Donman

I agree 100%

I appreciate all of the replies, but I was thinking that a compression test and vacuum gauge check were really only going to pinpoint which cylinder had the problem. I am actually not that concerned about WHICH cylinder to look at. If I`ve got any valvetrain problems, I`ll find it when I pull the VC.
My main concern here, was in asking if I was on the right track, in thinking I had a broken spring. I think the concensus here is that I probably do, but need to yank the VC to investigate.
I TRULY appreciate all of the suggestions. This is an invaluable forum with some genuine intelligence out there.
I am going out to work on the boat right now. I hope to find some answers. God knows I would rather be on the water than turning wrenches today.
I will post my findings later today.

Thanks for all the help !

SB

Here's your cam card. It has the recommended spring # and specs if you end up needing springs.

Part Number: 132561 Grind Number: H-228/312-2S-14 T1.2
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1967 Up CHEVROLET 8 FAIR IDLE, STANDARD CAMSHAFT FOR MERCRUISER 400, 405, 420, 425 HP AND 525SC-454 CU. IN. ENGINES, APPLICABLE TO 350, 365, 370 HP MILDLY MODIFIED ENGINES WITH FREE-FLOWING ABOVE WATER EXHAUST SYSTEMS FOR PERFORMANCE APPLICATIONS, 9.5 TO 11.5 COMPRESSION RATIO ADVISED. BASIC RPM 2800-5800
Engine Size Configuration
396-454 C.I. V

Valve Setting: Intake .000 Exhaust .000 HOT

Lift: Intake @Cam 312 @Valve 530 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 324 @Valve 551
Rocker Arm Ratio 1.7

Cam Timing: TAPPET @.005
Lift: Opens Closes ADV Duration
Intake 35 BTDC 83 ABDC 298 °
Exhaust 87 BBDC 39 ATDC 306 °

Spring Requirements: Triple Dual Outer Inner
Part Number 99893
Loads Closed 130 LBS @ 1.850 or 1 27/32
Open 330 LBS @ 1.320
Recommended RPM range with matching components
Minimum RPM 2800
Maximum RPM 6600
Valve Float 7200

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 5 BTDC 43 ABDC 109 228 °
Exhaust 57 BBDC (1) BTDC 119 236 °

Remarks:
CAMSHAFT IS GROUND WITH .0012" LOBE TAPER.

Donman

Glad you listed the cam specs. Looks like I`ll be needing a cam. Yup, Exh lobe, cyl #8 --- flat.
Everything else looks good...
I have to pull the engine to swap the cam. . .

stevesxm

don't foget... all the grindings from that lobe went somewhere.... clean clean clean EVERYTHING

John B

Glad you found the problem. A lot of poeple never let us know what they find, thanks. The hydraulic lifer is probably eaten up too. You must have almost no exhaust lift at all to pop thru the carb.