Hot Rod Magazine 300" Stroker Buildup!

Discussion in 'Small Block Tech' started by No Lift, Jan 14, 2011.

  1. bob k. mando

    bob k. mando Guest

    I think one of the coolest parts of Larry's write-up was where he was talking about using the flow characteristics of the port at different speeds to change the effective port area and coutour.

    i've been reading about 'dynamically reconfiguring ports' using the pressure waves for ... :idea2: must be close to 20 years now. it's usually found in high speed aerodynamics and rocketry ... and Popular Science magazine. :laugh: when Larry was talking about the F16 intake, that's actually one of the less baroque and more straight forward applications. there's rumored to have been black-ops ( just like the Blackbird used to be ) testing on a rocket which used no exhaust bell. it was supposed to have used the shock wave to shape it's exhaust.

    i had just never heard anybody apply it to IC engines. but once i saw Widmer write that i was all like, "Day-um".

    check out what he has to say about exhaust porting. that could be added to almost any engine, i should think. it would be dependent on piston displacement, rpm and valve size. i need to get ahold of a fluids engineer and ask how small the valve would need to be for a 6000rpm ~350ci. :confused:
  2. Jim Blackwood

    Jim Blackwood Well-Known Member

    If you just look at the way a toilet flushes, you see that at first the water flows slowly but once it establishes a spiral rotation it just roars down the drain. The highest velocity airflow we have in nature is a vortex, and vortical chillers move the air so fast they produce sub-freezing temperatures. So I have to ask, why are we using rectangular intake ports and trying to get straight laminar airflow down the runners? Even considering the pulsed nature of the flow wouldn't it seem to make more sense to develop vortical flow? It seems to me that, designed properly, the vortical flow could be made to stack up the air at the port between valve openings, creating a supercharging effect when the valve opens. Do you know of anyone who has experimented with such a design?

  3. bob k. mando

    bob k. mando Guest

    nope, as far as i'm aware Widmer only gets into that in the cylinder proper. it's amusing reading back through the old articles in chronological order. if you pay attention it seems that some of Larry's critics were more correct than he was about what was happening in the cylinder ...

    it's just that nobody ( Larry included ) were expecting super-lean conditions / stratified charge to actually be a good thing.

    why are we using rectangular intake ports and trying to get straight laminar airflow down the runners?

    you know, if you twisted the rectangular port between the plenum and the head you could use the cross section to force a vortex. :Brow: kind of like rifling ... just make sure you design it for CCW. :moonu:

    i dunno though, would any velocity gain even make up for the additional apparent length of the runner?
  4. exfarmer

    exfarmer Well-Known Member

    There were some round port engines designed. I think maybe Pontiac had some but maybe they were just experimental?? Perfaps the increased CFM/ port area of a round port does not make up for the increased area of a rectangular port.
  5. Jim Blackwood

    Jim Blackwood Well-Known Member

    I think you have to look at it like a dynamic system since the valve is constantly opening and then slamming shut. In a typical vortex the center is a low pressure area so I'm thinking that when the valve slams shut the air will stack up on the valve, spreading into the center of the vortex and slowing down the rotation. The real question would be how far up the runner this stack would have to go, and what optimum runner length and volume would give the greatest density at the valve between openings, and therefore the highest pressure and the most inrush when the valve opens again. To at least some extent this is likely to be rpm dependent. Bob, as much as I like your twisted ports I don't think the air would like them particularly well due to the corners. However it would seem much easier to make ports which have a set of small ribs projecting inwards maybe as much as a quarter inch, again, like rifling. The core casters would have a fit, but I think it could be done.

    The people who make fuel filler necks have been aware of this for decades. If you noticed, somewhere between the '70s and now fuel filler tubes decreased in size from around two inches in diameter down to about an inch and a quarter. This was because the smaller tube was the correct size to induce a naturally occurring vortex which allows it to out-flow the larger tube, while also venting the tank up through the center, where no liquid flow occurs.

    So the dimensions are probably fairly critical. I recall the old BBC had round ports on their lower performance heads and intakes. Also I think the Ford Modular engines use a round port.

    The potential for gain may be minimal. After all, the optimum shape would seem to be a trumpet and that would pose real problems due to space requirements. And as Marc pointed out, packaging does generally allow more cross section in a rectangular port shape.

  6. Fox's Den

    Fox's Den 27 years of racing the same 355 Buick motor

    Now tell me how the 350 did not make as much power as this motor did, it should have. The 300 used stock heads and intake. Stroking the motor made that much extra power?

    Ok, they ported the heads, this motor should have been known about by the other TV show. They had to have known of this motor.
  7. No Lift

    No Lift Platinum Level Contributor

    I pretty much explained my reasons over on the HP TV 350 thread. I think they way overcammed the 350. That stroked 300(349) used a smaller cam and peaked at 390HP at 5700. If the 349 peaked at 5700 with a 236/241 cam then an only slightly larger 355(?) with a 241/257 cam would try to peak at a rpm noticably higher. The 350 was way down compared to that and wouldn't get close to that HP even if you revved it to 6400.

    Now figure that the 349 would've been much more carefully built because for that article Sherman's shop was trying to show what they could do with an oddball engine to make it shine while at HPTV they were showing pretty much a basic rebuild with some extras. That is not a reflection on AMP's machine work, just the realities of a basic rebuild. HPTV had no dog in the fight to get the absolute best HP. That would account for some power.

    Different dynos and different locations would make for a few numbers difference.

    I thought I read somewhere that the 350 heads were good for 240 cfm on the intake after a small amount of CNC port matching with nothing done to the exhaust. To me that seems to be a ton of flow for a 350 head with minimal prep especially since they said nothing about bowl work. New larger intake valves were used and exhaust seats were done so something must have been done. All I know is 240 is respectable for "little" work. Who knows how bad the exhaust is? Stock 350 heads should flow as well as the 300 heads modified though. If they only did a port match like they said that is pretty much useless without bowl work except to match the intake if it has larger ports than the head so you don't get reversion.

    Maybe the larger 1.95 intake isn't the hot ticket for such a small bore 350. That valve has to be shrouded. If you know anything about the 400/430 BBB they don't recommend the Stage 1 2.125" valves because of a smaller bore. I don't think the 349 used that big of a valve.

    I'd bet that 350 isn't really 10:1 because they said they used 10:1 pistons and we all know that to get the true compression up there decking the block and head milling is necessary. I'm not sure how large those late model 350 head chambers are. That big cam needs really high compression. Do a DCR on it and see how bad it is.

    Lower friction, higher ratio, more accurate ratio rocker arms would tack some on.

    I still think the cam is the number 1 reason and something doesnt jive with the 350 headwork. The other stuff also adds up. Hey, if just stuffing an oversized cam in a SBB or BBB was all it took to make the big power half the guys on here would have 400 HP 350's and 550 HP 455's.
  8. gsgtx

    gsgtx Silver Level contributor

    the cam was 243/257 to add to what you saying about to big of a cam at 241/257. the 349 used a 1.8 intake valve, like you said not like the big 1.95 valve. if the comp wasnt really near 10.1 with that big duration cam, then on a 107 LSA on top of it with all that over lap,comp ratio could have been a factor too like you also said.
  9. sean Buick 76

    sean Buick 76 Buick Nut

    Sure, you might even get better results with a 340... Less machine work involved. If you had a good running 340 you could have the heads and intake ported and add a nice camshaft... No need for aftermarket parts to make power.
  10. Fox's Den

    Fox's Den 27 years of racing the same 355 Buick motor

    You are absolutly right about this. My heads were supposed to be 235 on the intake and 176 on the exhaust for the flow. I ended up with 395 hp and 370 tq. My comp was at 10.6 They should not have never put this big of a cam in if the heads did not flow this much. I expected them to pull over 350 hp just based on the cam that was being used and with the mention of the 10.1 pistons this is what I had expected here. If I take that same cam and stick it my engine right now the way it sits I would expect to get the same power as I did with the TA 510 cam. With the low power they got out of that cam and if the comp was not over 10.0 then I would have suggested a cam in between the TA 413 and the TA 212. When is someone going to give this motor it's due. I do not mean this particular one but one that is done a little bit more than mine with higher porting and maybe 11.0 comp
  11. 64 skylark mike

    64 skylark mike Well-Known Member

    Hello guys,
    I found this thread tonite kind of by accident. Only been withV8 board couple weeks, and have read some really interesting and informative stuff. Even started a couple threads so I could meet some other people with some of the same interests and type of car and options my car has. I really appreciate all the welcomes and helpful advice. I recognize many of the members that have posted here. A lot of you have posted replies to my posts, thanks.
    This 300 build is very interesting to all of us, especially if running the 300. I am glad to see this get back on track. It was getting pretty ugly for a while. Please forgive me if I am speaking out of place being new here, but this V8 Buick club is great, I sure would hate to see it self destruct.
    All of my experience here has been fun and encouraging. Keep up the great work, and thanks to everybody for sharing a wealth of info as well as a feeling of friendship.:TU: I plan on hanging around a long while!
  12. sean Buick 76

    sean Buick 76 Buick Nut

    YES this thread got WAY off topic and trouble maker caused issues BUT the build they did on the 300 was AWESOME!!! I should scan and post the article!
  13. roverman

    roverman Well-Known Member

    Jim, from what I've read so far,(David Vizard's Port and Flow Test), Inlet charge needs just enough swirl to effectively distribute aif/fuel within the cylinder,(keep it off the cylinder walls). Round intake ports don't make bends as well, towards the bowl/valve area as a flat floor intake runner. Round exhaust primaries are a different deal. Still, a flat floor in the exhaust port will help control the flow shape. If you had an extreme vortex swirl into the cylinder, think about where the heavier fuel would wind up ? What is the romance with a cast iron 350 head ? The bare TA rover/sbb heads are a pretty good deal for the $'s, and have lot of potential, in the right hands. Mike is claiming 270 cfm. with a 64'-300 port size, using bowl, guide slimming, and chamber work. This head is "very" strong, with major latitude for various porting configurations. 27 lbs bare means ample aluminum everywhere. "Oz" is claiming 600 hp. with ported version of this head,(stroked RV8). I might believe this, if there was a dyno sheet. In the mean time, I'll dig for myself. Onward, roverman.:Smarty:
  14. sean Buick 76

    sean Buick 76 Buick Nut

    Bump for a cool little engine build!
  15. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    I loved the Hot Rod article,and the engine,Dave did a great job! I'm in the process of doing something similar,and want to know how you are lovin' to drive your car now.And how happy you are with its performance? And thanks for building your obsolete gem,and sharing the results in HRM.

    Not sure if you posted it some where else,but I was wondering how the car runs,and if you made it to the dragstrip? And what kind of times you got out of it?

    Thanks in advance.

    WV-MADMAN Well-Known Member

    Looks like Dave and Karl fled this site for good.

    And who could blame them.

  17. 300S4EVER

    300S4EVER Well-Known Member


    I am about to embark on a low-budget build on a 67 -300. I am looking at stroking the bottom end and stiffening the valve train as explained in the article. The factory camshaft will most likely be used or a replacement if it is out of spec. As flow-benching anything means many $'s I do not have, a standard valve job and cleaning of the heads and intake will have to suffice. I am looking at adding a 4-bbl intake with a quadrajet and GM HEI ignition. If you have specific part#'s for pistons and rod bolts we could use it would be great information to have as it will save my machine shop time searching for these parts. Specifically speaking which of the rod bolts were causing trouble or fouling so we know which ones to look for? i saw in another thread something regarding oil pan clearance. were there any issue's using the stock pan?

  18. sean Buick 76

    sean Buick 76 Buick Nut

    Call and ask for Dave:

    ---------- Post added at 10:35 AM ---------- Previous post was at 10:34 AM ----------

    Call Dave Nelson:
  19. 300S4EVER

    300S4EVER Well-Known Member

    Cost does matter! I am working closely with Dave on my 300 re-build project. His experience and track record and the long hours discussing options have convinced me He is the man for the work I need him to do. I know this thread went WAY OFF track and became a back biting fest by a particular board member. That member hasn't been around in over a year. I am going to get very good results because Dave knows what he is talking about. Having credible document-able evidence and sound automotive knowledge always trumps hot-headed theory in my book. My motor will be going into a Rat-Rod. It will be all that I need for the weekend driver I intend to build.
  20. sean Buick 76

    sean Buick 76 Buick Nut

    You are right!

    A trouble maker showed up and started trouble and then was gone right after the turmoil....

    Dave will do a great job!

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