O0ooo..... I have a 4.9 liter 300 engine in a 75 ford F-100. I am planing on replacing the Cylinder head on it because it has just started to smoke a bit when started & while idle at times(white smoke/like a quick super blast of polution LoL...O0ooo..... .)
Ive come to the conclusion that the valves are worn and Hope that replacing the head will do the trick and solve many problem that may be developing in near future.
It seems that I cant get the truck to idle perfectly. Ive tried many things such as tune up plugs wires cap rotor Timing carb adjustments and im at wits end thinking my head may be leaking somewhere and is the culprut.
(im thinking this will be the awnser)
Its seem that head was replaced on the vehicle some time ago(only god knows when) However its the wrong head. There are large bolts in (smog holes or whatever u call em) so Im thinking maybe its leaking air from this area...
So im planing on replacing the cylinder head in like 1/2 day if anyone has any tips on making it a smooth/er running project please let me know.
Also some tips on making sure I get the right Cylinder head which I will be ordering off the internet.
The truck runs pretty good now howerver I would like her to run perfectly...
You may want to get a professional second opinion on your motor before going throught the expense and time to replace the head. Your post reads like the carb is acting up and your rings are shot. The plugs in the AIR injection ports shouldn't have and adverse affect as your describing...if they were leaking, you'd here a lot of ticking like noises. I also don't recommend using Ebay as a source for machined parts like heads... you're best off working with a local shop in case there is a problem. Buy a head that has new guides installed, not knurled ones...or you maybe doing a head R&R again soon.
A 300 head is 63 lbs without the valves, springs, retainers and rockers installed. Your looking at around 75 lbs fully assembled. For most guys I know, it is NOT easy to gently stretch over and place a 75 lb head on a fresh head gasket. The best one I've heard yet is two people with a 2 X 4 and some light rope to tie it up. A cherry picker is the best way to go on a one man install. Getting the old one off is a lot of fun too. But then again I'm just a scronnie guy -
Well ..I dont Think rings are going, however When i pull the old head off I would find that out (I hope not)....and wouldnt my plugs be oil fouled if my rings were going as well...and the smoke be blueish and not white?(but they will go eventually)
But somethings wrong id say.....maybe valves..
As far as using a local shop for the Head I would have to get a head from a junkyard then take it to the machine shop to be redone. Rather then the one on the truck now....
Ive been thinking about this route but it may cost me more or maybe less. I have to look into it..If i am goin this far i may as well get a block and drop it off at the machine shop as well.......
I do see your point as if anything is wrong with it at least you can tell them face to face... ha ha
So for now ill keep running it and see if it gets progressively worse while I shop for head or have one done by a local shop.
Might be the rings. My dad's 82 wouldn't idle right either, and a compression check showed 4 out of 6 cyls very low. When I got in there, I found all of the compression rings as well as ring lands on the pistons broken. I'm assuming from years of spark knock. Had to bore it .030" to clean up the bores. Oil rings were mysteriously still holding up, as there was no appreciable oil smoke. Used original cam and head, and truck ran and idled perfectly after rebuild.
You probably are right, from what I see the head was replaced before and the gaskest on timing chain cover is fresh(almost everything has been repaired except the parts within block) ...probably the block need to be overhauled at this point..I will have to check it out and see....
Check the compression before you do anything serious. If you rebuild the head without doing any block work, you can expect the added compression to put additional strain on the rings and accelerate their weakening. If you can afford it, have the entire engine rebuilt. Otherwise it's a good idea to do the block first, and then have the head reworked at a later date. The only exception would be if someone has already rebuilt the block fairly recently without doing the head. A compression check should tell you what kind of overall shape the engine is in.
A vacuum gauge can also indicate worn valve guides OR rings. The needle will vibrate rapidly at idle and "steady" with increased rpms if the guides are worn. Leaking rings are indicated by a steady 12-16 (17-21 is "normal" - depending on altitude) and a drop to 0, followed by a bounce back to about 21 as you hit and release the throttle. There are a host of other uses for a vacuum gauge - detecting sticky valves, restricted exhaust, burnt valves, vacuum leaks, blown head gaskets, carb adjustment, plug gap and timing to name several.
Definately do the compression test first. To tell if the rings are bad, I've been told you should do the following:
Do a compression test on cyl. 1 and write down the reading. Squirt a little oil or wd40 into the cyl., and re-do the compression test. If the compression goes UP, the rings are bad. If it doesn't, the rings should be fine, and the valves may be the problem. Repeat for all cyl's.
The oil will help seal the ring around the cylinder wall, but it won't help seal the valves. That's the logic behind the test.
I've done the test and my reading went way up, indicating the rings were bad. I haven't pulled the heads yet to verify this, but with compression ranging from 70 to 135, I know SOMETHING is wrong. The readings should be no more that 5 psi between cylinders.
Yes my 300 six did the same thing. I pulled off the head and took a look at it and got a good USED head. U rebuild that head and your piston rings will be shot for sure. I would do the whole compression test first though i just took a wild guess and did mine like that.
I will check everything out deeper on Monday. I am in no rush to spend 1000 bucks believe me LOL..and I may not have to..
(A friend of mine suggested while replacing the cylinder head, also the rings, rod bearrings and oil pump while engine is still under the hood LOL... It is possible if I buy him alot of beer lol )
Ive been looking into all of my options...as far as going to a machine shop (is about the same price as buying an engine from ford ..lol 1500) and its very expensive as opposed to buying a remanufactured short block or long block(I found one for 900) from one of these High volume machine shop factories/and 900 bucks is price of having just my block redone at the machine shop and alot of work on my part along with down time on the truck......
However i did re tune it up and re-set timing it is running great(motor is running strong) ....
all but the lope in idle and the ocassional puffs of smoke coming out of exasust...especially on start up..
(maybe the lope in idle is from a vacum leak around intake or elsewhere)
I will post the results of my compression test on monday or tuesday and hopefully I dont have to exchange motor as of yet..
I will probably ending up totally restoring the entire vehicle..
Here are some parts of other post saying that smoking can be from valve seals (guide)..
My truck did sit for several years..
factory remanufactured 223 and 3 speed PU tranny
with about 30,000 miles on the clock, that I will part with. It set
for several years allowing the "valve guide seals" to harden, so it
smokes a little. Valve guide seals are an easy fix, and at a 150
bucks this motor should go quickly.
'85 F150 with a 300 I6
with over 210,000 miles and all he ever ran was Pennzoil 10W-40 and
Motorcraft oil filters. It's still going, and going, and going. It smokes
a little on startup, but thats just the "valve seals". Nothing major besides
an oil pump change (relief spring stuck open) and water pump was ever done
to the engine.
Last edited by quantalimo; 06-07-2003 at 12:22 AM.
First of all before you start tearing everything apart. How many miles does your 300 have on it? You don't want to replace the head if the motor has over 100k on it. I was experiencing similar symptoms with my 84, so I went ahead and replaced the head with a remanufactured one. It ran beautifully for about 2 months, then all of a sudden the no.5 rod bearing let loose when I was going down the expressway. This made no sense because the bottom end of the motor was tight when I opened it. I talked to a couple engine builders and they said any time you do head work to a ford with over 100k on it, it is common for the bottom ends to let go. My Dad had a valve job done on his 88 Chevy Astro 4.3 at 120K, similar out come in his case it took the rings out. After a while it started to sound like a pressure cooker! He started to lose compression as a result the engine had to be replaced. The same engine builder said in the case of Chevys it usually will take the rings out or cause some kind of compression problem. From the sounds of it, it may be in your best interest to look into a complete rebuild of your 300, that is my recommendation from my experience.