Illustrated rebuilding of a L36 into a supercharged 3800... - Page 8 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 01-16-2007, 12:13 PM   #71
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I gotta question...since we are on the "cylinder head" chapter of this saga, is it a good idea to have the heads media blasted, or would a good soaking in warm solvent be enough to loosen all the carbon and gunk?
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Old 01-16-2007, 08:51 PM   #72
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Quote:
Originally Posted by sandrock
I gotta question...since we are on the "cylinder head" chapter of this saga, is it a good idea to have the heads media blasted, or would a good soaking in warm solvent be enough to loosen all the carbon and gunk?
Hmmm... only concern I would have with media blasting the heads would be damage to the valve guides, valve seats, and gasket area.

I soaked the heads for 24 hours in a bath of Acetone to clean most of the carbon out. (it gets in between the carbon and iron and causes it to peel off in layers, kinda like paint stripper.) You could also bathe them in carb cleaner (best), Kerosene, #2 Diesel, or Gas. Any of which would desolve the carbon and oil. There'* still some stubborn areas that need scraped, then it gets dunked again. I like Acetone because it evaporates quickly and really strips oil off the metal. They come out of the bath ready to paint.

I waited a little too long between painting and spraying the bare iron surfaces with oil, hence I got some surface rust on the valve cover area of the head. Nothing serious, it will be gone soon.
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Old 01-16-2007, 09:08 PM   #73
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Which brings us to reassembling the heads. Horray! The first of the major assemblies to be reassembled for use!

During the teardown, the springs, retainer caps, and locks were all checked over. For the springs, I don't have any means of checking spring weights (Ok, I do, it'* called a coffee can full of lead weights to hang through the spring) but it'* easy to check the free length of the spring in comparison to the others in the set. Also look for any obvious damage...cracks, coils missing, lop-sided springs, etc.

Back to the heads proper...After the grinding to gasket match the intake runners, I took out the valves and blew the entire head with compressed air it get rid of any grit from the grinding, stuff down in the threaded holes from the chasing of threads, etc. That brings the heads up to a point where we can assemble the valves.

First, I pressed on the new valve stem seals. Just put a drop of oil in the rubber cup and press them over the valve guides with you thumb. Note that they are color coded. The Green rubber ones are the exhaust valve seals (GM #88891775 ) and the Blue rubber seals are the intake valve seals (GM #88891774 ). Lube the valve stems with oil and slip them up into the guides.



Install the springs, retainers, and locks just like they were removed. Using a rubber mallet, give each valve a light tap to ensure the locks are fully seated in the retainers. With that, wipe the gasket areas with a little oil and set the heads aside till we need them.

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Old 01-21-2007, 12:55 AM   #74
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Took a little break from the narrative to assemble the second cylinder head. Also during the week, the rest of the L67 rods arrived along with all the bearings, gaskets, piston rings, etc. I spent today cleaning and inspecting the rods after removing the L67 pistons that came with them (They are STD bore pistons, so they are just going to get boxed up and set aside in case they are needed later on another motor.)

Now, here'* a little photo to drive home the idea that you DO NOT use anything metal to pry on a machined surface.



What you are looking at is the rod journal end of the connecting rod. Note the rough gouges in the machined surface, right by the rod bolt hole. That'* what happens when you try to pry the rod cap off with a screwdriver. What the person who dissassembled this motor should have done was back out the rod bolts a turn or two, then tap on them with a rubber mallet to pop the cap without damaging either the rod, or the crank.

Should you come across this, there are three ways to fix it: 1.) Pitch the rod in the trashcan and go get a new one. 2.) Break the sharp edge with a file, and live with the fact that the rod has a defect and may wear the bearing funny. 3.) Mill the rod to remove the damaged ends, refit the cap, and rebore the main journal a larger size, using a thicker rod bearing to make up the extra clearance.

Of those solutions, #3 is the correct one to repair the rod. However, due to the cost of the rods, #1 is a viable option too.

Got a PM from Ed Morad (who sold me the rods) and he will be sending a replacement. Thanks Ed.

Now, gotta wait for the rod to get here before sending the crank off for balancing. Had a really good weight set going on the rods, with 689.5grams being the average, heaviest rod was 692 grams, lightest 688 grams. That'* pretty consistant for a bunch of factory rods.

With that, I'll pick up tommorrow with installing the old cam, putting the crank in temporarily along with one cronnecting rod and piston, then going through checking the specs on the factory L36 camshaft with a dial gauge and degree wheel.
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Old 01-22-2007, 06:50 PM   #75
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A question on the head buildup post. The picture shows 2 different valve stem seals (which is like that on the S1 too....but they are black and orange). Are there any other differences between these seals, with exception of color?
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Old 01-23-2007, 12:18 AM   #76
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Quote:
Originally Posted by sandrock
A question on the head buildup post. The picture shows 2 different valve stem seals (which is like that on the S1 too....but they are black and orange). Are there any other differences between these seals, with exception of color?
Hmm, it'* probably diferences in the neoprene used to make them. Dimensionally, they are identical and use the same construction. These two PN'* are the latest and greatest from GM.

There were some other things I noted during the teardown. On one L67 head, the intake valve seals were black and the exhaust valve seals were black with a tan stripe. On the other L67 head, all the valve seals were blue, like the new intake valve seals. (The heads are probably off different motors.)

My guess is that this is just a series of revisions to get valve seals that work for a long time and provide the right amount of lubricating oil to the stems. Kinda like the three decade long quest to find valve stem seals that will work in the SBC V8, without producing that familiar wisp of blue smoke on a cold startup.
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Old 01-28-2007, 10:37 PM   #77
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Ok, another week gone by, time for a status update.

The crank, rods, pistons, harmonic balancer, and flexplate are now at Express Engines in DeLand, Florida to be balanced as an assembly. The local machine shop in Holly Hill didn't have bob weights that fit the V6 crank, so it had to go to a different shop.

While waiting, I can still do some work on the camshaft and the block. Here'* the camshaft along with the other timing components.



The cam appears to be a billet steel cam (meaning it was cut from a single chunk of steel rod stock as opposed to being machined from a cast iron core. In the photo, from left to right are #4 Cam Journal, #6 Exhaust Lobe, #5 Intake Lobe, #6 Intake Lobe, #5 Exhaust Lobe, #3 Cam Journal, #4 Exhaust Lobe, #3 Intake Lobe, #4 Intake Lobe, #3 Exhaust Lobe, #2 Cam Journal, #2 Exhaust Lobe, #1 Intake Lobe, #2 Intake Lobe, #1 Exhaust Lobe, and #1 Cam Journal. It'* the geometry of the motor that dictates the placement of the lobes on the cam.

Looking a little closer at the cam, here'* the back end. Note the three holes. Two of them are left over from the manufacturing process and only one serves a real purpose inside the motor.



The center hole is a lathe "Center". It'* a machined pocket that fits a dead center in the drive face of the lathe. To the left of it is a hole that fits a pin in the face of the lathe (called a drive dog) that will index the cam on the equipment. The hole on the right is also used during manufacture for a second drive dog, however it is drilled through the #4 journal. When the cam is in the motor, this hole serves as a relief to keep oil pressure from building up between the cam and the plug/cover that seals up the bellhousing end of the block. Without that hole, oil pressure would build up and pop the cover.

Cams are made on duplicating (or Pantograph) lathes and grinding machines. In the process, the workpiece (i.e. the yet to be made camshaft) is being spun by the lathe while a pattern is being spun at the same speed, parallel to the workpiece. The cross-head (with the cutting bit) follows the pattern and transfers it to the workpiece. It take 10 different patterns to cut and grind the cam to it'* finished form, so the index holes in the end of the cam keeps everything in sync with the patterns as the cam moves from step to step. If you are ever in Daytona Beach during race weeks, drop in on Crane Cams and you can usually get a tour of the plant to see them making cams.

Back to this cam... Here'* the timing chain end of the cam. Unlike most cams, the Buick V6 uses a key in the snout to drive the cam...same thing used on the crank nose to drive the oil pump and balancer. The reason for this is the Balancer shaft drive gear that also uses the cam. It'* easier to slot the end of the cam for a key and broach the timing gears. The alternative is a whacky pin and bolt arrangement.



Here'* the timing chain and it'* gears. Note the dimples in both the cam gear and the crank gear. When the set is installed, the dimples with be lined up with each other..that times the crank rotation with the cam rotation. The geometry of the motor comes into play again. The cam gear has twice the teeth of the crank gear, so the cam will always spin at 1/2 the crank RPM.



Here'* the drive gear for the balancer shaft. It has a dimple on it as well to line up on the gear on the end of the balance shaft, so it spins in time with the crank.



Time to put some stuff back inside the engine block. First item to go back in is the camshaft. It was the last item to come out because it is easiest to remove that way. It'* the first to go back in for the same reason. Use some engine assembly lube on the journals and on the bearings, then carefully slide the cam in. Stick your finger up inside the block to support it as it slides in. (The cam bearings are new, no sense screwing them up by gouging them with cam lobes.)



Next up is the cam retainer plate and it'* screws. Again, apply a little assembly lube to both faces and install. Torque the #30 Torx screws to 11ft-lbs. The purpose of this plate is to keep the camshaft from walking fore-aft in the block. The plate is trapped between the shoulder of #1 cam journal and the back of the balancer shaft drive gear.



Ok, gears go on next and then a degree wheel is temporarily installed on the nose of the cam. (Note: A degree wheel is usually done on the crank nose, but since I know the block centerline and have the dimple on the cam gear to reference, I can get a profile of the cam lobes without the crank.)



The pointer (pink wire in photo) is just a chunk of coat hanger wire bolted to the block.



A dial gauge is in the lifter bore with it'* tip riding on the cam lobe. In the photo it'* the #1 Exhaust lobe. Now, the tedious task of rotating the cam and recording the reading on the dial gauge. Again, because the degree wheel is on the cam, the markings on the degree wheel need to be doubled to represent the crank rotation...in other words, 10 degrees of cam rotation is equal to 20 degrees of crank rotation.

With that done, here'* the plot of the cam'* profile:



The valve lift numbers are computed with a 1.66 rocker arm ratio. (I need to mock one up to see if that is the actual ratio of the rockers.)

Next, I need to do the same thing to the stock L67 motor to see what it'* cam grind looks like.
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Old 01-29-2007, 12:29 AM   #78
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Ok, sat down with a calculator and figured out the "Grind Card" for the cam (for comparative purposes to other cams.)

Intake: opens 24 degrees ATDC, 191 degrees duration @ 0.050", lobe lift 0.258"
Exhaust: opens 6 degrees BBDC, 194 degrees duration @ 0.050", lobe lift 0.254"
Lobe seperation angle 115 degrees.

The lobes are asymetrical (dual pattern grind)
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Old 01-29-2007, 01:17 AM   #79
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Since I am only used to the vin "c" engine I have to ask this. Did they eliminate the cam sensor on this engine? I noticed there is no magnet in the cam sprocket.
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Old 01-29-2007, 07:38 AM   #80
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Quote:
Originally Posted by myfirstbonnie
Since I am only used to the vin "c" engine I have to ask this. Did they eliminate the cam sensor on this engine? I noticed there is no magnet in the cam sprocket.
No, the cam sensor magnet is there, or at least the hole for it in the photos. (bottom-right of the timing gear in the photo..the hole that is offset closer to the teeth of the gear.) I had to remove it before dunking the gears in solvent since there is a plastic housing around the magnet.

Before the timing chain is installed, the magnet needs to go back in along with epoxy to ensure it never comes out while the engine is running.
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