Top end rebuild debate

donstevens · donstevens's Garage

Guys,

My car is due for valve guides. It smokes on hard decel, uses a fair amount of oil, and there is high amounts of copper in used oil analysis. Otherwise it runs great.

What is the general opinion on top end rebuilds?

My mechanic tells me that he'd rather not do a top end stating that one might as well do the whole thing. Well I don't have the dough to do the whole thing. So I am thinking top end.

Comments? Estimated costs to have a top end done by a pro? I don't have skills, tools, or time to do it myself.

Don

LakeCleElum · 08-05-2006, 12:43 PM

If it's on a '72, we need to know how many miles are on it. The big question is how's the oil pressure.....If it's a '72 and never been opened up, now would be the time.....

H.G.P. · 08-05-2006, 12:59 PM

One of the early pages in out host's rebuild book gives some estimates, (I don't recall the engine though)
My question for my own rebuild came down to parts available. I have a 1969 E Coupe. Took some searching for parts, Pelican, EBS, and Stoddards. You might also post this in the 911 Rebuild Forum here also.

ianc · 08-05-2006, 03:56 PM

Do a top end only if the bottom end is OK.

How do you know it's OK?

How many miles on the engine? Ever been apart? What's the oil pressure like? Making any weird noises?

ianc

patkeefe · 08-05-2006, 04:25 PM

Don
As soon as you open the engine up, it becomes a can of worms. I'd leave it alone until you have the cash and inclination to do the whole thing. Apply the "is it broke?" rule.

I currently have three cans of worms in the basement and garage.
Pat

JeremyD · JeremyD's Garage

I'll second the wait to do it right or start shopping for a hot rod motor to swap it with. With the smaller bore being a little less desireable than the 3.2 to 3.6 - you might be able to make a deal on a punched out 2.4 to 2.7 and be out only the difference in a top end rebuild. Start saving =

dtw · 08-05-2006, 06:58 PM

A mag case motor seems to be one you don't want to open unless you have cash on hand to cover all the contingencies. I'd park it or reduce the mileage for a while till you save up some $$$

afterburn 549 · 08-05-2006, 08:13 PM

Like said..when you open the can, be prepared for whatever may jump out.....A leads to Z with no forgiveness

HarryD · 08-05-2006, 09:12 PM

I faced a similar issue a few years back when it was clear my guides were shot. My car had 118,000 miles.

I decided that I would go with a top end rebuild (and possibly a re-ring) only. If upon initial disassembly it looked like we would need to go deeper, I would stop and shop for a nice 3.0/3.2 to drop in as a replacement. I go lucky as I only needed the valves done. We left the rings and every thing else intact. I am now pushing 130,000 miles and the car is running better than ever. To me, it looks like I did the right thing but I was prepared to go the full course if it came to that.

As Mr Eastwood once said, do you feel lucky?

donstevens · donstevens's Garage

Thanks for the replies.

My car has 85,500 original miles and has never been opened to my knowledge. I don't drive it more than 1500 miles per year so I can go a while before I to open her up.

I'll either wait until I have the $$ to do it right or maybe swap a 2.7 or 3.0 in there for a while. The car is nice enough that it deserves to have the original engine rebuilt.

Don

HarryD · 08-06-2006, 09:43 AM

Don,

Hard call. Most likely you may get by with a top end as the bottoms should be good for 150k+.

The bad news about a 2.4 is the mag case. If you split it, you have some expensive machnine work to make it right. It is not like Aluminium 3.0/3.2's where you can split them, replace the worn parts, and put it back together.

How much oil are you using? I was at 300 miles/qt when I decided to go with my top end.

donstevens · donstevens's Garage

Quote:

Originally posted by HarryD
Don,

How much oil are you using? I was at 300 miles/qt when I decided to go with my top end.

I don't know exactly. Some is burned, some leaks. It only smokes heavy when coming down from 5000+ RPM. There is a trace of smoke at start up but only a trace. I can probably hold out for a while.

Were you fouling plugs when it got bad?

Don

HarryD · 08-06-2006, 02:36 PM

Don,

I never checked the plugs.

Nine9six · Nine9six's Garage

Quote:

Originally posted by HarryD
I faced a similar issue a few years back when it was clear my guides were shot. My car had 118,000 miles.

I decided that I would go with a top end rebuild (and possibly a re-ring) only. If upon initial disassembly it looked like we would need to go deeper, I would stop and shop for a nice 3.0/3.2 to drop in as a replacement. I go lucky as I only needed the valves done. We left the rings and every thing else intact. I am now pushing 130,000 miles and the car is running better than ever. To me, it looks like I did the right thing but I was prepared to go the full course if it came to that.

Excellent recommendation! For less than the cost to rebuild your motor, you could probably find a nice 3.2, or 3.0 with the necessary upgrades.

speedracer · 08-07-2006, 11:51 AM

I say to preserve the cars originality and keep the original engine in. I would wait until I could afford to do the whole rebuild then you know you will be good for a long while afterwards.

Rot 911 · 08-07-2006, 12:19 PM

I would have no problem just doing the top end with those miles on the engine. How is rebuilding the entire engine "doing it right" if the bottom end doesn't need a rebuild? And has been pointed out, splitting a mag case leads to a whole nother set of problems to be fixed. I needed a top end rebuild and decided to rebuild the whole engine myself, which I did. However the only thing that actually needed rebuilt were the heads. The rest of the engine was still well within specs. And this was a 3.2 engine with 130,000 miles.

donstevens · donstevens's Garage

Hmm - The debate continues

How about this idea? - Are E and T heads the same except for cams? valves? Would E cams work with T Pistons? I'd love to have a little extra torque but would E cams over T pistons accomplish anything?

For those discussing keeping the original engine in the car. That will happen. One of the reasons I am considering all of this is to keep the original engine in tact. I want to take the car to the track but I am scared to death of grenading the original engine. Not only would it be expensive to fix then the value of the "original engine" would be gone.
If I buy a bigger engine it will be as a "spare" that I can flog without worry.

Don

aigel · aigel's Garage

I would pull the heads off, send them out for new valve guides and slap them back on. Don't even touch the p/c and rings. It will give you many more years of service, especially at the miles you put on annually. You can do this yourself fairly easily, the cam timing probably being the most complicated part. That bottom end is barely broken in.

George

LakeCleElum · 08-07-2006, 07:31 PM

Don - Still waiting to hear what kind of oil pressure you have? Especially at a warm idle.....The '72 and '73 were kinda known for weak oil pressure. My '73.5 is weak in this area at 118,000 miles.......

donstevens · donstevens's Garage

Quote:

Originally posted by LakeCleElum
Don - Still waiting to hear what kind of oil pressure you have? Especially at a warm idle.....The '72 and '73 were kinda known for weak oil pressure. My '73.5 is weak in this area at 118,000 miles.......

Oil Pressure is normal (I think). 20+ psi at idle (hot) and 60+ at 3000 rpm. It fluctuates a little when the engine is real hot. It runs at 215F or so in 90 degree ambient. Even at the hottest (230F) the pressure is 40+ at 2500 RPM.

Comments?

Don