Cam recommendation for Blower Motor
 

Dang, here we go again. Nothing lives longer on this board than cam or oil threads!

Looking for a cam for Gen 6 502 with 8.75/1 using a B&M 250 with 5lbs. Boost. Lightning headers, 1050 single carb and Crane Hi6 ignition. I don not plan on spinning the engine much more than 5300 and would spend a good deal of time at the top of the primaries cruising. Fairly light 24 ft. boat (Baja Force 235) for a 502 with blower.

Called Crane Tech Line and they recommended the 168731 and not the 168741. This blower combo was used on a similar 502 with good results with the 741 cam. Crane rep said that the 731 would be a little better and was good to 6000 rpm. He also said that the 741 would tend to be a bit lazy in the middle. My hull will run a best of 70 in stock form (basic 502 crate engine, nothing special not the HP500 version). I know these guys just read from a sheet for most questions so that is why I am asking here, bear in mind the hull type, not a big 29 ft. single.

Anyone running a B&M 250 at 5lbs. Boost with either of these cams? I need to choose one or the other. As is said this combo came off an engine setup and the jetting was correct for the 741, boost reference etc. If I used the 731 would the jetting still be correct? If not which way would it tend to run going from the 741 to the 731, rich or lean?

Crane said I would be fine with my stock roller lifters and pushrods. I will use the Crane Gold rockers and the recommended spring or equivalent. This brings up another question, should I machine the heads for 7/16 or use the screw in adapters?

Other things I have considered as part of the project;
Upgrade Rod bolts
Use Fel Pro head gasket

In a nutshell-
741 or 731 cam
Rod bolt upgrade required?
Alternatives to Crane Gold Rocker arms?
Alternatives to Crane springs?
Machine the heads or use the screw in adapter?

Whew, almost getting there!

Tim T.

I ran that blower with a 731 cam, but in a 454. Ran great, never spun it over 5600 (I didn't have the good lower end, and was being conservative). If I had it to do over, I was thinking I would have gone with the 741...??

Almost forgot, 4 and later 6lbs boost with Nickerson 980.

Here is another twist, just talked with Lunati, they have a part 54849.

Lift at valve Intake .578 Exhaust .598
232 / 242
112 Lobe Separation
Intake Opens 6 BTDC
Inake Closes 46 ATDC
Exhaust Opens 55 BBDC
Exhaust Closes 7 ATDC

Crane
http://dab7.cranecams.com/SpecCard/...B1=Display+Card
http://dab7.cranecams.com/SpecCard/...B1=Display+Card

Might be best to stick with what has been done before?

I love the 741 and have had better results with it, through the rpm range from about 2,000 up. I have run this before. Your carb is too big.
I would use your rod bolts here. They are pretty good.
Crane gold tockers are good. I like to use Comp or Crower Stainless. They haver been bulletproof with this size cam.
Crane offers an "offshore" valve spring that is very good. Comp Cams also has good springs for this application. I don't know the numbers-I NEVER trust my memmory for those, but if you need them, post and I will look them up. Isky makes good springs, too.
If you use the screw in adaptors, use a stud girdle. 7/16 studs are better.
Your lifters and pushrods are fine if they are in good condition.
Don't turn over 5,800. Recommend the rev limiter be at 5,800, keep rpm below 5,600. :D :D
Happy boating!! If you want more, just ask:D

1500,
I was hoping you would chime in, seems like you have done this before! What would be a good source for the Comp or Crower rocker arms and about what cost am I looking at? The Cranes are not rebuild able, just a trade in for 244, not much less that new.

Yes I would like the numbers for the Comp springs. I would like to order this from one place if I could. I forgot to inquire about the exhaust valves. I was planning on having the seat angle changed. Is this really important? Seems anything you can do to keep the heat down is good. What would be the ideal temp to run the engine as measured at the intake manifold? Is too cold bad?

Tim T.

cpqtim, the Crane Offshore spring number is 99896-16. The Comp spring number is 924-16, and you will need rertainers for the Comps #741-16, and locks-didn't look up that number. You can get all your parts from Atlantic Racing at 1-803-329-8658. Ask for Scott or Pete. They know what we use and are very helpful-for Yankees!
We run stock valve seat angles with .080" wide intake and .100" wide exhaust seat width. Changing angles can help power, but there is a lot to be done to make that work, and I don't think it is worth it. Strongly recommend Inconel exhaust or better. Even Manley Severe Duty Stainless will come apart in a blower boat!!
Oil temp is the important thing for temperatures. Here(Charlotte, NC area), we commonly run as cool as we can for water temp, but if you don't warm the oil, you will cause problems!!!:mad:
Great Boating:D need more, just ask.

tHE 741 IN A LIGHT BOAT IS GREAT ! 1500 IS RIGHT ON THE REST
MANY VALVE SEAT WIDTH:D :D

Ok, seems like I have some answers! Only several small things before the order is placed. Are the Crane 7/16 screw in rocker arm studs sufficient and if not would the use of the Crane stud girdle be required?

Screw in studs 99152-16
Girdle 13602-1 (about 220 bucks)

If I were to have the heads machined for the full 7/16 stud is the girdle still needed?
Choice 1, screw the stud in and forget about it.
Choice 2, screw the stud in and use the girdle.
Choice 3, machine for full 7/16 stud.

You guys are great, getting this project off the ground before my wife finds out what I am up to!

Tim T.

Tim you would not have to have girdle but it would be safer to drill for full stud with the 741 cam,or 1500's

It sounds like you have more than enough info to make the right decision. I ran cranes 168761 in my 60 over 502's(8.6 comp) with good sucess at 6 pounds of boost and stock iron head with a bowl job, 420 b&m(no intercoolers) and a pair of modified 750s we pulled an honest 700+hp and over 700 pounds of torque at 5800. These motors were far from lazy. 230-236/ 598-610.

Good luck,

Mike

Obnoxious Thundr,
If you have the opportunity, try the 741. You will be glad you did!!!

Tim,
the 741 is the way to go. I had it my 502 and liked it very much

Like you said, Crane reads off a sheet when you call them. I called to see what they would suggest for my 598 (out of curiousity) and that's the cam they said to use.
I said on a blown 598???!!!!
"oh ya, you'll have great torque...blah blah blah"
I just said "ok, thanks" and hung up because I knew there was no sense in arguing.


DAVE

Just for kicks does anyone have a solid roller recommendation for this motor? I cannot relate to these hydraulic roller cams. I have never run one. I know a hydraulic flat tappet cam in the 244 duration at .050" and .550" lift is a pretty healthy cam, but if the same cam were in a solid roller it would be real wimpy. Maybe this would be a better scenario. I run a 272/280 duration cam @.050" with .714 lift on a 112 + 4 installation in my 498. What hydraulic roller would give a similar shaped tq/hp curve and control my cylinder pressures generated by 13.2:1 compression just as well and still idle. I am not buying a hydraulic roller anytime soon, I am just trying to learn. I currently run the motor over 6000 RPM and if that is a problem with hydraulic cams lets say I can live with 5700 or 5800 RPM. How much HP diff?
Thanks
Craig

Dave,

I know what you mean about the "reading off a sheet". I am sure that there are some very competent people there, just depends who you get. When I was quizzing them about the merits of the 741 vs. the 731 I was very clear I was running a blower. He told me the 741 did not have enough compression for the 741 and if I were to raise my CR to about 9.75 I might be ok. Lets see 9.75 to 1 with 5lbs. boost. How long would that engine live?
Tim T.

It would not live long on pump gas !!!!!
The 741 is killer for a blower we have used countless ,for real !!

Advance it 4 degrees and hang on ,you need to make about 7 lbs of boost and pump gas The blower will handle the comp. issue ,the guy must not have heard you say blown motor :D :D :D

Tim,
FWIW, Mine was installed straight up. 0 adv.

One word of experience, when I installed the new timing chain/gears with the adv and ret keyways, I was geeting a very fine oil fling from the balancer area. 2 yrs of looking for a leaking balancer seal or leaking timing cover gasket, only to find that was not it. Oil was finding it's way past the keyway somehow and out the balancer. After you reinstall the balancer, fill the key way with RTV before you put the washer and crank bolt in. No more oil flinger.

Vette,
For the 502 cube blower motor, a comperable solid roller cam, in my opinion, would be the Crane 138551.
It's a 238/246 112 .595/.615
Open/close @.050:
Int/Ex
12/46
60/6
Compared to the 741 hyd roller:
236/244 112 .610/632
11/45
59/5

Now, for your motor:
If it were a Gen 6, the biggest one in the catalog is:
168771, 240/248 114 .621/.632
11/49
63/5

For a Mark 4 block however:
The biggest one in the catalog is:
139661, 256/264 114 .632/.632
19/13
71/13

I think the 661 aughta do it
:D

DAVE

Wette Vette/

A couple years ago I ran the Crane 13R0003216 solid roller , 112, .714/.714, 262/270 with 1.8 rockers and made 750 @6700 in a 500 in natural motor, w/big chief heads. Went to a Crane 13HR00036 hyd roller with 112, .632/.632, 264/272 and 1.7 rockers and made 650 @5400 in same motor. Crane purposely tried to duplicate the soldi roller performance in a hyd and this cam did real well for a hyd roller.

My 502 with dart 360's with the combustion chamber worked and bowl ported by JimV with the 168771 a 250 blower 2-750 holley blower carbs made 700.0hp @5800 the brake was .55. This is a stock merc dist. and a msd 6, 30 degrees of total timing. This was 6.5 lbs, the static comp is 8.3 to 1.By the way the crane guy told me any Hyd. roller with .575 lift using 1.7 rockers needed to use aftermarket roller lifters. I have the carbs and linkage and top plate for that blower for sale. Good luck with your project. J

I think the tale is told more in the duration numbers @ .100" and .200" lift when comparing solid vs. hidraulic rollers with the same duration @ .050.
Bob,
What kind of compression ratio and heads were you running on that 500"? That is the closest combo to mine I have seen where someone has dyno numbers. As I mentioned I run 13.2:1 compression, Dart 325 pro1 heads (ported), Merlin single plane intake with an adapter and a Nickerson stage 5 1050 (1175 cfm).
Thanks,
Craig

I have 2 fresh Lunati p/n 50235RG roller cams for blower application cheap if anyone is interested.

Wette Vette/

Motors were actually de-tuned ex Merc Class 1's. 3.92 stroke, 4.530 bores, 6.535 rods, 9.5:1, Dart 14 degree big chief heads. The heads really don't even begin to work until you get .700" plus lift cams and they like 6000+. But they did ok.

Those class 1's must have been awesome!!! Was that the cam Merc ran with high compression or did you change it?
Thanks

What is the effect if you put solid rollers on a cam ground for hydraulic rollers? Anyone ever do this?

Herbert cams are ground for either one.

Hello, Guys,
Solid lifter cams, roller or flat tappet, have an acceleration ramp to get things moving. The ramp is usually several degrees of rotation and equal in lifter rise to the lash divided by the rocker ratio. The same is true on the closing side. Hydraulics do not need this as the hydraulic part takes up the initial shock of the movement. A solid lifter on a hydraulic cam will have no acceleration ramp to soften the blow to the valve train. This can cause rapid wear-kind of like striking the valve train with a small hammer each cycle. A hydraulic lifter on a solid cam will have a long duration at very low lift. Both are problems, both have been done with varying results. If you didn't need different cams, they wouldn't make the investment in the two designs.:D
WETTE VETTE has a good point also in that the numbers at .100" and .200", etc. are very important in the way a cam acts. Most manufacturers will give you these numbers in their catalogues under lobe specifications. Books are written on this subject:eureka:

Wette Vette/

We changed the cam when we went to lower compression. The Merc cam originally had lifts of .759/.714 with 1.7 rockers, the motors actually had 1.8's. Duration with 1.7 was 266/274 at .050. When they spent their time up around 7000 that's what they need to make their hp. I am setting up some small blower motors and I going to run a solid roller .678/.651 with 254/262 at .050 and 112 sep.. It's not a wild cam and I had great lifter life with them last year. From a hp standpoint it's not supposed to be as good as the 420 lobe cam (.714/.714) but lifter life is better. Good luck!

Bob, Isky has a cam 250 intake, 270 exhaust that will give you 50+ horsepower. Talk to Ron Iskenderian. Just trying to help. This cam is pretty easy on parts, too.

Blown 1500,
I have the above mentioned Lunati cam in a 502 supercharged Dart heads done by Jim V running about 6psi. In your opinion would the 741 Crane cam be worth switching to?
Thank You

Liquid Kroozir, I didn't understand which Lunati cam you are talking about. Please specify which one, lift, duration @ .050", and separation and I will tell you what I think. I don't have a Lunati catalogue at home. Need specs on engine also.

Blown 1500,
cam part #54899. 578 in/ 595ex 114 lobe seperation 232 in/242ex at .050 lift. Engine was a HP500 carb.Put Dart 310 cc heads bowl ported , exhaust ported, chambers opened up to 127cc. B&M 420. Cam is ground 4 deg. advanced. Grind #RRB1-232-242-A. Total timing 30 deg. No innercooler.
Thank You

Are the Crane hydraulic roller cams manufactured with smooth, easy going ramp speeds so that they are EASY on lifters and the entire valve train???

Right now I have Crower hydraulic roller cams and they have very easy, slow ramp speeds to help the valve train live. These cams are very simular in comparison to the Crane 741 as far as duration @.050" go. (236*/244* on 114* lobes) advertised duration is: 300*/307*

Actually, I prefer the slower ramp speed cams to help the valve train live longer and I am willing to sacrifice a few HP in order to do that, but was wondering how Crane's ramp speeds compare to a Crower.

Liquid Kroozer, the 741 will wake up your motor. A custom grind even more.
Kaama, the Crane and most other manufactureres have easy enough valve action that you shouldn't have any problems with cams in the ranges we run in these boats. The Crower you have is almost the same as the 741 Crane. Check the duration numbers at .100" lifter rise. If they are close, the cams are almost the same. If one is noticably longer, it has more aggresive valve action.

Blown 1500,
I am interested in a recomendation/purchase . I have a Gen 6 and would want to stick with hydraulic roller and how much if any idle quality would I sacrifice as my wife also drives the boat.
Thank You

Liquid Kroozer, I need more info. The same cam profiles are used for the IV,V, and VI. Is the motor FI? What prop, boat weight, fuel................pm a number and I'll call you.