ZZ502 - Best Replacement Camshaft??
 

I was thinking about the Crane 168731... Would this be a good choice? Will the lift on this camshaft still work with the current stock lifters? And of course I'll be reworking the heads with the proper springs etc...

Thanks,
Gary

Re: ZZ502 - Best Replacement Camshaft??
 

Now there's a debatable subject. Really do need more info on the motor. Completely stock? If so, what changes/upgrades do you plan? Remember, it's all about combination. Especially with the cam. Ok Chris Straub or RMbuilder, chine (chime) in.

Re: ZZ502 - Best Replacement Camshaft??
 

Yes, the 731 is the cam most people suggest.
No, you should not use the stock lifters. Some say you can, but they are on the edge.

Re: ZZ502 - Best Replacement Camshaft??
 

The motors will be bored to make 509's with flat top pistons, so the compression will be down just a bit over what I'm currently running. And, I'll probably do some head work to have the oval port heads matched up to the rectangular port intake manifolds that are currently installed. Will stick with the IMCO exhaust.

Re: ZZ502 - Best Replacement Camshaft??
 

Whats The Size # On The 731 L, C, D,

Re: ZZ502 - Best Replacement Camshaft??
 

I just installed the same cams in my motors and I used the stock lifters. They will work with no problems. They will not work with the 741 cam though.

Re: ZZ502 - Best Replacement Camshaft??
 

The heads on the ZZ's are not impressive flow numbers out of the box but with some work they respond real well. If you leave the heads stock these engines need about 12 degree split at advertised duration, an 8 degree split at .050" and need to be equal at .200" tappet height. Intake lift needs to be about .50" more then exhaust.

If ported a single pattern type cam will get you real close.

GM rates the chambers at 110cc. The last 2 sets that I dealt with were 114cc and 116 cc. Chamber size needs to be checked.

Re: ZZ502 - Best Replacement Camshaft??
 

I have a "barely used" 731 roller that I will sell. It was in my Gen VI 454. It was ran 50 hours, in excellent condition. I used it with the stock lifters / COMP springs. I upgraded to a bigger cam recently.
PM or email me if interested. I`ll sell it for whatever fair market value is for a nice used 731. I paid $350 for it 18 months ago from Summit Racing.

Re: ZZ502 - Best Replacement Camshaft??
 

AIRTIME Here are the specs for the 168731 Crane cam. I beleive it is offered in configurations to fit both the Mark IV & Mark V VI series engines. Intake lift .587, advertised duration 288, duration @ .050 226, opens 6 BTDC, closes 40 ABDC, max lift @ 107. Exhaust lift .610, advertised duration 296, duration @ .050 234, opens 54 BBDC, closes 0 ATDC , max lift at 117. These figures are based upon using a 1.7 to 1 rocker arm ratio which is standard.

Re: ZZ502 - Best Replacement Camshaft??
 

Thanks for the info guys...keep it coming...

Re: ZZ502 - Best Replacement Camshaft??
 

thanks too .

Re: ZZ502 - Best Replacement Camshaft??
 

Here are the before and after numbers on Rotax's heads:

Numbers are at 28" of of a SF600 Bench. This is flowed with a 4.500" fixture. Intake had radius fixture and exhaust is with 1 7/8" pipe.

GM #12363390 Alum Oval Port Head-stock
Intake Valve 2.250 " Exhaust Valve 1.800 "
Lift: inches Flow: cfm Lift:inches Flow: cfm
0.100 74.0 0.100 71.0
0.200 143.0 0.200 126.0
0.300 207.0 0.300 158.0
0.400 250.0 0.400 178.0
0.500 284.0 0.500 200.0
0.600 309.0 0.600 218.0
0.700 322.0 0.700 232.0
0.800 0.800

GM #12363390 Alum Oval Port Head-ported
Intake Valve 2.250 " Exhaust Valve 1.800 "
Lift: inches Flow: cfm Lift:inches Flow: cfm
0.100 85.0 0.100 73.0
0.200 161.0 0.200 141.0
0.300 230.0 0.300 175.0
0.400 283.0 0.400 208.0
0.500 332.0 0.500 234.0
0.600 354.0 0.600 257.0
0.700 361.0 0.700 274.0
0.800 363.0 0.800 287.0

Just referencing the numbers at .500" you are looking at a cam that needs about 6 to 8 degrees of split favoring the exhaust @ .050". The heads at 70% I/E ratio are actually really good for a BBC.

Power out put, based on the Super Flow formula of CFM x .2552 x No. of Cylinders = Possible HP at 100% VE. I will reference .600" and 309 cfm. HP could be 630HP

Now look at the ported heads. We reference .600" lift and 354 cfm and we have the potential of 722HP.

Now is it easier on a machine to run it at 100% capacity or 80% capacity. Making HP relies on how much air you can get in the engine. It is easier to make power with more air because other parts don't have to be maximized. If these engines were both going to run at 5200 rpm, 1 had the ported heads and one the "out of the box" heads the engine with the ported heads would have the smaller camshaft because the head is doing more work. Therefore the camshaft doesn't have to do as much. Long term this engine will be less maintenance.

I hope this helped some more.

Chris

Now

Re: ZZ502 - Best Replacement Camshaft??
 

I replaced my ZZ cams during my rebuilds last year with the Crane 168741's. I really didnt notice any big improvement over the GM cams though(maybe 100 to 150 rpm). I dont think it was worth the investment. Two very important points, if your going to swap cams though: do the lifter swap, the stock lifters drop pretty far down the guide on the new cams(I checked). I know there pricey, but its a gamble not worth taking(I used the 13532's, either will work). But more importantly make sure you buy the billet camshafts(gold cores), and not the induction hardened(grey core). Why you ask? Because the induction shafts can and will break(@ the dist gear end, where the two pieces are joined). I learned the hard way. After talking to Crane, they admitted that the cam could break in marine applications due to constant rpm, and harmonics(especially @ 4000rpm). The exact rpm I was running all weekend on a long cruise. Fortunately it just kills the distributor and oil pump, and the valvetrain stays in time. I was able to swap the cams out in the boat and with a strong magnet get the broken piece fed thru the journals. Surprisingly a very clean break, and Crane replaced the cams with billet ones. FYI, this happened to me one week before the July 4th weekend, and the only cams Crane could overnight me were Mercury HP525 cams(#OEM 0888), which have all the exact specs as the 168741's, except they are ground on a 114 lobe separation, as opposed to the 112 of the 741's. I guess that means I have HP525's in my old 311!

Re: ZZ502 - Best Replacement Camshaft??
 

Ditto on what Lake Effect has said. I have read alot about the difference on construction on the 731 cams. Am doing the exact same thing on (2) brand new zz502 short blocks. Purchased (2) 168731 cams from Jegs this week and they showed up with the black color (different hardening process) and have a somewhat history of breaking. Called Summitt and they pulled every 731 cam. As of right now they had 5 in stock. 4 were copper colored, the good ones ( I purchased (2) and (1) was black in color (buyer beware). The boxes in the warehouse were then marked in color so you should be able to dictact what color you want. If you want more info, call Crane and ask for Dave Maxwell in tech. He will confirm problems.

Ed

Re: ZZ502 - Best Replacement Camshaft??
 

Sounds like the HP525 OEM cam might be the best bet with the 114 degree lobe separation... Is that the actual part number (#OEM 0888)???

Re: ZZ502 - Best Replacement Camshaft??
 

i have a used 741 hyd roller cam if you decide to go with the 741cam. ratman

Re: ZZ502 - Best Replacement Camshaft??
 

and im still sitting on as full set of lifters and cam from a zz502, if interested, all brand new never run.

Re: ZZ502 - Best Replacement Camshaft??
 

FYI :

The 731 cam that I would like to sell is a billet ( gold ) cam.

Is $150 shipped, a fair price? That`s what I was thinking of asking for it. It looks brand new. Still have the cam card too.

Re: ZZ502 - Best Replacement Camshaft??
 

When Crane set me the new cams, they came with new cam cards, and thats the part# on the cards. OEM0888

Re: ZZ502 - Best Replacement Camshaft??
 

Thanks...

Re: ZZ502 - Best Replacement Camshaft??
 

If my memory is correct, the 114 degree LSA would lower the rpm peak as opposed to the 112 being a tad higher?

Re: ZZ502 - Best Replacement Camshaft??
 

You still got this camshaft?? $150 shipped..I'll take it.
[email protected]

Thanks