Well I am thinking of moving away from my predator! Have had it since 1984 and am getting a bit bored with it. ? is I have been used to the "variable venturi" design that gives my engine what it needs (so they say) I am at a loss as to what CFM to run. I am thinking of a demon carb (sorry, no good with holleys) and confused as to cfm etc.. here is what I am running.. 1968 block .030 over, forged flats, '65 289 heads with 1.94/1.60 stainless valves ported to match intake and hedders. Intake is a weiand accelerator single plane. Cam is solid (non roller) with .555/.575 lift duration is 288* Sorry, don't remember lobe center or life at .050. Bottom end is resized rods with arp and steel crank. Have a 125hp shot of laugh on it also. Tranny is rebuilt c-4 with 3000 stall (flashes about 2700) with 4.11 locker in rear.. Ideas for cfm etc????? Street car, some shows and MAYBE 10 runs a year down the 1320....(it is pouring rain here, gotta at least bench race!_ Thanks for the input.. Scotty P **new heads maybe in my future IF the right deal comes along. Nothing radical though performers or AFR 185 etc....
Demon carbs are nice... but are almost identical to a holley in their design and internal structure. In an attempt to tune one for a friend, I found that there were a few differences, but basically the carb is a over-rated Holley. If it were me, I'd try a HP series Holley 750 vacuum secondary for a street car, or a 750 or larger double pumper for more race-oriented usage. With the nitrous, you'll want to over-carb the engine a bit...I know a 302 "shouldn't" need more than 600 cfm, but I've never seen a well-built 302 that didn't pick up ET, MPH, and overall better driveability with a 750. The throttle response is better too with larger carbs due to their larger throttle plates. If you aren't a Holley fan, perhaps an Edelbrock 750 or 800 carb would be better. I like them as well, though I run a 600 on my old ragged Mustang....and after all the tuning I was able to achieve 32 MPG consistently (all highway) yet still make good power. Edelbrocks are more street-oriented than Holley-based carbs. They seem to hold a tune forever. Mine's working on about 50,000 miles since the owner bought it new, and all I've done is play with metering rods & jets.
Thanks, I guess I am not completely Holley shy! The car runs well and the old dbl pumper 650 holley woudl be too lean. So maybe a 750.. Scotty
edelbrock For simplicity I'd go with 750 Edelbrock or Carter AFB comp series there a piece of cake to setup and perform good too.
charles Here is my reason for buying a Holly, the last 6-7 times: Odds are much better you can find someone to adjust or fix it. The last thing I want to do is spend the night in East Opossum Trot, cuz some gizmo is on the fritz, and the cretins down at Elmo's lube rack can't figure it out. Charles
BMC, I think I had other "issues" with the 650dp. I was running 70's in front and 90's in back and still running VERY lean plugs w/o the laughing gas.. May be time to try the 750dp, will miss certain aspects of the predator though..Scotty P
I beg to differ that holleys and Demons are the same thing. Demons are wet flow tested and holleys are dry flow tested. A 650 Speed Demon would be about the same as a 750dp. 650 speed demon would suit ya fine. I have never tuned a car for NOS but I would imagine the rules would apply to any brand carb. I get by with a 625 roaddemon but my cam specs are a little milder on the duration 220@ .500. A E303 cam and 625 rd are a perfect match. I am running a 725RD on the 351w408 stroker I will le ya know how that works but I for see stepping up on that one. My little 302 Dynoed out at 370fwhp I will get dyno results for the 351w408 in the next few months as budget allows.
