454mag top end rebuild
10-10-2013, 08:03 PM
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454mag top end rebuild
Hey All,
As the title says redoing top end in my 89 Scarab III with 454mags, 460hrs. Currently, the rig tops out at 54 at around 4500rpm. Cruises at around 35mph at 3600rpm. This is gps on speedview phone app so not too sure about accuracy. What I know for sure are my compression numbers:
Starboard: Port:
1 145 2 140 1 135 2 140
3 140 4 123 3 130 4 145
5 143 6 145 5 135 6 89
7 139 8 148 7 133 8 139
If all goes as plan I should have my wood gantry/hoist built this weekend and motors pulled by next weekend. I will be working with Marine Kinetics on the cam. My pockets aren't deep so I'm all over the net looking for those sweet deals and then researching to see if it will work. I was going to leave stock heads and redo valves and worn components but came across what I think is a good deal on some Brodix heads.
BB2 plus with the 312cc intake runner and 119cc chamber bare heads for $1170 a pair. I know this is another rect port head and it's not quite the most optimal on 454 but it's got to be better than my current heads, right? And, these can be milled to increase the static comp.
The other more optimal set are the Brodix Race Rite Ovals. I found these for $1000 a pair but they are Brodix's "overstock" heads with 127cc chambers.(they messed up when casting these and pushed the seats too far into the chamber). I called Brodix and they said the most these can be milled would be to 119cc.
I can go on and on about all this but would like to stop here for now and ask your opinion on these heads and what would be the best approach on THESE heads and my stockers. The performance gains I'm looking for is overall higher mph at cruising and WOT RPM's. I don't pull anyone with this boat just cruise, anchor and beach.
FYI, through the help of this site and a few others I found enough knowledge to assemble a work of art a few years back, a stroked 496 that dynoed at 555hp 6000rpm and 578tq at 4000rpm
Thank you all in advance for reading this long winded intro and for your consideration.
Jeysson
As the title says redoing top end in my 89 Scarab III with 454mags, 460hrs. Currently, the rig tops out at 54 at around 4500rpm. Cruises at around 35mph at 3600rpm. This is gps on speedview phone app so not too sure about accuracy. What I know for sure are my compression numbers:
Starboard: Port:
1 145 2 140 1 135 2 140
3 140 4 123 3 130 4 145
5 143 6 145 5 135 6 89
7 139 8 148 7 133 8 139
If all goes as plan I should have my wood gantry/hoist built this weekend and motors pulled by next weekend. I will be working with Marine Kinetics on the cam. My pockets aren't deep so I'm all over the net looking for those sweet deals and then researching to see if it will work. I was going to leave stock heads and redo valves and worn components but came across what I think is a good deal on some Brodix heads.
BB2 plus with the 312cc intake runner and 119cc chamber bare heads for $1170 a pair. I know this is another rect port head and it's not quite the most optimal on 454 but it's got to be better than my current heads, right? And, these can be milled to increase the static comp.
The other more optimal set are the Brodix Race Rite Ovals. I found these for $1000 a pair but they are Brodix's "overstock" heads with 127cc chambers.(they messed up when casting these and pushed the seats too far into the chamber). I called Brodix and they said the most these can be milled would be to 119cc.
I can go on and on about all this but would like to stop here for now and ask your opinion on these heads and what would be the best approach on THESE heads and my stockers. The performance gains I'm looking for is overall higher mph at cruising and WOT RPM's. I don't pull anyone with this boat just cruise, anchor and beach.
FYI, through the help of this site and a few others I found enough knowledge to assemble a work of art a few years back, a stroked 496 that dynoed at 555hp 6000rpm and 578tq at 4000rpm
Thank you all in advance for reading this long winded intro and for your consideration.
Jeysson
10-10-2013, 08:05 PM
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I will be upgrading my account so I can add pics to show the dyno from previous build and progress of current build. Wait till you see the hoist I'm building to pull the motors.
10-11-2013, 01:21 PM
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Thanks for the info Borgie. I think I just found some bare Race Rites for the right price. Just waiting to hear back from BM on the oval or the rect port. Rect port is a 294 runner and oval a 270.
10-11-2013, 06:29 PM
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Heres a video of my buddy's Scarab III that had 454 Mags originally. TRS drives. I helped him do some engine mods. Boat runs mid 60's on GPS.
http://www.youtube.com/watch?v=X7olqjFN8p8
Engines stock mag bottom Ends.
Stellings headers
Crane 134561 Flat Tappet cams
Roller Rockers
GM Rect port heads, stock 454 mag heads rebuilds on them.
Professional products Hurricane single plane intake manifolds
Holley 750CFM Double pumper
Stock Merc Ignition.
Boat has a very distinctive idle. He's very happy with the setup. He's turning 22p 4 blade Hydromotives to around 5300 I believe.
Stellings headers
Crane 134561 Flat Tappet cams
Roller Rockers
GM Rect port heads, stock 454 mag heads rebuilds on them.
Professional products Hurricane single plane intake manifolds
Holley 750CFM Double pumper
Stock Merc Ignition.
Boat has a very distinctive idle. He's very happy with the setup. He's turning 22p 4 blade Hydromotives to around 5300 I believe.
10-13-2013, 08:35 PM
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I would go with the stock rect port heads you already have and spend the money saved on top quality valves and an all roller valve train. For cam I run the 139011 crane in my 454s and have been very pleased.
10-13-2013, 09:49 PM
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Take a look at this article. The cam really could be used in many marine apps from the look of its specs. But more importantly you will notice how easily they made close to 600hp with ovals. Put more cam in it and obviously 600+ is more than doable.
http://www.carcraft.com/techarticles...s/viewall.html
Yes, they are using a 496, but even a 468 with ovals would knock down some quite impressive numbers.
MILD THUNDER: That's a nice setup you posted as well! Very cool boat. I do have a question though. Why did he use a single plane intake? Seems like boats that run under 6,000 rpm would pretty much always do better with a RPM air gap. With the singles giving up quite a bit of low end torque and drive ability, and only benefiting a few hp up top. Just curious.
http://www.carcraft.com/techarticles...s/viewall.html
Yes, they are using a 496, but even a 468 with ovals would knock down some quite impressive numbers.
MILD THUNDER: That's a nice setup you posted as well! Very cool boat. I do have a question though. Why did he use a single plane intake? Seems like boats that run under 6,000 rpm would pretty much always do better with a RPM air gap. With the singles giving up quite a bit of low end torque and drive ability, and only benefiting a few hp up top. Just curious.
That article has some good info. Realistically , a 500 inch big block with 10.5:1 compression, should make those numbers with a good set of aftermarket heads. I'd like to see them test a 308 iron eagle against the other heads.
10-14-2013, 01:00 AM
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MT - good running boat your buddy has in that video. I miss that skyline. I grew up in NW Indiana just 55mi from downtown CHI. Live in Vegas now but with I could enjoy Lake michigan in my boat.
Borgie - thanks for that article. Yea, I've been looking everywhere for info on this. If the change happens it WILL be the Brodix Race Rites. I'm trying to find some comparative data on the rect/oval port race rites. They both flow about the same but different shape so........what's the deal here? I'm almost positive I wouldn't even feel the difference between the two but I figured if I'm buying new might as well try to find the best combo I can afford. Also, switching over to oval would require me to switch intakes now also instead of later. A necessary evil ($$) I suppose if I want the best combo. Already picked up some blue holley 800's so I'll need an adapter for the time being if I keep the stock intake.
BT - Thanks for the input. That is still a possibility. I was already set on new valves and definitely replacing worn parts, i.e. springs, rods....I figured if I can get my heads back to a stock quality standard and upgrade the valve train components I would be happy. I don't pull any skiers/tubes and I don't race anyone and don't gun it out of the whole but I do like to open it up while cruising. She comes on plane pretty easy as is. I already spoke to RM Builder about some quality solid cams and about the added expense but less headache roller conversion. I put new heads out of the equation until I came across these bare Brodix heads and for what they can be had for. I like the idea of bumping up my compression and still running 87 gas. Plus new tech and lighter ass end. Dumping the stock exhaust for some 496 aluminum mani's and al heads would yield around 375lbs savings.
I've spent all weekend prepping the boat for motor removal and building my gynormous gantry. Just finished it up tonight so motors should be coming out next weekend. 11W x 13' 4" high at it's lowest point. That gives me room for the chain hoist and clearance out of the bilge. I already listed my current heads on local CL so if any takers want them then I'll get new heads. If not I'll reassess once I remove them and check them out.
Thank you all for your comments.
Borgie - thanks for that article. Yea, I've been looking everywhere for info on this. If the change happens it WILL be the Brodix Race Rites. I'm trying to find some comparative data on the rect/oval port race rites. They both flow about the same but different shape so........what's the deal here? I'm almost positive I wouldn't even feel the difference between the two but I figured if I'm buying new might as well try to find the best combo I can afford. Also, switching over to oval would require me to switch intakes now also instead of later. A necessary evil ($$) I suppose if I want the best combo. Already picked up some blue holley 800's so I'll need an adapter for the time being if I keep the stock intake.
BT - Thanks for the input. That is still a possibility. I was already set on new valves and definitely replacing worn parts, i.e. springs, rods....I figured if I can get my heads back to a stock quality standard and upgrade the valve train components I would be happy. I don't pull any skiers/tubes and I don't race anyone and don't gun it out of the whole but I do like to open it up while cruising. She comes on plane pretty easy as is. I already spoke to RM Builder about some quality solid cams and about the added expense but less headache roller conversion. I put new heads out of the equation until I came across these bare Brodix heads and for what they can be had for. I like the idea of bumping up my compression and still running 87 gas. Plus new tech and lighter ass end. Dumping the stock exhaust for some 496 aluminum mani's and al heads would yield around 375lbs savings.
I've spent all weekend prepping the boat for motor removal and building my gynormous gantry. Just finished it up tonight so motors should be coming out next weekend. 11W x 13' 4" high at it's lowest point. That gives me room for the chain hoist and clearance out of the bilge. I already listed my current heads on local CL so if any takers want them then I'll get new heads. If not I'll reassess once I remove them and check them out.
Thank you all for your comments.
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