318 build suggestions?
A friend of mine has a 318 short block .060 over, zero deck engine that we’re going to build. It’s going into my ‘67 Barracuda convertible, which will be running a 904 automatic and 3.91 gears with 28” tires. Couple of questions:
1. What’s a fair price for the short block?
2. What’s the best top end combination out there to make 400 horses with it? Thinking some aluminum heads, and would prefer a complete package (cam, lifters, roller rockers, etc).
Do not burden yourself with all those whose first response is to build a 360. Nothing wrong with 318 engines. Yes it is easier to get 400HP out of a 360, but sometimes you go with what you have or have available.
What heads are you thinking about, and valve sizes? Aluminium are lighter and not much more cost than getting iron heads reconditioned. The fairly standard 2.02/1.6 valve combination is borderline tight in the proposed 3.97" bore, for shrouding. This not not by much.
Iron heads is a matter of what you can obtain reasonably, considering you will need to go through them and pocket port and port match them. LA heads can have Chev 1.9"1.55" LS valves installed. You will need to have either LS powdered metal guides or bronze guides installed for the 8mm stems. You should be able to use the Chev beehive springs, retainers and locks. This saves weight, and due to the millions built, the parts are cost effective. I would consider 1.6 ratio roller tip rockers for less guide wear.
What are you considering for the cam? A FT cam is less expensive up front, but you must be careful with oil selection to protect the cam and lifters. This means probably no oil changes at the Lube Tube as they will put in what comes out of the hose. One advantage of a FT cam is the valves can be accelerated off the seat quicker than an equivalent roller.
A roller cam system is going to cost up front, but oil selection is not a big concern.
For the displacement of the proposed short block, the LSA should be 104°. 106° would be acceptable. A cam with 220° to 224° intake duration @ 0.050" lift should be a good compromise. For valve lift, I would be looking for 0.500" to 0.550". If you get the exhaust seats and valves ground for 40° instead of 45°, the exhaust blows down at the lower lift more efficiently. With that you can use a single pattern cam for more low RPM torque and fuel economy.
Remember, it costs no more to get the cam ground as the cylinder displacement and cylinder heads want, than an off the shelf cam, and you will get better performance with the cam the rest of the combination wants. The wider LSA cams will tend to aid a smooth idle, at the expense of torque and power, while tending to flatten the torque curve. Yes, Pro-Stock engines are using wide LSA (120°) cams, but the rest of the combination permits/dictates that.
If you want stock appearing the LA heads may be the way to go. Magnum heads would hardly be noticed, while Aluminium heads are easily noted. The Magnum heads are more prone to cracking. A sound set could be fitted with 2.0" LS intake valves.
I hope this gives a bit to think about that helps.