Aurel`s engine rebuild thread

[Aurel]

I hope you guys don`t mind if I use this thread as my logbook

April 5, 2009: 115,391 miles on the clock. I am changing my oil to Kendall GT1 20W50 today. At $2.99/qt and 1,200 ppm zinc-phosphorous, it seems like the best choice in town to protect my valvetrain. I am also hoping that the thicker oil will reduce the little oil leaks I still have. The oil drain plugs were half filled with grey metal paste, but very thin, and not metal particles on the tip of the magnetic plug, so I think we are good there.

I also put a cat bypass about a month ago. Impressions: not much change in noise, but I like hearing the little pop pop backfires on deceleration. Power has not significantly changed. I`d like to think the low-end torque is a little improved and the high end is a little more free revving. But the difference is very faint, if any. I may have to try a richer mixture now.

One thing I noticed with the cat bypass though, is the huge cloud of white smoke on first cold starts in the morning, due to water condensation.

Gas mileage is in the 16-17 mpg range on a mixed highway and street drive to my work. I just get 300-310 miles on a gas tank. It is a little low to my taste, I was hoping to break the 20 mpg mark, but it may just be my right foot effect . And it still beats my SUV.

Cheers

[OldTee]

Gas mileage is about what I get on both the 78 and 79.

Re: Pop-pop. Things to think about. One is a exhaust leak can cause that. Also, look at your spark plug harness. If it is old you may be getting some cross talk and than can cause the pop pop. There are other things too.

[Aurel]

Originally Posted by OldTee

Gas mileage is about what I get on both the 78 and 79.

Re: Pop-pop. Things to think about. One is a exhaust leak can cause that. Also, look at your spark plug harness. If it is old you may be getting some cross talk and than can cause the pop pop. There are other things too.

Assuming that there is no exhaust leak, the pop-pop backfire could also indicate that the mixture is on the rich side, right? My spark plug harness was replaced, so I do not think it may be the problem.

I can definitely feel a difference with 20W50 oil: when cold, the oil pressure is pegged at 5 psi at idle, and when warm, my idle has dropped from 950 to 800 rpm. I am curious to see what effect it will have on gas mileage too.

[jsveb]

HI
I always thought that exhaust popping was indicating a lean condition, this is supported by you increasing the flow with a cat bypass, or am I wrong.

Jesper

[Aurel]

HI

I always thought that exhaust popping was indicating a lean condition, this is supported by you increasing the flow with a cat bypass, or am I wrong.



Jesper

I think you are right. That would make sense.
Time to richen a bit now...

[QueensEng]

Hey,

Just a great read... Aurel bien fait. I'm about to dive face first into a rebuild of my own on a similar car - 82SC - this along with the various books I'm picking up will make this a supremely rewarding experience I'm sure.

A couple questions: In the end, do you regret not having split the case? And also, what prevented you from rebuilding your own tranny, not having that outrageously expensive diff tool... fear of imprecision... no interest...?

- Dave

[Aurel]

Hi Dave,

No I do not regret no splitting the case. I did not feel like throwing another grand in that motor, and my application, street driving, is not too intense. I put in good oil with ZDDP and I expect another 100k miles from the crank and rod bearings.
I did not do the gearbox myself because I would have needed more special tools, there was no book like the engine Wayne rebuild book, and the initial quote was low enough, though it ended up costing about 3 times the initial quote. I also felt the engine would keep me busy enough (took 6 months), and it made sense to have the box done at the same time by a pro. At least, I knew I would end up with a good gearbox if I screwed up the rebuild .

Good luck with your rebuild!

[QueensEng]

Great thanks, that also answered another question as to whether a Wayne's type book existed for the 915... I'll be going the same route with a pro-rebuild. Hope all is well on your engine, I'll keep checking this thread-gone-logbook regularly. Salut.

[Rumble-Bee]

Awesome thread!!!

I was going to recommend that you switch from Castrol to Kendall -- and I see you've done that. I used to use Castrol until I converted my 914 to a high mileage 914-6 engine. When I tried Kendall the mild piston slap went away completely and the blowby was so greatly reduced that I gained about 8-10% horsepower. Even the valvetrain ran quieter. I've used Kendall ever since then.

[Aurel]

Until now, I was running 87 octane because I figured with 8.5:1 CR, it was enough. Well, I tried 93 just to see, and WOW! big difference. The car runs better, more powerful, the backfiring is almost totally gone. Idle is higher by about 500 rpm, and more importantly, my mpg seems a lot better: I have passed 200 miles at half a gas tank, while I used to get only 150 miles at the half tank mark. I am sure the better gas mileage offsets the higher premium cost, and the car is more fun to drive.

[snbush67]

Aurel,

Great thread, congratulations on your successful build. I had read that the valve clearance should be different than stock when you use a different cam grind. Did you have to make any changes from the stock cold valve adjustment? Additionally I believe the cams should allow you to advance your timing further as well, depending on how they were set up.

Regards,

Shane

[Aurel]

Shane,

No the valve clearance is the same, but the cam timing is different: 1.8 mm versus 1.0 mm or so for stock SC cams. Valve clearance is there to compensate for valve thermal expansion, so it should be independant from cam lobe profile.

Advance timing at max should be the same too, because it is mostly governed by CR and gas octane. However, the timing advance curve must be adapted to the cam profile, I believe. In my case, DC15 is close enough to SC that no recurving of the distributor was necessary.

[Aurel]

May 31st, 2009: 117,541 miles; added 1 qt oil. Also fixed wipers switch and heat/defrost fan.

[911 tweaks]

Thanks Aurel for the uypdate... anything else you can add to tell us more...?
Thanks for the follow up!!
Bob

[cgibson67]

How did the paint hold up on the bumpers? I was thinking of doing something similar, but was concerned that it would begin to flake.

Congrats on the rebuild....looks great!!

[Aurel]

Chris,

The paint held up very well on the bumper. It does not flake because it is a flexible formulation. You can go for it without any concern (use Krylon Fusion).

Best

[Aurel]

October 4th, 2009. 122,975 miles.

I put in a wider 10 mm fan belt (9.5mm was slipping), readjusted the valves (that was a pain) and replaced the oil with 10 qts Kendal GT1 10W40. Got new turbo tie rods, but haven`t had time to install them yet. I went on a 600 miles trip to the Finger lakes three weeks ago, and did 360 miles on a gas tank, which is close to 20 mpg.

[911 tweaks]

Thx Aurel for the update... just another testament to the greatness of these cars (and the great job you did too) !!
So, how many miles since the rebuild?

Bob

[Aurel]

Originally Posted by 911 tweaks

Thx Aurel for the update... just another testament to the greatness of these cars (and the great job you did too) !!
So, how many miles since the rebuild?

Bob

12,975 miles. She`s become a daily driver .

[mca]

How were your rockers? Any shifting? I am at roughly 9k on my rebuild and plan on adjusting the valves at 11k. Just curious to know if you rechecked the rocker torque.