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robertbj
02-08-2013, 10:04 AM
I have been talking to Rapido Marine out of Florida about a long block Ford 351w for my “66” 16. They have GT40 heads and I will get them put on for an extra charge. I was going to have the standard cam upgraded to a performance one but the guy there said that would be a waste of money. The standard cam specs are Intake 206 at .050 lift 445, and Exhaust 221 at .050 lift 453. He didn’t give me any specs on the upgrade cam but it did come with a valve spring upgrade.​(1) Should I get the cam upgrade anyway and what should it be? (2) Has anyone got anything good or bad to say about Rapido Marine?
Bob

BUIZILLA
02-08-2013, 10:09 AM
it would be pretty hard to garner an opinion on the cam upgrade, without knowing WHAT that upgrade entailed.. ;)

robertbj
02-08-2013, 03:05 PM
I guess I could request a specific cam spec like the one moody blue used in his 351.

Advertised Duration (Int/Exh): 284/284
Gross Valve Lift (Int/Exh): .488/.488
LSA: 112
RPM Range: 1500-5000

mattyboy
02-13-2013, 04:04 PM
I guess I could request a specific cam spec like the one moody blue used in his 351.

Advertised Duration (Int/Exh): 284/284
Gross Valve Lift (Int/Exh): .488/.488
LSA: 112
RPM Range: 1500-5000


just a heads up, going to a hotter cam can lead to two issues exhaust water reversion which means the exhaust may need to be addressed and hi po ford exhausts aren't cheap

and idle rpm I wouldn't want to be shifting a volvo and any higher than about 800-850 rpms so a cam that idles above that will shorten the life of a volvo . It will be a pleasure around the docks too if it needs a high idle.

here is a new 351 motor with gt40 heads. I think this motor is about 300 hp ( like the PCM pro Boss) a little above the 290 hp rating the 69 and 70 HM 351w had after that they dropped to around 260 hp
just to give you an idea of prices

http://www.ebay.com/itm/FORD-351W-Marine-Engine-H-O-GT40-Heads-BRAND-NEW-/370752987074?pt=Boat_Parts_Accessories_Gear&hash=item5652999fc2&vxp=mtr

I would not use the logs on this type of motor but

robertbj
03-02-2013, 06:06 PM
Thanks mattyboy,
I decided to go with the standard cam and I have already received the long block with the GT40 heads. I think it was a good deal considering the local machine shop was charging $1,500 for just the machining to my block. Rapido Marine did not require me to send them my engine as a core and claims to pressure test, magneflux, machine the block, balance the rods, assemble and ship the long block for $1,650 or $1,850 with the GT heads. Everything looks good visually and I will be finishing the build soon. I just wondered if upgrading the cam to something better than the one included from Rapido, would be worth it. It will never be easier to do than now.
Bob

joseph m. hahnl
03-03-2013, 11:20 AM
You need to know your Compression ratio before you do any cam change. I'll bet i'ts in the 9's, as most are. More duration like that 284 would dog out the dynamic compression.Go with a more agressive rocker ratio.The reversion spike will ocurr at the same time, and you'll have more cylinder pressure from the quicker opening valves. Your suppose to clay check the valve to piston clearance any time you make a change in the valve train, just to be safe:doh:. You can also check with a drop indicator with an engine that is assembled with the heads on.