Mike C Posted March 20, 2003 Share Posted March 20, 2003 Anybody have experience running a GM melonized distributor gear with a steel BILLET roller cam? GMs roller cams are CAST steel. Comp has a new polymer gear that is supposed to have 4-5 times the longevity of bronze. Thoughts? The GM gear is $35, the Comp, $99. But a new cam $250... Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 20, 2003 Share Posted March 20, 2003 I would stick with the Comp Cams or similar stuff. Especially if you are using a high volume or high pressure oil pump, keeping in mind it is the distributors job to supply the rotational power to the pump and the gear is the most-wearing item in that scenario. I have seen what happens when a sub-standard gear is used in a high perf situation and it always ends up in an ENGINE REBUILD or worse! I personally use a Comp brass gear on a billet roller and typically get two years of strip/street use before replacement. The wear usually shows up as a wandering timing light indication (a worn timing chain can also cause this of course) at which point it is gear swap time. I am very interested in the new polymer gear, but I have had no personal experience yet. Go with the cam manufacturers recommendations is my $.02 Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted March 20, 2003 Share Posted March 20, 2003 YOU MUST USE A BRONZE GEAR ON STEEL GEAR CAMS UNLESS THEY HAVE A CAST IRON GEAR INSTALLED ON THAT STEEL CAM, A STEEL CAM GEAR WILL QUICKLY WEAR ON AN IRON DIST. GEAR, STEEL GEARS REQUIRE A MATCHING BRONZE DIST. GEAR http://64.90.9.168/cranecams/pdf/257g.pdf http://64.90.9.168/cranecams/pdf/323e.pdf The bottom of a Chevrolet distributor housing can be modified to spray pressurized oil onto the distributor drive gear. The extra lubrication will reduce distributor gear and camshaft gear wear. This is especially important when the gear is used to drive non-standard accessories, such as a high volume oil pump, or a magneto that puts additional loads on it and the cam. When the distributor is installed, the bands at the bottom of the housing are designed to complete the internal right side lifter galley on all small and big block Chevrolet V-8’s and 90° V-6 engines. If you hand file a small vertical groove .030" wide x .030"( thats the diam. that crane recommends Ive always used the larger groove with no problems deep on the bottom band (above the gear), pressurized oil running between the two bands will be directed downward onto both the gear and the camThis procedure is recommended for all Chevrolet engines no matter what material gear (cast or bronze) or what type of camshaft (cast or steel) you are using.<P> keep in mind the groove MUST be lined up with the cam gear when the distrib. is installed Quote Link to comment Share on other sites More sharing options...
pparaska Posted March 20, 2003 Share Posted March 20, 2003 Wouldn't it be easier (alignment of the groove with the cam gear) to just make a groove in the block instead? That way the groove would always be lined up with the the cam. Quote Link to comment Share on other sites More sharing options...
Mike C Posted March 20, 2003 Author Share Posted March 20, 2003 Grumpy, your advice is the same I received from Crane. I called Comp as well to inquire on the polymer gear, but temper their advice to some degree since I know they are trying to sell me a gear... Pete, I am always hesitant to make a mod to the engine block that may prove detrimental in some way. (See below about oil psi.) Also it would be hard to do and keep shrapnel out of the motor, and much easier to replace distributor housing were the mod prove to be ineffective. Noted that a different motor combo, even just initial timing, might negate the effectiveness of the mod due to placement. If a STEEL cam always must use a bronze gear, why do GM and Ford use melonized gears on their STEEL cams? Admittedly they used cast steel and not steel billets, however. Crane also said that they had seen very good results with their billet cams and Ford's melonized gear, but that was not true with GMs gears. Most of this does me no good, however, as I am looking for something that offers a degree of reliability in street driving that I feel is lacking in the bronze gear. I was told to expect at least a 2# reduction in oil pressure at low RPMs with the grooved distributor housing. However, my most likely solution is going to be grooving the distributor, combined with a new bronze gear, at least for the time being. I will carefully measure housing to driveshaft clearance in order to maximize tooth engagement to spread the load. Any more thoughts other than a new cam, which isn't that much more than the $100 polymer gear, long term, that has 4-5 times the life of the bronze, but not more? Quote Link to comment Share on other sites More sharing options...
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