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Hagerty
Hagerty Employee

Replacing a cylinder head isn't as hard as you think, but know your limits

I'm nearly through replacing the cylinder head on Louie, my 1972 BMW 2002tii. This is the car I wrote about in the book Ran When Parked . When I bought it sight-unseen five years ago, I didn't know the left rear corner of the head was cracked-not through a combustion chamber but through one of the cylindrical bosses into which a valve cover stud is threaded.
https://www.hagerty.com/media/opinion/the-hack-mechanic/replacing-a-cylinder-head-isnt-as-intimidati...
28 REPLIES 28
hyperv6
Racer

Most car repairs are not difficult but the limits of knowledge and tools can make them a challenge at times.

No matter what the job make sure you know what you are getting into. Starting into something that you really have no knowledge of can really become an even more expensive issues.

Read up and study what you plan to do. Make sure it is in your limits and skill set. Also please make sure you have the needed tools. In some cases today some jobs take specialized tools that can make or break the repair. In come cases they can be very expensive just for one job makes no sense to buy so rent or just have the job done for you.

It is not a sin to defer an job to a pro as it often shows greater intelligence to recognize one's limits.

Often most repairs are on You Tube so you can gauge if the job is in your wheel house.
TomBrattin
Intermediate Driver

"Starting into something that you really have no knowledge of can really become an even more expensive issues", also is the number one source of "Basket Case" projects on Craig's List.
Marv48
Intermediate Driver

It's not just a rebuild, it's an adventure!
relton
Advanced Driver

While this article has a lot of good advice, there are times when it is not a good idea to attempt this job yourself.
For example, removal of the heads on a Lincoln Mark VIII, and some other Ford SUVs, requires removing the engine. Or the cab, on some trucks.
On other Fords, the head gasket blows because the engine block flexes, or has warped, not the head. 3.8 liter V6 engines are notorious for this.
There are other cars where the studs that hold the head on are actually stripping out of the block, causing the head gasket to leak. Fixing that can be a real challenge. Cadillac Northstars, and Corvairs, did that.
Heads often have bolts of different lengths. Put the wrong bolt in the hole in a flathead Cadillac, and you will crack the exhaust ports, or strip the threads in the block.
Some modern engines require special tools to hold the camshafts in a certain position when the head is reinstalled. An impossible job without the special tools.
Chevy Vega engines had no iron liner for the cylinders. A speck of antifreeze ruined the block, which was immediately visible when the head is removed. An overheated Vega engine should probably go straight to the junkyard.
Cars with timing belts should always have the belt replaced when the head is off.
But, other than that, changing the head gasket is pretty simple.
Good luck.
RJ
Detailer

"But, other than that, changing the head gasket is pretty simple."
Yup, you nailed it there. Step one, be honest with yourself, that you understand what you are getting into.
Oldroad1
Technician

Mid 80s and into the 90s I was averaging 2 cyl head reseals a week at the dealer for the Sable, Taurus and Continentals with the 3.8 engines. It was always the corner cylinder's combustion ring failing and blowing coolant into the chamber and thus the sweet white exhaust clouds going out the exhaust tail pipe. I was never told of a block flexing issue as you describe but a thermal issue with the head itself actually moving ever so slightly under heat as to cause a wear condition on the corner cylinder's head gasket combustion ring to the point of rupture. Early we were told to leak down both sides and look for bubbles in the radiator to identify which bank had the damage and reseal that side only. Many times though the car would return with the other bank blown. After a few of those Ford warranty was OK with both banks resealed at once. I've never had a head or the deck of a block warp as I straight edged every job and never had a repeat repair.
petersalt
Advanced Driver

Putting iron cylinder sleeves into Vega engine blocks was a land-office
business back when those cars were numerous; it was an nearly trivial
part of the rebuild. Original pistons were almost always like new, and only
occasionally was any additional work needed beyond inspecting a rod and
a main bearing, inspecting the oil pump, installing the sleeves, new rings
and a gasket set. I put 50k on the rebuilt motor, gave the car to a kiddo; he
put 100k more on it.
Oldroad1
Technician

Chevy Vegas were the reason small block Chevys were invented.

CarAnalogy
New Driver

Fun read. Good info. Some thoughts:

Non-Chlorinated brake cleaner is actually MORE harmful to paint than Chlorinated (and Non-Chlorinated especially damaging to powder coat). But Chlorinated emits poisonous gas if used prior to welding, which is why non-Chlorinated exists.

Use Chlorinated, unless you are going to weld the parts soon after, or you live in a place where Chlorinated is not available.
relton
Advanced Driver

Another thing to consider is the bolts that hold the head on. Many modern cars use torque to yield bolts, which is another way of saying they can't be re-used. Plan on new bolts, often a dealer-only item.
Olde cars sometimes see the bolts corroded, reducing cross section area and strength. Old cars, where the bolts are exposed, such as flathead engines, will sometimes have bolts with different style heads than modern bolts. Originality suffers when modern bolts are used. If replacing bolts, make sure the lengths are exact. Too short and you might not have enough thread engagement in the head, stripping when torqued. Too long, and you might damage something in the block, or the bolt might bottom out before clamping the head tightly.
Don't let this stop you from doing the job. Just be prepared.
Tinkerah
Engineer

Glad to see TTY bolts mentioned.

OHCOddball
Advanced Driver

Rule 1: Before buying a car whether classic or later, look it over well or have someone do it for you.
Rule 2: Know how much you can afford to spend--not on the purchase, but for maintaining it and doing repairs. Does no good to buy a nice car only to have it break and sit because you can't afford the fix.
Rule 3: If you are not mechanically inclined and don't have the money to have it done, DON'T BUY IT!
Rule 4: Join a club or read up A LOT about your car and all its possible problems and solutions.
Rule 5: (and most important rule) Don't tackle a job you can't finish properly or you will wreck the value of the car and someone else will have to fix your mess at much larger expense IF the car does't end up a basket case for thirty years that your estate will end up disposing of for scrap.
MattLaube
Intermediate Driver

Three cheers to the statement: Don't yank the head unless you are prepared fiscally and physically what may lurk within ....I tried 4 Alfa 1600-1750 heads until I found a good one that wasn't cracked. The good one was literally pulled out of a scrap pile at a junk yard that had a fire.
Deja Vu on the small 60's BMW 4 cyl.head job.....the 4's are tougher crack wise than the 6's especially if they had thermal reactors fitted stock... yuk!
thehackmechanic
Advanced Driver

I think I can guarantee you that every 6-cylinder head with thermal reactors cracked.
MattLaube
Intermediate Driver

Those 2500/2800 and Bavaria,s fitted with TR's should of had a voucher that came with it for a head replacement !   MB learned a similar issue with it's CA emissions diesel fiasco. My 85 300TD had a new engine at 8900 miles courtesy of MBUSA....still going strong at 301 k later l 

tmn
Pit Crew

My experience on doing just a valve job has been that usually withing a year the bottom end needs doing. This could also be a self inflicted wound.
Oldroad1
Technician

Always do both at the same time. It's alot easier to get at the bottom end with the cylinder head or heads removed.

Tinkerah
Engineer

Show of hands: Anyone else here done a head job because they didn't take the timing belt interval seriously? You can't see it but I'm ashamedly holding my left hand up while clicking "Post" with my right.
Oldroad1
Technician

Thank goodness those of us who own vehicles powered by 2.3 Pinto motors don't have to worry about that.

PaulinMN
New Driver

My ex had a Pinto I was driving when the belt broke, finally figured it out when I popped the distributor cap and saw the rotor wasn't turning. Easy fix, couple hours and back on the road.
On the other hand we have a Hyundai Accent that the belt broke on (10k before the change interval, I will never trust Gates again). It's a days work just getting access to be able to pull the head, and then you have to pull the cams to remove the head bolts. Variable valve timing DOHC 4valve head, 4 bent valves.
Next time I'll sell the car...
Gary_Bechtold
Specialist

I enjoy this series even though I don't have the time or patience to do this.
TG
Technician

Pulling heads is often a key part of troubleshooting, so if you are going to delve into DIYing older cars, particularly if you are not the type to buy the pristine 6-figure ones... it is a key skill to have in the toolbelt
label, label, label, photos, photos, photos
Correct tools and manuals are a must
clean, clean, clean - both yourself and the motor. The cleaner you keep your hands, the cleaner your work stays. I know a lot of folks like working in gloves, but this tends to be a crutch to avoid washing the hands, so keep that in mind. Keep a shop-vac handy and repeatedly vacuum up crud, gasket chunks, etc. as you go
I like to go over the block deck and head (lightly) with a file - palm flat on the file to keep it level. This will remove any lingering gasket residue and carbon, and is usually a dead giveaway if you have any warpage issues.
Overhead valves - no problem. Timing chains - no problem as long as you follow disassembly and reassembly instructions. Timing belts - might be time to call the pros especially if there are any peculiarities associated with belt tension setting - and especially if engine is an interference engine. I have been at this for a while and timing belts still make me think twice
Oldroad1
Technician

Look for combustion "flash over" between the cylinder combustion rings. Usually the center between 2 and 3 cylinder numbers. That is a good indicator of head warpage and most of the time you'll find a ditch between those 2 numbers with a straight edge.
Patrician
Detailer

As a professional mechanic for 45 years and owning my own shop for 42 years I'm very leery about cars getting head jobs. By time you need a valve job the timing chain and guides are stretched and worn out respectively. The rings are worn and the bearings are badly worn too. Cracked heads are sometimes due to design fault but most of the time overheating. Most of the time doing a head job is like only changing your tee shirt and never changing your jockey shorts. I have to guarantee my work and the end result. We do the whole motor considering today most valve jobs require engine removal. Years ago, the pre-front wheel drive cars, life was easy. We would take the heads off, drop the oil pan new rings and bearing right in the car if the crankshaft was good. Those days are over.
SAG
Technician

Once you have the 'top end' done, ditch the 'Green'
Time to paint it "china blue"
Ha
LTBimmer
New Driver

This article brought back memories of rebuilding the engine in my 2002 in 1977 when after 5 years and over 100,000 miles it started burning oil. While the pre disassembly diagnosis was most likely worn valve guides and seals, I pulled the engine to be prepared to do more and it turned out to need new rings as well -- but no block machining.

One comment about the step by step instructions in this article is that I would not pull the distributor until AFTER I turned the engine to TDC. I realize that the crank will be turned again to get to the top of the pistons but I always like to have a rotor reference mark with the #1 cylinder at TDC to insure the distributor gear is correctly engaged.
4RenT
Advanced Driver

What is meant by angle torque?
I thought at first it was using a beam type torque wrench
(I don't really trust click type torque wrenches).
But, then, what does the degrees angle mean?
I assumed (yes, we all know what that means) a 3 stage torque was to torque the bolts to approx. 1/3 the final setting, then torque them all to 2/3rds the final, and finally finish them up.
So, what does this really mean?
-Technoklutz

ryanwm80
Intermediate Driver

I'm going to be 100% honest and say that I think story is leaving out some really critical information regarding the valve train. I think the biggest and most likely problem a non-professional engine rebuilder will encounter with the head is to damage the camshaft, either by improper lubrication or lifter adjustment. Did I miss anything mentioned about lifters or tappets?

How critical is it to use brand new tappets? Can a camshaft be re-ground? What is involved with that in terms of time and expense? Does everyone know about the absence of zinc in modern synthetic oils, and what kind and amount of additive to use for a non-roller cam? I know about the Justice Brothers, but what about everyone else?