251 Chrysler Flathead Blown Head Gaskets...among Other Things

[First2Fargo]

Hello,

 

  first off let me say a pre thank you to anyone who takes an interest or provides me with any kind of insight.  I have for years been cruising automotive forums whenever my vehicles have started acting up.  i have found a wealth of information and helpfulness to pretty much diagnose, if not fix almost every problem. So far, so good...sort of. Anyway i have never signed up for any forum before and was content to just scout as a guest.  Well.

 

  Last November I fulfilled a boyhood fantasy and bought a vintage pick up.  I have since, been learning( almost daily it seems) about the joys of owning such a piece of history.  I thought it was time to sign up, while looking through this forum the first picture i happen across was a 49 Fargo 1/2 ton...just like mine.  i have since speculated mine to be a 50/51 as looking at pictures mine has the later grill, although the registration is 49.  though the engine does have a tag that say " remanufactured by the chrysler method" and is dated 1956.

 

  Ok, so i have had a pretty lovely intoduction to vintage vehicles thus far.  3 weeks after purchase my head gasket went( the first time).  Sad fargo sat for a month while i discovered how much fun it was to find parts for a 25 inch canadian made chrysler 251 flathead 6. Thank you vintagepowerwagons.com.  After pulling the head off and discovering the cooling systems was for lack of a better word, Hooped.  i set about gathering a new water pump, hoses, gasket set, APR head studs, rotor, cap, plugs, coil, leads,oil, etc.  I had the rad flushed, had the head planed and magnafluxed, cleaned the water distribution tube, wire wheeled the top of the block and pistons.  blew out all the water out of the intake.  got all the crud out ( at least i thought). cleaned up the carb as best i could( so not a carb guy), rebuilt the distributor( ok my dad did)

  

   So, old motor, no idea how long it had been like that.  Head gasket replacement, to be expected right. ya. ive heard these flatties will blow a gasket from time to time.  no worries, i installed studs so a head replacement is no biggie... ok im getting to the point.  so my head gasket has gone twice now, and im suspecting its going again.  just before the second time, it started making this weird flapping noise, which kinda matches the rpms and then it just gets kinda slower.  at first there is no loss of power, then it definitely does.  I shut it off before anything came gushing out the tail pipe, as i don't want the rods to hydraulic.

 

  First, does anyone know what this noise is? and is there something i can do to help eliminate the possibility of blowing another gasket. Could it be the timing.  As it is hard to set by gun, I've been told to "listen" for it. 

  Second, as its like 3 head gaskets in like realistically 3 months, am i fighting a losing battle here.  granted there are lots of determining factors , but I've combed through a lot of reading and have tried a lot of things to get it fixed.  Don't get me wrong, it runs great when it runs.  

  

  

  

[Don Coatney]

Is the head gasket failing in the same location each time? if so what does the engine deck look like in that area? Have you run a straight edge across the engine deck to look for imperfections?

 

Are you following the correct sequence when torquing the head? With the new ARP head studs what value are you torquing to? Head studs are fine thread where as the factory bolts are course threads so it takes less torque with the studs. Somewhere around 55 foot pounds as compaired to around 70 foot pounds for the bolts.

 

When you had the head planed how much material was removed? Are you using any sealent on the replacement gaskets? If so what?

[First2Fargo]

hey,

  it looked like the gasket failed the first time between the 1st & 2nd cylinder.  The second time it poured out the carb side of the block almost by a 3 or 4 inch wide space in the middle, but the place between the cylinders also looked fragged.  Quite a lot of the gasket got torn up taking it off the second time.  I didnt use any sealant on the gasket itself.  i used thread locker on the studs going into the block, and anti seize on the nuts

 

  The engine deck looked good.  I did run a straight edge across it and couldnt tell that there was any low spots or imperfections.

 

 I did follow the correct torquing sequence and i tightened the stud nuts to between 52 -57 foot pounds from the notations on vintagepowerwagon.com

 

  I cant say how much i had removed when planned.  I know the guy at the machine shop said it was fairly bowed.  Maybe 1 thousands, but don't quote me on that number.  i could be totally off

[Don Coatney]

Is your gasket failure causing a loss of compression or a loss of coolent? Several of the head bolts/studs go into the engind block water jacket. Recommended too use thread sealent as opposed to thread locker for this application.

 

Not recommended to use anti seeze on the nuts as this will change the torque value. Did you re-torque all the nuts after the first heat cycle?

 

When cleaning the cooling system did you remove the freeze plugs from the distributor side of the block and flush the internals completely? What is the normal system operating temperature?.

[JIPJOBXX]

Did you re-torque the head nuts? after it heated up?   I had a blown head gasket and to be on the safe side I used some permatex between the head and engine block and no problems after that.  I also had the head shaved .060" and this added a little bit of more compression and of course a little bit more power.  Good luck and hope you find the fix your looking for.

[Jeff Balazs]

Hi;

One thing I always use is a spray-on copper coat gasket compound. It helps seal any minor imperfections in the mating surfaces but will not solve any major imperfections. You might try that when you get any other issues you have sorted out.

Thread sealing compound like Permatex is a must anywhere you have threads going into the cooling passages also.

Jeff

[First2Fargo]

sorry I misspoke, i did use thread sealant not thread locker.

 

my gasket failure is definitely causing loss of coolant, big time. mostly it seems into the intake and valves.  I have my fargo parked right now, when i get back, im going to test the compression of each cylinder.  If its low in 1 and 2, at least ill know thats a reoccurring problem.

 

I did not re-torque the nuts.  I checked them, but my cousin has the expensive torque wrench at his place. if this turns out to be my problem im going to kick myself.  so you would recommend no kind of compound on the nuts?

 

  I did not remove the frost plug, but i did remove the lower square plug by the oil filler, and blew out the system dry with air after the second gasket( tons of brown sludge) then with water a few times to try to get all the crud out.  Each time i flushed more grit came out, til it was mostly clear.  since the frost plug was higher i thought it would suffice.  You recommend doing the frost plug?

 

  The normal operating temp was(after the first gasket) 175-185, after the second gasket it was 165 -170.  It would stay there all day long.  Once I saw the gauge go over 190, I knew it was trouble.

 

What is the maximum you can have the head planed? This next go round i was thinking about having the head panned again if its bowed.  i will use the spray on gasket compound this time and retighten the studs with permatex

[Don Coatney]

Square plug below the oil filter? Do you have a full flow oil filter or a by-pass filter? Is the location of the square plug between the distributor and generator? Same locatioon as the petcock in the picture below?

 

Are you getting any antifreeze into your oil pan?

 

[First2Fargo]

yes where the petcock is.  between the distributor and the generator. beside the oil filler pipe

 

sorry not sure which oil filter i have. its mounted on the head above the starter. 

 

 ill try to post some picts. having a little trouble figuring that out too

Edited May 14, 2013 by First2Fargo

[Don Coatney]

This (first picture) is what a full flow filter looks like. Second picture is only one of many examples of a by-pass filter.

 

 

[Don Coatney]

Are you getting antifreeze in your oil or oil pan?

Edited May 14, 2013 by Don Coatney

[First2Fargo]

definitely bypass oil filter.  

 

I get coolant in the oil when the gasket goes for sure.  I suspected it was going again because the temp went up and there was yellow gunk on the bottom of my oil cap and at the top part of my dipstick.  i know moisture can sometimes get in, but i wasnt taking any chances.

[P15-D24]

Do you think it overheated before the head gasket let go?  Was the water i the radiator boiling? Usually overheating is the base cause, which causes the head/block to warp and the gasket to fail. Removing too much material from then head (too high compression) is another root cause but a machinist should be able to determine if the head has been milled too far. 

 

You also haven't mentioned the water distribution tube which is critical for cooling of the rear half of the block.

 

If is was mine I would have both the block and head check for warpage, and over milling on the head.

Pull the radiator for cleaning, pull the water pump and water distribution tube, then remove all the accessible freeze plugs and clean out the block from the water distribution tube down.

Install a new 160 degree stat. 

Check water pump and replace if needed. 

Check your fan belt tension. 

[NiftyFifty]

Silly question...did you replace your radiator cap?  These old rads can only have a 11lb or 12lb cap I think if my number is correct, if you replace it with a modern cap it will create way too much pressure for a system not designed to run under much.  Typically the rad is the first to blow, but if your rad is good and you have any imperfections in the block it could be finding its easiest out.

 

As for finding parts, you can buy a Fel-Pro gasket set right from summit for the 25" 251 block, thats where my last one cam from and I really like that gasket compared to the first one I got which I think was Mr.Gasket or along those lines.  You deffinately should re-torque after a good warm up and cool down, so hang on to that wrench a little longer after your fix.  Check the plain of the block angain, and make sure you didn't warp your head again after the 1st fail.  My head was taken down almost 1/4", so there's lots of meat to play with. 

 

Also make sure your leaving a good inch in the rad tank below the fill neck for expansion, and if you put a new thermostat in, drill a hole in it about 1/8".  I honestly think after I rebuilt my 251 2 years ago it blew because the thermostat wasn't allowing enough coolant into the head to cool it down for the initail running.  I run my 50 without any t-stat and even when it's 25+ celcius in the city I never see enough heat to scare me.

 

Hope this helps!

[P15-D24]

Actually they are non-pressure caps. 

[First2Fargo]

hey guys,

  I cant be sure if the gasket went before it overheated or the other way round.  im pretty sure it overheated then blew the gasket.  i dont believe my head had been machined before i did it, so i dont think it s over compressed.  i will check the compression next chance i get.

  I cleaned out the water distribution tube the first time i change the head.  I replaced the water pump. i had the rad dipped and flushed. pretty much a hoses and belts replaced. new thermostat.  Ive seen 160 and 180 degree thermos.  do these engine require 160's? i didnt drill the hole, but i will next time i flush out the system

 

 I did not replace the rad cap.  I degreased and cleaned the one that came with it as best i could.  it looks stock.  I use felpro gaskets.  Strangley enough they are readily available at my local lordco.  although the gasket sets( i have one) are hard to get.

 

  seriously you run NO thermostat? That is interesting.  what are the pros and cons of that? never thought of it.

 

  Thanks for insight guys

[First2Fargo]

would they not have springs?

[NiftyFifty]

The coolant system isn't pressurized by modern standards, but no matter what they do run a certain amount of pressure at operating temp. The caps like I'm talking are more common now then the straight cap, and really just hold the coolant from puking out the overflow tube when hot or moving around.

The benefits to no t-stat is a unrestricted flow for the coolant from a-z, this way the head is always full from cold to hot. Out of 3 flatheads I've opened up here, none had stats in them. The downside is without the stat on a hot day, if your stuck in traffic the coolant can possibly flow so fast from the rad that its not getting a chance to cool, but I have yet to see this happen and last year I ran the truck lots on hot days and all of my trips were into the city and city driving.

[ggdad1951]

the old rads have the vent tube right at the top of the rad...these are for all practical purposed a ZERO pressure system, nada, zip, zilch.  there should be NO blockage of the vent tube, if there is...you're gonna have problems.

[48Dodger]

T-stats help slow the water to take the heat off the engine or, in the begining, to not let flow occur to help warm it up.

If the water moves to fast, your engine holds the heat longer. Restrictor plates help tune the flow in the modern V-8 (for racing)

.....I don't know how this is applied to the L6, or like 4mula implied, maybe not even important. 

 

48D

Edited September 4, 2013 by 48dodger

[wallytoo]

from the orignal poster, i don't see any information about the condition of the internals, such as the pistons and rings. do you know their condition? i ask because my truck had similar "symptoms" before i rebuilt the engine. i went through two head gaskets in short order, the truck ran beautifully nevertheless, and it didn't overheat (until the gasket blew). when i dismantled the engine, i discovered that almost every ring, on each piston, was broken (some rings were in as many as 20 pieces). one piston came out of the block in three pieces, and all but one piston had major cracks in it. portions of the rings were overlapping in the ring grooves, and were being hammered up through the top of the piston. after rebuilding, i haven't blown the headgasket again (knock-on-wood), and i've put nearly 1000 miles on it since (prior, i was blowing the gasket every 200 to 300 miles).

[NiftyFifty]

With broken rings and cracked pistons one would expect low to no compression, which should be even easier on the head gasket, but if those broken parts are creating more friction and excessive heat I can see it causing some gasket issues. I thought that I read the internals viewed from the top seemed good, but that's not much of a true tell.

[John-T-53]

It's imperative the stud nuts are re-torqued after first warm up, and then checked again at the second cycle, and then every few hundred miles up to the first 1k. Cheap insurance. I like to check mine at each oil change.

 

With the ARP hardware, you should use the ARP lube that should have come with the studs you purchased. This is important for correct torque readings.

 

Copper spray-a-gasket is the preferred sealant for the gasket before assembly, and thread sealer or PTFE thread tape on the studs in the block. Make sure the threads in the block holes are chased clean too!

 

I'd double check the deck for flatness again too - you need a machined straightedge and feeler gauges for this. Any dips greater than .0015" it might need to be decked, but this is a guess. The red 3M scotchbrite pads are great for cleaning the block.

 

Good luck, and keep us posted on the progress!

Edited May 16, 2013 by John-T-53

[Pipewrench_Dale]

Ive blown my head gasket two times in something like 7 years. Both times it was the studs that had come loose slightly during the winter. So now I always check their torque occasionally.

I also use a gasket adhesive on the bolts. Not the type that hardens but a adhesive that stays slighty sticky. Dont know whats is called in english but its almost like tar in substance.

 

Havent done this myself but older mechanics says that when the head gasket blows often one can use a special adhesive. Again dont know what its english name is but we call it "diesel seal". Think its the same that I use on the bolts. 

[MBF]

You've got to also make sure that the engine comes up to a temerature warm enough to raise the temp of the engine oil to a point where it will vaporize the condensation in the crankcase or you'll have sludge build-up problems.  I have found that a 160 t-stat along with a pcv system works well to keep the oil clean.