CayFomula

I have a 1989 Formula 272SR1 twin 96-97 454Mags (carbureted), motors are stock hydraulic roller cam, rectangle port heads with non-adjustable rocker arms and Thunderbolt V ignitions. I have added Stainless Marine exhaust and crossovers, intercooled Whipples, Marine Holley 850 carbs setup by GT Performance and MSD hi-vibration coils. I have Crane Gold roller rockers and HI-6M ignitions to install. The engines have almost 400 hours on them (30 since the Whipples), compression is about 140 on all cylinders and they run great. One cam has a burr in one lobe and the ticking is driving me crazy (actually it’s just an excuse to get to play with it some more) but to change the cam I will need to remove the motor.

The question is, do I remove both motors replace bearings, rings, cams and do a valve job or do I wait and buy some 502s (would love 540s) long blocks to bolt under the Whipples? I would like to keep the motors as reliable as possible with the current power levels or better.

If I go the rebuild root I would appreciate suggestions on which high performance cam to go with (currently running 6-7# boost with 28 degrees total timing on 93 octane pump gas).

This board is the Best! I have to be careful I don't get addicted.

Panther

What size are the whipples? they may run out of juice if your running a 502 or a 540? If the blowers are small I would just rebuild and update what you have. You would have to spin them so fast that the inlet temps would we high and more prone to detonation. you'll want something with a dual carb setup.

Dennis Moore

Cay Formula,

You should have at least 155 pounds of compression with a cold engine. Remove the cylinder heads and see how much cylinder wear you have.

I am a strong believer in saving money and if the cylinders look good you should keep the original forged pistons and just replace the rings (forged pistons won't wear out after only 400 hours).

Install some new bearings (it is possible that the crank just needs to be polished) and have a reputable shop grind the seats and valves (the valve job is the most critical part of the engine!).

Install a camshaft with aproximately 224 degrees intake duration and 230 degrees exhaust duration with a 114 degree lobe separation angle.
Choose a cam that DOESN"T have high valve lift for valvespring and lifter reliability. Somewhere in the .510 to .525 lift range.
A supercharged engine really responds to duration and is relatively unresponsive to higher valve lifts (unlike a NA engine).

If you have Comp Cams grind you a custom cam with these specs you won't have to change the valvesprings or go to an adjustable rocker arm setup, give them a call.

Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

cobra marty

Great plan as usual by Dennis. Keep it simple and cheap.

CayFomula

Dennis,

Thanks for the excellent advise, I think I will go the rebuild route with the cam specs you have suggested. I figure even if I decide to upgrade to more cubes later the rebuild will make my motors easier to sell.

Thanks,

Ian T.

Btw – I enjoy the magazine and it is very popular down here in the Cayman Islands.

CayFomula

Looking some more advise on my setup. When I install the Crane HI-6M ignition does anyone have any suggestions on what plugs to use and the gap?

Thanks,

Ian T.

Rambunctious

cay formula, you still afloat,
It's been a tough season weathering out those hurricanes

you surviving them ok?

formula31

AC MR-43T Gap them to .045

Quiet Storm

I thought the gap for the 454 Mag was .035. Are you suggesting .045 for the Whipples or the ignition?

formula31

The ignition. I assume you are gonna use a crane coil too, right?. And use good wires. The Crane system puts out quite a bit of voltage.