I'm looking for some advice on a set of 915 BB heads I have. Some background... I have twin boys who will start college in the fall - read I'm paying! So money is an issue. One of my boys wants to try his hand at som racing and we are planning to build a 440 and 727 for the 72 Challenger I have. It will probably see some street time as well. I am planning a quench motor with a decent bottom end - steel crank, studs, forged flat tops (probably six pac's but haven't decided yet), topped with a set of 915's that I have. I already have the 915's. They have been magnafluxed and are crack free. I already have stainless valves (2.14's and 1.81"s) and iron adjustable rocker gear for these heads.
I want to know what machine work I should be asking for on these heads. I know all the regular stuff - seats cut, valve installed heights, etc. Is it necessary/reasonable to have the valve throats plunge cut then bring the heads home for some blending, then back again to have the seats cut? What about the exhausts - have hardened seats installed before or after the plunge cut for the 1.81's? As far as the 1.81's are concerned do you really need to put in 1.81's? I've seen several posts here talking about killing the lower end power with the larger valves. Remember this is a "learner" motor and maxing it out is not the goal here. Just respectable, dependable power. I want him learn (and me too) then move up as we get better.

you should sit down and outline a budget and goals for the entire car then go from there. rear axle type and ratio, suspension, torque converter type, transmission mods, camshaft, valve springs and induction system, ignition ect. any improvement on the stock heads is a plus but unless done properly can harm performance rather then help it. to get the best overall performance the car needs to be a properly matched package.

There where two versions of the 915, HP with the 1.75 exhaust valve and the rest where 1.60 exhaust valves, which ones are yours? I have had several sets of later heads, 906, 346 and 452 upgraded to the 2.14 abd 1.81 sizes and those motors seem to like it If you can afford it do it, if your on a tight budget try and use what you have. I like having both sets of seats replace so the heads flow the most you can get out of them to start with, the seat hieght is critical in the wedge heads. As far as low end power the cam, converter and rear gear help determine that, not the valve size necessarily

As you have a good crack free set of heads and valves I would use them. If you didn't have the parts I would just start with a set of aluminum heads.
I did a set two years ago, putting in oversize valves allows you to cut new seats and set the heights where they should be. I had mine plunge cut first and then hand blended them. I was really happy with the way they worked with a .528 mechanical cam.

Sheldon

Hey Runnin74 -

Give a breakdown of how much you can afford to spend on your engine vs the rest of the car. Otherwise you're going to get responses from all over the map.