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07-10-2010 01:16 PM 406 Build Thread
Welcome to my 406 build thread.

It went into my "hotrod" '91 RCSB truck. The truck used to be a work truck for my Dad's shop, so after getting it from him 5 years ago, I started work on it. I didn't do a whole lot to the interior except a stereo system and remote start because it still looks really good. I did all of the body work and paint 3 years ago, and planned on doing the engine the year after that. Within months of laying the paint down, a rod started knocking so the engine had to be done sooner.

I've done some basic engine work as a hobbyist, but this is my first ground-up build. I bought a crate 350 4 years ago and swapped the cam before installing it. The 350 just didn't end up having what I was looking for since this is a street machine and I don't rev the hell out of it. The 350 started out life as a TBI-Vortec engine, and after years of trying to tune it, it always felt like it was still being held back. Finally, after years of people that actually know what the hell they are doing telling me to ditch it and install a carb, I finally did. It was definitely the right move for me. Power immediately increased and it ran like a bat out of hell. Not as refined as TBI during cold starts, but I can deal with it.

Like most uninformed individuals, I was looking for big peak horsepower numbers, when what I really needed was big torque numbers, further down the RPM range where I could actually use it. After my initial disappointment, I started reading books about small blocks. Many, many books, reading the better ones several times over. After all of that, I realized what I wanted was more torque than horsepower for a street machine. I read that horsepower sells cars, and torque wins races, and that made perfect sense to me. I also read "build the engine for what you will be using it for". That also stuck with me, and throughout my parts selection process, I kept that in mind.

Not to jump ahead, but for the most part, I ended up with exactly what I wanted. Like any real hotrodder, I could never have enough "power", but for what I spent and for the parts I used, it performs very well, and now my biggest problem is how to get it to hook up.

Let's get down to business.

Here is what I started with. It is a '79 400 block that lost a rod bearing that I found off of Craigslist. It is (was) a virgin block, and it is a "509" casting. The crank was junk, but luckily my Dad is a mechanic and he just so happened to have a 400 crank laying around. I had all of the machine work done at Cope Bro's Machine Shop in Tacoma,WA. I asked them to bore it the smallest amount posible in case I needed to rebuild it later, and unfortunately that ended up being .030, making the block a 406. The 400 blocks have siamesed cylinders, and are known for hot spots and ring sealing problems, so you can't bore them up to .060 over like you can a 350. If this engine ever requires the cylinders to be bored again, I'll find another block or upgrade to an aftermarket block. Besides the bore and hone, I had the block decked .008 to ensure the gaskets would seal and had it aligned bored because one of the caps was questionable. Here are some pics of the bare block after I painted it:




For some reason, I lost the pictures of the parts I had, but this is a list of what I put into the short block:
Scat cast crank
Eagle 5140 I-beam rods with ARP bolts and a floating wrist pin bore.
Kieth Black Hypereutectic pistons with a 22cc, D-shaped dish.
Comp Cams 276HR cam. The specs are 224/230@.050 and .502/.510 lift with a 110 lobe separation angle.
Comp Cams hydraulic retro-fit roller lifters
Speed-pro tri-metal rod bearings
Clevite H-Series tri-metal main bearings
Double roller timing chain with a torrington bearing against the block
Comp Cams roller cam buttom and lock plate
Milodon reinforced timing cover
Adjustable timing tab
Moroso 6-qt oil pan
Standard capacity Melling oil pump
8" Pioneer damper
Fel-pro gaskets

I chose not to use forged pistons because it's a bit overkill for what I'm doing. If I was supercharging it or running higher RPMs, then forged would have suited the application better. Having said that, I have a supercharged vortec engine that is completely stock with cast pistons and nothing has went wrong yet...knock on wood.

I found out that the Eagle rods I bought are made overseas, but no one seems to have a problem with them. I would buy Scat next time just because I like to keep Americans working.

I chose to spend the extra dough and go to a full roller set up. My brother had a 406 that started with a flat tappet cam and later he changed to a roller cam. He said he didn't know what numbers he gained, but it was well worth the money. I went with that theme for the entire engine; if it can roll, it does (except for roller cam bearings).

Because I haven't done a whole lot of this before, I relied on Comp Cams to chose a cam for me. First I downloaded their CamQuest software and then ran the cams it came up with through DynoSim to help me choose which one to use. Then I contacted them and made sure it was the right choice. Luckily, the cam they chose was one of the two that I chose.

In my books, I ran accross two different opinions in regards to a timing set with a torrington bearing installed. One opinion was to avoid it completely and the other was to spend the money and get it. The arguement to avoid it was because if it ever failed, those little bearings would get into the engine. After talking to my machine shop, he said that he uses them in all of his high-performance engines (300+ built by him) and has never had one fail. Good enough for me. Plus it helped me with my "if it can roll, it does" theme. I read the same opinions on the roller cam buttons.

All of that, and here is what I ended up with:


Of course there was a lot of measuring involved to get to this point. I have a few mechanic friends that had some tools I could borrow, and I bought some myself. I took machine shop (non-automotive) in school, so I knew how to use them. I measured everything several times, documented what I found, adjusted what I needed to, and then double checked bearing clearances with plastigage.

Here is a list of measuring tools I used:
Bore gauge (helpful in ensuring I was getting a virgin block also)
Micrometer set
Dial Calipers
Dial Indicator
Degree Wheel




I decided to go with AFR 195 Eliminator heads. I took them to the machine shop and had the steam holes drilled in them and had the springs checked to make sure they were up to snuff with what the cam needed. The pic above is with Vortec heads, but I ended up switching to the AFR's.

Here is a list of what I used to finish off the long-block:
AFR 195 Elimintaor heads w/ 195 cc runners and a 65cc combustion chamber.
Compcams springs, retainers, and locks.
Scorpion full roller 1.6 rocker arms
Comp Cams push rods
Fel-Pro MLS head gaskets

There wasn't a whole lot of measuring to installing the heads, but I did measure for pushrod length with the proper tools.

After everything was adjusted and the finishing touches were done, this is what I ended up with:



Here is a list of what I initially used to finish the project:
Holley 770 Street Avenger Carb
Edelbrock dual plane air gap manifold
K&N X-stream air filter system
Doug Thorley Ceramic coated Tri-Y headers into 3" exhaust
MSD Pro-Billet Distributor
MSD 6AL Ignition box
MSD Blaster 2 Coil
MSD 8.5mm wires
Aeromotive adjustable fuel pressure regulator
Holley regulator bracket
Holley throttle cable bracket
Holley TV bracket
Earl's fittings and hoses
Billet wire separators
Electric fans

I say "initially used" because there is not a completely happy ending to this build. After careful assembly, the truck was driven about 20 miles and I noticed it was spark knocking. I put a timing light on it and reved up it had 55 degrees of timing! I thought my distributor took a dump, but what happened was that the cam ate the distributor gear, sending lots of metal throughout the engine. It did a lot of damage, so I rebuilt it. When I removed the distribtor from the last engine, I inspected the gear and it looked good, but it just didn't stand up to wearing into another new cam. In Comps instructions, they say that they recommend changing the gear, but it is not required, so I didn't since it looked good. Big mistake. It ruined all of the main bearings, and only one of the rod bearings. I replaced them all anyway because I don't like doing anything half-assed. I have a magnet on my oil filter, so I think that helped me also. The oil pump looked surprisingly good, so I just cleaned it. All of the oil passages in the block were cleaned. The distributor was badly scored, so I replaced it with a MSD Billet Distributor with a 6AL CD box. The crank still looked good and the cam bearings looked good. I talked to Comp cams and though they didn't admit anything, they replaced my cam under warranty. I think I should have replaced the gear anyway, but it would have been nice if they would have said it was required. Oh well, live and learn. It's all repaired now and runs like a top.

In the rebuild, the nice Proform crinkle finish valve covers I bought broke around the mounting holes. That was the second set that I broke using the recomended torque setting and a very nice torque wrench. Needless to say, I will never buy anything Proform again. I can't believe GM would call them "officially licensed". They have since been replaced with a nice set of fabricated valve covers.

Here is the finished product:



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