318 REBUILD IN 67 BARRACUDA

67BARRICONVERT said
Hi everyone,
I just pulled the 318 out of the car so i can paint the car including the engine bay. The engine ran ok so originally I was not planning on a complete rebuild but after doing a compression test (120 psi low to 170 psi high) and disassembling the engine I don't have a choice. There is a piston ring ridge at the top of the cylinder wall that will catch your finger nail and the nylon tooth timing gear was the loosest I have ever seen. You could almost walk the chain off of the gears even though all the nylon teeth are still there. I am going to have to make some decisions on some things like cam choice, and valve size.

First let me tell you about the car and what direction I am going with it. Its a 1967 Barracuda 273 with the commando option, 904 trans, 7 1/4 axle with open 2.76 gears. The original owner (I am second owner) swapped the original 273 for the 318 years ago. Other than the engine the car is very original and I would like to keep it as original looking as possible. The car will probably never see a drag strip (maybe?:)), just a nice driver. In fact i am building this car for the wife. I understand with its 7 1/4 rear end and 904 trans we cant get to crazy.

So, back to the engine.......The block is a 1969 casting # 2586030 and the open chamber heads are what I believe to be original to the block (sorry, i dont have the casting numbers in front of me but they are 1969 castings also). I would like to improve performance but I realize the limitations that will hold it back. One would be the exhaust because I would like to use the original exhaust manifolds and the Accurate exhaust Hi-Po system (already purchased) with the optional Magnum muffler which should flow better than the original single exhaust. Accurate claims this system will out perform dual exauhst but I am not going to bank on it. The exhaust manifolds are part number 2843953 and 2780946 which I believe are the original 273 manifolds which came with the car.

So my plan with new pistons is to raise the compression to around 9.5 to 9.75:1 (has to run on premium pump gas) and since the heads are going to be rebuilt install larger valves. How large should I go? I have seen as large as 2.02 intakes, is that a possibility or should I go with more like 340 or 360 size valves? I do think I want to keep the stock rocker shafts and push rod length because I don't want it to get too complicated.

I am going to run the LDB4 aluminum intake which was already on the car. It says Chrysler on it and has a Chrysler part #. It leaked coolant at the thermostat housing because there was pitting on the aluminum mating surfaces and one of two bolt holes threads were pulled out. I machined the mating surfaces, installed a 3/8" heli-coil in the stripped hole and glass bead blasted the intake.
I have two carbs to choose from. On the car was a Carter AFB #9626S which is 625 CFM. I would assume its been on the car since the 1970s and it ran fine with it but it is kinda crusty looking so I would rebuild it. The other option is a Edelbrock #1406 600 CFM that I have which is new and has the "Endura shine" finish on it.

The distributor has a electronic module in it and a Direct Connection orange box.

I was planning on using the the stock crank and rods if they are serviceable, and doing some port matching on the intake and exhaust manifolds if needed.

So that leaves the camshaft and that's where I get a little lost. What do you guys recommend for a build like this???? Any help on a camshaft or advice on the rest of the build is greatly appreciated since this is my first LA small block build.

On the camshaft I'd shoot for around 260-268 duration and .450 to .490 lift. Honestly, call Racer Brown and any other cam grinders and honestly tell them what you want. Get valve springs to match the cam you pick. You should have a nice 318, so I'd just rebuild what you have. Have the big ends of the rods redone .0002 undersize with ARP rod bolts. They should be the early light weight, bushed rods. Make sure the decks are equal on the block, bore and hone with torque plates with mains torqued to spec also. Add a windage tray, high pressure oil pump, and a true roller timing chain. I like Speed Pro ductile, file to fit, moly rings. Have your bottom end balanced. Mill the heads .020 and .019 on the intake side of the head, that should give you around 64 cc chambers. You can run stock valve sizes, or bump them up to 1.88 intake and 1.60 exhaust (360 sizes) not really necessary though. I would run stainless steel exhaust valves and the later Viton positive valve seals from Fel-Pro. Spring for a Competition valve job, and just clean up the bowls under the valves. Find true TDC and centerline your cam while the heads are off. On the exhaust, delete the heat valve on the passenger side manifold and consider "Jet Hot" coating the manifolds to keep the heat down in the engine bay. You will like the Accurate Commando exhaust. Your intake is great and either carb will work. I think the 9626s was designed for a 383, so it might be a tad rich. Play with both and pick the one you like best. When port matching, just do the top and sides. The Commando 904 has some nice parts from the factory. You could probably just reseal it, adjust the bands, change the fluid and filter, and be done for the next 100,000 miles. HP cars usually had 3.23 gears but we used to swap in 2.76 gears for highway cruising. We ran a 67 Barracuda like yours, except we kept the 273, for about 50 years and 300,000 miles. What a great car, still have it. Good Luck!