another head, cam suggestion, post
 

There is allot of posts on cam suggestions for 454's, but I might need something a little different. I am thinking of doing some little modifications over a period of time. I want to upgrade to hydraulic roller cam's and head changes. current setup are merc 425's with large rectangle Chevy high performance heads bowl ported (088's I think).

I want to save up and add the cam and lifters first thing in the spring, then add a set of heads maybe in the mid summer, and then next winter I would like to stroke to 496's.
I am looking to get the most bang out of the 496's when finished. This might compromise a little power when it is still in the 454 stage I understand, but would it be that drastic, or will the 496 components work better with the 454 components I already have. I don't think It would hurt to go with a roller cam.

I know that the heads that would be suggested for a 454 is different then a 540 and you hear allot of head suggestions for 540's and not to many for 454 or stroked 454 (496's)

Heads suggestions, World products, Dart, Afr, my existing heads, other Chevy oval or rectangle port heads. short runners, single-dual plane intake?

Let the replies come!
Jason

Re: another head, cam suggestion, post
 

Merc made a 454-450 hp in the mid 90's. It had the same sq. port heads, Dart manifold, 800 holley, and Gil exhaust as the 500 hp. It used a hyd. roller cam, probably from Crane. Unfortuately it had a reputation as being overcammed with poor drivability. The fix was more cubic inches in the 500 hp. I'm afraid that's what's going to happen with your engine. If you put optimum components for a 496 on a 454, you'll end up with a doggy 454.

However, if you want to go ahead with the plan, these are the parts I would use to build a hot 496. Afr 305 rect. port heads, Dart single plane, Holley 800-850, Crane 731 hyd. roller cam or custom cam with a little less exhaust duration. Flat top pistons will give you about 9 to 1 compression if the block is zero decked. A 10 quart oil pan and larger oil cooler and lines are required if you want it to last very long. Good luck.

Re: another head, cam suggestion, post
 

I see that the 731 is a little hot for my 454, but good for the 496. It seems that the 721 would be good for a 454 but would need to go to the 731 for 496's. my engines are .030" over but I don't think that will make any difference. Would I be better off to keep the heads I have on now with the 731 to keep it somewhat restricted. I know these heads can make good HP but everyone said it is at 7500 rpm.

10 quart oil pan? Do I have insuffecient oiling now? I know this is probably for heat displacement. But I use 7 quarts of oil now per oil change and thats not draining ay hoses.

Re: another head, cam suggestion, post
 

Gm sq.port and Afr 305's have the same size ports but the Afr's flow about 30% better. I don't think the Afr's will cost you much low end but will be worth an extra 50 hp at top end on the 496. A lot of $$$$ however. Neither is a good choice for a 454 but they will work. An oval port head like an Edelbrock would be better there.

As far as the oiling system, you will be adding at least 150 hp. You will have to make modifications to the oil system to remove a lot more heat. A 10 quart pan is a good common size. A Melling M77HV pump is my favorite. Replace all oil fittings and lines with 1/2npt to -10. A number of places sell a 3 x 18 oil cooler for about 200.00. This may sound overly complicated and expensive but if you don't do it, your engine won't live.

Re: another head, cam suggestion, post
 

do you think I'll have less performance with the head and cam change to my 454's then just running my 425's. If the performance would be the same or a little better with just the heads and cam I would be fine with that. I am looking down the road at the big picture. I just don't want to get into the bottom end of the engines this year. and 150 hp would be good was optimistically thinking maybe 100. 575/ side would be nice.

Re: another head, cam suggestion, post
 

It depends on how high you want to wind that 454. I bet it'll make over 500 hp but it will be at about 6000 rpm. And it will be a pain trying to shift and dock. The 496 combination will be a little tempermental also but you wanted a powerfull 496.

Re: another head, cam suggestion, post
 

Rookie,
Save your money and do the engines complete at one time. You'll save money, your time, and boating time if you do.

Re: another head, cam suggestion, post
 

cstraub, i agree.
What cam, head, intake, compression, carb combo would you recomend.
I would like to use the existing carbs, my Holley Barry Grants.

Re: another head, cam suggestion, post
 

First what is your goal?
Next what is the budget?

An engine combination must satisfy the budget and achieve the goal.

Re: another head, cam suggestion, post
 

i have a 496 just back form michine shop will sell $7000. edebrock alm heads roller cam 14qt pan etc have all parts need to be assamble 314 265 3876 john do not have boat for motor.

Re: another head, cam suggestion, post
 

Rookie, with those Merc 425hp engines you have they should have the GIL exhaust manifolds on them although they may actually say "MerCruiser" on the sides of the manifolds. If you have those as Patriyacht has mentioned, then you are pretty much good to go with a cam, and hi-perf upgrades/mods. It's got to have an exhaust system that breaths well such as a GIL exhaust to help realize your cam/head, etc, mods----and having the GILS is at least a significant chunk of money that you DON'T have to spend as you do your mods. Have fun. :)

Re: another head, cam suggestion, post
 

Kaama, I have Stainless Marine.

Re: another head, cam suggestion, post
 

cstraub,
1. goal would be 100-125 HP increase. 2. budget is unknown as of yet. I wanted to get info from people to get a realistic amount to see what I needed to budget for. 1. price for a specific roller cam and lifters needed for either 454 or 496, 2. heads $1000-$1500 3. stroker kit $1200-1400 and machine work $400-600. (which I see that you had broken down on another thread concerning 496's).

But, after doing some reading on some other stroker threads it might be bigger bang for the buck to do the roller cam switch and stroke it, then to do the roller cam switch and new heads. My heads are bowl ported and after doing some research they will flow but are just overkill on my 454's. from what I have read.

Re: another head, cam suggestion, post
 

100 hp will not make your boat go much faster if at all unless its an 18' jet or v drive!Ive done what your trying to do in a different way and it wasnt worth it!Save all your money until you can go big!Youll have more fun boating and using some of your money on gas untill youve got the dough! :D

Re: another head, cam suggestion, post
 

JJONES, 100-125 x 2 = 200-250 HP
Thats no difference? oh.

Re: another head, cam suggestion, post
 

You Might Gain A Few Mph But Not Much,if Your Boat Is A Big Deep Vee,it Takes Alot To Push Them!then The Next Thing Youve Got To Think About Are The Props, Once Youve Got That Figured Out Youll Need Stronger Drives!theres Alot That Goes Into Makeing A Boat Faster Than A Couple Hundred Horses!i Just Upgraded My Boats Engines Maybe 150hpx2 And It Only Made A Slight Diferance Once I Found Props That Worked Ok!believe Me,if I Could Take It All Back,the Money And Hard Work I Would And Save Until I Could Make Big Hp!what Kind And Size Boat Are You Working With?

Re: another head, cam suggestion, post
 

JJONES, I'm thinking everyone might be right, I liked the reliability factor that I had last year, oil, gas and go. I did burn down some valves last year but that was cause the carb floats went lean, out of adjustment. caught in time and only had to weld the head and resurface, new valves and springs. it isn't to deep of a vee i don't think, scarab panther. I would stay in the hp ratings of the drives, 550hp on a twin 6800 lb boat shouldn't shouldn't be to much. Maybe I'll pull the engines and just put new gaskets in to stop the oil leaks and leave them together. Just had some money laying around that I would like to use on some upgrades.

Re: another head, cam suggestion, post
 

I Used To Own A Scarab Panther,good Boat,probable Has Borg Trans With Trs Drives,it Shoud Be Spinning Cleavers Also.when I Had Mine I Blew An Engine,ingested Salt Water!i Ended Up Building Two New Engines Hence I Wanted More Power And Both Engines To Be The Same.i Started With The Same Setupas The Boat Had In It But I Increased The Com,used Big Valve Heads,demon Carbs,edlebrock Manifolds,a Cam To Complement The Comp And Heads,hei Ign,power Torque Exhaust,eliminated Circ Pump And Used Crossover!what A Differance!i Did Blow A Trans Though!i Also Tryed Alot Of Differant Props From The 21 Cleavers That It First Had To Bravo 1 23 All The Way Up To 25 Mirageplus,and Each Time I Went Back To The 21s!the Hull Seemed To Like This Set Up The Best!i Cant Remember The Specifics Of The Engines But It Was Great,i Did It All At Home On 2 Stands For About 8k!believe Me It Was A Rocket After All The Work!

Re: another head, cam suggestion, post
 

The OEM heads on the mags are plenty for a 496CID engine. Adding a .250" of stroke can really broaden the powerband giving you more useable power all over. Unless you want to knock off 140# off the back end of the boat I would use the heads you have since they have some work already.

For your power goals a nodular cast crank will work just fine. These are very budget friendly and will easly support 550HP. This along with a cam change would make for a couple of nice pieces that would give you some long hours with low maintenance.

Re: another head, cam suggestion, post
 

JJONES, thanks for the info on the cleavers. I run quicksilver 25's at 5250 @ 70-71mph gps. i tried some hydro-motive 25's but could only get 4800 out of them. I have a set hydro 24's that I am going to try next summer. did you have any problems planing out with the cleavers. I had problems planing with my quicksilvers when the cupping was washed out, but it would also spin 5400 @ 73mph. I will be looking for some cleavers to try out. and yes the 425 TRS package. I think if I can get 100-125 extra ponies/engine, and my prop slip from 17% to 12-13% I should be in the mid to upper 70's that is the goal, shoot it could touch 80.

Thanks Chris, that is what I wanted to hear about the heads. Do you believe that stroking these engines, with a cam change, and the existing large rectangle bowl ported heads chevy heads will be over the 500-525hp range? you still haven't brought up a cam selection that you would feel would work for these mills, the 731 does sound like a good choice. would I have to worry about piston clearance? I know my heads are 118cc, but they have been milled down to 114.5cc. the compression is high 175lbs on one engine, and 185-190 on the other.

Also I was reading up on some intake threads, and was thinking of going with a single plane intake, I have a friend that has a 496 with a brodix single plane that seems to work well for his setup and runs good on the top end. I have Weiand stealth dual plane intakes and was thinking of upgrading. I have no issues with low and midrange twins in a relative light boat. but at 5000 rpms it hits a wall, it takes forever to get that extra 200rpm's.

Re: another head, cam suggestion, post
 

Sorry about my last post,I must have some setting anabled that changes all the letters! Sorry it was so hard to read!

Re: another head, cam suggestion, post
 

Rookie, the Stainless Marine exhausts are fine....and about the same with the GILS as far as performance goes. And like I said, that's money you DON'T have to spend! By the way, I would have to say that adding an additional 125hp per engine should push your 30' Scarab faster---how much faster remains to be seen, but it's always harder, and takes more HP to go faster in a boat anyway. Of course it's always worth hearing experiences from others, but you're ultimately the one who has to decide it's worth doing.

Re: another head, cam suggestion, post
 

Dont discount those Weiand Stealths so easily. They are way underrated. I ran a pair of real healthy 560 hp engines with them up to 6000 rpm and they did fine. Actually did better than the dart single plane up to 5400 (and idled at 600 rpm, the dart wouldnt).

Re: another head, cam suggestion, post
 

The OEM heads vary on the castings with core shift quite a bit and this effects flow. So I don't know what your heads are doing. General rule of thumb though out of the box you need about a 10 to 12 degree split crutching the exhaust. BBC are very forgiving as far as Piston to Valve clearance so PV should not be an issue.

Intake on your mill I would go an air gap.

Re: another head, cam suggestion, post
 

I am doing the same setup on my boat right now. With the same heads. But I am putting reflashed 502 mpi injection setups and stellings headers. did every decide that the 731 cam was the ticket?