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Rebuilding a Corvette L79 327 350hp Engine A Photo Essay by Lars Grimsrud
Although not a C3, I thought this small block C2 engine build would be of interest to you guys here on the C3 Forum - the process and procedure is the same for any Vette small block:
Received this ’66 L79 327/350 4-speed car with a suspected flat camshaft for repair from a Forum Member on the other side of the country:
A quick engine check showed that not only was the cam flat, but cylinder leakdown rates were between 25% and 72%, indicating that a complete rebuild was in order.
So here is the process:
Pulled the engine out. I left the tranny/bellhousing in the car, and didn’t pull the radiator or the fan shroud (yes, you can get the engine out easily without removing radiator or shroud):
Got it on an engine stand:
Unbolted the easy stuff:
Used the right tools to get things apart. Note the wrong diameter balancer previously installed and the incorrect timing tab
Finished tearing it down, took the heads off, and got the pistons and crank out:
Organized the parts:
Measured things to see how bad it was. This block was bored .060 over, and the work had been poorly done, with cylinders having been bored at 4.0645. This block will need to be bored .070 over for cleanup. “Sleeving” a 327 on all 8 cylinders is a risky ordeal, and will often result in at least one cylinder cracking between the head bolt hole in the block and the water jacket. This destroys the block. So I opted for a .070” overbore, which is still safe:
While the block and heads were being machined, I cleaned up and fixed all the other parts. Rusty exhaust manifolds were sandblasted and coated with the Eastwood Stainless Steel exhaust coating. Corroded aluminum components were bead blasted with a fine grit glass bead, and then rubbed with fine steel wool to bring back the natural sheen of the parts without the artificial “bead blasted” appearance:
With the block back from machining and a torque plate hone, I cleaned it up and prep’ed it for assembly. Block work, machining, and balancing was done by the nationally renowned “Block Shop” in Denver:
Crankshaft had been incorrectly ground, with .015” differences between cylinder strokes and position. Crank was offset index ground and polished to correct all the bad workmanship, and ended up at .030/.030. The snout was drilled and tapped for a balancer bolt. Crank grinding work was done by the famous Dave Olson of Mile High Crankshafts – “crank-man” for many of the top national race teams and engine builders:
Although not my top preference in a piston, Keith Black makes an off-the-shelf Hypereutectic .070 oversized piston with a slight dome, resulting in compression ratio at a street-friendly 9.98:1. Rods were re-sized and fitted with nice ARP bolts. If ultimate performance had been the goal, I would have had some custom, forged, light-weight JE pistons made. But for this build and the intent of the car, the cost penalty was not justified:
Crank installed and bearing clearances verified:
Pistons/rods installed and torqued:
Cam installed with chain and gears in preparation for degree’ing and checking:
Accurately determining Top Dead Center (TDC) – an essential operation before degree’ing the cam:
TDC nailed down, and the degree wheel locked in place. The timing tab has been accurately located on the timing cover and welded into the correct, accurate location. The “pointer” being used for the degree operation is actually over on the left side of the photo:
Working with “the numbers” obtained from the degree process (I like to degree the cam using both the “intake centerline” method and the “Open/Close @.006” method, and I compare the numbers to see if they are consistent), the numbers showed that this engine was running the cam 2 degrees retarded. So everything was disassembled, the cam was advanced, and the entire process was performed one more time to verify correct cam installation. The numbers after advancing the cam came in right on the cam card specs (good reason to check this stuff – a cam running 2 degrees retarded would have given up a lot of performance in the usable rpm mid-range):
The 2.02 “Camel Hump Fuelie” heads were given a nice 3-angle valve job, but were not ported or altered. Just a nice, precision machine job. Head work was done by noted cylinder head machinist and Bonneville Salt Flats Record Holder Dave Sarno of Sarno Racing Heads in Arvada Colorado:
The existing valve guides had been “knurled,” and I don’t like that. I had some nice bronze guides installed (visible through the new valve springs):
Heads installed, and timing chain/gears installed in the advanced position to correct the retard error. Note that the timing dots are installed “straight up” to put the engine at TDC with cylinder #1 on compression stroke in the firing position:
Valvetrain installed. The hydraulic flat tappet L79 “Nostalgia” cam (Comp P/N 12-671-4 Advertised duration @ .006 276/283°, Duration @ .050” 229/236° Lift .468”/.462” 108° Intake Centerline) was given a liberal coating of moly cam lube on all lobes:
Corvette oil pump pickup screen is different from the standard Chevy pickup screen. The screen was installed and verified to be ½” off the bottom of the oil pan using a wad of tin foil:
Bottom end buttoned up (after removal of the tin foil check wad):
Masked off and ready for paint:
Primed with catalyzed epoxy primer:
Topcoated with actual Chevy Orange mixing formula in catalyzed urethane:
Final assembly complete with a custom built stainless hard fuel line to accommodate the Speed Demon 750 carb:
Flywheel and starter installed, and engine ready for installation on the engine run stand:
Engine installed on the run stand with partial exhaust system with mufflers and wideband Air/Fuel probe up the tailpipe:
Oil system being primed. Note use of an old distributor housing to correctly complete the internal oil passages and assure proper oiling and pressure:
Nice oil pressure at 60 psi:
Setting the valves. Valves were set at ½ turn. Note oil has been pushed up into the rockers:
Oil verified to be coming from all 16 rockers:
Distributor re-installed, and static timing set to assure that the engine will fire on the first hit of the starter. Engine ready to start for cam break-in:
Carb bowl filled with fuel to assure instant start:
First click of the starter resulted in instant startup. Engine brought up to 2400 rpm to assure proper cam break-in:
Instruments monitored. Oil pressure 60 psi, and manifold vacuum rock steady at 17.5 inches:
At the elevated rpm during cam break-in, total timing was checked and verified at 36 degrees total. Vacuum advance was hooked up and verified. Engine checked for leaks. Cam break-in duration was limited to 15 minutes. Coolant temp stabilized at 190. Rpm was then dropped down to 950, which is about right for a cam of this size. At 950 rpm, manifold vacuum ended up at 12 inches, which is pretty good for this cam. Oil pressure eventually dropped to 40 psi at 190-degree hot idle:
Carb idle mixtures were right on the numbers at 14.7:1. No leaks, no problems, and the engine test was deemed successful:
Bolted up the new clutch and pressure plate to the engine with a new pilot bearing in the crank:
Lowered the new engine assembly into the chassis (note that fuel pump and starter are removed to clear the frame rails):
Engaged with the tranny and bolted into the chassis:
Hooked up everything, fired it right up and drove it outside:
Hooked up a wideband to monitor carb performance on the first test drive. Mixtures were right on the numbers:
Whew! That's a truck load of work. I think your overly generous with your help here lars. Not many shops would spend the time to detail the build like that. Actually I don't know any build shop that would dial in the tune after rebuild.
So you even left the fan shroud in the car. It looks like you must have a ceiling beam to hang a hoist on? If you have more pix of the blueprinting keep'm coming. I'm still collecting tools for my 400 block build(s). Just got my straight edge this week. Still need a ring filer. Hoping to avoid a rod vice.
So the motor is now 338". And it still has room to go 0.080" over for another day.
Perfect! A very nice demonstration of how to do it RIGHT...
I bet she runs pretty good with that cam. I've never seen it myself. I have a Crane "L79" cam in my stock 350 and it was close to the oem L79 specs...(222@050" etc etc)
Also, nice choice on the pistons....When we rebuilt my dad's 66' L79, pistons were a problem. We didn't want to run the original style TRW 11-1 pistons, and didn't want to spend $800 for custom pistons..We ended up using a Sealed Power forged flat top, 4 valve relief...and they ended up .050" down in the hole since we couldn't deck the block.... The compression ended up in the 9.3-1 range and I feel like we gave up a bunch of power.
Thanks for the write up and pics.. That really shows every one the correct way to do a quality rebuild.
Thanks for the nice comments. Yes, I hope this encourages others to "do it right" and have some fun with their cars and engine builds. This engine and cam feel really good, especially in the low- and mid-rpm ranges. The stock heads and manifolds limit the true high-rpm potential.
The total cost on the builds that I do are so specialized and unique that it would not be fair to say that "this engine build cost $XXXX." I run across so many odd, little things, especially when the build includes the engine R&R, that the "cost plus" fee is not reflective of any valid cost that can be used for comparative purposes. In this case, I had to add costs for complete clutch system, fabrication of fuel lines, replacement of rusted & incorrect parts, and on and on... The total package still came out at an affordable cost - a price that many people pay for just a delivered crate engine.
I second Lars's comments based on my cost to rebuild/upgrade my OEM L-82 in 2014. I paid an expert builder in my area to do the machine work on the block, recondition the OEM L-82 forged crank that needed straightening, reconditioned the OEM L-82 rods, installed and degreed the Roller cam, oil pump, Forged JE racing pistons etc. I assembled the top end with the AFR heads, intake, new clutch kit, etc. The builder came to my house for the priming and initial start up (yes, we broke it in for 20 minutes at 2,000 RPM and varying the RPM's despite it being a roller cam-that is another discussion since folks think rollers do not require breakin). Lots of custom work, extra care touches, attention to detail and TOP parts for everything and the cost was still about what one pays for a GOOD quality crate engine. I have zero regrets and would do it agian in a heartbeat.....Looks like an OEM L-82.............BUT GOES LIKE HECK
I like everything except the 1/2" gap of the pickup screen / oil pan. That could be an issue when you are doing wheelstands down the street.
That's what I like about this Forum: People bring up things that I just haven't considered before...!
On street driven cars, I don't like to put the pickup much closer than 1/2" to the pan bottom. I have seen too many of these cars take a hit to the oil pan and smack the bottom of the pan up against the pickup screen. This can dramatically reduce oil flow to the pump and to the engine, resulting in unfortunate results to the engine. In fact, this engine had the oil pan caved in and smashed up against the oil pump pickup screen, and the engine had evidence of multiple failures, including oiling system failure...
Thanks for the nice comments. Yes, I hope this encourages others to "do it right" and have some fun with their cars and engine builds. This engine and cam feel really good, especially in the low- and mid-rpm ranges. The stock heads and manifolds limit the true high-rpm potential.
The total cost on the builds that I do are so specialized and unique that it would not be fair to say that "this engine build cost $XXXX." I run across so many odd, little things, especially when the build includes the engine R&R, that the "cost plus" fee is not reflective of any valid cost that can be used for comparative purposes. In this case, I had to add costs for complete clutch system, fabrication of fuel lines, replacement of rusted & incorrect parts, and on and on... The total package still came out at an affordable cost - a price that many people pay for just a delivered crate engine.
Nicely detailed Lars, looks like a very nice car with a great engine in it now. I really like your dial in on the stand, then you know once it's in the car it's done.
There is a “can” at the back of the lifter valley. What is it?
It's an oil separator that was used as part of the crankcase ventilation system on the early engines (up through 1966). It was a left-over from the old days of the "road draft tube" crankcase vent system to prevent oil from being sucked out of the crankcase. In the first versions of the PCV-equipped cars, they kept the lifter galley oil separator can in the engine and simply attached a tube to the top of the block to go to the air filter base as the PCV air return rather than running the tube from the block down towards the road surface. You can see the tube attached to the top rear of the block in this photo. There is a hole in the block under the orange tube that connects to the "can" inside the lifter galley for crankcase ventilation. In the early 60's, that tube did not go up to the air cleaner base - it went down the side of the bellhousing and vented the engine vapors towards the pavement.
The oil separator "can" in the lifter galley. Notice how it connects to the big vertical hole in the back of the block that the orange tube is bolted to in the top photo:
Notice the PCV in the oil filler tube on the '66 engine. But the engine has no holes in the valve covers for PCV fresh air inlet into the crankcase (vent). The PCV crankcase inlet vent is the old road draft tube oil separator can:
If you are ever at a stop light on a hot day next to a worn-out 1962 Bel Air, you will see oil smoke coming out from underneath the car. That's ring blow-by crankcase vapors expelling out through the oil separator can and out the draft tube.
Originally Posted by GTR1999
Nicely detailed Lars, looks like a very nice car with a great engine in it now. I really like your dial in on the stand, then you know once it's in the car it's done.
Outstanding work.
Thanks, Gary! Yes, the engine break-in and test on the run stand provides assurance that nothing is going to go wrong or leak once the engine is in the car - I know it will start and run, and all tuning will be right on the money. You bolt it in the car, fill the radiator, flick the starter, and just take the car for a drive...!
with .015” differences between cylinder strokes and position. Crank was offset index ground and polished to correct all the bad workmanship, and ended up at .030/.030
Lars, excellent work as always. Can you explain what these statements mean?
06-30-2018, 12:18 PM
Building a 327 Small Block - A Photo Story
The compression ended up in the 9.3-1 range and I feel like we gave up a bunch of power. 
It's an oil separator that was used as part of the crankcase ventilation system on the early engines (up through 1966). It was a left-over from the old days of the "road draft tube" crankcase vent system to prevent oil from being sucked out of the crankcase. In the first versions of the PCV-equipped cars, they kept the lifter galley oil separator can in the engine and simply attached a tube to the top of the block to go to the air filter base as the PCV air return rather than running the tube from the block down towards the road surface. You can see the tube attached to the top rear of the block in this photo. There is a hole in the block under the orange tube that connects to the "can" inside the lifter galley for crankcase ventilation. In the early 60's, that tube did not go up to the air cleaner base - it went down the side of the bellhousing and vented the engine vapors towards the pavement.
