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8.1 496 reliable build questions

Old 07-14-2017, 08:11 PM
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Originally Posted by mouse4x4
Just a quick question while I have everyone's ears, my engine being the hp1 version 375hp what is different between it and a regular truck engine. Hard part wise are the cranks and cam the same?
Same for the base 375hp model. 425hp model has larger cam and different PCM.
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Old 07-14-2017, 08:22 PM
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So if ever needed I can source a truck engine and marinize it and have the same thing I have now. I have kinda decided on just going forward with stainless marine exhaust and the custom risers he makes for my boat as it moves the water exit about 18" further back then stock risers. Thanks for the quick responses.
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Old 07-14-2017, 08:31 PM
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If you have a stock Mag motor. To do a cost effective rebuild, re-use connecting rods, install rings, pistons, valve springs and roller rockers and be done. I would use all stock parts then use forged pistons (diamond or Raylar), Raylar rockers and Raylar valve springs. If you change cam, you have to change ECU.

Dont start swappping truck parts, it ends badly - ask me how I know...
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Old 07-14-2017, 08:40 PM
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Yes I have a complete Volvo 8.1 375hp with 1 bad piston right now. I am looking to do a full set of pistons have the heads redone and what ever machine work needs done. I was just curious if a truck long block was the same specs as a 375hp long block.
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Old 07-15-2017, 11:14 AM
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So good information so far, this is the plan now with what I have received from you all. Stainless marine exhaust, forged pistons, valve springs and rocker arms, possibly go ahead and do connecting rods while I am in to it. And make sure I have inconel exhaust valves installed. This motor will never turn over 4500-4600 rpm and if it does that it is for a very short burst just to make sure she still has it in her. Next question is if I do the rocker arms and the ratio is 1.7-1 do I need to have anything done to my mefi 4 controller tuning wise.
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Old 07-15-2017, 01:32 PM
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Originally Posted by mouse4x4
So good information so far, this is the plan now with what I have received from you all. Stainless marine exhaust, forged pistons, valve springs and rocker arms, possibly go ahead and do connecting rods while I am in to it. And make sure I have inconel exhaust valves installed. This motor will never turn over 4500-4600 rpm and if it does that it is for a very short burst just to make sure she still has it in her. Next question is if I do the rocker arms and the ratio is 1.7-1 do I need to have anything done to my mefi 4 controller tuning wise.

You should only use 1 type of rocker arm from Raylar. They (496/8.1) require a different nut than other big blocks. All other rocker brands will require bigger valve covers due to the nut, different rocker nuts for a standard scorpion or crane, then you have to change the mounting of the valve covers then you have to change the mounting of the coil packs... If you use generic rockers and save $40 you will spend $500 getting the rest of the stuff to fit correctly. Buy the stainless rockers from Raylar and you are done - no other modifications. The 496 has metric studs. Also, scrap the stock head bolts for metric ARP head bolts - the stock bolts are TTY and are junk/non-reusable for a rebuild.

Change the pistons, rings, and call Raylar for springs and rockers, maybe even valves if you need them. Have a nice short block done and have the heads done correctly. You cant swap parts with other big blocks - they are a different generation. The 496/8.1 may as well be Ford or Chrysler - its not the same. The only thing you can get from Summit is the pistons and a timing chain IF ITS A 496/8.1 spec - other parts have to be stock or Raylar.

If you use the truck block understand that the marine block is all metric, the truck block has SAE threads for the bolts on the bellhousing and some of the mounts are SAE - not metric so the install gets a little confusing.
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Old 07-15-2017, 01:52 PM
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Yes I see what you are staying about rocker arms I was planning on sourcing everything g thru raylar just for ease of purchase. I am not out to cheap out for a buck like I said earlier I am here to make a solid engine that will run worry free for a while. So nothing needs to be done to my ecm for installing the rocker arms?
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Old 07-16-2017, 08:58 AM
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Originally Posted by mouse4x4
Yes I see what you are staying about rocker arms I was planning on sourcing everything g thru raylar just for ease of purchase. I am not out to cheap out for a buck like I said earlier I am here to make a solid engine that will run worry free for a while. So nothing needs to be done to my ecm for installing the rocker arms?
Good choice sourcing parts from Larry @ Raylar. Sounds like you will have a stout reliable setup. No changes needed to the PCM swapping to Raylar's roller rockers. Factory ratio is 1.7 .
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