Here’s the stock 307 in all...
Here’s the stock 307 in all its glory. With decent compression and positive results from the leakdown test, we decided to leave it be for the time being, but not alone.
After purchasing my ’68 C10, it became obvious pretty quickly that the engine was in need of a little attention. Not only in the looks department, however, but in the performance aspect as well. Don’t get me wrong, it pulled strong and ran like a clock, but it just didn’t do it with any quickness of expedition. Couple that with the emaciated performance provided by the three-on-the-tree transmission and suffice it to say I was going to be making some changes to the powertrain in the C10.
Before I chose what road to go down though, it would be necessary to see what kind of shape the engine was actually in. I ran a compression test, dropped the pan, and checked the rings/cylinder seal with a leakdown tester from Summit Racing and was pleased to find out that the motor actually checked out pretty well. It also didn’t knock or smoke while running, another good sign. The previous owner mentioned that he only drove it occasionally to haul large items to the dump or to pick up something from the hardware store so I figured it probably hadn’t seen much abuse. Upon further investigation (okay it was one of the first things I noticed!) was the fact that the engine was not the usual Chevy Orange for the period, but Chevy Corporate Blue, a color not adopted until 1977 when GM began their “corporate engine” edict. I ran the numbers and sure enough, they matched the truck, being identified as a 307ci motor from 1968. A closer look revealed that the timing cover, valve cover, head, and intake gaskets were not painted, which told me that someone hadn’t just inadvertently decided to paint the whole kit and caboodle (as I was about to!), but painted everything in pieces. This means that at one time in the past forty some-odd years, the engine was taken apart, at least that far. Long story short, someone rebuilt the 307 at some point, most likely between 1977 and 1982. Either that or they rebuilt it last year and painted it blue for some strange reason, but I digress.
That said, I figured I had a pretty sound foundation to build a super-mild, little hot rod engine for the C10 until my future plans for the drivetrain come closer to fruition.
My original plan was to leave the motor stock and to bolt on Holley’s new Avenger EFI system once the truck was up and running with the new T5 transmission installed. That was a great plan, however, until I found myself at a crossroads while McLeod built my clutch. With the truck sitting, I figured I wouldn’t get a better opportunity than that to detail the engine. I set off on my beautification phas e by dismantling the engine down to the block and heads to get rid of the Corpo Blue and return it to its original Chevy Orange guise.
Though I planned on making some contemporary upgrades, I wanted to make all of them in a conscious effort to maintain the late ’60s period of the truck; nothing too out of place under that hood, at least in an aesthetic sense. I stuck with orange, grey, and black under the hood in order to build a hot rod motor that comes across as though it were factory, at first glance anyways. The end result really speaks for itself when compared to the initial motor, and the added power and performance really woke the truck up and made it transform from a junkyard dog to a highway hauler. CCT
We’ll start with that restrictive...
We’ll start with that restrictive 2-bbl carb and intake and toss those straight in the recycling bin. The smog-era exhaust manifolds will follow suit as well as the original water pump and ignition system.
Here are the three colors...
Here are the three colors (Cast Iron Gray, Chevy Orange, and GM Black) we’ll be spraying under the hood, all Summit Racing products.
The first step is to carefully...
The first step is to carefully mask off the engine compartment. I used some EZ Sheet plastic from Summit to cover any areas prone to overspray and simple aluminum foil to mask off things I didn’t want orange such as the wiring, engine mounts, transmission crossmember, etc.
Surprisingly, the extra time...
Surprisingly, the extra time I took to mask everything off paid dividends and the end result looked pretty good with almost no overspray in the engine compartment. It does help that the firewall was already Chevy Orange for the most part, and the rest of the engine bay had a nice oily sheen to protect it!
Since I pulled the stock intake...
Since I pulled the stock intake off to detail the block, I figured this would be the perfect time to install the Weiand Street Warrior that I was going to use for the Avenger EFI install. It will also give me a more even baseline when it’s time to compare carb vs. EFI.
After scraping the paint off...
After scraping the paint off the mating surface of the block and heads, I applied RTV to the gaskets and dropped the intake in place. New Grade 8 fasteners tightened to 30 foot-pounds will hold it steady.
Like I said, I wanted to retain...
Like I said, I wanted to retain a stock vibe to the engine compartment, so it was a no-brainer when it came to picking a set of exhaust manifolds. These beauts are Speedway Motors’ new Tru-Ram manifolds and they’re stainless, which means you can polish them nice and shiny, paint ’em, or just leave them as is, like I did.
One thing worth mentioning...
One thing worth mentioning about the Tru-Ram manifolds is that you’ll need to figure out what brackets will work on your particular application. I opted to contact Alan Grove Components (AGC) to get the brackets for the alternator, A/C compressor (which I’ll be installing at a later date), and the power steering pump. That said, I had AGC send out a matching set of pulleys as well so there’s no guessing game when it comes to putting together a set. The crank pulley is a triple groove while the water pump pulley is a double groove. Also pictured is the single groove pulley for the power steering pump.
Here’s a good example of what...
Here’s a good example of what can happen when you start combining different pulleys, accessories and such. The Weiand aluminum water pump has a fairly large housing area so the AGC pulley wouldn’t clear it. Luckily the stock GM pulley did and we were back in business. Since our engine is stock internally, spinning the water pump a bit slower should be okay. Once the A/C condenser is added in front of the radiator though, we may have cooling issues. Time will tell, but for now it’s fine.
Since the damper and the timing...
Since the damper and the timing indicator got painted, I marked each one so that it would be easier to set the timing later on down the road.
With the number one cylinder...
With the number one cylinder at top dead center (TDC), it seemed logical to install the MSD Pro-Billet distributor.
To be sure that you’re at...
To be sure that you’re at TDC number one cylinder, watch the valves open and close as the engine is rotated. Both pushrods should spin freely, meaning the valves are closed and the lifters are on the heel of the cam.