Can I use a Turbo Head on an NA Engine? - PeachParts Mercedes-Benz Forum

Graplr · #1 05-08-2014, 03:25 PM

For my 79 wagon, I'm fairly certain I have a valve (stuck and/or bent)problem. I picked up an 81 wagon (cheap, rusty and needs work to be a dd ). I originally planned on doing the entire drivetrain swap along with the climate control to get away from the servo but now I'm considering just the head.

I've discussed the problem at length in another thread. It is an intermittent problem where I will have no power, lots of smoke one day then the next day it will act as if everything is normal. PO did a compression test and found the #5 cylinder very low. I assume the test was done when the issue was present but don't know for certain.

Since I have the old York a/c compressor and the servo for climate control it would be an intensive swap...doable but all in all the NA has enough power for my daily needs so perhaps I'd cut down on the time involved if I could just swap the heads and solve the problem.

I'm assuming the answer is yes for a turbo head on a NA engine and no for a NA head on a turbo engine but thought I'd double check.

Thanks!

pawoSD · #2 05-08-2014, 03:49 PM

It should work fine.

ROLLGUY · #3 05-08-2014, 08:05 PM

If you are thinking to move over the entire head, manifolds and turbo, I would say no. There are several issues with this. One, the bottom end is not going to handle the extra strain on all it's parts. Two, the IP is set up for the N/A head and will need to be changed out as well. You might as well just put the complete turbo engine in and be done with it. Just my opinion though, so take it for what it's worth....Rich

Junkman · #4 05-08-2014, 10:24 PM

There is normally a different compression ratio between NA & boosted engines. Dished pistons and more chamber volume in the head are on the turbo engines. How did Mercedes accomplish this? Or I guess an easier way to ask: What are the differences between NA & turbo?

Graplr · #5 05-09-2014, 02:13 PM

Quote:

Originally Posted by ROLLGUY

If you are thinking to move over the entire head, manifolds and turbo, I would say no. There are several issues with this. One, the bottom end is not going to handle the extra strain on all it's parts. Two, the IP is set up for the N/A head and will need to be changed out as well. You might as well just put the complete turbo engine in and be done with it. Just my opinion though, so take it for what it's worth....Rich

No, just the head. Keep it NA. Literally just swap in the head and keep the original manifolds. That seems like about 10% of the work of swapping the turbo engine as you suggest.

If I did the entire engine I'd have to pull two engines and transmissions. Swap all the front lines of the a/c (actually purchase new lines as a PO of the parts car cut the condenser out and I have the York right side mounted compressor), swap the exhaust (actually get a new exhaust as the parts car is in terrible shape and I just bought a new exhaust for the NA last year), swap the climate control (or at a minimum move the servo which I may not even be able to do), swap the rear differential and the speedometer (and fix the odometer), and probably other things I'm not thinking of. So when you say JUST put the turbo engine in, it is a bit more complicated and costly versus swapping heads (assuming a head swap is viable).

So since I don't mind not having the turbo I was just looking for a way to save money and boat loads of time...if I have to go that route maybe I should just look at getting a valve job done instead.

Maxbumpo · #6 05-09-2014, 02:22 PM

I'd swap in the entire engine/transmission. Head work is no fun and fairly easy to mess up. You will need a hoist or a really strong buddy to lift off old head and place new.

Leave your current HVAC intact; remove AC compressor mount, leave compressor in place and re-attach to "new" engine. Is there a problem I don't see?

I'd leave the original differential. 4th gear is 1:1 regardless of transmission, so your RPM at highway speed will be the same as now. Keep the donor car diff and axles for possible future upgrade / replacement.

ROLLGUY · #7 05-09-2014, 02:42 PM

Quote:

Originally Posted by Maxbumpo

I'd swap in the entire engine/transmission. Head work is no fun and fairly easy to mess up. You will need a hoist or a really strong buddy to lift off old head and place new.

Leave your current HVAC intact; remove AC compressor mount, leave compressor in place and re-attach to "new" engine. Is there a problem I don't see?

I'd leave the original differential. 4th gear is 1:1 regardless of transmission, so your RPM at highway speed will be the same as now. Keep the donor car diff and axles for possible future upgrade / replacement.

Agreed on all points, and I will add: It is not worth the effort to remove 2 heads and put the good one on the car with the bad head, only to have a previously running turbo engine without a head. I would also never put a used head on without rebuilding it first. It is not worth the labor and parts to install an unknown quality head. You would be better off just rebuilding the N/A head and leave the turbo engine intact. All things considered, it would actually be a cheaper and quicker job to just exchange engines.

Graplr · #8 05-09-2014, 04:20 PM

Quote:

Originally Posted by Maxbumpo

I'd swap in the entire engine/transmission. Head work is no fun and fairly easy to mess up. You will need a hoist or a really strong buddy to lift off old head and place new.

Leave your current HVAC intact; remove AC compressor mount, leave compressor in place and re-attach to "new" engine. Is there a problem I don't see?

I'd leave the original differential. 4th gear is 1:1 regardless of transmission, so your RPM at highway speed will be the same as now. Keep the donor car diff and axles for possible future upgrade / replacement.

Yes, there is a problem you don't see. As mentioned I have the old York compressor which looks like a big rectangle and is located where the turbo on the turbo engines are...won't work.

You are acting like an engine/transmission swap is much easier than pulling a head. Granted pulling a head is not a 10 minute job but it is now where near as intensive as tackling everything mentioned. I still may go the engine swap route, but just wanted to know (and actually I have only one person answered with a "It should work fine." which is not necessarily a definitive answer) if the head swap will work.

Also, how would the highway RPMs be the same between a 3.11 and a 3.46? Why does everyone talk about changing to an 85 2.88 for lower highway RPMs then?

Graplr · #9 05-09-2014, 04:26 PM

Quote:

Originally Posted by ROLLGUY

Agreed on all points, and I will add: It is not worth the effort to remove 2 heads and put the good one on the car with the bad head, only to have a previously running turbo engine without a head. I would also never put a used head on without rebuilding it first. It is not worth the labor and parts to install an unknown quality head. You would be better off just rebuilding the N/A head and leave the turbo engine intact. All things considered, it would actually be a cheaper and quicker job to just exchange engines.

Your post makes the most sense so far. The only thing I can disagree with is that it would be a quicker job to swap engines. Having the head overhauled would be maybe a week? And cost maybe $500 (assuming I didn't do any work other than pulling it and putting it back on)? Even if I was working nearly nonstop on the swap to do all the climate control and other stuff there is no way I could get it done under a week. Sourcing all the necessary parts would take a couple weeks in and of itself.

I may call around and see what I can get the NA head rebuilt for locally.

I'm still hoping someone can shed some light on if the turbo head on the NA engine will work out...not necessarily going to go that route just looking if it is an option.

GregMN · #10 05-09-2014, 04:28 PM

Quote:

Originally Posted by Graplr

I'm fairly certain I have a valve (stuck and/or bent)problem.

If the valve is only sticking, then address that problem. I had the same problem on a 606. Occasional loss of power with smoke, then fine for awhile. A few minutes of MMO therapy and it is starting and running better then it has in a long time.

My thinking on bent valve is, that it would not be an intermittent problem, but a constant one.

Graplr · #11 05-09-2014, 04:41 PM

Quote:

Originally Posted by GregMN

If the valve is only sticking, then address that problem. I had the same problem on a 606. Occasional loss of power with smoke, then fine for awhile. A few minutes of MMO therapy and it is starting and running better then it has in a long time.

My thinking on bent valve is, that it would not be an intermittent problem, but a constant one.

My intermittent seems to be different than your intermittent. Mine comes and stays for a few days and then goes away for a few days and then comes back for a few, etc. where yours seemed to be for a minutes at a certain speed and then fine. So perhaps it could be bent as it lasts for a while when the problem is present.

When I have time the next thing I will do is pull the valve cover while running and see if I can see anything funny with the valves on the rear cylinder. Perhaps I am barking up the wrong tree to begin with. Then if I can verify that is the issue I'll get an estimate on the job and go from there.

It seems most of you are against swapping heads.

JB3 · #12 05-09-2014, 06:55 PM

Quote:

Originally Posted by Graplr

Your post makes the most sense so far. The only thing I can disagree with is that it would be a quicker job to swap engines. Having the head overhauled would be maybe a week? And cost maybe $500 (assuming I didn't do any work other than pulling it and putting it back on)? Even if I was working nearly nonstop on the swap to do all the climate control and other stuff there is no way I could get it done under a week. Sourcing all the necessary parts would take a couple weeks in and of itself.

I may call around and see what I can get the NA head rebuilt for locally.

I'm still hoping someone can shed some light on if the turbo head on the NA engine will work out...not necessarily going to go that route just looking if it is an option.

on the 123 you could have both engines in and out in a day, call it an active weekend to do the whole thing. If we are talking time invested, id say it would a fraction of the time invested for you to pull the head, as to pull the drivetrain and put it in the other vehicle.

Ive had a 123 turbo engine and transmission out in a relaxing 3-4 hours of work/dithering, and thats with breaking the motor and tranny apart first, dealing with tons of rusty fastners, ect. As a comparison, it might take that long just to undo all the accessories to free the head on either motor, then you actually have to pull it, get it redone, reinstall, redo everything right, get it dialed in, and so on.

personally I agree with rollguy, you are going to end up with a turbo shortblock that was a perfectly good engine and now can't be used, and a NA head that won't go on it.
If I wanted to run it NA, Id pull the turbo and manifolds and rig the turbo motor with the turbo head to run naturally aspirated, but IMO it would be a big waste, thats about 50hp right there not utilized

Yes you can probably do it though, it should definitely bolt up. Probably some time involved with fuel delivery to get it dialed in, but seems to me like a waste of a decent motor to get a less powerful version running better

Junkman · #13 05-09-2014, 10:33 PM

I would do the homework to determine that the turbo head won't significantly lower compression ratio when installed on a NA engine. You don't want an engine that is slower than the current engine.

AND a turbo would certainly be an upgrade. Isn't an engine swap considered maintenance on a 25 yr old vehicle?

ShaggyDiesel · #14 05-09-2014, 11:14 PM

you could swap just the head over from a turbo to a N/A, but not the other way around. it has to do with the way the turbo head was design to take on the riggers of forced induction, ei more heat on the exhaust side, stiffer valve springs, ect. with that said you're going to need the N/A cam and valve springs swapped onto the turbo head, or you may run into hard start and timing issues.

the easiest way to is to swap the donor engine and transmission, it looks like a big job. there is a lot of room to work with in the engine bay in these cars, the motor/tranny mounts are easy, disconnect the driveshaft, drain fluids, and disconnect the rest of all the little things. then take the whole thing out as a single unit.

this is a cake job compared to say pulling a cummins.

just my 2 cents.

ROLLGUY · #15 05-10-2014, 12:41 AM

Another option is to find an N/A SLS head and rebuild it. You will have less down time, as you will just remove and replace one head. The job can be done in about 6 hours, give or take.