454 rebuild with blower... Pistons and clearances.
02-03-2015, 10:03 AM
#231
MarineKinetics
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Question;
Tony, back in my motorcycle/sled/watercraft wrenching days, I remember that they used to make these things called "case stuffers" or "reed stuffers". Basically, a molded plastic piece that would fit in the intake port of 2 cycle motors in an attempt to pick-up velocity/airspeed. In fact, the OE's did this.
Would there be an advantage for something like this for the 305's? Seems easy enough to make and install, bet the smaller cube motors would love it.
Tony;
Its called our oval port line.....LOL
The rect port design simply has more CSA at the entrance than most of the heads/applications we are discussing need. Till you start moving 400+ CFM's on aggressive engines with very large appetites for air the rect port opening of a BBC head is larger than it needs to be. Thats not where the air is restricted anyway.....its all about the bowl and negotiating the turn into the valve and chamber area.....thats where the port is very sensitive to shape, CSA, and valvejob/chamber design.
Bottom line is you could epoxy the floors of your intake port as well as your intake manifold exit and pick up ET and throttle response if you did it correctly with the aid of a flowbench to guide you (and alot of time and patience).....or you could buy a kick azz oval port to net you the exact same thing right out of the box.
Ported Vic Jr with a one inch open or possibly tapered spacer assuming you have the room for a spacer.
Perfect intake for that cylinder head
Tony, back in my motorcycle/sled/watercraft wrenching days, I remember that they used to make these things called "case stuffers" or "reed stuffers". Basically, a molded plastic piece that would fit in the intake port of 2 cycle motors in an attempt to pick-up velocity/airspeed. In fact, the OE's did this.
Would there be an advantage for something like this for the 305's? Seems easy enough to make and install, bet the smaller cube motors would love it.
Tony;
Its called our oval port line.....LOL
The rect port design simply has more CSA at the entrance than most of the heads/applications we are discussing need. Till you start moving 400+ CFM's on aggressive engines with very large appetites for air the rect port opening of a BBC head is larger than it needs to be. Thats not where the air is restricted anyway.....its all about the bowl and negotiating the turn into the valve and chamber area.....thats where the port is very sensitive to shape, CSA, and valvejob/chamber design.
Bottom line is you could epoxy the floors of your intake port as well as your intake manifold exit and pick up ET and throttle response if you did it correctly with the aid of a flowbench to guide you (and alot of time and patience).....or you could buy a kick azz oval port to net you the exact same thing right out of the box.
Ported Vic Jr with a one inch open or possibly tapered spacer assuming you have the room for a spacer.
Perfect intake for that cylinder head
02-03-2015, 10:13 AM
#232
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correct me if I'm wrong but doesn't Alex build motors for a living and is his profession? I can tell you that i have heard phenomenal things about him from reliable resources. Grouping him in with Internet expeers isn't only insulting it's flat out disrespectful. That comment right there is why guys like Alex that have a wealth of data and real life experience don't post on forums anymore. I didn't even see that being directed towards you for what it's worth.
02-03-2015, 10:45 AM
#233
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This whole debate has stemmed from me being told the 305 heads were not the optimal choice in Paytons supercharged 454 build. I simply asked, has anyone built a similar combo, with a blower, and the afr rovals, and what were the results. Why I asked? Because I simply havent seen that build, and honestly would have liked to.
I've seen a few supercharged builds in person with the AFR rectangles, and thought they were very impressive. Upon my quest to seek out the results of using the ovals on a similar build, have come up empty handed. Even on AFR's website, out of the 27 BBC articles posted, several of them being small bore BBC supercharged engines, the supercharged ones were all built with rectangle ports.
Either way, it doesnt matter anymore. The only thing I've gained from this thread, is to simply keep my mouth shut, and stop wasting my time via PM's and emails, when in the end, just be told I'm an incorrect internet expert.
So I ask this of my oso friends. Please do not waste my time asking me too figure compression ratios for you, look up piston part numbers, which bearings and clearances should be used, which blower, which carb, which gaskets, and other things, when in fact, you already have the answers provided by the higher authorities, or plan to do so anyways.. And I say that without any sarcasm. You will honestly be better off talking with the experts that do this day in and day out. I am just a do-it-yourselfer who tinkers with my own stuff, more than builds things for others.
02-03-2015, 11:31 AM
#235
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think about what you just said.alex is responding to this thread so that puts him in the [internet engine expert]group.alex is a sharp guy and yes he has a shop and is a professional BUT,i see no need to take shots at the people responding that do not own shops.again just my opinion.putting alex in the group of internet experts is no more disrespectful than the internet engine experts statement to begin with.i have no problem with alex but he needs to remember that you will get many opinions when you bring it to the internet.ealesh,i don,t feel like an arguement today and you have all the answers so i will leave it alone because i have other things to do right now.maybe in the future you should just pm alex and not get the opinions from people you disagree with.
02-03-2015, 12:01 PM
#236
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My 454 B&M 250 project has really started to get moving, and in the process I've come across some stumbling blocks. I found that four of my pistons showed evidence of detonation; definitely one for sure (#3... Slight erosion around the intake area at the crown extending to the top ring) with the other three having blemishes in the crown's face. Needless to say, these won't work with the blower. My bearings all came out looking good, and my crank should require polishing to put it back together so that's good!
My question centers around pistons: what to use and how should I have the block bored for proper clearance? My plan is to run less compression than the original LS6 pistons provided. I figure a flat-top with a zero deck, .040 gasket, and a 120cc chamber will give me right about an 8:1 compression ratio, maybe a touch over would be good for supporting 9-10 pounds of boost with aluminum heads.
The block will go to the machine shop this week to have it cleaned, sonic checked, decks trued, and finally bored and honed. I'm hoping that I can go with a .060 over piston to take advantage of the extra cubic inches as well as unshroud the intake valves of my heads. If I was to use a JE 139478 piston, ould it be safe to say bore it to 4.31 (if it checks clear), and then finish hone the bores to 4.315 to give the proper piston to wall clearance (assuming .003-spec'd piston clearance plus supercharged and cold water application). Thinking that ring end gaps should be set at .022 on the top ring and .025 on the second (plasma-moly rings). I guess I'd need to have the pistons in-hand first.
Looking for some advice from the experts here. Thanks!
My question centers around pistons: what to use and how should I have the block bored for proper clearance? My plan is to run less compression than the original LS6 pistons provided. I figure a flat-top with a zero deck, .040 gasket, and a 120cc chamber will give me right about an 8:1 compression ratio, maybe a touch over would be good for supporting 9-10 pounds of boost with aluminum heads.
The block will go to the machine shop this week to have it cleaned, sonic checked, decks trued, and finally bored and honed. I'm hoping that I can go with a .060 over piston to take advantage of the extra cubic inches as well as unshroud the intake valves of my heads. If I was to use a JE 139478 piston, ould it be safe to say bore it to 4.31 (if it checks clear), and then finish hone the bores to 4.315 to give the proper piston to wall clearance (assuming .003-spec'd piston clearance plus supercharged and cold water application). Thinking that ring end gaps should be set at .022 on the top ring and .025 on the second (plasma-moly rings). I guess I'd need to have the pistons in-hand first.
Looking for some advice from the experts here. Thanks!
This was the question that started the entire thread. Pretty simple really. I'm sorry that it has evolved and progressed towards what it has become.
As for the plan now... I pick up my parts from the machine shop Friday. The block checked out fine at being standard as did the crank and rods. The rods are being reconditioned to use ARP bolts. I have my bearings, rings, gaskets. 525EFI cam, and the rest of my top-end ready to go with the exception of the springs and super alloy valves (they will be ordered this week). She'll be together in a few weeks dependent on my schedule, and then I'll strap her to the dyno to see what's what.
Thanks to everyone that contributed with trying to help me; greatly appreciated. Sorry that it had to turn into such a b!tchfest between some. I think it ruined what could have been a really informative piece here on OSO.
02-03-2015, 12:36 PM
#237
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