400chev standard stroke 6 inch rods clunking - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-12-2007, 02:03 AM
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400chev standard stroke 6 inch rods clunking

Hi all,ive just put together a 400 chev,standard stroke crank with eagle 6 inch rods and Je pistons. I seem to have a problem with maybe clearance,every thing felt fine but i have a slight click\clunk on turn over when i started to do the valve lash,seems to be just after top dead center.
I have looked under the sump with a torch and cant see any where its hitting.
I have now been told that i need a small journal cam and or have to grind a bit off the rods,i cant seem anything on the clearance problems on the forum,any help much appreciated.

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Old 06-12-2007, 06:15 AM
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Must have a big cam , the picture below shows what has to be done for 383 cam clearance.
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Old 06-12-2007, 07:23 AM
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Thanks for the reply,this was exactly what i was looking for,where to grind or what to replace

cam is fairly lumpy solid

Part Number: 114681 Grind Number: F-280-2 (REPLACES CC-28OA)
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1957 1987 CHEVROLET 8 ROUGH IDLE, MODERATE PERFORMANCE USAGE, GOOD MID-RANGE HP, 3600-4000 CRUISE RPM, 10.5 TO 12.0 COMPRESSION RATIO ADVISED. BASIC RPM 3400-6800
Engine Size Configuration
262-400 C.I. V

Valve Setting: Intake .026 Exhaust .026 HOT

Lift: Intake @Cam 3454 @Valve 518 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 3574 @Valve 536
Rocker Arm Ratio 1.5

Cam Timing: TAPPET @.020
Lift: Opens Closes ADV Duration
Intake 29.0 BTDC 71.0 ABDC 280.0
Exhaust 77.0 BBDC 31.0 ATDC 288.0

Spring Requirements: Triple Dual Outer Inner
Part Number 96877
Loads Closed 126 LBS @ 1.850 or 1 27/32
Open 324 LBS @ 1.350
Recommended RPM range with matching components
Minimum RPM 3200
Maximum RPM 7000
Valve Float 7400

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 14.0 BTDC 50.0 ABDC 107 244.0
Exhaust 62.0 BBDC 10.0 ATDC 117 252.0


I didnt pick up the problem on assambley as i only checked bottom end without the cam in ,ive also heard that its only on no 3cyl ,but i guess ill soon find out thanks again.
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Old 06-12-2007, 01:31 PM
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You have to get a small base-circle camshaft as I had to do when I put a 282HR in my 6" 408. 6" Eagle h-beams might help clear it but I-beams do not.
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Old 06-12-2007, 02:43 PM
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Make sure you ck the cam real close for damage to a lobe!


mark
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Old 06-13-2007, 07:46 AM
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I agree whole heartedly with JMark. If you heard clunking, and it was 'cause you lack clearance, there is almost certianly some damage to the cam. If the rotating/reciprocating parts have already been balanced, replacing the cam is the easy way out, as it won't impact your balance job.

Pat
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Old 06-13-2007, 09:48 PM
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If there was any interferance you would not be able to turn the engine past it by hand. Does the engine lock when it clunks? If not, I would look elsewhere. Did you check your bearings to make sure they are not over sized? That would cause a clunk like you are talking about.

I had to clearance a little on my rods for my 6 inch rod engine with I beam rods, but it was very little. I used a standard base circle cam.
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Old 06-19-2007, 09:55 PM
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Hi all thanks for the reply's,i rapped electrical tape around the lobes and turned over the engine by hand,pulled the cam back out and found the the taped buffed on 4 lobes,it has only been just nippen it,lobes are still fine,i droped the rods\pistons bck out and ground abit on all just to be safe.
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