lorne

Could some one give me a referance point to jet a850 holley vac sec carb on a chevy 502 that has bin bored .060 over.Compression is 8.5:1 with je dish pistons,cam is a comp xm284,heads are aluminum 110 cc.THe jets that were in the carb was 78 pri &82 sec.The motor ran good for about 5hours then scuffed #4 &#6 cylinder.The engine idles with 10 inches of vacuum.could you tell me what would the right power valves to use?The motor is in a 26 foot wellcraft prima that weighs about 10000 lbs.Engine would turn up 5200 rpm. thank you for your input have a great day Lorne.

blue thunder

Recently posted on speedwake by Kidnova. He had this carb tuned by Nickerson over the winter and this is how they set it up. Should be close for you.

82/88
4.5 PV
850 Vac
500+,- ft. elev.
ZZ502, 500hp

BT

Kidnova

BT, I was thinking of posting my carb specs for lorne to give Lorne a place to start. I didn't post the info because of the likely cam difference between lorne's engine and mine, the compression on my ZZ is 9:6 to 1, and a big weight difference. Being carb "challenged", I wasn't sure if posting the info would be of help or hindrance to Lorne. But I certainly hope it does help.

Lorne, Like BT says Nickerson did my carb for me. Before I sent it out to them they had me fill out a spec sheet that had about 35 or 40 questions regarding engine specs + info about my boat, and elevation. They dialed the carb in just about perfectly. I mention this because Nickerson does get very specific when setting up a carb.

The thread BT is referring to on Speedwake is "What Size Carb Jets Are You Running". Check it out. There's about 50 posts. You might spot one closer to your engine specs than mine.

Good Luck.

Bill