Now I know this is a Ford forum and Pontiacs a GM, but spare me the ridicule I dislike GM as much as any of you. BUT my girlfriend's dad has an old '74 Grandville (basically a high-trim package Bonneville) that I've been doing some work on because it's been sitting a while and her dad isnt really the mechanically inclined person (think putting 2 stroke mix in a 4 stroke )

Anyway, after pulling it out of the garage to work on the trans, I noticed it had a very rough start, longer than the normal warm up time for an engine. On top of that, it was blowing a TON of white smoke out of BOTH tailpipes (true duals, no cross/cats) and when I tried to get it back in the garage it had almost no power. So, when I was working on the trans I checked the vacuum modulator to see if there was any fluid that it could be sucking up, no dice. I didn't really wanna get the $42 blown gasket checker from NAPA since it isnt my car (yet ) so I'm just gonna pull the heads, its got a leaking intake and valve cover gasket anyway.

So to my main point is, any tips for replacing a head gasket? Especially specifically for a '74 Pontiac 455 4bbl -> TH400. General tips would be great as well, I've done some searching in the dentside forum for tips.

Thanks a bazillion,
Dan

 

take the heads in and have them magnafluxed for cracks , and checked to see if the decks are straight , no warpage on both the heads and block . a lot of these old cars got run hot and have some issues with warpage and may just flat out be beyond repair from it . to check the deck on the block just get a good metal straight edge and lay it down and look for daylight where there shouldnt be any . the machine shop can check the heads out . make sure the heads and block are spotless before reassembly , use thread sealant on the head bolts . make sure you know the adjustment process on the rocker arms . i know that seems stupid , but im in possession of a 292 that the fool ran the rockers down tight like some other motor he had and bent all the pushrods , and bent some valves , and flat spotted the cam .................. why you got it this far apart if you want to really wake that ol' poncho up replace that oe camshaft !!! the pontiacs had ridiculously small cams in them to meet emissions requirments , and just a oe replacement for a late 60's or early 70's gto or bird can make a huge difference in the driveability in 'em !!!!!!!!!!! i personslly likr the real tin indians !!!!!! raced one on the dirt tracks here for awhile and it gave the chevs fits !!!!!!!!!!!!! oh and retorque the head bolts after it's been run a bit !!!!!!

 

Doing those heads is easy. From memory you don`t even have to touch the distributor.
However I think, if it was me, I would do a compression test before tearing into it.

 

thanks for the advice, both of you!

Lazy K, when you say do a compression test do you mean with a dial indicator or just grounding out the cylinder when its idling and writing down the rpm drop? or the $42 thing from NAPA?

And would a Haynes manual have head gasket replacement in it? This will be my first head gasket replacement and I dont wanna mess anything up

 

IF memory serves me, the '74 Poncho 455 was a neutered version of the older 455s, but, they still hold a place of honor in my 'torque' listing!
Stump pullin' torque!

Dad had a '72 Bonneville (w/ a 455) and that car would fly!

IF you decide to do the head gaskets yourself, get the manual and don't go cheap.
Do it by the book, or have a reliable shop do the job and pay the $$$ to get it done.

 

A compression test is where you remove all the spark plugs and fit a pressure gauge to each cylinder in turn while you crank the engine over on the starter to measure the compression pressure in each cylinder.
A low reading can indicate a problem with that cylinder. If all good then no point in taking off the heads. It could also indicate a problem with only one cylinder so only one head would need to come off.
It should be possible to hire a gauge from autozone or similar.
A Haynes manual should give you a step by step. Not difficult on that engine.

 

blue thats why i suggested a cam swap while he's in it that far !!! that's how they got them to pass all the gov regulated crap by nuetering the cams on the poncho's . you are so right about the torque they make !!!!!!! just watch pulling bolts out of any aluminum parts like the timing cover . they're likely seized in it and will break off and create more work for you !!!!! . i had the carterville illinois ex squad for a number of years . bought it for 300 . it was a 73 catalina more door with , get this a 455 super duty and police package suspension . that behemoth would get going in a hurry !!!!!!!!!!

 

 

Ranger I'm planning on doing it myself or he will never have it done, he'll just hydrolock it one day and wonder what happened. I will definitely get a Haynes and I'm just beginning my research.

Alright cool Lazy K I was just wondering if you were thinking go that route or the more sketchy rpm drop method haha. My dad has one, he used to work on his Torino's that all ended up mysteriously totalled haha

55 f350 I'd love to cam this sucker up but he really only wants to drop a 100 on parts on top of what hes paying me and im just about at 90 with a haynes and gasket set

haha Phinxter what are you eeking about?

 

This guy is about to tear an engine apart and doesn't know what a compresson test is, thats what I'm ing about. Yes get a manual, Haynes is better than nothing.

 

I know what a compression test is, I may have never replaced a head gasket but I'm not a total noob. There's more than one way to skin a cat and there's more than one way to test compression.

I wasn't looking for a roast of myself, I was looking for advice by the way

 

well ok than besides using a gauge how do you measure how much pressure your cylinders are building?

 

its not gonna tell you exactly how much psi difference it is, but grounding out a cylinder will tell you if you have a bum cylinder. Connect a tach and then disconnect the spark plug wires from the spark plug one at a time for like 3 seconds each, and then if one cylinder's rpm drop is considerably less that the others, theres your bad cylinder

 

Have used that method as an easy first step myself.

Tells ya where to look at least.....

 

Thank you! That's at least 2 people that have used this method haha

Anyway back to the topic, any other tips?