Just bought a rebuilt 454 that has had a bit of work done to it. I really don’t want to tear it down to figure out all the particulars. It was in a boat. Supposedly has a 280 comp cam in it. Want to make sure what it is because I don’t want to have any problems with reversion. It had CMI exhaust on it but I only have stock exhaust at the moment. Not even sure if a 280 cam would be a problem with reversion or not but don’t want to find out. Looking for suggestions before I install it. Thanks in advance

Jeggs has a cheap degree kit for $100 with dial Guage.you can at least get lift duration and separation angle even if you won’t know manufacturer

Too funny, you posted while I was typing. Ha

Thanks guys. Great info. Main thing I’m concerned with is reversion. According to the person I got it from it’s a comp cam 280 duration. I really didn’t want to start pulling it apart if I didn’t have to as it doesn’t leak so doesn’t need to be re gasketed. I may pull the pan to see what the bottom end has as the casting number shows it could be either be a 2 or 4 bolt. And also to see if it has the good forged crank and big rods. Someone spent some money on upgrades. It has roller rockers. Holley 850 marine carb, Edelbrock intake so hopefully will be significant over the stock 330

Not sure if it’s enough info but if it is a comp cam 280 cam do you think I would have reversion issues and would I restrict this cam with stock Mercruiser exhaust? Engine also has edelbrock air gap intake for oval port heads and Holley 850 carb. Reason I’m asking is because i already have a brand new set of manifolds and risers but if I’d be better off I’d try to get a set of stainless marine manifolds and risers. I’ve tried researching cam specs but still don’t totally understand what it all means

There isn’t enough information about the cam yet. You might ask the builder for the cam card or if his exhaust was dry or not. On another note , Holley carb tech says the 850 cfm is a torque killer on engines making less than 600 hp. You may want a smaller Holley for a heavy boat like a 242. If it was my engine, I would be inclined to pull some things apart and have peace of mind and a reliable boating season. Best of luck.

Unfortunately the person I bought it from didn’t have much info on it. I do know it had CMI exhaust with 3” taller risers. Not sure if the cam is flat Tappet or roller. Hoping to use an inspection camera over the weekend to see what I can find out. Wish I had more info but for the price I couldn’t pass it up. Basically I know it has around 100 hours on rebuild. 165-175 lbs on all cylinders, roller rockers, crossover instead of water pump and comp cam valve train parts. Hopefully the camera will shed some light on other things otherwise I probably will pull the intake and oil pan. I’ll let you know what I find out

I agree that the 850 will work. I did a lot of carb testing on my 502 mag in a boat identical to the OP and picked up 150 rpm by going from an 850 to an 800. This was with a mercruiser dual plane intake. This is definitely apples and oranges when talking about your 454 Skirby. Just food for thought. SB: Did they offer this in a roller?