some pitting and carbon buildup on the seat, but it looked liked I may be able to clean it up by lapping the valves.

Still stumped about the oiling issue since the oil rings were not stuck, we checked ring gaps and #4 was about .065”. It should be .012”-.015”. So we checked #1 and it was about .050” gap. Given the worn rings, it would seem that all of the cylinders should be oil-washed. The difference in the gaps from #1 to #4 doesn’t explain the dramatic difference in the condition of the cylinders.

I had modified the oil sump years earlier by adding a baffle per the Special Tuning manual to help reduce oil sloshing/starvation. Trying to figure out why #4 started oil fouling some time ago and the same with #3 recently, we speculated that oil sitting on the added pan baffle and not draining down quickly enough toward the rear of the engine might be causing more oil windage in those cylinders. The closer to the rear, the more oil being thrown around by the crankshaft? Combine that with the worn rings and those two cylinders are getting oil washed/fouled.
Baffled oil sump
Baffled oil sump
So adding some drain holes in the rear area of the baffle seems like a good idea.

Now that I have a plan of action, it’s time to order parts and do a lot of cleaning…
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Larry Kluss
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Re: 1967 MGB Engine Project

Post by Larry Kluss »

I managed to find some time to get back to the engine project. I decided to tackle the head work first, mainly so I would know if I could clean up the valve seats well enough by just lapping them. If not, it would give me some time to send it out to a machine shop while doing the rest of the work.
Disassembly complete
Disassembly complete
I removed the carbon deposits off the valves and combustion chambers, as well as inside the polished ports, the old fashioned way…by scraping and wire wheel. The valve guide clearances were decent, so I lapped the valves using a drill motor and lapping compound. They all cleaned up pretty well.
Cleaned chambers and lapped seats
Cleaned chambers and lapped seats
Cleaned and lapped valves
Cleaned and lapped valves
I checked the surface flatness of the head which was also within spec, then re-assembled the valves into the head adding new valve stem seals. I re-checked the valve sealing again using lacquer thinner and all were good after the lapping. So the head is now ready to go.
DSCN3316a.jpg
Next up is the pistons, bores, and rings.
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Re: 1967 MGB Engine Project

Post by VWNate1 »

? What's the status now ? .

Some times I miss my old 1967 MGB GT.......

I still have the girl though so that's a plus :D .
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-Nate
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Larry Kluss
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Re: 1967 MGB Engine Project

Post by Larry Kluss »

This update is way overdue as I got the car running again back in May. So here’s the rest of the story.

…the next step was to clean the carbon off the piston tops, including from the ring grooves. Then I used a flexible ball-hone with some light oil to clean up the bores for the new rings.
Honed cylinders
Honed cylinders
DSCN3377.JPG (126.92 KiB) Viewed 17611 times

Next was fitting and gapping the new piston rings. Surprisingly, all the ring gaps were within spec right out of the box. Once the pistons were installed I checked the clearances of the new rod bearings with Plasti-Gauge. All good.
Pistons ready to install
Pistons ready to install
DSCN3380.JPG (126.15 KiB) Viewed 17611 times

I drilled some drain-back holes in custom sump baffle to hopefully reduce the windage that might have been the issue with the #3 & #4 plugs oil fouling. After that it was just a matter of reassembly and fresh paint.
Drain-back holes
Drain-back holes
DSCN3381.JPG (123.23 KiB) Viewed 17611 times
DSCN3384.JPG
DSCN3384.JPG (127.87 KiB) Viewed 17611 times

Once I got the engine back in the car I had a little issue with the engine not rotating…at all! I traced it down to the Datsun 5-speed trans adapter plate fouling the back of the crankshaft due to the new backplate gasket being thicker than the one I removed. But this necessitated removal of the engine again, separating it from the trans, and grinding a bit more clearance in the adapter plate.

With the engine back in, it fired right up. Though it has a significant rear main seal leak now, I think due to disturbing the seal when I pulled the adapter plate off. The engine may need to come out again…Ugh!

Dean kindly let me barrow his exhaust air/fuel ratio meter so I could fine tune the Weber carb. The car has never run better. I’ve put a few hundred miles on it since then, including running an autocross, and it hasn’t used any oil and the plugs look good. Combine that with sticky new Nitto NT-01 tires and the car is a blast to drive again. :drive
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Re: 1967 MGB Engine Project

Post by VWNate1 »

Great :thumbs: .

Always nice to hear of a happy outcome .

? Did you add a rear main seal ? .

IIRC, '67still had the screw typ seal (?) .
-Nate
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Larry Kluss
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Re: 1967 MGB Engine Project

Post by Larry Kluss »

Thanks, Nate. It's a modern press-in seal and I did replace it when I did the engine refresh, but not again when I modified the trans adapter plate. :hammer:
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Engine Seals

Post by VWNate1 »

O.K., got it ~

I used to take my old seals to King Bearing (now Applied Industrial Technologies) in No. Ho. near the airport, they'd order me in the same seal in Viton and I've never been able to wear our or cook to death, a Viton seal .
-Nate
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Larry Kluss
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Re: 1967 MGB Engine Project

Post by Larry Kluss »

Update on the MGB engine story. I did pull the motor again shortly after the last post in 2017 to replace the rear main seal. That all went well and I've put roughly 2,000 miles on it since and I'm happy to report zero oil consumption!
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Re: 1967 MGB Engine Project

Post by Steve Simmons »

I'm envious. My '67 goes through a lot of oil. Some burns, some leaks. Lots of miles plus supercharger will do that though.
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Larry Kluss
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Re: 1967 MGB Engine Project

Post by Larry Kluss »

You also put lots of miles on your car.
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Re: 1967 MGB Engine Project

Post by tannyo »

That’s what happens when your MGBGT is your daily driver. I’m about 2500 miles away from rolling over the second time on my odometer.
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Re: 1967 MGB Engine Project

Post by Steve Simmons »

Mine just rolled over for the third time (I think) a while back, but the first one was before I got it.
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Re: 1967 MGB Engine Project

Post by tannyo »

Wow!
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Larry Kluss
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Re: 1967 MGB Engine Project

Post by Larry Kluss »

Wow, that is a lot of miles!
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Re: 1967 MGB Engine Project

Post by Steve Simmons »

Believe it or not, there are as many miles on my '65. Probably half from my dad, and a good potion from his dad also. That engine is in my GT right now so the engine actually has close to 400K miles at this point even though the chassis is a bit over 300K.
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Larry Kluss
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Re: 1967 MGB Engine Project

Post by Larry Kluss »

That's impressive.
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