Thread: stroking a MKIV 2-bolt main?

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Situation: Built a 454 several years back motor went into storage with what I now think was a ruptured mech. fuel pump (fuel in the oil)... so it sat like this for years.
motor has: Scat cast crank and 6.135 rods
SRP small dome pistons (around 9.5:1cr)
Dart Iron Eagle 308's

So... I KNOW I have to replace the bearings - freshen things up

however I was thinking of stroking this motor with a 4.25 or 4.375 crank
OR
keeping the stock stroke but replacing the Rods for some taller (6.535) BME's and maybe some tall dome pistons around 11-12:1 cr with a solid roller high lift cam and getting some head work done

what would you do???
car has a m-21 Muncie and a spooled 12 bolt w/ 4.88's. motor is a 2bolt main

forgot to mention:
the pistons are currently already .30 overbore (460cid)

&
I don't know If I can stuff the 4.375 crank in the bottom end and how the mains would hold up to it. was hoping someone had tried this with a 2 bolt

Is this a race only motor? With that compression ratio, you may be hard pressed to find fuel of sufficient quality to run it on the street.

Pat and/or Jerry should be along and they've forgotten more than I've ever known with the BBC. I'm more of a Blue Oval guy... LOL..

Welcome to CHR!

I'm sure Pat and Jerry will chime in soon as they are certainly our resident BBC experts and have built some of the best engines anywhere. I'm far from an expert on much of anything, but your question about longer rods did recall an article you may want to read - ISKY Racing Cams - Do It Right. Race with the Legend. Camshafts, Connecting Rods, Valve Springs, Lifters
See the Tech Tip 2005 on rod lengths.

As already mentioned, your compression ratio is a bit too high for comfortable street use especially with cast iron heads..

Hang around a bit - hope you find what you're looking for.

Regards,
Glenn

You can always use splayed caps if the 2 bolt is a concern. They are better than a factory 4 bolt anyway.

Look at this thread before even thinking about converting to splayed caps. It's a big undertaking and for almost all engines short of full-tilt dragsters it's not necessary.

Splayed 4 bolt upgrade

Note that Pro-gram link is defunct - go instead to American Made - American Proud: Pro-Gram Engineering Corp - Manufacturer of Race Engine Parts - Home

done many bbc in 4.250 that i know it more then 4.000 i built over the years and many 4.375 .rod works at 6.385 no need for more rod in the 9.800 deck block any more the pistons start getting short and ring pack start getting tight for space as the wrist pin is in the oil rails. with the 4.375 crank there not many making the pistons for that stroke less it a 14to1 a race pistons. i use the 6.385 is a shelf rod evey one makes this size rod and can come many ways in Ior H and in forged finish like stock rods for the street you still can get a piston with a good ring pack. or the 6.535 rod with a 1.070/1.065 piston ch wiseco makes them but a race piston hi CR . a K1 rod they make off size rods and work with a shelf piston like 1.120 ch but word need a rod around 6.500 long and i think makes 6.410 /6.420 long then 1.180ch piston i di not have my K1 book here but you get the ideal . the best bet is with a 6.385 rod with a Ch of 1.220 now in a custom made piston. that will get you 511 CID but there abit of work . Mahle makes a piston with a small dome but most companys make the piston with a bit less Ch on the piston so you can deck the block. old stock blocks all should be deck. if you tru-deck it. like i do .you can find your self taking abit more off to get the block true .so most of the time its not hard to be at 9.790 or 9.780 . most all the time its not a big deal and piston companys have this in mind . but not Mahl . i have talked to them asking to speak to the dumb ass that made a piston that works only on a 9.800 deck block. no room to clean cut the block and you can forget about a tru deck as when your done you will be looking for a head gasket 060 thick this is not the way i like to do things. so they pushed this screw up on there bbc piston on the eagle as they told me they made them for eagle so i talk the them trust me i save some time on the phone after taking to them clowns i think they such my brain matter out when i was on the phone .but mahle sell it to any one it is not proprietary to eagle? this piston is the only piston they offer built with no room to clean up the block . so do not buy the mahles i will say they do make nice pistons but some one truly someone head his head up is ass less your not going to do any work and if you fine the pistons hanging out of the deck your going find head gasket s at 100. bucks side and you need to make sure the crank counterweights are cut for the 6.385 rods you should use a cap screw rod as with a threw bolt rod there will be to much bolt hanging out of the rod and that is more cutting on the block to have the rod swing threw the crank case . now the 4.250 cank just about drops in and i done many of the 4.250 cranks with a 6.385 rod every one makes pistons for them it just the way to go . know what most guys thing two bolts just will not hold up and i must need two more to make my world right this is plane bull shit . the bbc bottom end is one of the best built and one of the better oiling blocks it.s not a sbc the main caps are 1/2 not like 7/16 that sbc are .and the big block as a 6.135 rod stock they been some test done i built longer rod bbc most all the time i was looking to hook the piston to the rod the longer rod engine would be very hard to see any gain and go threw the work to find the power on a longer rod engine

Originally Posted by glennsexton

Look at this thread before even thinking about converting to splayed caps. It's a big undertaking and for almost all engines short of full-tilt dragsters it's not necessary.

Splayed 4 bolt upgrade

Note that Pro-gram link is defunct - go instead to American Made - American Proud: Pro-Gram Engineering Corp - Manufacturer of Race Engine Parts - Home

milodon cap or howards make caps now its not a big deal i done many of the 2 bolt to 4 it is more of a time deal if you have it done they need to watch were they drill as they can open up a main feed to the main . if you know your going past 700 hp then just buy a big m block when all siad an done you would be very close to 700.to800 cap job fitting the caps drill and tap block aline bore easy 400. and caps are 240 for the 3 main caps in milodon 400 for howards cap 1threw5 . as for Pro Gram there cap are some of the best and howards are right there with them . i am dealer for program and howard my catalog 2012-13 shows there still making caps ? not sure they were off line i hope there back up and runing i use to buy timed out off shore race blocks. just about all them had program caps but dart makes there own caps and many do so that may have been a big cut in them making caps

thanks guys,

- I wanted to try and keep it a 2 bolt main at most maybe a stud girdle.
- curiosity was more or less to see if I could turn a two bolt main into a 511or if anyone had tried this (496 shouldn't be a problem for the main caps) was just thinking of doing something different
- if not maybe just try to put a new rotating assembly (possibly a 496) in with some lighter rods and higher comp. pistons. take it up to 7000rpm
- ultimately I want to have fun and kind of push the limits in an affordable way at most replacing the rotating assembly and valvetrain
- kind of had my heart set on trying to stroke it to 511 if possible - wondering if a machinist had tried this and if the main caps could handle it if so - I would love to try it!

haven't called yet but it seems as though there are plenty of companies that would make custom pistons for this combo - maybe not though... maybe Arias or Venolia just thinking off the top of my head

Originally Posted by 67cherry

haven't called yet but it seems as though there are plenty of companies that would make custom pistons for this combo - maybe not though... maybe Arias or Venolia just thinking off the top of my head

if one thing that need s to be custom not the all of the piston then its not to bad so lets say you see a piston in a company stock you like. you call them and give the number of piston and then give them the pin height you need most all companys will want you to sign off on the bulid sheet that states what you want change on them before they start 1/2$$ down so you will own them if you screw up thats on you. if this is to much then have your machine shop or engine builder call them and if they can not then i would not spend any money with them .there is many rings out there so you many be asked about ring pack radial width and what forging 400 or 2618 so it can take time filling the sheet out but changing just one thing on a shelf piston you want to start with a 496 piston with the same rod so CH and net shape of the dome cc as piston CR with raised. so the 4.375 cranks are bit more work . as for max out with stock block is 511 and 541 with the tall deck . and 9800 big m 582 to 587. the 4.1/2 crank tal deck Gm 525. then big M others blocks 632/638. as for custom i had JE /wiseco . Ross . Racetec. BRC .Diamond .and the list of reworking them is much longer right now in the shop for a shelf or a stocking number piston. i like the Icon line by united engine and machine company . and for big money builds like a pro stock head like big chiefs then wiseco customs builds Diamond as there close to the shop and have been using them before they were fully in to just making pistons . most all the companys i listed over the years i ran in to problem with .like getting piston out on time. calling me and asking if i would take a 9 set of pistons with the one of 9th with a flaw in the intake fly cut. radial width to deep on a 043 ring and 1.5 there is no SAE on . making a piston with a top ring that i did not ask for then they did not make a ring for . putting the valve anges off on a big chief heads .not putting fly cutting in the right place on big chief pistons . not drilling gas ports in to top ring land busting a drill off in the piston. over sizing the pin holes to .003 and that just the ones i can think of now. the ring pack or oil rail it a no mans land with all the sizes of rings and made up there no SAE on some stuff so you need to tell them what you whant . ring sets so you need to be on top of your game . you better know more then the guy on the other end of the phone about pistons bad thing s can happen most all thing i listed was just poor help sad thing that realy reflex on the company name .and a sure bet i will see them at the PRI show face to face for some talking

7000 not a big deal for the bottom end if you keep a eye on parts valve train is the biggy . try some thing new ? well for you but your taking about a engine thats been built from 1965 what ever you think of its been done .there is no if i could i done it many time its more if you can find someone or yourself could. its not to big of a deal like said its the cost. i been building bbc for many years and using two bolt blocks the 511 to 496 has nothing to do with the main caps. i put many street/strip 496 together with a 454 two bolt block and had one customer used a two bolt 454IV block to 496 in a pull truck were he had it for over five years of pulling with just ARP studs in the two bolt mains. first time he built it last time i did caps did not move this engine was making steam up to 7500 every pull .i have done over 40 of the 4.250 9.800 deck builds its not much of a deal. but you still need to know what the hell your doing better have more then just a few builds under your belt . even after building 100s of engines the brain drop in to Neutral so a build like this takes time it not like baking cookies

One touchy area for newbies strking a bbc---when your gringing block for rod clearance---your close to the main oil gallery along the left side

I found a 510cid rotating assembly Scat offers with around a 13:1 piston they also have another option with a 8:1 flat top piston. when I get a chance ill call them but that sounds like a plan.
projecting a solid roller cam around .720'ish on the lift (off the top of my head)
maybe some shaft mounted rocker arms just to be safe
and maybe a tunnel ram with dual 750's just for a little taste of nostalgia
-it's all about baking cookies ha!

Originally Posted by 67cherry

I found a 510cid rotating assembly Scat offers with around a 13:1 piston they also have another option with a 8:1 flat top piston. when I get a chance ill call them but that sounds like a plan.
projecting a solid roller cam around .720'ish on the lift (off the top of my head)
maybe some shaft mounted rocker arms just to be safe
and maybe a tunnel ram with dual 750's just for a little taste of nostalgia
-it's all about baking cookies ha!

better ask if there mahle pistons bbc228310d41 and still has a ch of 1.228 ?i bet they are if so lets do the math 4.375 crank 1/2 of that is 2.187.5 now CH 1.228 now rod is 6.385 add 9.8005 . you will never deck the block but ask them and if so ask if it comes with supper thick head gasket just want to make sure your cookies do not crumble. on you first cooke off .i use scat and dealer for just about all of them but be a cold day in hell would i let some one sell me pistons when i can get them the way i want . 720 off your head were the rest of the cam ? in your stomach? . here is one for free try cc2969r8 @050 261/271 life.680/.680 lsa 108 work very good if you have some CR there others but was not hard on valve train . good luck have fun