PatriYacht

Because of a nasty water skiing accident, my boating season is ending early. That means the winter project time is starting early.

Last seasons modifications included freshening the 540 shortblocks and adding AFR 335 cnc heads. The engines already had Crane 651 hyd. roller cams, Holley 1050's, Merlin single plane intakes and MSD ignition. The oiling and cooling systems were also upgraded by plugging the oil bypass, adding Mellings HV oil pumps, Dooley 8 quart oil pans and adding Eddie Marine 3 x 16 in. oil coolers. Oil pressure sender was moved to the front of the block to get a more accurate reading.

The result from all of this was mixed. The boat's top speed went from 68 to 73. However the idle quality went right in the toilet and the engines started reverting water like crazy. Apparently the huge increase in air flow with the new heads acted the same as a larger cam. I put a bandaid on that problem for the rest of the season by conveting my tailpipes to dry and dumping the water over board. I tried to get some idle quality back by locking the distributers at 34 degrees but then the boat started eating starters about once a week.

One thing I did like about the boat was the great cruise speed. Spinning labbed 24 Bravo 1's with 1.36 gears the boat ran 51 at 3500, 60 at 4000 and 73 at 5000. At 60 the water temp was 150 and oil pressure never moved from 60 lbs. I know I should prop down to get more r's out of it but I ran out of time for testing. Also I kind of like the relaxed cruise.

So who has ideas for what I should do this winter? One that I like is a smaller cam with the same lift as the 651 (.630 intake and exaust) but less duration, say about 236 intake-240 exaust @ .050. Then maybe I could unlock the distibs. and stop eating starters. Thanks for any ideas.

Cord

iTrader: (2)

If you want to lock the distributor, then ad a retard for starting. MSD has them. I'd also back down to the 741 cam. I'm wondering if you wouldn't be better off with some smaller heads too. Somebody else would be better qualified to answer that though.

PatriYacht

Thanks Cord. I went with the larger heads thinking that I might supercharge in the future. After using these I am inclined to think that the 315 cnc heads are enough for any 540. A lot of people are saying that the AFR exhaust port is so good that you should have more of a single pattern cam than a standard Chevy cam . Have you ever had an existing cam reground?

RLW

For what it's worth, I went with the anodized AFR 305 CNC Chamber heads for my Dart based 540. I didn't feel it was worth the extra money for what the 315's were going to give me in regards to the flow numbers.
I am also running a custom ground Comp Cam. This was determined by my builder as I am far from knowledgeable with engine building.
.630/.635 valve lift, 112 LSA, 236/[email protected]" hydraulic roller.
Single Plane Merlin with 1050 Nickerson.
Engine produced 700 hp@5300 rpm with 700 ft/lbs@4900 rpm on the dyno.
We were still making horsepower at increased rpm's.
At 3000 rpm, the motor made 615 ft/lbs of torque and 352 hp.
This motor has terrific midrange acceleration.
If I were to try anything different, I would go with a 4150 series Carb versus the 4500 Dominator. Also need a better set of exhaust as I am still running the Stainless Marine Hi-Torque.
Presently, my idle quality is good but I think a 900-930 cfm or similar might be more efficient.
I am also running 34 degrees locked and have an MSD Digital-6 Plus ignition. Probably a little overkill but I liked the 20 degree start retard feature. It goes to full locked timing at 800 rpm and will not retard again until it hits 500 rpm. Lately, I have disabled the start retard feature and have been starting the engine at locked timing with no problem. Once in awhile I get the slow groan but rarely. Part number on the MSD is #6520. I also use the MSD Blaster HVC coil, part #8252.
Hope this helps.
Russ

PatriYacht

Thanks Russ. I got your e-mail with the cam numbers. I may order a couple of those. I called Crane and asked about custom cams and they tried to steer me to the 741 cams. You still find the idle is better with the timing locked? That's a lot less duration than what I have.

CMS Racing

I would change the heads their to big for the rpm vs the ci of the engine I would use a cam around 242.int and 248. exh at .050 with around .600 lift to make valve train live. would replace the carb with 950 holley the package should idle resepctively and make good power 650 hp this is a package that I sell at my shop and we have great relibiaty whit CMS RACING ENGINES 410-335-2226

RLW

CMS,
Let me see if I understand what you are recommending. You want to leave the intake and exhaust valves open longer with less lift versus shorter duration and higher lift. I am not discounting what you are saying just trying to get a grasp on cam geometry.
Thanks!

PatriYacht,
The locked timing was a recommendation by my engine builder and Nickerson. I use to run 29-30 degrees locked on my blower motor. It idled better than my present 540. Like I said it idles good. Not like EFI but good. This cam thing has me thinking once again.
Russ

articfriends

iTrader: (1)

Russ,do you know what your flow #'s are on your heads? I'm freshening my 540 this winter and might change heads(i'm running the merlin vr's with 320 cc intake ports),Smitty

RLW

Artic,
Check out the www.airflowresearch.com website.
It has everything you are looking for. There are charts to compare the numbers. Look under the 305/315cc Magnum BBC section.
The price difference between the CNC Ported 315cc and the CNC Chamber 305cc is $518.00. Not a huge amount of money in the grand scheme of engine building.
Russ

articfriends

iTrader: (1)

Russ,thanks,there flow #'s are impressive!!I am going to have my merlin's flowed when they come off this winter and make a decision,Smitty