454mag top end rebuild
10-30-2013 | 12:01 PM
#101
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Sold my 188 casting heads and full valvetrain from stb side last night. I'm eager to see this guy on the water next year. He's pushing a 23 scarab with 454MPI and wieand 250 blower. Says he built the engine this year and 18hrs into the season ingested water and sand due to exhaust mani/riser gasket failing. That's right, still had stock merc exhaust on that set up. He brought his mech/builder with him last night and when he saw that my stock pushrods were thicker than his he recommended to take my rods as well. He ended up taking the whole setup. I sold them what they wanted and suggested upgrading the valves.
10-30-2013 | 12:03 PM
#102
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If your crankshaft just needs a polish, same size bearings go back in. Does the crank have any deep scoring at all? The machinist will need to measure all journals to assure all are same size. Not truly knowing the history of the engines completely, nothing can be assumed as you know.
10-30-2013 | 12:08 PM
#103
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If your crankshaft just needs a polish, same size bearings go back in. Does the crank have any deep scoring at all? The machinist will need to measure all journals to assure all are same size. Not truly knowing the history of the engines completely, nothing can be assumed as you know.
10-30-2013 | 12:12 PM
#104
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I didn notice that the prt "stock" engine had the rods and main caps stamped with their respective position number. Did merc stamp their engines or would this be an indication they were apart before?
10-30-2013 | 12:15 PM
#105
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Always the smart approach. Never know if the rods have been ground or cranks. Even when my stuff is marked ie 10/10 for crank and rods, I still double check it. I don't trust someone's previous work. It's a good feeling being confident that everything is properly set up! Great news about selling those heads. You are getting there slowly but surely!
Regarding the numbering question, I'm not sure on the mag motors. I've only been into the 330 motor and know the rods are not marked. Mild thunder should have an answer for you on that.
Regarding the numbering question, I'm not sure on the mag motors. I've only been into the 330 motor and know the rods are not marked. Mild thunder should have an answer for you on that.
Last edited by Borgie; 10-30-2013 at 12:43 PM.
10-30-2013 | 07:48 PM
#106
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From: Ontario, Canada
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!
Last edited by stimleck; 10-30-2013 at 08:47 PM. Reason: update
10-31-2013 | 12:34 PM
#107
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From: IBX
Any merc mag engine I've been into from original did not have rods marked.
Stimleck, if it has a flat tappet cam I would change it to a roller setup or become schooled on how to properly breakin a flat tappet cam.
Stimleck, if it has a flat tappet cam I would change it to a roller setup or become schooled on how to properly breakin a flat tappet cam.
Last edited by blue thunder; 10-31-2013 at 12:37 PM.
10-31-2013 | 12:58 PM
#108
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I didn't think merc would stamp their rods and main caps. I'll find out more next week after shop takes a look.
10-31-2013 | 01:18 PM
#109
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From: chicago
10-31-2013 | 01:24 PM
#110
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if duration on a cam is in the 230's, is there still a necessity to keep a high LSA? Or is 112 ok to go with? How would LSA of 112 compare to 114 in power? I've done some reading but still not sure on this one.
