68 amx head gasket

my 68 amx 390 has a blown head gasket ... can any one give me any tips .... on what i should do .. thanx CHANCE MOORE

Well first thing you need to do is change it. This will not be that easy of a task. The question you would have to ask yourself is, can you do this? If you have never done it before but are willing to try, than either find someone near you that will gladly help or you could ask MrPbody. He will guide you through it with ease. He has helped me and many others before. Just PM him and tell him about this thread.

Changing a head gasket is a pretty basic repair.
Get a decent service manual, it should show you the steps involved. The procedure is very similar to most other older domestic OHV V8's

Just be sure to send the head to a machine shop for crack and warp testing. Often, a gasket blows because of a defect that must be repaired, or else the new gasket will blow again fairly soon.

And on that same note, if you mill one head, you really SHOULD mill the other one the same amount. It's often neglected. It leads to a power-pulse "imbalance" which contributes to nasty harmonics within the engine (compression ratio is different from one side to the other).

Matt, thanks for the plug!! MagicRat was there to save the day!

Jim

tack this one on tho the others.: never ever reuse head bolts. especially when the head is blown (< the other example being a rebuild.)

When I bought my 1969 Cutlass it had a rebuild engine with the original head bolts in it. I saw no problems whatsoever. Could you share some info on why to get new ones?

head bolts are a one time use because they stretch (< i know it sounds wierd). but when headbolts strech they get weaker (most of the time the cause is the constant hold down. its even more evident when the head is blown because when you set them in a row the lengths will vary. but the bolts as i said constantly hold the heads onto the motor even when it isnt running. and over houndreds of thousands of miles, or years those bolts will get weaker and weaker ( think high school chem... is glass solid? no over years you get those wavy lines thats from the glass flowing down itself. headbolts are holding 2 things together under more pressure then to just "snug them up" we are talking like 85 to over 100 lbft (depending on your application) so think about the rebuild those bolts where holding that motor together through hot and cold, and through usage and not and more damning of all time. so think of it like this those bolts stretched once, now they are weakened and they are being stretched again. that is why my car's head blew the second time> the bolts i had the head warp tested, no warp, we tested the bolts. they were an 1/8th of an inch (longest to shortest) and they all varied in between.

its lengthy i know but true. also consider your aplication, i highly doubt you are going to take that car to strip and run it alot, or make it your daily driver. im under the assumtion that that car will be an... investment much like my cougar. the reason it might be ok, is it wont be beat on, or runn til she gets too hot (<which is one cause of headgasket problems).

Well thanks for the input. I already have some ARP hardened head bolts. The 350 that I am currently building will be taken to the track and a weekend driver. I won't run it hot either, heat is the engines #1 enemy.

ZX2guy,

Not to be rude, but your discussion of head bolts is inaccurate. We routinely use head bolts over again, on virtually ALL engines made before around '86 or '87. That's when "torque-to-yield" (TTY) bolts were beginning to show up in cars. TTY bolts can only be used once.

We upgrade to ARP when higher-than-stock compression ratios are used, or the bolts show physical damage (or, of course, the customer asks for them). With virtually all modern engines, you're 100% correct. Replace the bolts! That Rambler has good bolts. No need to replace. The head gasket will not blow due to worn out bolts (unless poor torquing methods were used and damage was missed). It WILL due to too much timing, not enough timing, too much heat, not enough cooling, etc. Poor machining to the block and/or head can also cause it.

One "test" you can make is visual. Measure the overall length of all "like" bolts. Use a precision measuring device like a dial caliper or micrometer, not a ruler... If all the bolts are within a a few thousandths, they'll be fine. If one is significantly longer, it's stretched. If one or two are shorter, the bulk are stretched. If you find some that won't "take torque", they too, need replacement. If they will "snap" the torque wrench, they're fine!

Lastly, most TTY bolts have the threads extended well beyond that of the "normal" bolts. Example: 302 Ford old-style head bolts have 1" of threads turned on them. TTY bolts for the same 302 (later years) have about 2" of thread turned on them. This isn't a "blanket" rule, but one "of thumb"...
Another way to identify TTY bolts is by the torque requirements in "the book". If there's just a straight torque spec, like "95 lb. ft.", they're not TTY. If there's a "torque angle" involved ("Torque to 22 lb. ft. , turn 90 degrees"), they're definitely TTY.

Jim

my bad, with more research mr pbody's right. my knowledge on cars is that of late 80's and up(shows my age). but im ussually pretty accurate on older models as well ( i worked on mustangs, mopar, and some chevy's).
but not to argue mr pbody.> but maybe you can clear something up>
we had a 60 sum eldorado in the shop with a blown head ( i believe the motor was rebuild 3 times and still had the original head bolts) when the master tech mic'ed the bolts they were streched out...so this lead me to believe they should have been replaced ( see my confusion). what could have caused these bolts (non-tty's) to stretch?
(you right though, the cause of blown heads mostly heat, timing, or imperfections)
but if it were my car... if it used repalce it, if its wore or not. especially considering how for an extra 25 bucks on a re build kit you can get things like oil pumps, and replacement head bolts.

from xperiance my grammar sux
but my wrench -xperiance is ok
tip
use a super quality head gasket like the felpro permatorq they should have a steel side and a composite side .. use the permatex copper head gasket spray on the steel shim side &
tip # 2 factory sent out service bullitin to
"pretorq outside headbolts to 20 pounds {you can leave this overnite at 20 pounds on all ouside head bolts}
then un turn them then retorq all headbolts in the usual fashion taking them down in steps to 20 pound incraments
thats 20, then torq to 40m then 60 then 80 the the recomended 100 for 1/2 inch HEADBOLT HIGH DECK 70 UP BLOCKS
BTW i chucked some antifreeze with my 390 running it xtra hot in 100+ heat doing a burnout contest i pinned the stock heat gauge in my gremlin 1 too many times and had to do the above m had to undo all my isky slider guide plate's .. oh well some ten years later i still have antifreeze in my mill same stuff from 95! cars just laying around here i take it out and woop on it every few months ...
its the shorty 390 too

thats actually kinda cool, ild like to see that bullitin. but i dont see the good of torqueing them then remove and torque them fully. maybe you can illaberate?

elobarete...
ok amc seam to have a problem with blowing the ehadgasket on the outside bolts so for some reason if the factory did this the problem was helped .
i have had 2 blown head gaskets 1 in my javelin witha 71 304 no water in the radiator and it was sucking oil up out of the drainback and on the outer head area..
the other was my gremmy it barfed nice constant stream of green on the outside part of head

i guess if it works, it works. you have a javelin too? man i love those cars. ive been tryin to find one that i can rebuild for my mom (who owned i think it was a '73, only way i could identify the year was by the square turn signals in the front)

ZX2guy,

The bolts on the Eldo were probably over-torqued the last time around. If they're stretched, they're stretched! Simple as that.

Felpro "Perma-Torque" (pn 8266PT-1) gaskets are the blue ones (the suffix "PT" is the clue). They use NO SEALER. EVER. We se this a lot. What fits and works well on older cars may or may not be similar to what works on modern cars. The laminated gasket discussed above is more for modern engines.

There was a yellow Gremlin running around Tuscon about 15 years ago, with a blown 401 in it. Talk about a BEAST! It could hold the front wheels through 1st and into 2nd. I heard it ran in the low 10s, but was never there to actually see it. I DID see it pull the front wheels in the IBM parking lot after a "hobby" show.

When we build hot rod Ramblers, we add an extra row of head bolts on the bottom. The gasket problem is well known. By drilling four well-placed holes and using 3/8" bolts, we rid ourselves of the problem. We also use Pontiac intake valves and some Chrysler trinkets inside.

Ramblers are pretty cool... Doing a 360 for an '87 Jeep J-10 right now!

Jim

Hot rod Ramblers? Got my attention, can you elaborate?