76 GTB Major Service with Sodium Extraction

The time to give 20621 some TLC has arrived. The last major service was in late 2009 at just over 67,000 miles. The car now has 74,000 miles with regular use and fluid changes but has reached the point of a major service.

This forum has been very valuable as both a source for finding a car and as a technical resource. I wanted to give back in my small way and decided to post some pictures and comments on some of the work and small things I learn along the way in the hopes that it might be of help to other fellow 308 enthusiasts.

Since winter is upon us here in the Great White North, it’s time to begin the work with the intention of having the car back together well before winter is out.

I am planning a little more than your typical major service as the heads will be coming off to replace the sodium exhaust valves. In addition, I plan to replace all the rubber hoses in the engine compartment so I have a line in the sand with what is fresh vs what is old or even original.

Based on the above work, it was clear that the motor should come out. This would allow for a good general engine bay clean up and easy access to all hoses including the driver side vacuum and coolant long hoses. I also wanted to take the opportunity to remove the front header heat shield which has been rattling and sitting on the shift shaft for some time. The rear header had the heat shield removed previously, so I’ll send both out for a black ceramic coating.

I am performing the work with the help of two close friends and fellow f-chat members Nuvolari and Rosemeyer - both are well versed in the 308 and 246 era cars, the later of which they just finished a complete restoration on so I am very lucky to have some excellent knowledge to draw from.

Before starting, it was decided to give the engine a compression check. We decided to perform a hot and cold compression to compare results and see if there would be a significant difference. This was then followed up with a leakdown test once the engine was out of the car.

For the hot test, we did allow the engine to cool down about ~30mins so we could keep some of the hair on our fingers intact. The results were as follows:

Hot compression: Cylinders 1-8: 178 – 185 psi (3.78% variation)

Cold compression: Cylinders 1-8: 175-180 psi (2.78% variation)

Cold compression was performed the next morning with a fully charged battery.

Not bad for a 40 year old motor that we are pretty sure has never been apart. Regular use and fluid changes probably have helped. It also verifies that the documented mileage in my records is real mileage rather than an under estimate. 

Once the fluids were drained it took approximately 8 hrs to have the motor completely out working at a steady pace. We also took the time to label and collect items methodically as a little time now will pay great dividends when re-assembling. Another tip here that became really apparent later was – YOU CANNOT TAKE TOO MANY REFERENCE PHOTOS.

We used the method on the Birdman website for securing the motor - a strap in front of the forward cylinder head. This technique works well, just remember to make sure your engine hoist has sufficient vertical reach – double check with your strap length before lifting. We used a 6ft lifting strap. The strap secures itself quite well with all the studs present. We also used the engine leveling cross bar attachment that comes with the hoist as a slight adjustment side to side seemed to make removal a bit easier. We had 3 guys for pulling – 2 spotting and 1 manning the lifting hoist.

Also, don’t forget to disconnect the hidden ground strap passenger side rear cross member, it will not let go on it’s own……ask us how we know

We tried to leave the front header in place but in the end, it was disconnected and left on the frame – believe me, it was not coming out with the front header on!! Best to remove before pulling the motor.

Engine was removed without headers or airbox but carbs in place, we just located the strap carefully not to touch the carbs. Driveshafts were just disconnected at the diff flanges but also left in place. We’re I to do another car, I would remove the driveshafts completely as well, they only got in the way and ended up coming out later for a re-pack and inspect.

Multiple layers of yoga mats were used to help protect the rear glass and bodywork and front firewall.

With the engine out we proceeded to perform the leakdown. I bought an OTC leakdown kit online and this worked pretty well, The only thing is the hose that comes with it is on the short side. So if we were to do this in the car, I believe a hose extension would be required.

The results were 2.44% - 6.25% with cylinder number 5 having the highest value. Again like the compression results, we were pretty happy with the figures.

Next up, head removal.
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To the best of my knowledge all 2V 308's Carb and Injected and all GT4's came with sodium exhaust valves form the factory.

 

Purchased the valves from Superformance. I ended up replacing only the exhaust as the intake valves were in fantastic shape. I was ready to buy whatever was needed, but I went on the recommendation of our engine builder.

I'll post a bit more detail in an upcoming update, I am a bit behind with my write ups.

Best Regards

Dave

 

Thanks for the comments.

I didn't take as many photos at the beginning as I would have liked, but I got better as the work progressed, still new at making a documentation thread but I promise as many decent pictures as I have.

 

With the motor out it was time to remove the heads so we could have them inspected and complete the list of items to purchase.

Before removing the belts and cams we wanted to check the alignment marks and luckily all 4 cams aligned with the cam cap marks with the engine at PM1. So we would use this as our reference for reassembly.

After 6 years the belts looked like new and the tensioners (I believe there are the old SKF type based on the blue bearing seal in the photo) turned very freely with no play. Lower cam drive pulleys had no play as well, but I planned to replace the lower (outer) cam drive bearings anyway for my piece of mind since the access with the engine out is unparalleled.

Finally, it was time to remove the heads. We tried a standard first approach - some taps with soft mallets and 2X4 wood but this did not do much. We did see coolant start to leak form the exhaust side of both heads indicating we broke the seal but no real movement of the head on either side.

We had read about heating the heads and hanging the entire assembly from the head itself, but decided to make a fixture for what we were hoping would be a less dramatic removal method.

This took some time as we measured all the head, cam and valve cover stud locations and then had a plate fabricated that we could bolt all the hardware to. The plan was to use the 10 head studs to push and react the load on all the cam and valve cover studs – distributed evenly over 30 studs, we felt this would be quite gentle on the heads.

It worked like a charm, without much force and being sure to torque down on the 10 head studs as slowly and evenly as possible, both heads lifted off without much drama. I highly recommend this method to anyone attempting to remove heads that have been in place a while.

The bottom end looked to be in fantastic condition which aligned with our pressure/leakdown figures so we stuck to our plan of head work only. It’s quite tempting to go deep and do everything once you have things apart but based on the overall condition of the engine we stuck to our plan of sodium valve replacement.

With heads on the table, it was time to send them out for teardown. We sent the heads with cams and caps to a local performance engine builder that we have used for years on our road race motors. We know he had worked on numerous 246, 308 and 355 engines over the years as well so we were quite comfortable with his capabilities and the quality of work that we would get back on this project.

Based on his feedback of what would be needed, we began to finish our overall grocery list.
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We ended up removing it since I needed to give the system a charge anyway (was not blowing as cold this year) and also to improve overall access and not have it in the way - it is one big pump!

Dave