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pure ndn

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i want to be blown
« on: February 06, 2011, 09:06:21 pm »
ok i have a 420 mega blower gonna put it in a elimanator day cruzer it has a 396 in it now whats the best route on the bottom end? dont want to push rods out the bottom and kill the fishys the guy i got it from said with the pulley set up 6 or 8 pounds of boost will a stock bottom end die idk never played with a blower before any info would be appreciated thanks guys
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propless

  • Karma: +12/-0
Re: i want to be blown
« Reply #1 on: February 06, 2011, 09:51:57 pm »
 What size motor was it on where the pulleys you have made 6/8lbs of boost ?  Reason I ask is, if it made 8lbs on a 454 that could be about 12lbs on the little 396 with the same pulleys.  Thats going to take some good parts in there to make it survive.  Also, what is your static compression ratio, and what fuel are you willing to pay for (pump swill, race fuel, E85, Methanol, Nitro). ?

 In my opinion, I wouldnt mess with the 396.  Sell it to someone that needs it for an old car resto and get a 454 block.  Then pick up a good forged rotating kit, some decent heads, and a cam designed for a blower.  You probably wont save any money by building the 396, and all you'll end up with is a smaller motor (less power). 
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Welcome to the club of broken boats :o  Pay here$ bend over and move along.

IRRebel

  • Karma: +16/-0
Re: i want to be blown
« Reply #2 on: February 06, 2011, 11:06:45 pm »
I'm with Proppy on this, but will elaborate. Built a weird blower motor myself, and gotta tell you this , theres a LOT more to it than just the blower itself. Take the sublime warning in Enginedoctors "moron" post. It isn't cheap to do this even HALFWAY right.

Most times we here tend to tell everyone what WE would build or WISH we could build, but in this case theres not a lot of wiggle room. Not only does the bottom end need to be as bullet-proof as possible, head flow, gaskets, o-ringing.......all come into play, then you have the ignition issues, particularly if you're going to run pump gas. Many I know are running severely retarded ignition timing to avoid detonation at everyday use speeds, and CAN crank that up when at...say....the Tom Papp memorial or the Yuma power tour or something speshul running race gas or avgas. Counter productive to my thinking.

Just an FYI, was poking around Mallory's website the other day and never knew this. Their HyFire 6, not the 6A or 6AL, has the capability and special harness available to advance/retard ignition timing based on rpm and boost levels for blown and turbo engines. Can be user  customized as well, without some box the size of an 8x8x16 concrete block or require a laptop to program the silly thing.

All that being said, now understand this. PSI of boost is really back pressure measured at the intake manifold. Normal atmospheric pressure is, as I remember it, is around 7 PSI, which would be zero on any boost gauge. So ANY pressure registering on a boost gauge is ABOVE that number, whatever it is. Boost will increase with RPM, basics yes, but when boost numbers get into the rediculous digits, its really showing inefficiency in the system. Now, top fuel cars, drag boats, many more, get into or close to triple digits, but their entire gig is 1000 feet at a time no matter what the cost, with millions of dollars on the line. They also rebuild the motors every run and can afford to destroy a $200+k engine or two. Volumetric efficiency, durability, and low maintenance go completely out the window in applications like that.

I think I had some guy try and challenge me here very recently on this information, and I ignored it, but Proppy and I did a LOT of research on building blown E-85 engines which is what I ultimately went and did. All the physics remain the same, whether on pump gas, E-85, Alcohol, Nitro-Methane, whatever. You will be battling detonation when you are at the edge of your chosen platform. With E-85, Alcohol, or Nitro, you can get away with a LOT more compression and overdrive rates. No matter what fuel platform you build the engine for, if you want to be at the ever loving ragged edge, be my guest, crank the PSI up and replace/rebuild as often as necessary.  I think that guy was talking in the 20 PSI range which is CRAZY to me in a pleasure boat, or car for that matter and was asking about using block fill.  :screwy:

I beleive, with a solid engine for the given fuel and platform, at the top of the RPM range, you should be looking at 10-15 PSI on the gauge if you're into performance and rebuilding somewhat often. On a boat, that would be every year unless something stupid happens. For longevity, keep it at 5-10PSI. The HP difference between the two is negligeable IMHO. Still a LOT of planning, building and hardware involved in building a reliable and daily usable blown engine in that category. 

Just my LONG .02

Ray
 
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"Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways totally worn out shouting 'Holy Shit what a ride!"---Crewcheif22 AKA Keith

tryklon

  • Karma: +0/-0
Re: i want to be blown
« Reply #3 on: February 06, 2011, 11:59:12 pm »
Ive heard this quite a bit on here getting less power from a smaller motor but arnt we all just looking for higher rpms?

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obnoxious001

  • Karma: +4/-1
Re: i want to be blown
« Reply #4 on: February 07, 2011, 01:41:51 am »
ok i have a 420 mega blower gonna put it in a elimanator day cruzer it has a 396 in it now whats the best route on the bottom end? dont want to push rods out the bottom and kill the fishys the guy i got it from said with the pulley set up 6 or 8 pounds of boost will a stock bottom end die idk never played with a blower before any info would be appreciated thanks guys

I have been talking to a guy who has a 402 BBC asking similar questions.  I told him that the first logical step was to see what components were in his engine,, cast or forged crank,, 2 or 4 bolt mains,, and small 3/8" bolt factory rods or something better. 

It may make more sense to start with a 454 block if the 396 parts are not the "good stuff".  Depending on your budget and goals, you might even want to buy a stroker crank and do a 496 combination.  More cubic inches would require somewhat less boost than the smaller engine to make the same power.

With any engine project, it makes sense to take enough time to think through your power goals, intended usage (including RPM range) and type of fuel. 

I ran a 505 cubic inch engine in my Schiada, first with an 8-71 blower, and then I switched to a Gentry turbo kit after I broke the original (well used) Hank the Crank crankshaft.  I ran about 8 lbs of boost with AV gas with the blower setup, but changed to a maximum of 15 lbs of boost with the turbo engine, running primarily 110 octane racing gas.  The turbo engine ran 6 years of water ski racing as well as recreational river use with no issues until I finally sold the bolt less engine.  It was put together with all American parts, prior to the Chinese parts becoming so popular. 

The E85 fuel sounds interesting.  I have built one 496 turbo engine that has been running on it already, getting ready to assemble a 621 cubic inch all aluminum turbo engine for the same guy that will also run the E85 fuel. 

Back to your question, it makes sense to start with lower boost, make sure you have adequate fuel pressure and volume, and conservative timing,, I would say start with 30 degrees total timing, and don't exceed 32 degrees.  If the engine is assembled properly, and everything is set up correctly, there is no reason it can't be reliable and last a long time. 

That blower didn't come from a guy in Washington, did it?
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crewchief22

  • Karma: +66/-0
Re: i want to be blown
« Reply #5 on: February 07, 2011, 06:35:25 am »
Ive heard this quite a bit on here getting less power from a smaller motor but arnt we all just looking for higher rpms?

Higher RPMs in a jet boat application comes from more torque (it takes torque not RPM to push the water out of the pump).  More torque comes from more cubic inches along with the right combination of parts.

 
  • Boat #1: '77 Hondo Pantera GT Jet
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"Racing is life!  Anything that happens before or after, is just waiting"    Steve McQueen

The problem with America is stupidity. I'm not saying there should be a capital punishment for stupidity, but why don't we just take the safety labels off of everything and let the problem solve itself?

TJS Nordic

  • Karma: +2/-0
Re: i want to be blown
« Reply #6 on: February 07, 2011, 09:19:16 am »
A lot of good advice here. I also would go with a 454 based block. It took me one full season to get my boost and tune dialed in. I am running an EFI set up and went really conservative with the boost at first for the season. I was running 6.5 Lbs of boost. I still sawed off others that so called claimed more power and this and that to their boat. I put the “shut up” on at least 4 shit talkers the first season. For the second season I did a tear down with some new parts, bearings, and double keyway crank machining, Romac blower balancer with drilled and tapped holes for the blower pulley. I did not like the MLS headgaskets I was using so I changed back to composite ones. My compression was 9.6:1. So I really could not go crazy on the boost. I am running CNC Ported BB2 Brodix aluminum heads. I then upped the boost to 11 PSI, and did a 2 day dyno session with a good EFI tuner. This tune was the “reliable and safe tune”.  This past season this thing was downright scary. So as others state, start the boost at the low end of the scale and then move up from there. You will also run into other weird problems like, blower pulley alignment, alternator mounting etc. I had a hell of a time to get everything all lined up cause I am running a crank trigger. I had to machine and weld many custom parts to make it work.
T.J.

pure ndn

  • Karma: +0/-0
Re: i want to be blown
« Reply #7 on: February 08, 2011, 09:06:16 am »
thank you guys this will all help us out very much i think where going to up the cubes and drop compression to about 8.5 with the heads hes got is that a good start and he wants to run pump gas but idk 

 he really wants to put the steel crank out the 396 into a 454 block by some h beam rods and good forged pistons i told him whatever can be done 427 i think

and ya from wash. blower chiller and intake  the boat already had all the pluming for it all the guy gave us when we picked it up
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HDriderTH

  • Karma: +12/-0
Re: i want to be blown
« Reply #8 on: February 08, 2011, 05:09:48 pm »
Run whatcha brung. I say Slap it on the '96 and see what happens. I mean it's not like if it dont like it's gonna instantly explode. I dont think it's gonna see 6-8 psi at the R's Ur gonna spin it, maybe 6 g or better. Arent all '96 cranks steel, like the 327? I'd say worst case it's pukes a gasket. Start around 28*.
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'82 Sanger Bubble deck, Blown 454....V-drive

HDriderTH

  • Karma: +12/-0
Re: i want to be blown
« Reply #9 on: February 08, 2011, 05:10:57 pm »
Oh and dont forget to GPS first
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'82 Sanger Bubble deck, Blown 454....V-drive

enginedoctor

  • Karma: +7/-0
Re: i want to be blown
« Reply #10 on: February 08, 2011, 07:04:10 pm »
Blown engines are really simple to build...You would really be suprised  :thumbup:
  • Boat #1: 1970 Horizon Cheby powered Jet
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jet boat performance

  • Karma: +25/-0
Re: i want to be blown
« Reply #11 on: February 08, 2011, 07:10:51 pm »
Blown engines are really simple to build...You would really be suprised  :thumbup:
X's 2 ,doing two right now not cheap but certainly not difficult  Tom
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TJS Nordic

  • Karma: +2/-0
Re: i want to be blown
« Reply #12 on: February 09, 2011, 06:37:02 pm »
X's 2 ,doing two right now not cheap but certainly not difficult  Tom

Yup not cheap is right. Fun though.... ;D


enginedoctor

  • Karma: +7/-0
Re: i want to be blown
« Reply #13 on: February 09, 2011, 09:20:47 pm »
Sweet, salty, sexy  :thumbup:
  • Boat #1: 1970 Horizon Cheby powered Jet
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pure ndn

  • Karma: +0/-0
Re: i want to be blown
« Reply #14 on: February 13, 2011, 05:24:17 pm »
very nice ha ha :thumbup:
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HomeBlown57

  • Karma: +0/-0
Re: i want to be blown
« Reply #15 on: February 15, 2011, 05:53:54 pm »
Your best bet is to listen to the guys that have done it before like TJ and Obnoxious. You learn more from doing.

Do you know what the compression ratio is in the 396? It does have a forged crank, unless it is a rare industrial engine. I have pulled apart 5 stock 396 engines 2 1965 325 horse engines, 1 1966 375 horse engine, and 2 others that I can't recall their origin, all standard bore and all with forged pistons.  I say run the 420 on the 396.  Good head gaskets and crank case evacuators.

I like the MLS gaskets as long as you don't mind a little seepage sometimes (even with the copper sealer). TJ says he didn't like them. They do have some disadvantages. They do not seal the water or oil as well as a composite. He can probably lead you in the direction of a good composite gasket.

And ALWAYS remember! If someone has a hot engine in the garage and not in their boat, they are probably a dreamer and not a person that does! And if someone challenges you on your BS, you can always ignore them!

Boost is fun DO IT!
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pure ndn

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Re: i want to be blown
« Reply #16 on: February 22, 2011, 08:45:52 am »
well paying the machine shops rent this month just took down four blocks to get done splayed caps and such my friends broke open there tight ass piggy banks and where going 496
 we got three boats that want motors and they con me into doing most the work is it bad when your friends call u say i got beer and food come over then 2 days later they got half your parts on there boat so you dont have to hear them cry anymore
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