LT1 Intake Conversion = Engine Failure!?
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 878
Likes: 2
From: BC
LT1 Intake Conversion = Engine Failure!?
I'm very tired right now, but after tearing down my block and taking it to a specialist here in the UK it looks as if my LT1 Intake Conversion has cost me the engine.
Gen1 Flat Tappet, 2pc Rear Seal...
To cut a long story short, it looks as if the distributor hole wasn't 100% perfect. Although there are no grinding marks on either Distributor Gear or the Cam gear something was making the Cam "walk" backwards/forwards.
The end result is I've got a snapped timing chain, every tooth broke off of the Crank sproket... and the casting behind the Cam sproket has been chewed away and groved. The sproket must have been grinding away at it.
I'm getting the casting re-leveled so I can use the block again, but I'm VERY concerned about using the LT1 Intake manifold again. I'm converting to a Roller Cam, retro fitted with Comp Cams Retro Roller Lifters but I don't think thats going to make any difference.
Gen1 Flat Tappet, 2pc Rear Seal...
To cut a long story short, it looks as if the distributor hole wasn't 100% perfect. Although there are no grinding marks on either Distributor Gear or the Cam gear something was making the Cam "walk" backwards/forwards.
The end result is I've got a snapped timing chain, every tooth broke off of the Crank sproket... and the casting behind the Cam sproket has been chewed away and groved. The sproket must have been grinding away at it.
I'm getting the casting re-leveled so I can use the block again, but I'm VERY concerned about using the LT1 Intake manifold again. I'm converting to a Roller Cam, retro fitted with Comp Cams Retro Roller Lifters but I don't think thats going to make any difference.
Melting Slicks
Joined: Aug 2004
Posts: 2,907
Likes: 229
From: Oakbank Manitoba
The distributor hole in the intake doesn't have to be dead accurate. The distributor is held in position internally in the block by the two machined bosses. The hole in the intake is oversized by a good margin. If it dropped down into the block without any great effort (force) then it was held in the correct position by the block. The intake hole is just used to set the correct height and to hold it in place firmly. Was the correct size spacer made up for the intake? It should have been 1/4" thick and cut on a 5 degree angle (from memory). Hopefully the distributor wasn't bottoming out on the oil pump drive. If you installed a new cam then a new distributor gear also is required and must be of the correct type depending on what type of cam was selected.
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 878
Likes: 2
From: BC
It seemed to fit into the block really easily. No force required at all. On second thoughts, you right the block should have held the Distributor in place. I did have a spacer with the Intake when I got it. It wasn't attached so we lined it up by trial fitting the distributor so the spacer sat flush all the way around.
Any idea what else could have caused this damage to the block? Its the casting that the front cam bearing its in. The bearing normaly sits back into the block but in this case the casting has been worn away so the bearing is actually protruding.
Regarding the distributor gear, I assume the cam manufacture will tell me what I need? Its a Comp Cams LT1 CC306
Any idea what else could have caused this damage to the block? Its the casting that the front cam bearing its in. The bearing normaly sits back into the block but in this case the casting has been worn away so the bearing is actually protruding.
Regarding the distributor gear, I assume the cam manufacture will tell me what I need? Its a Comp Cams LT1 CC306
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Sounds like you had cam walk. Some blocks are front walkers and others are back walkers. This is normal, seldom do you find a flat tappet setup that walks so much as to cause excessive wear or damage.
To control that you need a timing chain set that comes with a 3-piece Torrington bearing to address any rearward cam movement AND a roller thrust button to control front movement.
Check the inside of the timing chain cover to look for any witness marks. If you see any you have a front walker. Since the marks/wear are on the block, you've got a back-walker.
I doubt it's the intake because it would have to be quite a bit off to cause that amount of breakage and wear.
With a flat tappet cam normally the bearing/button setup aren't needed but clearly you need something for cam movement control.
Jake
To control that you need a timing chain set that comes with a 3-piece Torrington bearing to address any rearward cam movement AND a roller thrust button to control front movement.
Check the inside of the timing chain cover to look for any witness marks. If you see any you have a front walker. Since the marks/wear are on the block, you've got a back-walker.
I doubt it's the intake because it would have to be quite a bit off to cause that amount of breakage and wear.
With a flat tappet cam normally the bearing/button setup aren't needed but clearly you need something for cam movement control.
Jake
