468 bbc help

nitrous guy needs help for A friends 468.10.5 compression 8.71 bb3 cnc heads injected for dragster.Clearance, cam, rods, and boost.Trying to make good power but not hard on parts.thanks

 

It would help if you were a little more specific on your questions. Also you should search through the archives, there have already been a few threads on this topic.

 

I just naad a good cam,what rods are best,and about how much boost.only running eighth mile in dragster

 

Here is some good info:

http://www.insidetopalcohol.com/showthread.php?t=24247&highlight=cheap+blown+alky&page=3

I'm not an expert but am putting together my own blown alky 460 BBC with a cast GM block, and have done a lot of research on what others are doing that works, so here's some of the info i've found.

Cam: First I would give either either one of the cam manufacturers (Comp, Engle, Isky) or one of the blown alky bbc specialists (Brendan Murry would be good place to start), and get their recommendation. If you're wanting to be easy on parts, you're probably going to want to go with .700-.800 lift, 280-290 duration @ .050, and 114 centerline. You're not going to rev it to 10 grand so no need for a real big cam, but you'll still want to go with a roller.

Everyone's got their own opinion on rods. I've got Brooks 65's (they came with the short block I bought) but my motor's not done yet so the jury's still out for me. I personally will probably buy either Bill Millers (BME) or R&R rods when the time comes. A lot of guys have good things to say about GRP or MGP also. The only one I've heard questionable things about is Howard's. If you've not got pistons yet, get the rods with the big 1.094 pins. If you're stuck with .990's, make sure to get the thick wall tool steel ones. Stay wide on your bearing clearances and get a good oil pump that'll put out 120 lbs pressure (Titan or dry sump)

As for the blower, it really depends on how good the blower is. You stated it's an 8-71, but the range of efficiency between a older, standard helix big opening blower and a newer, high-helix, retro case, small opening top and delta bottom is huge. The older standard helix you might spin 50% over and only get 20 lbs boost, and the newer hi-helix retro you could only spin 25% over and get the same 20 lbs boost. Regardless of overdrive, you probably don't want to go much over 25-30 lbs boost if you want the cast block to live. Everyone seems to agree that around 1500-1600 hp is all that a cast block can take before it starts to rattle the caps (transfer metal).

Hope that helps

Chris

 

As far as blowers are concerned, I am very impressed with my std helix 8-71, I had littlefield put new stripped rotors in it and it makes 15 psi on a 572" motor @ 28% over, around 1500hp.