AI Coupe Driver Posted May 18, 2007 Share Posted May 18, 2007 My AI 306 is fine but I can't figure out what the problem is with my kids street/weekend drag car. Replaced stock pump and shaft with a Melling +25% pump and hardened shaft. Less then 3000 miles and about 30 1/4 mile runs in the low 12's shaft broke again. Both times at the bottom of the distributor. Bottom end is fresh stock with Roush heads and Holly Systemax set-up. Both broken shafts look like a Barbers Pole (twisted), the first pump had a small piece, about 1/8" square of gasket material stuck in between the rotors, I haven't taken the second apart yet. Does the Melling +25% oil pump need a larger capicity pan as one shop suggested... should I go back to a stock pump and stock or hardened shaft? Anyone experienced this before in a 302sbf? Any ideas? Thanks, Ron Quote Link to comment Share on other sites More sharing options...
Frank Corkran Posted May 18, 2007 Share Posted May 18, 2007 Well, the first one you know why it happened - FOD in the pump. Lock up the pump and the stock shaft will twist up like that every time. Shoot, with a HV pump you can twist the stock shaft from the load produced by the pump in extremely cold weather with thick oil. I don't know what you mean by a hardened shaft, you want to use an ARP, FMS, etc. larger diameter shaft, though they are probably made of stronger materials as well. If something gets into the pump and locks it up, it'll either twist off the heavy duty shafts or clean the teeth off the distributor or cam. As for using a larger pan, a HV pump will just dump the extra oil back into the pan unless you have extremely loose bearing tolerances or a stuck pressure bypass, which would produce extreme pressure. I had a Melling HV pump (and ARP shaft) in my '83 302 for 15 years with the stock pan. 100k+ miles later, many of them track miles, and no problems with the pump/shaft/cam/dizzy gear or oiling related issues. Threw in new rings/bearings and it did 2 full seasons in AI. So no, I don't think a larger pan is necessarily required with a HV pump. Even if your motor's oil flow rate requires a bigger pan to keep from running it dry, that wouldn't increase the load on the pump shaft. You'll probably find something wedged in the pump gears again. Did you replace the pickup tube/screen after the last time? Quote Link to comment Share on other sites More sharing options...
Gfaules Posted May 18, 2007 Share Posted May 18, 2007 My AI 306 is fine but I can't figure out what the problem is with my kids street/weekend drag car. Replaced stock pump and shaft with a Melling +25% pump and hardened shaft. Less then 3000 miles and about 30 1/4 mile runs in the low 12's shaft broke again. Both times at the bottom of the distributor. Bottom end is fresh stock with Roush heads and Holly Systemax set-up. Both broken shafts look like a Barbers Pole (twisted), the first pump had a small piece, about 1/8" square of gasket material stuck in between the rotors, I haven't taken the second apart yet. Does the Melling +25% oil pump need a larger capicity pan as one shop suggested... should I go back to a stock pump and stock or hardened shaft? Anyone experienced this before in a 302sbf? Any ideas? Thanks, Ron I have seen this more times than I can count. When you replaced your oil pump I bet you reused the same oil screen. NEVER reuse an oil screen. If you take apart your old oil pump you will find such a small piece of carbon/grit in between the gears that you will not believe it was enough to seize the pump thus resulting in a twisted off shaft but it is. Many times there can be a build-up of carbon on the inside of the oil pump and when it begins to flick off it gets between the gears. Oil screens are an inexpensive part so toss the old one regardless of how many buddies tell you they have used the old one for years. Then replace the distributor shaft with a stock replacment. And remember always use a high VOLUME oild pump and NEVER use a high pressure oil pump. Quote Link to comment Share on other sites More sharing options...
AI Coupe Driver Posted May 18, 2007 Author Share Posted May 18, 2007 Yes, we did leave the original pick up and screen in when we did the first swap. I'll get it right this time! Thank you... Quote Link to comment Share on other sites More sharing options...
racercosmo Posted May 18, 2007 Share Posted May 18, 2007 Now is the perfect time for an LS1 swap, and you have due cause. Quote Link to comment Share on other sites More sharing options...
AI Coupe Driver Posted May 18, 2007 Author Share Posted May 18, 2007 Now if we went ahead and did the LS1 swap, we would have to become one of the Camaro guys that we beat (EZ) every weekend at National Trails. Maybe you know a street Camaro that runs 12.2 all night long... we haven't found one yet. My kid drives his 89 fox body to the track, we bolt on his M/T's and he kicks ass then drives home. The oil shaft is the only problem we have had with this motor in four years. I'm putting him in my 90 AI GT in July at Mid Ohio... we'll try to show him what real racing is! See ya! Ron Quote Link to comment Share on other sites More sharing options...
pederb Posted May 18, 2007 Share Posted May 18, 2007 What track does he run 12.2 on? is that seconds or minutes BTW? What is M/T's? Quote Link to comment Share on other sites More sharing options...
Frank Corkran Posted May 19, 2007 Share Posted May 19, 2007 What track does he run 12.2 on? is that seconds or minutes BTW? What is M/T's? He's a drag racer. National Trails is a dragstrip. 12.2 seconds 1/4 mile. M/T is Mickey Thompson rear drag tires. Or were you just being funny? Quote Link to comment Share on other sites More sharing options...
AI Coupe Driver Posted May 19, 2007 Author Share Posted May 19, 2007 I can see that you've spent some time on the tree... Ron Quote Link to comment Share on other sites More sharing options...
Frank Corkran Posted May 19, 2007 Share Posted May 19, 2007 Who, me? Never. My first Mustang came with a 7.5" axle, so I always envisioned my first pass ending just beyond the tree in a trail of axle fluid and gear teeth. I did attend one pro drag race as a spectator in the early '80's in the Hampton Roads area of Virginia. I think I sustained permanent hearing damage from the sound of the Funny Cars, not to mention lung damage from their exhaust fumes. Quote Link to comment Share on other sites More sharing options...
pederb Posted May 19, 2007 Share Posted May 19, 2007 What track does he run 12.2 on? is that seconds or minutes BTW? What is M/T's? He's a drag racer. National Trails is a dragstrip. 12.2 seconds 1/4 mile. M/T is Mickey Thompson rear drag tires. Or were you just being funny? Mostly funny, I used to be a crew cheif for a pro stock team before I saw the light. Quote Link to comment Share on other sites More sharing options...
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