chain vs gear drive cam

Discussion in 'Cams, Heads and Valve Trains' started by grumpyvette, Nov 25, 2008.

  1. grumpyvette

    grumpyvette Administrator Staff Member

    Gear drive VS chain cam drives, ... es/117.pdf

    viewtopic.php?f=52&t=5734&p=17492#p17492 ... -20325.pdf ... 0-7892.pdf

    read thru these threads and sub linked info also


    Id first point out that a CLOYES true roller chain cam drive will work just fine in most applications, but you need to check the slack every 20,000 miles or so after 60,000 miles or more if your using the car for serious performance applications and higher rpm operation, replace the old timing chain after about 60,000 miles if you want to maintain precise timing,under the conditions most guys put street engines, but I constantly hear guys repeating the MYTH that all gear drives cause harmful harmonic loads to be transferred to the cam, I,ve tested, and checked extensively and all the gear drives I've looked at very closely, tend to maintain the correct timing longer and have no bad problems and certainly last far longer than the chain drives WHEN CORRECTLY INSTALLED AND INDEXED
    drilling an oil passage plug with a .oo31 hole to provide a constant bath of hot oil spray on the gear or chain drive timing set tends to add too and aid durability.
    drilling the pass side oil passage plug with a 1/32" bit so oil constantly sprays on the timing gears helps extend chain and gear life.

    BTW if you soak a new timing chain and gears in a pan , covering them in a mix of synthetic oil and moly assembly lube and heat them to about 220 degrees to allow the oil to penetrate into the metals pores it will tend to pre-lubricate the chain and gears more effectively than just installing them dry, and from what Ive seen they last slightly longer, a cheap tin pan can be used, and if you don,t have an IR temp gun(you really should get one) adding a 1/4 teaspoon of water to the oil and watching it boil off as an indicator that the oils up to temp is a good idea, as you don,t want to over heat the oil or smoke up the kitchen

    I tend to favor QUIET gear cam drives, in some applications

    in PERFORMANCE ENGINE BUILDS,over chain drives , because chain drives get slack and tend to allow the cam timing to vary with rapid engine load changes like during shifts ... fault.aspx
    except in cars with KNOCK sensors, where the slight gear whine might cause the knock sensor to randomly retard the ignition timing.
    Ive used several different brands and find nothing wrong with a CORRECTLY INSTALLED Pete Jackson dual idler gear drive, in fact Ive used that (QUIET) Pete Jackson gear drive, in the 383 thats been in my corvette for several years with zero problems
    as with most parts, installation must be correct, clearances checked, ETC. or youll HAVE PROBLEMS!, READ/UNDERSTAND THE INSTRUCTIONS, and ASK, QUESTIONS and know the reasons and answers , before installing any part or youll probably run into problems, Id have changed several chain drives bye this time, but the same gear drive I installed over 8 years ago still works fine and maintains the correct clearances
    but Ill also point out I run a high volume oil pump, a 10 baffled QT oil pan and have extra oil jets drilled (#60 drill bit)in the oil passage plugs behind the cam gear
    the two outside plugs

    thats part of the install process place (with the gasket) using a large lump of modeling clay , and dial calipers

    Under the timing cover and test bolt it in place, remove the clay an carefully measure the clearances..
    (BTW spray the inside cover and the block with WD 40 first it tends to prevent the clay from sticking)the axles on the idler gears should have about a .002-.010 clearance between the cover and the block, this keeps the gears running in the same basic track once the engines assembled, you don,t want the axles to bind/or be in constant contact, under tension with the cover, as that might tip/bind the gear, and a light coat of moly on the gears wont hurt. This frequently requires a light touch of a file to shorten the axles a few thousands, but youll not know without TESTING for the correct clearances with the clay :grin:

    youll also need the retaining plate, cam button and loc-tite

    Last edited by a moderator: Nov 7, 2017
  2. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    Ive occasionally been asked what you can do too reduce the slack in the timing chain if your blocks been line honed,
    to straiten the main bearings and that resulted in a slightly closer crank to cam center-line distance,
    that results in a slightly increased slack in the stock timing chain sets.
    a negligible amount of metal is generally removed from the main bearing saddles in the block, they usually try very hard to minimize that, metal removal so standard parts still fit,during a line hone , but they do sell slightly tighter timing chain sets to correct excess slack if that's required.


    Timing Chain and Gear Set, Original True Roller, Double Roller, -0.005 in., Iron/Steel Sprockets, Chevy, Small Block, Set
    for line honed blocks where the crank is .005 closer to the cam
    for line honed blocks where the crank is .010 closer to the cam
    Timing Chain and Gear Set, Original True Roller, Double Roller, -0.010 in., Iron/Steel Sprockets, Chevy, Small Block, Set

    related info
    Last edited: Nov 7, 2017

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