Can someone PLEASE provide me with as much information as possible on the TRS 400 Hp merc engine (cyclone). I'm doing a twin rebuild and the builder wants to know anything I can come u with about it. (ie. stock compression, cam specs, etc...) Thanks in advance.

P.S. Model year 1985

prostock85,
Cam specs are as follows:
HYD-FLAT
298º/306º @ .005"
228º/236º @ .050"
.312"/.324" lobe
.530"/.551" valve
114º LSA
109º ICL
Bob

I think I have the original manual at the house. I am going to be out on the boat all weekend but I should be home on Sunday. I could fax you or send it as a *.pdf with what I have Mon morning. I know I have a complete repair manual with all the info from 1988. That should be the same as yours. I also got some stuff from 1984. I'll have to look.

The Merc 454cid 400hp Cyclone engine is a 4-bolt main block with all forged parts....crank, 7/16" dimpled rods, and pistons. It came with GM's rectangle port heads with 2.19" intake valves, and 1.88" exhaust valves, Crane Gold aluminum roller rocker arms, cast (finned) aluminum valve covers, and an aluminum hi-rise dual plane intake manifold.

These are good base engines to build from. And even thought the large rectangle port runner heads will still work they are still a bit too large/over kill for a 454cid marine engine. Usually, the smaller oval port heads with some bowl work will run better on a marine hi-perf engine destined to run at 5500rpm.

Thanks alot. The guy looking to build my engines said the same thing about the heads. He thinks the rectangular port heads should be scrapped in favor of oval. Any one have any???

Also thanks to KAAMA, gofastlvr, and rmbuilder for the info

One more thing, what can a 454 be saftly bored/stroked to?

Usually, .060" (468cid) is about the most/safest you can go on a non-siamese cylinder walled GM big block. You CAN go further, but the block should be sonic checked before doing so.

I built a 454 like you are talking about and I opted for the large oval port heads with 2.19/1.88 valves bowl blended and gasket matched and flowed the motor is in a 23 nova spyder runs 73 on gps and it has pulled a friend of mines 24baja that has a 502mag