Head inspection
Thread Starter
Pro
Joined: Sep 2002
Posts: 690
Likes: 1
From: near Memphis TN
Head inspection
I took the driver's side cylinder head off to see the extent of damage after my engine was diagnosed with rod knock. I was afraid that a piston hit a valve and damaged the heads since a pushrod bent as well as the knock in the bottom end.
After busting two ratchet wrench's and most of my knuckles the heads are finally off, but that's another story. The heads themselves look fine - no cracks, no scoring, no visible damage to the valves EXCEPT in cylinder #6 (this is where the bent pushrod was) I see a worn semicircle area about a 1/4 way around the piston on a slightly raised area of the piston and a corresponding worn area around the head in the same area, almost like these two parts were hitting. I've heard about pistons hitting valves but pistons hitting heads? Is this possible? The worn area doesn't look bad, just a clear area down to the metal from the carbon build up with just a slightly rough surface.
I have already resolved that I need to rebuild or replace the bottom end. My question is are the heads damaged? The valves and seats look OK. Anything else I should look at with the heads off to see if the heads are damaged?
After busting two ratchet wrench's and most of my knuckles the heads are finally off, but that's another story. The heads themselves look fine - no cracks, no scoring, no visible damage to the valves EXCEPT in cylinder #6 (this is where the bent pushrod was) I see a worn semicircle area about a 1/4 way around the piston on a slightly raised area of the piston and a corresponding worn area around the head in the same area, almost like these two parts were hitting. I've heard about pistons hitting valves but pistons hitting heads? Is this possible? The worn area doesn't look bad, just a clear area down to the metal from the carbon build up with just a slightly rough surface.
I have already resolved that I need to rebuild or replace the bottom end. My question is are the heads damaged? The valves and seats look OK. Anything else I should look at with the heads off to see if the heads are damaged?
Melting Slicks
Joined: May 2002
Posts: 2,508
Likes: 0
From: Wisconsin
Re: Head inspection (SpyderD)
Are the heads some nice aluminum ones? If not, don't worry about it and buy some! If they are, take them to a machine shop and they can fix a lot of that. It doesn't sound bad at all. My dad has these set of big port Brownfield's that his buddy is going to fix up. They are full of little knicks and scratches, the seats are gone in some, and along a valve guide is cracked, but they can be fixed and will look like new. The crack will be welded, the knicks filled and ground back down.
Want a porting tip? This is what my dad told me about what he used to always do to his heads for better flow. See the area by the exhaust port and how there is some flat head material inside of the circle where it shows where the seal was? Put the heads on the block, mark the inside of the cylinder wall where it meet with the head on the exhaust side then grind the material down to that line. When the pistons goes up before the porting the air hits that little ridge and gets tossed around, but grinding it off, it pushes it right out the valve. If you are going to junk these heads, might as well mess around with porting, but they can most likely be fixed.
Want a porting tip? This is what my dad told me about what he used to always do to his heads for better flow. See the area by the exhaust port and how there is some flat head material inside of the circle where it shows where the seal was? Put the heads on the block, mark the inside of the cylinder wall where it meet with the head on the exhaust side then grind the material down to that line. When the pistons goes up before the porting the air hits that little ridge and gets tossed around, but grinding it off, it pushes it right out the valve. If you are going to junk these heads, might as well mess around with porting, but they can most likely be fixed.
Instructor
Joined: Apr 2002
Posts: 121
Likes: 0
From: Ringgold GA
Re: Head inspection (Schmucker)
I would have the heads checked and fixed in needed but do not get rid of the heads.
These heads are aluminum Corvette heads that have been fully ported (intake and exhaust runners, bowl ported, changed over to 2.02 & 1.60 stainless swirlpolished back cut valves).
These heads flow very well both at low lift and high lifts. I do not remember the flow specs but Dave might have them, I think I gave them to him when he bought the car from me.
These heads are aluminum Corvette heads that have been fully ported (intake and exhaust runners, bowl ported, changed over to 2.02 & 1.60 stainless swirlpolished back cut valves).
These heads flow very well both at low lift and high lifts. I do not remember the flow specs but Dave might have them, I think I gave them to him when he bought the car from me.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Re: Head inspection (SpyderD)
I don't recall if you've specified the extent of damage (if any?) to lower end. Apparently you find this contact only @ #6. If rod bearing on #6 was trashed, this could allow the rod & piston to be "tossed" higher than intended ... contacting the head. Also, if piston skirt is broken, this could allow piston to "rock" too far ... allowing contact ... inspect bore for tattletale streaks/gouges. Sounds like the head's OK ... have it checked though. You must verify & correct root cause of this contact before proceeding further.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
Re: Head inspection (SpyderD)
Don't worry about it. The semicircle sounds like exhaust scavaging due to the bent valve not closing completely, thus a large part of the expansion from exhaust gases would rush out through the unclosed valve and blast away the crude on the piston and head. Just take it to a machine shop and get a complete valve job done. while you have it apart look into a CompCams Magnum 270H and some stronger springs. :)
Thread Starter
Pro
Joined: Sep 2002
Posts: 690
Likes: 1
From: near Memphis TN
Re: Head inspection (candyapplevette)
Thanks Rob, I plan on saving these heads, I know they are worth alot. I don't remember you ever giving me the flow specs however.
Jackson - I really don't know the extent of damage to the lower end. With the oil pan off I didn't see any visible damage but I did not proceed further since I was getting out of my league mechanical-wise when messing with the lower end. I did see some metal slivers in the oil pan. With the piston sitting low I see no gouges at all in the piston walls.
That worn area on the heads don't look bad at all, if not for the black carbon on the rest of the bottom I probably wouldn't even have noticed it.
Jackson - I really don't know the extent of damage to the lower end. With the oil pan off I didn't see any visible damage but I did not proceed further since I was getting out of my league mechanical-wise when messing with the lower end. I did see some metal slivers in the oil pan. With the piston sitting low I see no gouges at all in the piston walls.
That worn area on the heads don't look bad at all, if not for the black carbon on the rest of the bottom I probably wouldn't even have noticed it.
