A guide to building the lil guy. The Mighty 300

Discussion in 'Small Block Tech' started by Joe65SkylarkGS, Oct 27, 2009.

  1. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Hey Jim, sbb rods have a .060" offset from the big hole to the small hole. The extra material is on the chamfered side, if you don't maintain(or get as close as possible) the offset the small end of the rod won't be centered on the wristpin.

    On the Carrillo rods, they are more than likely centered and if they are .900" wide all the material will need to be taken off of the non-chamfered side. So you end up with a .055" offset which is within .005" of the .060" factory offset.(probably way closer than what the factory tolerance was)

    The Pankl rods may already have a .040" offset so material will need to be removed from both sides. If your Pankl rods are .900" wide you mathematically remove .020" off of the non-chamfered side then divide by 2 the remaining amount to be removed and remove that amount from both sides;

    .900 - .845 = .055"

    .055" - .020" = .035"

    .035" / 2 = .0175" to be removed from the chamfered side.

    .0175" + .020" = .0375" to be removed from the non chamfered side.

    Fortunately the chamfer is WAY bigger than it needs to be so removing the .0175" from the chamfered side isn't enough to worry about.

    To measure the offset of connecting rods, set up an indicator with enough travel to measure at least .100" to be setup on the large end with the small end held or bolted down to a 1-2-3 block. Try to zero it out on the low side then flip the small side on the 1-2-3 block and read the indicator for what the offset is on the big end.
  2. Jim Blackwood

    Jim Blackwood Well-Known Member

    Thanks for the tips Derek, that's what I thought but it's always good to double check proceedure. I really don't think a .060" offset is going to make a significant difference in the operation of the engine. Yes the rod won't be centered in the piston exactly but being that wide I'm not sure it matters. The line of thrust is still well contained within the rod's width, and generally there's some side play that will accommodate the offset. But I'll check it before I cut the rods and take it into account. A quick look seems like what you said is correct.

    Do you still have that bearing info on these smaller rod journal sizes? I have bearing numbers for the Pankl rods but need to come up with some numbers for the Carillos. I measure the big end at about 2.009" or right at 51mm. (The size on the box tag was incorrect) That should be a standard size for something, right?

  3. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    It has been mentioned that the 300 is a fairly strong engine in it's stock form, and also that some have spun it to 6,000rpm countless times without any problems. Also that some components interchange with other engines, some requiring additional machine work. I've always thought it would be fun to turbocharge my original engine for my `65, which is the 2bbl. 300, but I have a few questions.
    1) How much boost could a basically stock rebuild 300 withstand? (stock rods, crank, etc.)
    2) The GN 3.8 pistons could be used if the block was bored .050". Did the GN 3.8 come stock with cast, hyper, or forged pistons? I've seen a ton of those cars take some serious beatings and hold together.
    3) Forced induction in my limited experience can make great power without a great deal of other mods, i.e. big cam, ported heads, etc. A little more cam, heavier valve springs of course. I understand that more airflow=more power potential but I know of an original owner `87 GN that runs 10.90s and has never had the heads off. I've seen those 3.8 heads apart and the ports don't look very big to me.
    4) Could a person realistically build a fairly stock 300 with the intention of going turbo big enough to run, say, a low 12 in a 3,600lb car or would that be courting obvious disaster?

    I know I would need a 4bbl. intake to use either a blow-thru Holley or aftermarket F.I. It would be a fun project but I can't justify spending huge money on it.
  4. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    I don’t see why a stock 300 engine couldn’t make 500 hp to the crank with the right turbo and fuel injection. Reliability would depend more on the accuracy of the tune instead of the HP applied. A bad tune will kill even strong parts. A good tune can be super easy on parts.

    If the engine runs well just have a custom turbo cam specced, fab up a single turbo setup with an intercooler and a self tuning EFI.

    For prospective we took a 74 smogger 350 bone stock right down to the cast intake and cam and it was 175 hp on the dyno NA and 350 hp with twin turbos on low boost with no intercooler. It ran reliably for years and got 18 mpg.

    My old car that I sold was 3700 pounds, super mild 350 with no expensive parts and it made 460 hp at the tires and ran mid 11s. With 3.42 gears and a 4 speed auto. The heads were not ported, stock valves, 9:1 compression, single plane intake and a carb. Cruised at 120 mph easy.

  5. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    Thanks Sean, that was the answer I was hoping for. The 300 did run well enough but it was tired. I still have it and always wanted to rebuild it and put it back in the car but clearly 2bbl. 300 isn't a whole lotta fun. I put in a 350 sbc, a fresh engine that I already had, with the intention of it being temporary until a decided what to do with the car. Well, I later ended up with another sbc, a perfectly streetable 406 that dyno'd at 470hp and 526lb.ft of torque at the flywheel on a hot humid day, the torque being over 500 from 3,600rpm to 4,800rpm. I have not been to the track with it yet I have to say it is a blast to drive on the street with the 200-4R and 4.10 gears. I had a new `87 Turbo T and always wished I had another one. That car was also a blast to drive even though it only ran a 14.11 in the 1/4. It was bone stock. I guess I mainly just wanted another turbo car and have dreamt of doing that with my original 300. If I could get it rebuilt with the stock 9.0 compression and not a ton of high dollar parts and machine work I would probably pursue that a little more aggressively. I won't apologize for the Chevy engines because in their defense they are a great engine, strong and easy to make good power with but I would really like to get back to a Buick engine in my Buick.
  6. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    There are small journal forged sbc aftermarket rods(6.00" that are available in I-beam and H-beam or 6.125" that would be H-beam only) that aren't overly expensive, that with minor altering will work in your sbb 300. Also there are the TA rover heads that flow 225 in. CFM right out of the box that would be easy to make 400 + N/A HP, sprinkle a little boost in that equation say 8 psi and you would probably be over 600 HP!

    The AutoTec 4032 alloy pistons are suppose to be good to use with low up to IIRC 10 psi. of boost. If you want to run more than that you'll need the 2618 alloy pistons that are capable of much higher cylinder pressures.

    Unfortunately no one makes an aftermarket intake for the sbb so you would need to find a factory one or make one. Other than that the cost to build the sbb 300 for boost would be right inline with the cost to build a similar sbc.

    There is also the option to use a sbb 350 crank in your sbb 300 to make it a sbb 350 or with a set of nascar take out rods and a little offset grinding of the crank the cubes can be pumped up to 362 with the same .050" overbore as the 350 version.
  7. Jim Blackwood

    Jim Blackwood Well-Known Member

    No joy on that bearing shell Derek? That's fine, I can sort it out. I was just hoping you had a ready suggestion.

    Bill, it sounds like you're all over the place with this 300. On one hand you want to do a cheap basic build with boost and then you get to talking about all this other fancy stuff. that's all great fun, but I think you need to decide what your goals are. Now you can take a stock iron head 2bbl 300 and slap a blower or a turbo on it and right out of the box make very decent power. The engines are port restricted and the boost will overcome that. You have an engine that makes gobs of torque but not a whole lot of horsepower with a 9:1 CR. You can pump a lot of boost into that before running into problems, first off because the SCR is low, it is probably under the advertised figure and will be happy with boost and second, because of head restriction you are going to be showing a lot more boost than the cylinder is actually going to see. By contrast a set of TA heads will show a lower boost pressure but have more charge getting to the cylinders. So they will make more power at a lower boost level. The boost pressure is not a valid metric of engine power output. It can however be a yardstick for performance improvement. For example, I had a stock low compression 215 that I boosted by 16 pounds. Because that is twice atmospheric pressure it would be fair to say it was burning twice the charge, acting about like an engine of twice the displacement and in fact that's just the way it felt.That little 300 just as it sits is capable of surprising performance. However, it's far more common to also include other performance enhancers, a cam change at the very least, which changes everything. Now you no longer know the relationship between the boost level and the power output. What you need to watch is EGT. Keep that and the ignition advance in line and you can boost the crap out of it.

  8. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    Jim, I'm not sure I understand how I am all over the place with my ideas. What other fancy stuff? I thought I was fairly clear about my intentions. I know the induction side is going to be a little costly but other than that I was hoping I could get by a little cheaper on the bottom end. So just to be clear, are you saying that I can't? Please don't misunderstand me, I am here to learn and value everyone's opinion.

    Other than the new `87 Turbo T that I had, I have never had another turbocharged car and know almost nothing about them but I am willing to learn. I have seen a lot of them run at the GS Nationals and I can't help but think if they can make that kind of power out of 231 inches then why couldn't a person do just as well with 300 inches. They seem to be basically the same engine (same bore and stroke) with the exception of the number of cylinders, right? It is my understanding from reading this thread that the 300 is a fairly sturdy engine to start even in stock form. I doubt if my car saw a lot of abuse during it's lifetime, at least not before I got it, but the original engine had somewhere around 142,000 miles on it when I removed it and it still ran pretty good, just smoked a little, leaked a lot and needed a valve job. I hoped that I could get a fairly basic rebuild done without spending gobs of money, maybe $2,000 plus parts. I can't imagine the 3.8 in the GN having a lot of exotic parts in it in their original form yet they seem to be able to withstand an awful lot of abuse. I'm sure a lot of them got destroyed from being pushed beyond their limits but I'm also sure a lot of them didn't. It's basic hot rodding, we push things to their limit. It's in our blood.

    I read an article some time ago where Super Chevy magazine put twin turbos on a 4.8 LS engine with the intention of seeing how far they could push it before it broke. The did 60 dyno pulls, 50 of them over 1,000hp and ended up making 1,204hp and never broke it. Does this mean all 4.8 LS engines can tolerate this? No, it doesn't, and I am certainly not gullible enough to believe they would but it was still an interesting read.

    Again, I am here to learn and I figured this thread would the place to do it and get some guidance. I'd love to take on this project and I am fully aware that pennies add up to a dollar but if I think for a moment that I'll end up with $10,000 or more in it then I'll just forget about it.
  9. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Bill, here is a set of rods that would work for your 300 build;


    You won't break the bank with the above rods. The factory sbb 300 rods are 5.960" long, the ones in the link are .040" longer at 6.00" long. Using these you can probably make the v6 turbo pistons work? Probably an extra $100 to alter the rods to work but still under $400 for a set of 4340 forged rods with ARP2000 rods bolts.

    That would give you a rock solid low end and maybe leave enough in the budget for some porting?

    Sorry Jim, I must of posted those part numbers 5 or 6 times and use to be able to find them without barely looking for them but for some reason I can't seem to find them.:oops::(
  10. Jim Blackwood

    Jim Blackwood Well-Known Member

    Thanks for trying Derek, if you run across them though... I'm sure I'll get it sorted out eventually. Still have a crank to turn and a couple of blocks to prep first.

    Bill, don't get all hot and bothered, you can get this. Pay strict attention to your bearing clearances and do the oiling mods, that's job one in any Buick build. Use the rods Derek suggested. Although guys can and have made lots of power with cast rods, they do break easily and it's the weak link. Next is the pistons, if you can use turbo pistons that'd be a real good idea. If necessary the crowns can be trimmed a bit. Stick with your iron heads, maybe a slightly hotter cam, add boost and you're there.

    But first, have the block sonic tested for core shift. No point throwing money at it if it has issues.

  11. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    Jim, I didn’t get all hot and bothered and I apologize if it came across that way. It’s always a roll of the dice when communicating such as on these forums. It’s way too easy to misunderstand someone as opposed to talking in person, which is why I try to avoid texting if I can. Anyway, I really appreciate the guidance on this, although I admit that I haven’t completely convinced myself that it’s a good idea to do it yet, mainly because of the cost. What I am convinced of is that it would be a really cool project but I am going to start compiling a list of everything I need including the cost and will make my decision based on that. So far I think I’m not far off track. What helps is in the end I can sell my 406 Chevy and recoup some of it.
  12. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    I looked and unfortunately I couldn't find any standard bore 3.800" v6 turbo pistons.:( The least oversize I could find were .020" v6 Buick turbo pistons and those were a couple hundred more than the .030" over sets!:eek:

    On a good note, you can alter an LS turbo kit to work on you sbb 300. The LS turbo headers have a similar spacing as the sbb 300, with the LS flange cut off and a bit of fire wrenching to position the tubes to weld the sbb flange on shouldn't be that bad of an alteration. Then the reast of the kit would be installed as directed. Look for a kit for a '64/'65 Chevelle should be a relatively easy install?

    These headers could be made to work;

    Last edited: Oct 15, 2019
  13. Duffey

    Duffey Well-Known Member

  14. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Cool stuff but I think the crank is more than double of the entire budget! Can get a billet crank for less than half of that price.:eek:

    Those manifolds are cool but I don't think there would be enough clearance on the drivers side? Would be a cool option if there is though. Can probably use one on the passengers side with a cross over pipe for a single turbo though?
    Last edited: Oct 15, 2019
  15. Duffey

    Duffey Well-Known Member

    Yeah I don't know how they would work clearance wise.

    That crank is pretty obscene, but I also have not idea how much custom cranks like that are to begin with. If you could get one for half the price it would be like getting the heads for free!
  16. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Just noticed that is an Australia company, what is the exchange rate from the USD to the Australian dollar? Shipping would be a killer though.
  17. Duffey

    Duffey Well-Known Member

    Looks to be a but under 4k. Shipping would most definitely kill you though. Another option would be to use a Rover 4.6 crank. Nodular iron vs normal cast 300 crank. If I remember correctly you can offset grind them to 3.4" or close to.
  18. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    ALL of the Buick cranks were nodular iron. Nodular iron cranks are still made from the casting process. I have drilled on a few of them, they ARE tougher than regular cast iron for sure! Usually you get small broken shavings and dust when you drill cast iron. With a sbb crank you actually get those long chips like you would get drilling steel.

    The sbb 300 crank can be stroked to 3.540" to use nascar take out rods.:cool: Can make a 321 sbb with a .050" over bore and it will fit without any mods in a sbb 300 block. Still with a stroke that size there won't be any cam to rod clearance worries.
  19. Duffey

    Duffey Well-Known Member

    Ah ok. My understanding was that nodular iron wasn't used widely in auto manufacture (at least in crankshafts) until later but I might have had my wires crossed.
  20. Jim Nichols

    Jim Nichols Well-Known Member

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