8.1 496 reliable build questions
#22
Registered
Thread Starter
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.
#23
Gold Member
Gold Member
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...
Dont start swappping truck parts, it ends badly - ask me how I know...
#24
Registered
Thread Starter
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.
#25
Registered
Thread Starter
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.
#26
Gold Member
Gold Member
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.
#27
Registered
Thread Starter
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?
#28
Registered
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?