454mag top end rebuild
10-14-2013, 07:25 AM
#11
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Ah I see! They actually did test the Dart 308 heads and they produced less hp. I need to locate the article. Before I bought my 275 oval pro 1's I spoke to a engineer at DART at length. He said that the 308 head are awesome but that the 275 outflow them and the aluminum composition obviously allows more compression to be run. That and the 275 head makes more torque sooner. I was seriously considering iron eagle 308's until I saw the dyno pulls and spoke directly to dart. Don't get me wrong the 308's are a definite step up from the 088's, but fall short of the PRO 1's.
Some folks won't accept the fact that oval ports are better under a certain HP. But results don't lie. The 088 rect port head is ok, and I agree it should be considered for a build that's restricted budget wise, but it's proven that the AFR 265 and DART 275 flat out spank this head into the gutter HP wise. Some folks don't like the fact that their big port heads are getting trounced by high velocity small ovals. To each their own I guess.
One thing to remember regarding the above article is that this 496 tested was using a pretty mild camshaft: 224/232 DUR/ 555/565 LFT 112lsa
Add a larger cam into the mix and the full potential of these heads will be seen!
Some folks won't accept the fact that oval ports are better under a certain HP. But results don't lie. The 088 rect port head is ok, and I agree it should be considered for a build that's restricted budget wise, but it's proven that the AFR 265 and DART 275 flat out spank this head into the gutter HP wise. Some folks don't like the fact that their big port heads are getting trounced by high velocity small ovals. To each their own I guess.
One thing to remember regarding the above article is that this 496 tested was using a pretty mild camshaft: 224/232 DUR/ 555/565 LFT 112lsa
Add a larger cam into the mix and the full potential of these heads will be seen!
Which brings up the cost again. 500 bucks each for the race rite bare castings is a good price. However, keep in mind what you will have in these heads, by the time they are fully dressed and ready to bolt on. Stainless intake valves, extreme duty Inconel ex valves, springs, retainers, machine work, etc. It adds up quickly.
Another nice option for a 454 Mag Upgrade on a budget, is the edelbrock 290cc ovals. With the 110CC chamber, it will yield around 9.3:1 using the stock 454 mag bottom end. Usually you can find them for around 900 each, ready to go just add your springs. Now your getting into a price point that doesn't hugely exceed rebuilding the stock GM heads.
At the end of the day, its all about the budget for most. A pair of stock 454 mags, are gonna need pretty much the following parts, not just heads, for a nice upgrade
Exhaust manifolds. Stock irons have to go.
Intake manifold
Carb
Roller rocker arms
Cam and lifters.
Gaskets, etc
A lot really depends on how much power you want to make, and how fast you want to go. Hands down the biggest improvement on those engines, is a cam swap and exhaust. My buddy's scarab in the above video, gained a bunch just by ditching the stock exhaust, larger cams, roller rockers.
I redid my 454's two years ago. I am running Dart 308 Race series aluminum heads with some port work, a 236/245 114 LSA hyd roller .630 lift, B&M 420 blowers making 6psi, no chillers. They made 804HP at 6000RPM and been running great for 2 seasons. My boat with stock 454 Mags, would run about 65mph. It runs upper 80's now and still need to play with props.
10-14-2013, 08:25 AM
#12
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Engine masters did a build up related to what we are talking about. They took a 454HO crate engine, and did a top end upgrade. In stock form, the crate engine is similar to a 454 mag as far as bottom ends. Forged components with mini dome pistons. This engine was actually going in a Jet boat.
Baseline engine.
Stock GM Iron rect port heads.
Edelbrock Performer Dual plane
Holley 850 carb
211/234 HR Cam .510/.540
8.75:1
New setup
Dart pro 1 310 Rectangle ports
Dart Single Plane intake
Holley 850
236/242 .521/.540 HR cam
8.55:1
By adding the darts, they lost a little compression due to the larger chambers.
Baseline engine made 434HP at 5200RPM, 486FT lbs at 3800. Peak numbers.
Modified Version made 524HP at 5600RPM, and 518FT lbs at 5000RPM.
You might say, well, yes, but what about the low speed numbers????
At 3200RPM stock, 464 FTlbs. Modified 472 FT lbs. At 5200 where the stock engine peaked at 434HP, the modified version was making 509HP.
A 8.5:1 Aluminum headed engine should be able to run on 87 octane all day long. 500+ft lbs of torque, and 525HP is nothing to sneeze at considering the compression ratio, 454CI, and RPM band.
The other engine article posted was comparing a 496CI 10:5:1 setup using good flowing oval port heads. Of course that's a stump puller combo. The oval Brodix on that 10.5:1 were making 597HP at 5600. 73HP more than the above engine with almost 2 full points less compression, and 42 less cubic inches. No magic there.
A 10.5:1 marine engine in a heavy old scarab, using a somewhat small camshaft in quest for peak torque down low, is a recipe for detonation on pump gas. Its unrealistic. And, the camshaft part # in that article is for a ford small block, so who knows what it really had for a cam.
Oval port heads can work well, especially in a street engine, where low rpm stump pulling power is needed. They definitely have their place. Nice thing about the 310 Darts talked about here, is that if the 454 mag owner bought them, ran them, and decided a couple years from now to build some 502/540 Short blocks, he can reuse those heads. I know of several marine 540CI builds making 700+ with them. Not gonna happen with some 265 ovals.
Baseline engine.
Stock GM Iron rect port heads.
Edelbrock Performer Dual plane
Holley 850 carb
211/234 HR Cam .510/.540
8.75:1
New setup
Dart pro 1 310 Rectangle ports
Dart Single Plane intake
Holley 850
236/242 .521/.540 HR cam
8.55:1
By adding the darts, they lost a little compression due to the larger chambers.
Baseline engine made 434HP at 5200RPM, 486FT lbs at 3800. Peak numbers.
Modified Version made 524HP at 5600RPM, and 518FT lbs at 5000RPM.
You might say, well, yes, but what about the low speed numbers????
At 3200RPM stock, 464 FTlbs. Modified 472 FT lbs. At 5200 where the stock engine peaked at 434HP, the modified version was making 509HP.
A 8.5:1 Aluminum headed engine should be able to run on 87 octane all day long. 500+ft lbs of torque, and 525HP is nothing to sneeze at considering the compression ratio, 454CI, and RPM band.
The other engine article posted was comparing a 496CI 10:5:1 setup using good flowing oval port heads. Of course that's a stump puller combo. The oval Brodix on that 10.5:1 were making 597HP at 5600. 73HP more than the above engine with almost 2 full points less compression, and 42 less cubic inches. No magic there.
A 10.5:1 marine engine in a heavy old scarab, using a somewhat small camshaft in quest for peak torque down low, is a recipe for detonation on pump gas. Its unrealistic. And, the camshaft part # in that article is for a ford small block, so who knows what it really had for a cam.
Oval port heads can work well, especially in a street engine, where low rpm stump pulling power is needed. They definitely have their place. Nice thing about the 310 Darts talked about here, is that if the 454 mag owner bought them, ran them, and decided a couple years from now to build some 502/540 Short blocks, he can reuse those heads. I know of several marine 540CI builds making 700+ with them. Not gonna happen with some 265 ovals.
10-14-2013, 10:57 AM
#13
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Dude chill out. Nobody's picking on your oval port heads.
You have a raging boner over a 496 that made 600hp with 10:1 and aftermarket heads in some magazine article with a unknown camshaft.
I've had buddy's bolt box stock edelbrock marine rect ports on a 502 with same compression and a Hyd roller make the same numbers.
There's a lot more to putting a solid marine engine together than flow numbers or intake port shape/size. I'm not saying the rectangles are superior to the ovals. But there's more to a package than that. Cam size, bore size, valve sizes, piston design, chamber design etc. plus a engine on billy bobs dyno vs a good dyno can tell a different story
You have a raging boner over a 496 that made 600hp with 10:1 and aftermarket heads in some magazine article with a unknown camshaft.
I've had buddy's bolt box stock edelbrock marine rect ports on a 502 with same compression and a Hyd roller make the same numbers.
There's a lot more to putting a solid marine engine together than flow numbers or intake port shape/size. I'm not saying the rectangles are superior to the ovals. But there's more to a package than that. Cam size, bore size, valve sizes, piston design, chamber design etc. plus a engine on billy bobs dyno vs a good dyno can tell a different story
10-14-2013, 11:31 AM
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[ATTACH=CONFIG]509872[/ATTACH]
Whoa guys, getting a little heated in here. This should calm everyone down a bit, an actual dyno sheet from my previous build a few years back.
MKIV block 498 stroker
Ultradyne 230 intake 238 exhaust, 601 lift with 112 lobe sep
Heads were gm performance aluminum with Baker stamped on them. My machine guy said they looked like ovals that were hogged to be rect. there was a steep ramp at the bottom of each runner. Cam and heads were bought used from a gentleman who said they came out of his marine 502. I used flat top pistons and heads were milled to achieve 9.8 static comp. It was dynoed on 87 gas. Almost forgot, RPM airgap and BG Demon 850 marine carb.
Never quite got it tuned in on the water before selling the whole thing due to getting my scarab. This motor was in a 89 Maxum 23 open bow that originally had stock 454 with B1. It ran great but I just couldn't leave well enough alone and built the new motor and cannabalized the stocker for accessories. Ended selling the stocker for $400 just to get it out of the garage.
Whoa guys, getting a little heated in here. This should calm everyone down a bit, an actual dyno sheet from my previous build a few years back.
MKIV block 498 stroker
Ultradyne 230 intake 238 exhaust, 601 lift with 112 lobe sep
Heads were gm performance aluminum with Baker stamped on them. My machine guy said they looked like ovals that were hogged to be rect. there was a steep ramp at the bottom of each runner. Cam and heads were bought used from a gentleman who said they came out of his marine 502. I used flat top pistons and heads were milled to achieve 9.8 static comp. It was dynoed on 87 gas. Almost forgot, RPM airgap and BG Demon 850 marine carb.
Never quite got it tuned in on the water before selling the whole thing due to getting my scarab. This motor was in a 89 Maxum 23 open bow that originally had stock 454 with B1. It ran great but I just couldn't leave well enough alone and built the new motor and cannabalized the stocker for accessories. Ended selling the stocker for $400 just to get it out of the garage.
Last edited by ramos45; 10-14-2013 at 11:45 AM.
10-14-2013, 02:15 PM
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I am not defending "my heads" and im far from being pissed off on a boat forum by some guy i really could give two s**ts about. I would venture to say that the small oval has proven itself beyond the flow numbers and different magic dynos and I'm speaking in marine applications not your cousins 70 Chevelle. I realize it's the combo and the sum of the parts, but it all is made or broken power wise in the heads. If he wanted to make above 600hp sure I agree rect is the way.
And I'm sure your buddy's make this power all day long blaaaah. All talk
And I'm sure your buddy's make this power all day long blaaaah. All talk
You were raving about how those aftermarket ovals will stomp a GM rect port head on a build like this, and they would. But it's not the port shape size , as much as its the crappy flowing GM port designs
10-14-2013, 11:03 PM
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Lets try to get back on track here. Turned into a which head is best, who knows engines and who doesn't, etc.
Lets talk about the 454 Mag for a minute. Its weak points are
Flat tappet sissy cams
GM 1960's castings for heads. They can work depending on your goals, but any good aftermarket head would be a improvement.
Exhaust Manifolds. They suck if trying to make anything over 375-400HP.
Intake Manifolds. They are decent, the old days cutting down the center divider and adding a 1" spacer helped them out.
Quadrajet carb. Great carb, but if serious about power, they can be limited, and tuning can be a little tougher than a holley.
Rocker arms. Stamped steel style.
Some of the strong points are
4 bolt mains
Forged Cranks
7/16 Dimple rods
Forged pistons
Now, I know your not at sea level, so that will change things. But, generally speaking, to get a Scarab III to run mid to upper 60's, is gonna take around 500HP per side. Mid to upper 70's, around 600HP per Side. In the 80's, 650-700HP per side. Once you establish what you'd be happy with as far as speed/power, then maybe we can start spending your money. If you'd be happy with 75-100HP increase per engine, there's really no reason to go spending 10k dollars worth of fancy aluminum heads, exhaust, roller cams, and other goodies.
The 365HP mags respond well to a cam swap, exhaust upgrade, roller rockers, intake and carb. The old 420HP, 440HP, and 460HP 454 based mercury engines used basically a 365HP bottom end and heads. They got better exhaust, better valvetrains, intakes and carbs. If your gonna be using the 496 exhaust manifolds, I'd be careful with cam choice, from a reversion standpoint. They are a improvement over the old iron manifolds, but they aren't long riser'ed dry pipes.
In my opinion, what makes someone a good engine builder, is knowing combinations, and what each combination will produce. To be able to meet a customers budget, and most importantly, deliver a reliable product. HP doesn't mean squat if it doesn't stay together. In todays world, you can almost make 600HP from a big block chevy by accident. Making a 600HP marine engine that lives takes a little knowledge. I'm not gonna keep going back and forth on the whole oval vs rect port thing. I posted up a video of a buddy's old scarab III's setup, and Borgie seems to question the choice of parts used. Could he have made more power with different parts, surely. In that 10k lb scarab, 20HP doesn't mean $hit. He liked the look of the single plane intake, so we went with them. he could care less if the boat goes 65 or 65.8mph. But I can tell you this, that kid runs the ****T out of that boat every single weekend. Theres no cruising, its WFO everywhere he goes. Theres no issues whatsoever with the engines. A blown TRS, sure. But the engines run great, 89 octane.
Lets talk about the 454 Mag for a minute. Its weak points are
Flat tappet sissy cams
GM 1960's castings for heads. They can work depending on your goals, but any good aftermarket head would be a improvement.
Exhaust Manifolds. They suck if trying to make anything over 375-400HP.
Intake Manifolds. They are decent, the old days cutting down the center divider and adding a 1" spacer helped them out.
Quadrajet carb. Great carb, but if serious about power, they can be limited, and tuning can be a little tougher than a holley.
Rocker arms. Stamped steel style.
Some of the strong points are
4 bolt mains
Forged Cranks
7/16 Dimple rods
Forged pistons
Now, I know your not at sea level, so that will change things. But, generally speaking, to get a Scarab III to run mid to upper 60's, is gonna take around 500HP per side. Mid to upper 70's, around 600HP per Side. In the 80's, 650-700HP per side. Once you establish what you'd be happy with as far as speed/power, then maybe we can start spending your money. If you'd be happy with 75-100HP increase per engine, there's really no reason to go spending 10k dollars worth of fancy aluminum heads, exhaust, roller cams, and other goodies.
The 365HP mags respond well to a cam swap, exhaust upgrade, roller rockers, intake and carb. The old 420HP, 440HP, and 460HP 454 based mercury engines used basically a 365HP bottom end and heads. They got better exhaust, better valvetrains, intakes and carbs. If your gonna be using the 496 exhaust manifolds, I'd be careful with cam choice, from a reversion standpoint. They are a improvement over the old iron manifolds, but they aren't long riser'ed dry pipes.
In my opinion, what makes someone a good engine builder, is knowing combinations, and what each combination will produce. To be able to meet a customers budget, and most importantly, deliver a reliable product. HP doesn't mean squat if it doesn't stay together. In todays world, you can almost make 600HP from a big block chevy by accident. Making a 600HP marine engine that lives takes a little knowledge. I'm not gonna keep going back and forth on the whole oval vs rect port thing. I posted up a video of a buddy's old scarab III's setup, and Borgie seems to question the choice of parts used. Could he have made more power with different parts, surely. In that 10k lb scarab, 20HP doesn't mean $hit. He liked the look of the single plane intake, so we went with them. he could care less if the boat goes 65 or 65.8mph. But I can tell you this, that kid runs the ****T out of that boat every single weekend. Theres no cruising, its WFO everywhere he goes. Theres no issues whatsoever with the engines. A blown TRS, sure. But the engines run great, 89 octane.
10-15-2013, 01:41 AM
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Well, I have plenty of time to think of what will be done. Pulling the motors this weekend and opening them up will give me a better picture of what's needed. Plus, I just spent quite a bit on bigger oil coolers, carbs and exhaust so need to recoup some $$. This will be an ongoing project with end date around the March-April 2014. For now, after motors are pulled I'll focus on redoing my bilge, painting outdrives and odds and ends while still deciding on a package for the build.
While I do appreciate all of the head combo suggestions if I do change heads they will be the Brodix aluminum heads. I found them to be the most affordable for a set of bare heads. Aside from machining and specific clearance checks that I may not have the proper tools for I plan on doing a lot of the assembly myself this time around. New valves will be on order no matter what head is used so I consider them a sunk cost as is. The springs come with the cam and the rest of the hardware is just that, hardware. Dolar for dolar a set of bare aluminum aftermarket heads for around 1200 is pretty good when doing alot of the work yourself.
While I do appreciate all of the head combo suggestions if I do change heads they will be the Brodix aluminum heads. I found them to be the most affordable for a set of bare heads. Aside from machining and specific clearance checks that I may not have the proper tools for I plan on doing a lot of the assembly myself this time around. New valves will be on order no matter what head is used so I consider them a sunk cost as is. The springs come with the cam and the rest of the hardware is just that, hardware. Dolar for dolar a set of bare aluminum aftermarket heads for around 1200 is pretty good when doing alot of the work yourself.
10-15-2013, 01:47 AM
#20
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I used a Holley 800 on a mildly hopped up 454mag with no problems.
