Cam Specs
 

What are the cam specs for the 900sc merc engines? I do know that they are solid roller.

The solid roller ones come into play in the 950-1075 sci engines. I will double ck however I am pretty certain the 900 sc still used the old original flat tappet cam.

Looks like it might be the same as the sci specs.

900 SC, [email protected], 252, lift is .672
Exhaust@ .050. 257, lift is .672


I know these are the same specs are what I got from a member on the 1075 sci and do believe the 950-1075 sci all have the same solid roller.

For some reason I thought the 900 was different but evidently was wrong according to another post that provided the 900 specs. You can order the cams from bullet.

800sc used a flat tappet hydraulic. 900sc was a solid roller.

Correct. Did 900 sc use same as 950-1075 sci roller though?

i copied and pasted 900 sc cam specs from another thread. Those specs are the same as what I have for 950sci-1075sci. So evidently 900"sc" - 950"sci"/1075"sci" are the same. If anyone knows any different please post.

i did not know merc had a sc950,i thought sc850/1075,and the sc900 the op is asking about.

The part #'s for the camshafts, are not the same in merc's parts diagrams, so I would say, no , the 900sc carb engine, did not use the same camshaft , as the 1075 EFI.

The 900sc's were known to be valvetrain eaters. I wanna say they had something like 714 lift solid rollers. They used conventional rockers, basically old school blown big blocks like alot of us have. Nothing fancy.

Personally, If I was rebuilding a 900sc merc, I would go for a milder camshaft setup .

Your absolutely right Mike. Not sure why I had 950 on the brain other than having vertigo for a week now (Not fun btw) I dug into this a while back for some personal information a while back but evidently screwed up on the 950sci rather meant 850sci. Regardless if op does a Google search on 900sc cam specs there is a link to OSO dating back to 2002 with above posted specs for 900sc.

Not much info on any of those cams going past the old 525-800sc hyd flat tappet .559 lift cam that was used forever it seems.

There are a few things I'd like to add but don't want to confuse OP more than I already have.

The 800sc (not 800sci), 600sc (not 600sci), and 575sci, used the same cam. Which was a 240/240 @ .050 .559/.559 lift 110 LSA hydraulic FLAT tappet cam.

525SC, used the same 228/236 at .050 530/551 lift 114 LSA flat tappet cam, that was used in the 400hp, 420hp, and 425hp mercruiser 454ci engines.

Ok Bob.... Pop quiz... What was the 850csi cam now that the op got his answer the best we can figure anyway.

I meant MT. :rolleyes:

I dont think he got his answer yet. He was asking on the 900sc cam specs. I think the specs you gave earlier, were for the 1075sci cam.

Im so confused now lol

I think 14 apache or someone recently had some 900sc mercs in their shop, maybe they know the 900sc cam specs, or have a grind number off them?

Joe, if I remember correctly the part # differences (in part) MIGHT be due to the various cam gears they came with but I can't remember for sure.

and the sci engines don,t have a cam lobe for a fuel pump so the part number will be different.

I confused myself. What can I say. Anyway when I originally tried to help OP out this is where I got the info from however you very well may be right. They are however the same sutphen30 sent me recently for the 1075 cam specs. Lift and dur anyway. I did just read a thread that 900 sc was something around 714 lift SR also but again I read it I and can't actually confirm it. So let the mystery continue. Lol

Bullet will build what ever way you need it. Without fuel pump lobe with lobe. With or without dist gear. You name it. Good company.

i agree but the op still does not have his answer.i will make a call in the morning to get the answer if no one posts it sooner.

Hey Mike I believe it is a solid roller 252/257 672/672 on a 112 with an Iron gear .030 hot lash, but if you can call to find out that will clear this up quickly for the OP

Yes Mike that would be great. Last thing I like to do is misinform someone. I really do appreciate it. Tks
John
Btw Hope all is well.

.050 intake opens 18.0 BTDC Closes 54.0 ABDC 108* 252*
Exhaust Opens 64.5 BBDC Closes 12.5 ATDC 116* 257*

Lobe .395 @valve .672
Advertised I 290* Ex 295*

Crane PN CHB2900009
Lash .030 HOT

Thank you to everyone. That is the information I was loking for!!

if you subtract the .030 lash the lift at valve will be .642.if i were rebuilding a sc900 i would go with a tight lash cam.some think tight lash cam,s are something new but i remember using them 20 years ago.

Almost spot on what I have on cam card from bullet for 1075 also. Lift, duration as well as timing events. Cool. Tks for posting. Appreciate it.

Why is that Mike and what is it that determines normal vs tight lash on SR. I've seen them advertised and know it's nothing new but just how does that work on a SR? (Lobe profile)? Now tight lash solids rollers on a billet hyd roller cam is something we've been doing with great success for many years also zero problems.

tight lash means the camshaft,not the lifters,i am not sure but t think the lead in ramping is different on a tight lash cam vs normal lash cam,normal being .024 to .032.i recently used a tight lash solid roller cam and the cold lash is .004.try setting that with a stud girdle.

Last one I did was .002 cold

How much more on the exhaust?

I never understood the old school .030" lash cams. Way too much clearance.

If you are going to get a Bullet 'copy' ask them first what lash.

I ask for tight and when the cam shows up,,I look at the card for the recommended lash.

That was exhaust intake I set at 0 on all tight lash solid rollers cold

If setting cold u subtract .006 with aluminum heads? I always have. I know it's best to set when hot but seriously how many people really do that in real world. Especially in marine applications.

I would rather have a .030 lash cam and be able to catch it before zero. It don't mater tight or loose grind as long as its smooth running. My new cams are .030 from bullet.. And so post to live Recommended from MK.
Just used MK for a magnet. LOL

Think its - .005 intake And -.007 for exhaust..

Have you used the cam in discussion in an NA by chance? I've heard 540 plus engines like it but no first hand knowledge of.
Tks
John

From the owner's manual;

900 SC Mechanical Valve .016 cold; .020 hot.

That throws a little monkey wrench into things. assuming it's the same cam/lobe why the .010 diff unless there is something else. Also I would think merc uses a custom crane grind vs the bullet grind. Still why the difference in lash? lobes maybe slightly different I would guess.