So I have a pair of Mercruiser 454 which appear to be Cyclone 440hp according to numbers,
valve covers,the trs drives were also marked as 440hp ,had mercruiser offshore race mounts,
hydraulic steering, Gil exhaust with dry tips,,drive,tranny and engine numbers all matched,
did not look like anything had ever been changed or removed,
I have talked with original owner,and thats what came in it,,ran 72mph in a 10,000lb 30ft..
when we took boat apart nothing seemed to have been changed. Engines have hi-perf rect ports,
mercruiser/Gil manifold and dry pipes thru the transom.. Confusion is with cams,
my friend Doug Schiller measure the lobe lift using an indcator and we took various readings and we came up with
257/281 engine with steering pump
269/283 other engine..

with 1.7 rockers
437 / 477
457 / 481

with 1.8 rockers
462 / 505
484 / 509

This seems WAY too small to be on these engines,,did we measure wrong or has someone
after original owner changed cams for some reason? Engines seemed untouched but cant be 100% sure..

pic:
https://scontent-lax3-1.xx.fbcdn.net...bd&oe=57386EE2

this what they sounded like before we removed them..
https://www.youtube.com/watch?v=V37BRGPEJso

Where was the lift measured? On the cam lobe?

yes,, I had removed intakes to check everything out..

According to Merc Service manual #9 those sound more like a 330 B-W, 454 Mag(old), MIE 340 which are .271/.282 lobe. .461/.479 valve. The 440 Cyclone had .323/.328 lobe and .549/.558 valve.

440 would have aluminum roller rockers too!

Also I don't think the 440s ever came with Gil exhaust. And they were a single plane intake too I think. The 440s had a pretty rough idle.

yep. 232/239 110LSA for the 440HP Cyclone 454 engine.

I think they came with Gils and dry pipes because of the rough idle.. At least thats what I have read..

As far as I know, the Merc 420's went single plane, but the Cyclone 440's kept the dual planes. Will have to dig some archives.

Thank You..
,why someone would swap to those cams is beyond me..

Sucks cause I wasnt planning on swapping cams and now I have to spend money for a roller swap s I wont waste my money on current flat tappet parts.. Had very bad experience with that already..