BBC cam question up grade XR288HR
 

I built my engines from a 454 Mag 365 HP set up. I used the Lunati Vodoo cam #10110704 flat hyd cam with 233/241 @.050 with a 110 lobe center. This equals out to a 17 deg overlap. I want to up-grade to roller cams and I am looking at the Comp Cams 11-433-8 XR288HR with 236/242 @ .050 with a lobe center of 110 which comes out to 19 deg of overlap. I am running a modified Gil dry exhaust (the pipes were cut and the water mixes right before the transom at the exhaust tip). I had zero reversion problems with the Lunati cams, would the comp cams cause any issues with 2 more degrees of overlap???

i,m no cam expert but i would be afraid to use any cam with a 110 lsa and gill exhaust unless it was totally dry.

lol, I like the preface, who are the cam experts?....Guys like you that have proven Dyno HP.

I'm no expert at anything, but I've read too many instances of reversion with even a wider lsa. My current cam has 110lsa with headers that dump at the tips and no evidence of reversion, but I'm switching it out this winter to comp cams version of the 525EFI cam just to be safe. As a side note, the 110lsa gives a nice raspy idle that sounds like a quarter mile gasser that sounds impressive at the dock but can get tiresome in long idle situations. I like open pipes but the gf has envy of the quiet ski boats that roll up to the docks. It may be easier to just get a new gf in my case though.

Id try to find a 525 cam, being ground on a 114 split vs the 741 at a 112....if memory serves me....jmo

Tons of guys have ran the 741 crane with wet exhaust. I ran it with short stainless marine risers, no reversion. The 741 has 16 degrees of overlap. Lots of variables when it comes to whether or not it will revert. A simple adjustment of base timing can make a difference.

If you know a good tig welder, extending the pipes thru the transom is not a big deal.

How about a Lunati 20010671. Duration moves up and a bit more lift. Still 114 lsa.

i have a 525 efi takeout cam that i might sell,the only difference from it and a crane 168741 is the lsa,114 on the efi cam and 112 on the 168741.i have used quite a few 741 cams and did exactly what mild thunder said,extend the pipe through the transom.

their is a reason mercury marine uses a crane billit core camshaft and it is not because they like to spend more than they need to.i won,t install a cast core hyd roller camshaft in any high performance marine engine,same as mercury marine.

^^^ Is the Lunati a cast core?

Im interested in that cam if it becomes available.

yes sir.

Crane 731 will be good to about 5500 rpms on a 454. https://www.summitracing.com/parts/crn-168731
If you want more, go with a 741 or 525EFI cam https://www.summitracing.com/parts/crn-168741

Do cast core cams break often? It seems the damage would be terrific in that event.

im running the comp version of the 525 efi (114) it has a nasty sounding idle, but it's tame when it's time to dock.

Lets say you had 3 cams. All were 236/244 duration, same lobe family, same lift, same 4* advance ground into them. Only difference, was their LSA's. The 114 may peak at 6000, the 112 at 5850, and the 110 at 5700 rpm.

The 110 LSA version of that cam, will have the most overlap. However, the 114 version, will have the latest closing intake valve.

You can can call Lunati, they will grind you any of their cams on a Billet core. I wanna say the cost is around 400 for the billet stick with iron gear. Same for Howards, comp, etc. The profiles are in their systems, its just a matter of core selection. I personally would spend the few bucks more for the billet camshaft.

Is duration related also to cubic inches when you looking at cam choices? I be read the advertisement in Summit/Jegs/Teague and they all have CID and CR ranges. I've noticed more duration seems to correlate larger CID to an extent. Cams are a black art to me so flame on:bananalove:

I spoke with Lunati the other day and that was their pick for my iron headed 565s. Called around a few others and similar specs lsa may differ between 112-114 and duration/lift moved a small amounts. All except Crane who recommended me to keep my 741 cams in the engines. I even spoke to a friend who had Bob M spec his top ends for his 540s years ago (afr heads, etc) and his cam specs were very close to all the recommendations I had received. Only real reason I'm looking as my engines run out of steam around 5k-5200 no matter how I prop the boat.

Chris, duration is directly related to the rpm capability of the engine. It does not matter if it's 8:1 compression, or 10:1 , or 12:1. The engine needs xxx amount of duration to reach a specific engine speed

Cubic inch absolutely matters. Stroke change is the biggest difference , more so than bore size.

In my opinion, the 741/525efi cam, is simply too small for a 565ci. At least one that is trying to spin say, 5700-6000 range. Heck, mercury uses that cam in the 525efi. That's a 502ci that spins 5000-5400 range. Can't expect a 565 to make power higher than that , with same camshaft. We are pretty limited with valve lift in marine engines, so when lift is limited, duration is even further needed to reach the peak rpm goals.

The problem I've seen with cam companies , is often they are extremely conservative with duration. The water reversion class has been taught to them, and once they hear marine, immediately it's wide lobe separation and short durations. Most aren't familiar with fully jacketed tailpipe options, or say, a pair of 565s going in a 35 fountain or similar. Not every boat is a 30ft single engine deal that weighs 10k lbs.

On your builds Chris, i firmly believe a cam swap , the new parveys designed manifolds to replace the old gil style, and you'll see the engines wake up from 3500 to wot. They will be uncorked so to speak.

My cams are similar to the 525efi cam. With a blower on top, installed straight up, there were fizzing out at 6000ish. That's in a 468 with a blower. In an NA 565, not surprised they aren't pulling so well above 5200

the 525 cam or the 168741 will pull past 5400 in a 454 or a 502 if everything else in the engine is set up to do so but i agree with joe,in a 565 that cam is to small and the engine will not pull much over 5000 rpm.

Surprised no one has mentioned the 500 EFI cam yet. 230/236 .598/.610. This cam works good in my 454's

Yeah that 630 lift is a little scary with dogbones. My next attempt is with a ZZ cam I got free. Dry to tip Gils.

Believe someone mentioned it, but that Lunati 20010671 looks like a very nice cam.

• Advertised Duration (Int/Exh): 301/311
• Duration @ .050 (Int/Exh): 242/252
• Gross Valve Lift (Int/Exh): .640/.629
• LSA/ICL: 114/112
• Valve Lash (Int/Exh): Hyd/Hyd
• RPM Range: 3600-6800
• Includes: Cam Only

Part Number: 20010671
Previous Part Number: 54871LUN

Jobber Price: $285.08

Your existing hydraulic flat specs at 233/241 on 110.
And you are considering a hyd roller at 236/242 on 110?

Your Voodoo has fairly fast ramps for a flat hydraulic and 554/572 lift.
The Comp HR has fairly slow ramps for a HR and 521/540 lift.

Explain to me what sort of improvement you expect from the HR you have selected.
Listen to the crowd here - tight lobe separation does 2 things - makes the torque plot peakier - encourages reversion at idle.
Wider lobe separation does the reverse - flattens the torque plot - discourages reversion at idle.

I absolutely LOVE a tight lobe center in a stickshifted street/strip car. Throttle response is awesome, power comes on like gangbusters - DEFINITELY "less civilized" than a wide lobe center.
We are running a flat hydraulic on a 104 lobe separation in a Mopar 440 and it is a brutal dude compared to a similar B-body 440 that is running a 112 separation cam with similar compression, heads, induction, and duration.
But cars don't have water reversion problems.