What to check before buying cam & avoid piston to valve clearance problems?
 

I am getting ready to buy a roller cam for my 1976 454 engine with 781 heads. The short block was built by some shop before I purchased the engine from my brother. Here are some of the specs that I know for sure about the engine. The engine is not how I would have built it but I got it for a good price.

454 at .060
Silvolite cast piston 1434-060 dome no valve reliefs and .015 below deck
Bore= 4.31
Stroke=4.00
Stock 781 cylinder heads with stock size valves


Before buying cam is there anything that you check?

I am aware that the only way to know for sure is to buy the cam and lifters,install and go through the necessary procedure to make sure there is proper valve to piston clearance but I was just wanting to know if there is anything I can check BEFORE buying a cam as far as lift goes?

I already know about cam selection in regards to compression,cylinder head flow,intake manifold selection,etc,etc, but that is not what I am asking about.

The hydraulic roller cams I am looking at are in the .550 to .600 lift range.

Re: What to check before buying cam & avoid piston to valve clearance problems?
 

This article will run you thru the easiest way to check for maximum lift that will work with your engine....

https://www.hotrod.com/articles/pred...rdering-a-cam/

To make is easier I usually replace the original springs with light weight springs for the measurement process..

Highest rate of interference comes on overlap of exhaust closing and inlet opening....

It is a must that any new cam be degreed in correctly...do not trust any new cam or gear set is actually correct as advertised.

Hope this helps...

:chevy::chevy::chevy:

Re: What to check before buying cam & avoid piston to valve clearance problems?
 

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Speak to a few cam manufacturers tech help. They are likely to put your mind at ease. But do go ahead and place modeling clay on a piston and a head on your block with OUT a head gasket, install light test springs, lifters, push rods, rockers on a cylinder and roll her over a few times to get a good measurement.

I retrofitted a roller setup into a 396/402 and can tell you with certainty you do not want to use COMP CAMS roller lifters. I wasted 450 dollars of my money to be able to tell you this absolutely. Those COMP lifters are POS Junk. I have since pulled them out and replaced them with about 500 dollars worth of Howards 91161 retrofit lifters. I've only put 50 miles on these so far but they have already quieted down far, far more than the COMPs did over about 2000 miles ( yes...adjustments made no difference ).

My little 402 specs... dome pistons @ 9:1 with #063 heads stock valves:
CAM: comp 11-422-8 ( 270/276 dur, .510/.510 lift, 110 sep )
long tube headers
mild stall

RPM 1600-5400

She's a ripper!

-klb

Re: What to check before buying cam & avoid piston to valve clearance problems?
 

max valve lift really shouldn't be your concern...at max intake lift the piston is nowhere near the valve.

the Amount of Duration and the installed centerline is what you are looking at.
the earlier you open the intake the tighter it gets...most cam places can give you a fairly accurate range of duration and installed Intake CL that should clear.

think about the intake lobe, valve starts off the seat Before TDC, we often see on the cam card the degrees BTDC at the .050 lift point (5 to 15* typical numbers)

The amount its lifted at TDC and right after that is where it will be closest to the piston top.

Re: What to check before buying cam & avoid piston to valve clearance problems?
 

All good information and yes I always check with clay as well.

Re: What to check before buying cam & avoid piston to valve clearance problems?
 

With that lift you should be good, degree your cam and then verify clearance with the clay. Valve to Piston Clearance depends mostly on Size of Valve reliefs and Dia of Valves and Inversely Proportional to Duration of the Cam - That is the longer the duration the tighter the Valve to Piston Clearance. Basically do not worry about Valve to Piston Clearances with Cams under 300 Advertised Duration Degreed per Specks in STK OEM Specked Engines as Cam and Piston Manufactures take this into account. Ensure when Clay Modeling that you have enough Piston Valve Relieve Diameter when running Large Dia Valves.

Valve to Piston Clearances are closet when the Intake 1st Opens and the Exhaust Valve Closes - Advancing or Retarding the Cam by 2 Degrees generally changes the clearance by .010" respectively.

Head Gasket thickness, Milling either Deck or Heads change the Valve Seat Height and affect Valve to Piston Clearances - Generally Lobe lift has very little affect unless you running extreme (310+) durations.