Bent valves on 3 cylinders, fix head or do a motor swap for the same cost?

[golangti]

Here's my dilemma, I was quoted by my mechanic about $2,500 for a complete head work, or I can get a motor for 2k or less and swap it myself.

My stock motor has about 130k miles, the motor that I can buy got about 110k miles or so on it.

I'm leaning toward the motor swap because of couple reasons:
- it'll cost the same and I end up with a motor with less mileage
- I dont know what else I'll find upon removal of my damages head, damaged pistons etc.

Also, how difficult is a motor swap on M3? I do most of the work on the car myself, brakes, suspension, cooling system replacement, and even replaced my clutch 4 years ago.

TIA

[Hova]

You should have no problem doing a motor. It is very straight forward.

[imola e36]

If you could do a motor swap, not sure why you couldn't check the head / pistons and your current motor and replace what's necessary yourself? That would be the cheapest solution by far.

[dano670]

How damaged are the pistons?

Also, the valves from 92 to 99 are almost all identical, from your 325 to you 3.2l M3. I have a box of valves laying in the garage just in case.

If you don't have the skills to R&R the head, get the cyl head from the mechanic and take it to a machinist. R&R a head should be around $1200. You cut out the middle man, and bring the mechanic a serviceable head. I was going to say "a good head" but another adjective was needed.

[pbonsalb]

It is about the same labor to do a motor swap as to pull the head, fix it and reinstall it. I'd probably go for the motor swap and sell your shortblock and sell the head if it is ot damaged. You could do it in a weekend, but I generally go slow and clean stuff along the way so I would prefer three days.

[99MPower]

FIX IT!!!

then you have a refreshed, perfect, brand new HG, brand new cylinder head motor...

dont buy a junkyard, then you STILL dont know what you have

[dano670]

It is about the same labor to do a motor swap as to pull the head, fix it and reinstall it. I'd probably go for the motor swap and sell your shortblock and sell the head if it is ot damaged. You could do it in a weekend, but I generally go slow and clean stuff along the way so I would prefer three days.

I have pulled my motor and done a head swap on the same car. I reinstalled a cracked head and then eventually replaced it with another head. I would gladly do swap heads then pull that motor out again.

Gladly.

The short blocks on these series M/S 50 and 52s seem to hold up really well with miles. 200K plus. My 150K motor still had the crosshatching from the original bore visible.

[golangti]

Thanks all for chipping in.

Well, here's some more info in regards to your comments:

- The motor I'm considering buying is on a running car, I can test drive it
- I may buy the motor & tranny for even easier swap and sell mine to reduce cost
- My current motor just got machined and new head gasket about 5k miles ago it got overheated on the track, I just don't think this motor worth investing more into it

My impression was that you need some specialty tool for head R&R, timing etc. isn't that the case?

[cmzwirner]

Thanks all for chipping in.

Well, here's some more info in regards to your comments:

- The motor I'm considering buying is on a running car, I can test drive it
- I may buy the motor & tranny for even easier swap and sell mine to reduce cost
- My current motor just got machined and new head gasket about 5k miles ago it got overheated on the track, I just don't think this motor worth investing more into it

My impression was that you need some specialty tool for head R&R, timing etc. isn't that the case?

I pulled my head for the first time last weekend. It really isnt that hard. You will need cam blocks and a sprocket rotating tool. The rest can be made easily, or you can rent them.

IMO, i think it would be better if you fixed it. As Calvin(99mpower) said, you will have a fresh head and a brand new HG. You also get the chance to do some preventative maintenance while youre in there. You can rebuild the VANOS, replace the CPS, install ARP studs, and do virtually any other form of engine work since the head and manifold will be off. You will the have the reassurance of knowing that your engine is in tip top shape. If you go with the motor swap out of a donor, you really dont know how healthy the engine is.

[dano670]

I pulled my head for the first time last weekend. It really isnt that hard. You will need cam blocks and a sprocket rotating tool. The rest can be made easily, or you can rent them.

IMO, i think it would be better if you fixed it. As Calvin(99mpower) said, you will have a fresh head and a brand new HG. You also get the chance to do some preventative maintenance while youre in there. You can rebuild the VANOS, replace the CPS, install ARP studs, and do virtually any other form of engine work since the head and manifold will be off. You will the have the reassurance of knowing that your engine is in tip top shape. If you go with the motor swap out of a donor, you really dont know how healthy the engine is.

Exactly. Also, the first time i pulled my head I used the rental tools. The second time I found some oak and cut my own. Do it yourself and safe some money, If you cant do it yourself, be in charge of the process.

[gk325is]

VAC offers a machining service for about $1500, give them a call and see what they tell you. If you use them and do the work yourself you will have a nice fresh head with a valve job

[pbonsalb]

I have pulled my motor and done a head swap on the same car. I reinstalled a cracked head and then eventually replaced it with another head. I would gladly do swap heads then pull that motor out again.

Gladly.



I can go either way, having done both. I have pulled the head 3 times on my car and swapped the motor once. A motor swap is pretty easy if you have a crane and remove the front end and radiator support. You can pull with the tranny attached that way (you can also pull with the tranny attached and the front end in place but you need to have the car higher in the air and it is trickier to get the engine out of the confined engine bay). Either the motor swap or the head refurbishing will likely solve the OP's problems.

[Hova]

VAC offers a machining service for about $1500, give them a call and see what they tell you. If you use them and do the work yourself you will have a nice fresh head with a valve job


:eyecrazy

I payed around $200 for my head to be decked, valve stems replaced, head cleaned, and valves all ground down to match the head again at a local machine shop.

Machine work can be very much hit or miss. Make sure to talk to people who have used the people you choose. Go visit them, look at their work, talk to their machinists. It is an investment, know what you are doing before hand. Don't pay more than you need to either. Expensive is not always better. I'm sure VAC does a great job though.

[pbonsalb]

I think VAC sells a refurbished head for under $1000. Add your trays, lifters and cams. But VAC wants a core and you do not yet know whether your core is good. And $1000 is expensive, though for good work.

But as others have said, your head may not need much work. You may be able to replace some guides and install some used valves and have the head pressure checked and decked for half that amount, maybe less.

You can find videos and DIYs of the head gasket replacement (the labor to pull a head) and also for the cam timing. Search in this forum.

A top end gasket kit is $287 from Pelican. Figure on $200 from the machine shop if you are lucky. Maybe $50 for some used valves or two or three times that for some new aftermarket ones, depending on how many and which ones you need. Rent the cam tools for $50. You are about $600 into the job, and adding your own labor.

Buy the used engine for $2k. Sell your crank for $250, your pistons and rods for $150, your oil pan for $50, your cams and trays for $250, your vanos for $75, and you are in it for only $1250. If you are lucky, you could do even better -- maybe your head will be OK and you can also sell the casting for $250, or you might be able to sell your M3 shortblock for $1000 instead of disassembling and parting it.

[golangti]

Another question, how can I tell what head gasket thickness I need after head is being decked once or twice?

[controller]

I would buy the spare motor and swap it. Then, later when you're bored or have some extra cash, send off the old head to get reworked and reassemble it yourself. That way you can have a spare motor just in case. If you end up selling the car or a need extra cash, you can always easily sell the motor. Just keep the build sheet of the motor as proof it was assembled correctly.

As far as the head gasket thickness, the machine shop should be able to help you with the correct measurement that they removed and possibly make a suggestion as to the proper thickness needed.

[golangti]

Thought I'll report back..

Took the head off couple weeks ago, looked at the valves, everything is fine, looked at the pistons, nothing wrong there, looked at the head gasket and this is what it looks like.

[john325i]

So who told you you had bent valves? What does the block and the head look like where the gasket was torched?

[weaksauce]

looks like a failed head gasket to me...... :D

make sure the head and block are nice and clean and flat and put that baby back together!

[golangti]

looks like a failed head gasket to me...... :D

make sure the head and block are nice and clean and flat and put that baby back together!

yes sir! that's the plan ;)