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View Full Version : 2 Bolt Mains vs. 4 Bolt Mains in Marine SBC?



Riley
08-04-2003, 01:55 PM
I was wondering what the consensus would be here on the board for the necessity of 4 Bolt Mains in a warmed over SBC, in a marine application. I'm in the process of getting parts and pieces together for a re-power project, with the intent of using the 350 Mercruiser block and crank that I currently have. I plan on running GM powder-metal rods and forged pistons, and balancing the rotating assembly. The finished engine should be in the 350-375 hp range, and never see the high side of 5500 rpm. Should I look for a good deal on a 4 bolt block, or can I stick with what I have? Opinions?

BUIZILLA
08-04-2003, 02:12 PM
You don't need a 4 bolt block, or forged pistons. Just GOOD quality parts, and your 2 bolt block, correct machine work, balance the rotating assembly, and your on your way.

J

just my opinion, your wallet size may vary..

mikev
08-04-2003, 03:50 PM
you dont need a 4 bolt unless your running a blower or real high compression and high rpms you should be fine with your 2 bolt setup. just be sure and use new bolts and locktite.

Rootsy
08-04-2003, 06:00 PM
i prefer studs in my stuff that takes a beating time after time after time :)

BigGrizzly
08-04-2003, 06:45 PM
$ bolt is not a nsssety in that motor. Just a good balanced rotating assembly

BillG
08-04-2003, 07:21 PM
I believe I would worry about the rods before you need a 4 bolt block.
Just a thought.
Bill G

mphatc
08-04-2003, 08:12 PM
Everyone who replied that you do not need a 4 bolt block is correct!

What you do need is a very good machine shop that can balance everything precisely, a good lubrication set up and focus on the details of the build.

Extra time spent on properly chamfered oil passages, studs instead of bolts, proper oil clearances, improved oil return to sump and many other details will provide you a long lasting engine.

It's all in the details, and the quality of the components!

Good Luck!
Mario L.

about to build a killer 302 for the Corsican!

MOP
08-04-2003, 08:23 PM
I'm with the rest of the guys on 2 bolt, only addition is I would line bore the block, have the rods sized and use full float the pistons. I know a few guys running the GM rods and turning them way higher than I would care to they seem to be Ok.

Cig Man
08-04-2003, 08:33 PM
Hey,
Riley would your first name be Chris ?If so this is Rob S. From The MSDRA Days .I Agree with the others on the two bolt block,Stock Rods will work to 5500 rpm and balancing is important as is a good oil cooler and run an oil temp gauge plumbed after the oil cooler.

Rob

Riley
08-04-2003, 09:36 PM
Thanks one and all for the excellent advice! My thoughts seem to run along with the group, in that the 2 bolt main block with studs, quality machining, and a balanced rotating assembly should get the job done.

Rootsy, any advice on a machine shop in the Lower Peninsula?

Hey Rob, yes my first name is Chris. How are things down your way....ever see Bill Porter? Maybe we'll see you at Onsted this year?

Rootsy
08-04-2003, 09:56 PM
Chris,

i use a guy down here just outside of coldwater... he does fantastic work.. and is extremely reasonable... and FAST...

there are a myriad of machine shops around... but i have been using dale for a while and know a lot of folks who have and he does top notch work... burton's motor had all the work done by him also...

if you don't take teh time to make it square, flat and true then you might as well toss the old crap right back in and button it up...

and for torque retention, eveness, repeatability and accuracy i go with main and head studs (WITH ARP MOLY LUBE) when i put anything performance oriented (over 350 hp) together... yes it might be overkill but to me worth the added expense for piece of mind... i am a firm firm believer in arp moly lube on all threads and washers... and hylomar on all threads and fasteners entering water jackets... and a think smear of loctite gasket eliminator on all gasket surfaces

and avoid those arp wavelock rod bolts... those things are a royal bitch to get apart... i ended up making a rod seperator just to get em apart... and torque those rod bolts by checking the fastener stretch...

hypereutectics and pressed pins are plenty for what you are doing...

and balance it... anything 5500 and over it should be SOP..

BUIZILLA
08-05-2003, 07:09 AM
If you do use the hyper pistons, read the instructions CAREFULLY pertaining to the ring gap on the SECOND ring, it doesn't follow the normal pattern of forged or cast piston thinking wink

J

Riley
08-05-2003, 07:19 AM
Buizilla, could you please educate me on what you are referring to on the ring gap on those "Hyper" pistons?

Which brings up another question in regards to rings: Has anybody had much experience with the Total Seal "Zero-Gap" piston rings, and are they worth the price/effort for installation in an application like mine? I've heard they can be worth some power, and they keep the ring gap sealed tight for a lot longer than a standard ring does, over the life of an engine.

BUIZILLA
08-05-2003, 08:03 AM
Riley, I could go on for days about this, but simply, you tend to need to run a slightly wider gap on the second ring than the top ring with hyper's, due to their material and expansion/contraction rates, ESPECIALLY on a cold running marine engine like we have. If the second ring is too tight, the end gaps butt together, the ring breaks, and you'll have a piston that looks like HM's did in another topic. (I'm not saying HM had hypers)
.016-.018 on the top gap and .022-.024 on the second gap seems to work best with hypers.
Total Seal, and Childs & Albert, both make a *zero gap* design. Their *coupling method* differs however. They both have their positive and negative merits, in certain applications. I have used both brands extensively. I swear by them in certain applications, I loathe them in others. You DO NOT need those piston ring styles for *your* application. Stick with a KNOWN good brand moly ring set, and PROPER cylinder wall finish, to the ring manufacturers spec's, and your good to go. Cylinder wall finish and EXACT roundness of the hole is EVERYTHING, no matter what parts you buy. You can spend $200 for a ring set, but if the hole isn't dead nuts round, you wasted $200..
If you use the hyper's, just READ the piston ring gap spec's REQUIRED, and adhere to them EXACTLY. When the hypers were first introduced, they became popular quickly, but so did broken pistons/rings in the field. And I mean a LOT of broken parts. 99% of the time, it was wrong ring gaps. The engineers then revamped the second ring gap profile and skirt clearance spec's, and VIOLA, the failures stopped. They have changed the spec's a couple times.

Depending on piston material selected, the piston/wall clearance measuring parameter location will be different (above pin, below pin, bottom of skirt etc) Not all pistons are round, bet ya thought they were right? NOPE !! They are cam-ground. They will be round from the bottom oil ring land UP, but usually oval from there down. You may want to reverse the gap method, depending on YOUR engine operating temp application... ask your engine builder for insight.

Standard rule of thumb skirt clearance for hypers and cast is .001 for every inch of piston diamter. For forged, I use .0015 for every inch diameter. This is what **I** use, that doesn't mean it's the industry bible.

Do NOT, and I can't emphasize this enough, DO NOT use press pins or hypers in a worked over blown, supercharged or turbocharged application if at all possible, unless your engine builder is top notch and knows the pitfalls and ramifications. You CAN use pressed pins for those setups, but I would open the pin clearance to .0013-.0015, instead of the normal .0007-.0009 spec.

Each piston material has it's virtues, and design parameters, much like shoes. You don't use loafers for track & field events...

There are a LOT of low boost supercharged conversions running around with pressed pins, but under 6#-7# working load, they will work. Over that, and your in uncharted waters.

J

Rootsy
08-05-2003, 08:40 AM
Jim,

it is actually the other way around... .022 on the top... .016 - .018 on the second.. that is straight from hastings rings and keith black... i've spent a fair amount of time researching it... i'll see if i can dig out the writing, just so no one thinks i am bass ackwards :

BUIZILLA
08-05-2003, 09:04 AM
BUIZILLA:
You may want to reverse the gap method, depending on YOUR engine operating temp application... wink

BillG
08-05-2003, 09:16 AM
I didn't get the part about ARP wave lock rod bolts. The wave lock is in the rod not the cap, so how does it affect gatting the cap off? I also say again why do all that work and use powdered-steel rods. I would not turn them at high RPM for any length of time. Most auto co. replace them on the high output engines.
Bill G

Riley
08-05-2003, 11:25 AM
Wow, the amount of knowledge on this board never ceases to amaze me! You guys are the best.

Regarding the rods, I'm not dead set on using the PM rods....they just seemed like a good compromise between cost and durability, and seemed to be an upgrade over the stock 350 Mag rods. When I'm finished, I'd like to have an engine at least as powerful and reliable as the marine roller crate 350's that are out there. I'd prefer to get the pieces and parts and do the work myself, but the crate engines do offer an attractive alternative when looking at performance per dollar spent.

Like all gear-heads, I'd love to go balls out and build a hot sbc with 400 hp+, but I'm pretty much stuck with an Alpha outdrive. frown