Buick 350 Shortblock build

Discussion in 'Small Block Tech' started by DauntlessSB92, Jul 20, 2014.

  1. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    With the possibility of having a hurt motor (wiped cam, bent valves, or other issue) its time to think about starting a hot SBB build. Instead of taking the car out of commision I plan on building a replacement engine that I can swap over when done so I can keep the car in running condition and take my time for the build.

    I'm looking to build a 450hp+ motor, trying to center it around the upcoming TA heads and single plane intake as much as possible given the limited info available at this time. Of course I can't do to much without knowing more about the upcoming heads. And I have to plan for the unfortunate possibility of a delay in head manufacturing and using iron heads instead.

    I'm looking at picking up a running 72 350 from Bruno. So at this point I'll be looking at breaking it down, doing a little bit of inspection and getting some measurements before machine work. I'd like to stick to a shortblock budget of $2000. It's going to be a roller motor and N/A although I'd like to build it in such a way that it could be used in a mild boost application ( <6psi)

    I would like to be one of the first to build an engine for the upcoming TA parts so I don't want to sacrifice performance for cost, I see this getting expensive.

    After tear down I'll be taking the block to the machine shop for cleanup and testing to make sure its a good motor. As long as it can take a .030 overbore I'm not too worried about having a perfect "unshifted" block. I suppose the best way to go would be 73+ rods but what benefit would there be in using aftermarket rods in this application and what is availble? I know it would most likely be custom and this will be a sub 700hp motor so I don't need anything too crazy. Not looking to shift higher than 6500rpm.

    As for pistons I know there are the Auto-tec forged pistons, which seems like the best choice but if I can order through a dealer that supports this community I would like to go that route if anyone has some suggestions who to order from.

    What should be done as far as block modifications at the machine shop besides clean up? I know this is broad and some stuff I know already but I would like to have a list started to get a better idea of costs.

    Cam will wait until there is more info on the heads but I guess after cleanup and testing I will have to make a choice on deck height and pistons in order to keep the CR within range depeding on what head size TA comes up with. Or will I have to wait in order to get the best combination?

    Sorry this is so broad, it would just be nice to get some brainstorming done on here.
  2. alec296

    alec296 i need another buick

    I would suggest drilling out oil passage from pick up to oil pump to 1/2 atleast and get 5/8 pickup tube from melling #20SI5 and p20i booster plate ,opening up other oil passages like what is done for 455 and v6 would not be a bad idea.
    remember that the single plane is really going to increase rpm capability and you could easily go north on 6500 rpm fast. clean up deck of head and block. autotec will customize piston to your needs if you ask.decide if you really want boost as the wiesco turbo v6 piston with 1.860 compression height might be better(stronger metal/designed for boost) it comes up to about 8.8 for compression if you have block deck milled to blueprint spec. balancing is needed at this level or you will see problems.
    2000 is not expensive when building an engine . $ 6500 is about the range that Trishield and AM&P cost for a bullet proof 350@ 350hp- which leads me to another point that AM&P uses the 310 cam for a 350-360 hp build and trishield uses a 212 for same hp build.
    we already know that almost 400 hp can be made with 8 to 1 and a single plane intake with Seans 398 hp build before boost with the 212 and a smaller carb.
    so build engine for strength as with new intake and better heads these engines are going to rev hi and hard.
  3. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    my $2000 budget is just for the Shortblock (really just machine work and rotating assy) So I am not factoring in heads, roller lifters, rockers and intake and other top end stuff yet.

    I'd like to hold off on the cam too until I know what head specs will be. I am really on the fence for compression. I want a snappy high compression N/A motor but what is tough is that if I go that route I would have to change everything to go down a forced induction path. But I guess if I can get close to 500hp out of an N/A motor I would be happy without boost.

    So lets say that is the lofty number im shooting for. If 400hp can be made on a low compression motor with mild cam and ported stock iron heads I can't imagine a relatively wild cam that pulls to 6500rpm and almost 11.1 compression wouldn't make another 100hp. Just bench racing but that is the motivation behind this.

    So now that the number is out there I need to build a bottom end to take the rpm and power. The concensus seems to be that stock 73+ rods and pistons would be good to 550hp. Lighter forged pistons might be good to 650hp and 6000+rpm. I know others have spun more than that but this is NOT a race motor. Definitely looking for a hot street/strip setup. What can be done as far as the crank? What kind of money would I get into?

    I want to get a "fantasy" list of all the work that could be done to an SBB assuming the heads and intake are made. Then I can take that list and make more cost effective choices where it impacts reliability and power the least.

    I don't want to walk away wishing I had a 455.. I already have 455 springs in the car and I had a torn down block sitting in my garage last year that I almost built:spank:
    Last edited: Apr 17, 2015
  4. alec296

    alec296 i need another buick

    A lot of the big powered 350s have some type of custom single plane intake and big money into the heads . if TA makes the heads and intake or just intake many will see major increases in power and rpm range.
    cranks seem to hold up well.
    with a custom roller cam ,good ported big valve heads and a single plane intake and around 9.5-10 to 1. I could easily see you getting over 450 hp. 500 depends on cam and heads.
    as far as short block build it best you can. maybe arp studs.make it as strong a possible. good quality stuff.TA cam bearings. short block should be easy. its the top end that wont be cheap.
    im doing the same thing only mine is a stroker. custom rods custom pistons around 9 to 1.nitrated crank, roller cam and rockers. im hopeing for 450 ish hp but Derek is more optimistic
  5. pmuller9

    pmuller9 Well-Known Member

    Most of the big cams you might be using will have around a 290 advertised duration and be set with an intake lobe center at 106*.
    If that is the case a 10:1 compression ratio will get you about a 7.6 DCR which is good for an iron head.

    However if you end up with an aluminum head you can push the compression ratio to 10.5:1 and as you already stated we don't know what the new heads will have for chamber volume

    You don't want to build a short block for one compression ratio and end up needing something different.

    The new heads should be closed chamber so having the piston at zero deck would be beneficial for quench.

    The most I would do at this point is get the block and crank cleaned and checked, line bore the block and deck only enough to straighten the deck and make it parallel to the crank line.
    Then start collecting whatever the best rods are for the job and get them prepped.
  6. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    Running some numbers yesterday I have a good idea of what to do depending on what happens with the heads but you are right I can't choose a piston or deck the block too much yet until we have more concrete information. Hopefully by the time I have the motor apart and looked at by the machine shop we will know more. I am still unsure if I will go with the 73 cap screw rods or if I will look into some form of aftermarket rod. But at 500hp it shouldn't be necessary, just nice to lighten up the rotating assembly
  7. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    You can try ebay for a set of nascar takeouts that are 6.300" long or longer and make sure they are at least .845" wide on the big end because you can have them machined norrower less expensively than having them welded and machined to the right thickness. The rods with the 2.008" housing bore can be opened up to the Buick 2.125" bore housing size,or you can stroke the crank .100". The takeout rod pin size will be smaller than the sb Buick size,but won't be a big deal if you plan on using customs anyway. These rods usually end up weighing about 100+ grams lighter each and WAY stronger than any race prepped stock rod you can use.

    Sounds like you will end up with a nice running sbb.GL

  8. pmuller9

    pmuller9 Well-Known Member

    How about these?


  9. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    So those rods are the same length as 3.8 rods, which leads me into the stroke ratio question. For a pretty hot street strip motor what would be better, a larger or smaller rod? I know the concensus seems to be that longer rods are better and if I go with custom pistons then the compression height can simply be adjusted to match the finished block height available to with. Excuse my ignorance this is still a pretty fresh ttopic for me
  10. alec296

    alec296 i need another buick

    3.8 rods are 5.960 . stroker 3.8 rods are 6.350.
  11. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    Ah, that makes more sense thank you. same as the 350 in the other dimensions?
  12. alec296

    alec296 i need another buick

    Yes 3.8 pistons rear wheel drive are same piston.
  13. pmuller9

    pmuller9 Well-Known Member

    One of the advantages of using a longer rod is the piston gets shorter and a whole lot lighter.

    I just did a combination on a 300 Ford six where I went from the 300 six 6.2" rod to the 240 six 6.8" rod.
    The piston CD went from 1.8" down to 1.2".

    The original piston and pin weighed 819 grams.
    The new piston and pin weigh 574 grams.

    300 piston 1.JPG

    The same can be done for the Buick 350 if you use the 6700 Scat rod for the Flat Head Ford.

    It is 7.00" which is .613" longer than the 350 rod


    The piston will need a CD of 1.250" and a .750" pin diameter.

    The BE width is .865" which can be accommodated by widening the crank rod journal.

  14. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Or,the rod can be narrowed to .845 for the Buick crank.(which I am told is preferred from most crank grinders,not sure you might want to ask) But also a great rod option for a sbb 350! Jim Blackwood used the FHF aftermarket H-beam 7.00" rods in his sbb 340 build,but he had to machine some cam clearance into them to make them work.

  15. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    Picked up a running 72 350 over the weekend, I was so tempted to tear it apart but for now just took the maniolds off (and of course broke 4 bolts in the head.) So before I tear it apart, where is a good machine shop to have the block cleaned and inspected? I know of some places already but would prefer to have the block inspected by a place that deals with Buicks often so when Im ready I can bring it back to them.
  16. StfSocal

    StfSocal Well-Known Member

    I have a set of TRW Forged pistons, 10.1, 30 over, with some moly rings for sale if want to do pistons. Let me know!!!!

  17. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    Scott, thanks for the offer but right now I'm still in the planning stages. I'm trying to work out what rods to go with and that may warrant a piston with different specs from standard. Someone should scoop those off you quick though.

    BUICKRAT Got any treats?

    Call t/a and get a time frame on the heads. Even if you gotta drop 2500-3k on heads, you gonna put em on a shoddy short block? Aluminum heads on a good shortblock will set you back 10 g's ,cause if your putting big heads on it, yer not gonna cheap out on the bottom end. plan your build around that. 2k for a shortblock gets you nothing...except grief...
  19. alec296

    alec296 i need another buick

    10 g is abit much. Mike at AM&P and Jim at Trishield Performance with do a complete 350 with 350-360 HP dyno tuned in the area of 6 g. But if you want more power then expect to be higher.
  20. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    I am assembling the engine myself also. Looking to do as much as I can outside of machine work. So a 2k+ budget for basically machine work and parts doesn't sound unreasonable. Especially if I try to make something using existing stock of rods and pistons on the market. That's the trick. But like was said I can't plan anything until head specs are set in stone by TA. It's killing me though I want to tear the motor I have apart but I know I shouldn't touch it till I'm ready to start machine work

Share This Page