[chipmechanic]

A friend I work with just bought a new 393 shortblock from someone who is abandoning a project. Actually its a 399 because of the .060" bore on the '70 351 block. Its already assembled with speed pro forged L2482F 302 type pistons. They have the smallish valve reliefs and he doesnt want to disassemble the short block to recut the valve reliefs and he isnt comfortable with cutting them in place. Balance works been done and he doesnt want to disturb it plus I dont think he's trying wring every bit of power out of it.

I was helping him look at heads today . It looks like he'll need 1.92 intake and 1.60 exhaust . Not sure any bigger will clear the valve reliefs. Anyway the Dart 175 pro 1's look like theyre pretty good flowing heads for the money . Anyone have any opinions on these? Its going into a cobra replica with a T5 and 3.73 gearing and he's looking at a [email protected]" ish duration solid roller cam. He's wanting to get 500 HP out of it.

<font size=-1>[ This Message was edited by: chipmechanic on 4/18/06 3:18pm ]</font>

 

[rcm600]

I figured just about the same thing. I just bought a set of the 195cc heads for my 331. For the money I think they should be fine. At least I hope so. I was thinking about the same for cam. There is a Car Craft article on a Dart head 302 in their archives. It gives dyno charts for both the 195s and 170s. Why not 195s for that 393? Not much info about the Pro 1s out there. Good luck.

 

[dfree383]

Your kinda in a compromised situation, those 175cc heads are going to be a little on the small side and the valve sizes your looking at are away to small and probably wont make the hp you looking for.

It would probably be worth while to fly cut the pistons as the cam your describing may need the clearance anyway. You can usually go lighter on the reciprocating components with-out hurting the balance (their is a limit) Talk with your machine shop.

I would recomend looking at heads in the 200-215 CC intake range. The small ones you are looking at will make great torque but are going to weeze out when you start spinning it.

 

[qtrhors]

Chip

As you well know that much cam isnt gonna do all it should with the "wrong" heads for the cubic inch. If that is a stock reconditioned 351W rod combo then rpm should be kept under 7K maybe even under 6.5k. Ford's own 393W crate with small GT40X heads made 450 hp with a slightly smaller hyd roller cam and only 9.7-1 comp. I think he would be close to a 500 hp goal if static comp is at least 10.5-1 and street solid roller like you mentioned even with the small port/valve aftemarket heads like the pro 1 175's. The compression is gonna be were the power increase is going to come from....I would even try 11-1 with alu heads if you have access to 93 octane. Doesnt Isky or some one make a tool for cutting larger valve reliefs that is not that tuff to use? I would look into that myself. That would make this a no brainer.

 

[chipmechanic]

Ive used the isky tool before and its probably not the best working piece of equipment in the world.
I think the real problem here is going to be the lift of the solid roller. I'm thinking the those valve reliefs are awfully small especially compared to the canyons in my 438. Since it does use stock rods albeit with ARP bolts I have also advised against going over 6500 RPM. The cam I believe he was considering is the compcams 286 roller. With the 175 pro 1's (at least according to their published flow numbers equivalent to the AFR 185's) I think it would be a good runner and should rev cleanly to 6500. 261/172 is pretty good airflow and would be more than capable of 500 HP with a mild roller like that 286. Sticking point is the lift on the cam though. I think notching is in his future whether he wants it or not. Its my duty as his friend to whack him over the head with a bridgeport.