Engine rebuild 3.0 regrets?
 

Hi all in the middle of a total rebuild. I am sending out heads, valves to be redone. New rings on pistons and shafts being inspected and machined if necessary. New bushings, timing chains, tensioner upgrades, etc. entire top end be addresses as well.
My plan is to keep everything stock on my 78 sc cal targa. I do not plan on tracking the car or doing auto cross. I do plan on spirited drives and using it for the occasional short work commute through town.
If you had it to do all over again?

Thanks,

Gary

Cams... Get them reground to a streetable grind that will add some top end. I did the elgin "super SC" on mine, very nice.

Web Cam 20/21 grind if your sticking with CIS
Did that with some minor head work and SSIs on an
83 I had. Really fun after 3000 rpm and pulled strong to 6500.
I have a 78 now that I just got a couple months ago. Did 22/28
T-bars with new bushings and SSIs but will probably do cams and maybe
higher comp J&E 3.2 98mm short stroke pistons next winter. More displacement+++!
Spend the $$$$ now and you'll enjoy it without regret!

You don't mention the headstuds. The bottom row should be replaced with your choice of better studs. The originals are timebombs.

-Andy

Engine rebuild........
 

Gary,

Are you also doing the bottom end rebuild?

Tony

since you live in Ca. I don't think you can pass smog with cams:( for the street.

Bob

Replace all exhaust studs on the heads no matter how good they look!

Hi tony, No bottom end rebuild. I decided to leave the cams be as well since they look perfect. Also this way i don't have to worry about smog.
Machine shop said the cylinders were the nicest mahle he had ever seen. Still charged me 2500 bucks though. Of course everything is much cleaner now. Valve guides and a couple of springs replaced. No vales replaced. Everything cleaned. Surface areas that meet machined and all exhaust studs replaced. One a real bugger that I broke a tap off in the stud.
I guess this is called a top end rebuild. I also bought the tensioner upgrade kit and new sprockets as well.
I did put the new seals on each long engine stud that joins the two halves together along with the rtv.
Realistically I won't have the engine, tranny and rear end done until August.
Buy that time though I will pretty much have gone through and replaced almost everything on this darn car. I am definitely pushing the 20k mark. And he still need paint.
Can't take it with me:)

You're building too strong a top end with valve job and rings you ll be stressing the old worn bottom. I wouldn't have done the rings
Bruce

I think I'd have regretted not opening the bottom end and installing new sprockets on the intermediate shaft had I not done it. Or inspecting the int shaft and main bearings and ultimately replacing them.

Also, you'd be fine with the super, 964, and many other grinds in terms of smog tests, assuming a healthy motor.

I'm a big fan of top only overhauls. The bottom end is very robust. If it's original with less than 200k miles it should go many more. If it's been rebuilt in the past, then I would open it up. Many times you will find things done wrong when someone else has rebuilt the engine.

You still didn't say you replaced the bottom row of headstuds. I would go cheap on these and get some used steel studs and replace the bottom row of dilivars. I got mine from my machine shop that saved them from other rebuilds.

-Andy

Hi gents,

Yes, all the studs have been replaced. I certainly could do a bottom end rebuild. Not afraid. So many have advised not necessary. Motor does have 188,080 miles on it. I am the ultimate while u r in there person, but I have been told not necessary by quite a few in the know. With that said, I can be persuaded, but nothing with car has raised concern with current porsche mechanic, and many knowledgeable friends.
Again, I can and will be willing to go the whole enchilada if needed.
Thanks for all the input and advice.
Much appreciated

GarySmileWavy

+1. The bottom end is a 930 Turbo case, pressure cast aluminum, with compression that is favorably wimpy. 8.5:1 or so in the 78? It don't need jack. If your head faces were cut a few thousandths to true them up then you may be running 8.8:1.

If you do not address the lower studs, I will kill my cat. Change those things out even with "all-thread". As Jeff Foxworthy says, "If I'm lyin, I'm dyin". I put Raceware top and bottom in my 81 back in '97. Overkill for a street car when sufficient alternative options were available.

Do new chain ramps.

You can still do new Rod Bearings and new Rod Bolts without splitting the case.

That's good stuff Bob.
Your cat can rest easy. I not only replaced all the bottoms, but went ahead and did the tops as well.

If I was pulling top end off for refresh at almost 190K, I'd certainly do the bottom end. With the miles these are getting these days, it'll last forever.

What are you using the RTV for you mentioned above? RTV has no business in one of these motors.

Hi Ed, I have been following Wayne's engine rebuild book. He says to replace the little rubber seals and put a generous amount of rtv silicone sealant on both ends of the engine housing through bolts to prevent leaks. Although at this point I am close to undoing that and just doing the bottom end. Can't hurt anything other than the pocket book...correct?

If you do use RTV, get the red stuff and don't be too generous when applying. I replaced all my thru bolt o-rings in 97. Nary a leak without RTV.

As noted above, you can pull a connecting rod or two to check the rod bearings. If they are fine, your mains are fine. If tired, I would pull the big trigger. Did not know you were close to 200k miles. Not saying the engines is flamed, just would be a shame to have to pull it again. The top end re-assembly takes a lot of time. $ or hours.

That said, if your trans is tired but working ok, now would be a great time for a refresh. About $2,500 for basics and that includes a few $200 parts. New throw-out fork as well.

Spending your dough is sweet!

I'd simply go with new Viton o-rings and Dow 55.

Bushings, bolts, nuts, Cleanroom wipes #8nose bearing all on order. Will take apart and look at status of teeth on gears. Spending my money is sweet :)
1st n 2nd gear are being addressed as well.