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Project Blown 305
I picked up a gmc 305 V6 that I plan to hot rod out a bit.
I was lucky enough to find another in the junkyard to snag some parts from. My goal: punch out the 305 with aftermarket/custom internals (ideally offset grind down to BBC or SBC rods and use an off the shelf piston for a BBC, if not able to bore it that far use off the shelf BBC Pistons and aftermarket rods with as much stroke as possible) -Upsize the hole in the rocker arm shaft pedestals, use (BBM BBB or FE full rollers dependent on which is closest to fitting) the shaft size isn't far off. -build larger shafts for this -if necessary build new pedestals -have cam redone for performance and potentially a roller setup(if only defining characteristic is needing to be flat vs banked to work with a roller lifter) -machine next to lifter bores for link bar -bush the bores to the correct size for a common engine lifter -laser cut flanges for the intake to fabricate a steel blower manifold to mount an 8v71 supercharger off an old diesel generator(regardless of if it adds power, it needs to look super mad max-like) -modify the pan for a deep sump -build headers using laser cut flanges from thunder v12 (hoping to find magnum heads in the meantime) -few other ideas but they aren't coming to mind. My questions: Does anyone know how thick the bores are? Did they cast one block and bore to desired displacement? Or did they cast multiple blocks with bore thickness dependent on end displacement? I ask because if I can I'd like to punch this out as far as I can go (5.125" if possible) and want someone who's had theirs apart and at the machinists testing the cylinder wall thicknesses chime in if possible. |
Re: Project Blown 305
These engine blocks are All water jacket. From what I have read, .060 over would be tops. There's plenty of bore to begin with anyhow so I'd be looking at stroking as much as possible. If not, find a bigger v6. There's an old story of a guy who hot rodded a 478 v6....made tons of power...more than enough to take on spiced out 454's. And it could handle 5000 rpm. The 478's have a 5.125 bore.
Also...in for the build. Be sure neat for sure. :thumbsup: |
Re: Project Blown 305
Ah, I wasn't sure. With some engines they leave them thick stock (older Chevy 283s and 352 FE fords) so you could overbore to the larger setup.
I would one to snag a 478 block/crank. Does anyone in northern Cali have one sitting around? My goal is to put down as much torque as I can under 4500rpm. The Piston speed with the max stroke (ideally 5.18" with a 2.0" rod journal) 4500rpm is max. It would produce a 644ci if I can use a 5.125" bore and 5.18" stroke. I want to put a smack down on a lot of the big motors. This has the biggest architecture I've ever seen and 6 bolts per cylinder should allow for a good chunk of boost. Maybe we can get these motors on the map! Even hot rod didn't mention these on their forgotten motors article. I wonder if we could locate that guy who built a modified one |
Re: Project Blown 305
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Let me know when you start having valve train parts made, I would be willing to double your order which should get us a little better price (maybe). Actually, if we could work together through the whole thing with identical setups (different cam grind and piston CR would be the only difference), we may be able to get a better price overall, and I wouldn't mind having more expertise than just I can provide. |
Re: Project Blown 305
Awesome!
Yeah I may be limited in what I can do with this thing but I'd like to know he maximum. When I sort the rocker system I will definitely post updates. I need to get a FE/BBB/BBM rockers to see what's similar enough. Those 3 are relatively cheap to buy a set either eBay for Chinese ones or off summit and you can buy individuals of them which is nice. Ideally I'd like to just upsize the shaft just enough to open the mounts up and move along with that as it's only .05" larger (.79 to .84 with I believe a mopar rocker) The lifters are a bit trickier because the spots they sit are pretty filled in so it will take milling the spot between them down and pressing a bushing to match the diameter and make a link bar. It may be easier to bush the hole, run some inexpensive standard mechanical lifters and a big cam |
Re: Project Blown 305
With those rods and offset grinding getting to 383 from a v6 would confuse so many lol
Need to have a big v6 badge and 383 badges lol |
Re: Project Blown 305
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Yeah I'm thinking my 478M with offset ground journals (2.811 down to 2.375 plus 3.86 stock stroke = 4.3" stroke) will net me a 538 when bored .030" over. While it might be able to go bigger, the fact that we are shoving all the air through 6 smallish ports (compared to 8 large ports on most big blocks) will just mean the bigger we go, the more low end we have with out much top end benefit. I'm thinking that 450 to 500 HP and 700+ ft lbs of torque won't take too much to get out of a properly setup 538.:ahhhh: |
Re: Project Blown 305
I am hoping to have some weird controversial CI to paint on the hood.
I want to use one of the 8v71 style blowers cuz they have a mad max style. |
Re: Project Blown 305
I agree, that would be awesome. My goal is double the torque output, I was hoping to find some magnum heads to use just cuz even with the 305 and a blower it's gonna require as much flow as I can get.
I really need to track down a 478 out here, that would open up my options for cubic inches so it's not all stroke if the bore cannot be taken to a much greater size. I guess I'll need to pull everything off the block and take it in. Also cool is all of these are old motors so they are prolly high nickel content which is supposed to be good for this kinda stuff and hard to scuff. This whole thing is going in my 66 C20 I'm converting to 4x4, I'm in California so they have have those stupid "clean air vehicle" stickers id like to copy and change the wording on and put on the back with the cubic inches next to the blower protruding old nascar style. I need to chase down the GMC V6 emblems for the hood too. |
Re: Project Blown 305
The 305's are super common down there....so I'd grab a couple blocks and experiment on one with how far you can overbore. I'm speaking from what I have seen more than anything...when I had mine apart with the casting plugs pulled out of the block...it was nothing but huge water jackets between the bore spacing. Thereby somewhat confirming a Huge over bore would either cause premature cylinder failure or you'd hit water real fast. .060 over seems to be the common safe overbore size on most old engines. These things produced pretty decent torque as it is....so a bottom end lightening...more cam....lighter pistons....and some boost will wake them up big time anyhow. If I can't find a 478, eventually I'm planning on rebuilding the 305 somewhat like you are.
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Re: Project Blown 305
Yeah, it's hard to say really. It's probably me being hopeful haha.
I'm figuring even the 305 stroked out to whatever I can get away with will suffice at that point. Definitely let me know what you come up with. Once I get the mopar rocker from a friend to compare with and get time for a junkyard run I'll have an fE rocker to test as well. |
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Re: Project Blown 305
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.060 over Flat top aluminum pistons that are lighter and 4 ring. 0 decking the block. Shaving the head if I can still get away with .450- .500 lift on the cam...and pending on rocker ratio I'm not sure what that will be on the valve lift so that will have to be calculated. Keeping the total cam duration low so peak power is at 4000 tops. Opening the head where ever I can....magnum heads for sure with bigger valves. Issue then might be the 4.25 bore may be to small and valves may hit. Rods are beefy enough, but I want to see about taking some weight off the crank and doing more balancing. Magnum manifold has already been machined for a 4 barrel so I have that done, and then need to make some headers. Hoping for 9.5.1 or 10.0.1 compression. If I can make 340 foot pounds naturally aspirated out of 305 cubic inches I'll be super happy. Can really make an embarrassment out of 350's then. :upyes: |
Re: Project Blown 305
Yeah that would be awesome on a set of rockers for an FE, 1972redneck I'll try to shoot ya a PM today about it.
Sounds like a solid build! I'm sure you'll make a good chunk of torque. Thunderv12 sells flanges for exhaust if that's helpful for both magnum and normal exhaust ports. I may try to get a few sets of intake flanges cut in case others would like to build a manifold as well. Felpro sells a gasket kit for the 305's on summit, I just recently received mine but haven't opened it. My machinist out here has done a few of these so that's good news. I think if I drop in some 60 over flat top Chevy BB Pistons I should be set, then it's just a matter of matching up some rods and stroke it to fit. Based on info I found online with various sources the deck height is roughly 11.5" I'll post my findings soon. |
Re: Project Blown 305
Sounds great, big block pistons and different sized rods would probably be cheaper than going stock with customs.
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Re: Project Blown 305
Yeah definitely and a load lighter too.
I'm thinking this thing won't be much of a liability overall as everyone claims once it goes on a diet internally. I'll have the machinist shave as much out of the crank as possible. |
Re: Project Blown 305
Maybe we can get these motors on the map!
Even hot rod didn't mention these on their forgotten motors article. Years ago(1974) I came across a magazine from around 1960 or 61, it mentioned how the 702 V12 would make a great drag engine. Basically it was an answer column and somebody was looking for something that was different from the rest. I think the magazine was Custom Rodder. |
Re: Project Blown 305
Ahh, what was cool is mad max remake had a gmc V12 in one of theirs. It kinda led to my friend mentioning how cool one of these would be in my C20.
I was chasing something different and found this had next to no one who had built one. There has to have been someone experimenting with these somewhere. I'll try as best I can to make a couple sets of each part so that a few other people can upgrade too or post enough info so it can be recreated. I'd love for this motor to become a hit and be used more often. It's such a sturdy platform for power: giant forged crank, oil bath for the cam, insane water pump and oil pump, 6 bolts per cylinder, fully supported lifters, shaft mount rockers. Just the absence of better intakes, better exhaust, and a lighter rotating assembly make it not so great. |
Re: Project Blown 305
It's not even that anymore....this new dumb trend is "Buy for cheap, sell for a rip off" or "If it ain't some junk chinese crate 350 that you can get for 2K; it ain't worth nothin."
Seems to be what drives most forums and I'm sick of it. lol People pull out good running v6's and treat them as Junk...yet when one of us Wants it they want over $500! :banghead: Experimentation has been done, if you look through old threads here in the 09-12 years it seems like a whole roll of people were into making these things perform....but suddenly they seemed to disappear off the map....probably had to have that dumb 350 or Life got in the way....I have no clue. lol Even on google! I've done tons of research at just about Every forum and lot's of people had great ideas for these in mind...but all the threads just end without anything ever actually Happening. So be prepared...even with the advantage of having hot rod parts on the market people are still to stinkin cheap to buy them. My 292 I6 for instance, TONS of hotrod parts on the market for that, yet you still don't see many around! Oh I forgot to mention....it cost more than a cheap junk crate 350 to build a healthy, unique 292. lol Taste and Unique is going down the drain anymore....shows are really boring when a line of chevy's and GMC's all have the same engine. What's worse is people are treating SBC like they're something special, when in reality...they are over used and boring as heck. Only thing that interests me is my 572 big block. haha |
Re: Project Blown 305
I 100 percent agree.
I love being innovative and am shocked that I'm one of the first to attempt this with the full intent and means to make it come together. I'll have to search the forum a bit, when searching on Google I didn't find much that was finished. I'm actually in the process of swapping the 3 sbc's I have in cars removed in favor of something far more unique, everyone's point is I can easily do a blah blah for less money that will be faster or whatever. It's far less about the money, far more about end look/cool and the process of getting there. My chevelle will be the one that would make any Chevy fan cringe but the 36 Chevy is getting a Nailhead because it's period correct and the truck getting a GMC V6 because they are so cool! Yeah those I6's are def unusual. I do see em built now and then. Try looking up Argentina stock car racing. They only race I6's. I'm very ready for Chevy people to be mad, my chevelle has lit a fire thus far I'm excited to put up giant torque numbers and show why it's better than the 350 Chevy in there. There was one of those 6ms posted for 900 out here like it was gold yet I'm sure they would be first to talk smack. I paid 50 for mine so I was stoked! I also know people will prolly be slow to throw money out there it's very similar in the celica community. But I figure if I can offer shafts for cheap so people could have their pedestals opened up or if I make new ones. It will all kinda fringe on if it costs me less to make like 5 pairs vs one pair and if it's cheap enough I can sell them relatively quickly. The rockers could be purchased separate from summit so I wouldn't supply those unless for some reason I can setup as a dealer for Harland sharp or something haha |
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Whatever you come up with keep us posted, Will be one of your customers for sure in the future. lol It'll be a few years before I do my 305 again. But yeah, the 292 in my 66 with make around 310 hp and 340 torque and it's backed by a tko600 5 speed. Will make a great cruiser and tackle some sbc's if I want to. haha
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I know right? Everyone's always so far away but I'm sure the smaller parts can shipped pretty easily.
Definitely will post all of my progress. I may just model the whole rocker system in cad do I have a starting point. Sounds like a healthy I6! Prolly going to be a blast with the tko |
Re: Project Blown 305
72redneck...We probably would. haha
Yeah it should be fun with that trans....3800 pound truck with 3.73 gearing and a close ratio trans should make for some easy burnouts and quick shifting. Plus the way I built the engine it should peak torque around 2500 so it'll be perfect. |
Re: Project Blown 305
Here's all the info I gathered so far.
Some of it does conflict a bit. Valve spring installed height=2.141" Od 1.367" Wire od=.0188 Lifter 2.317" tall 0.988" od Pushrod 7 13/16" long Shaft 17 7/8" 0.791" od 0.496 id Multiple 0.1" oil holes 0.335" hole at each end 2 bolt pedestal 2.233" tall 0.385 bolt hole 0.972 hole to hole min 1.119 shaft hole to base 0.791 shafthole One bolt pedestal 0.147 from small from top to flat Depth of 0.814" 0.84 from oil hole to round face Roundface to flat 0.112 0.166 offset boot hole to oil hole Rocker 2.719" tip to tip 1" thick Valley cover 19" Rockers Width=1.01" Hole od=0.789" Distance between= 3.3" Cap width=1.226" 2.75" length 73-up 28" between rails(inside of C) 702 v12 -3.124" mains (thunderV12.com) -1.6" pins -~7" rods ^last two are from (http://www.bangshift.com/forum/forum...cu-in-v6/page2) Confirmed 1.24" OD wrist pins 2.811 rod journal ^http://www.bangshift.com/forum/forum...3-478-cu-in-v6 -Exhaust Valves New Old Replacement Stock (NORS) made in USA by TRW. * Head Dia 1-53/64 * Stem Length 5-13/16 * Stem Dia .434 * Type Grooved * Seat Angle 45° TRW SC2330N GM 2383318 ^ebay listing 221603150615 Melling exhaust valve * Head Diameter: 1.565 Oriellys V0580 Intake valve guide * Vintage * Standard Size * 0.342 Inch I.D. * 2.75 Inch Overall Length * Guide Type: Plain * Inside Diameter (In): 0.342 Inch * Inside Diameter (mm): 8.687 * Outside Diameter (In): 0.502 * Outside Diameter (mm): 12.751 Oriellys VG5037 Pushrod * 7.989 Inch Overall Length Oreillys RP3099 Pushrod * Diameter (In): 5/16 Inch * Length (In): 7.645 Inch Oreillys MPR121 211-2036*CLEVITE intake valve fits GMC: 351cid v6, 1964-1967, Diesel*Engines, 2.260" Head Diameter 351cid v6,*1966-1969,*2.260" Head Diameter 401cid v6,*1966-1972,*2.260" Head Diameter 432cid v6,*1973-1974,*2.260" Head Diameter ^ebay listing 371009149096 -Intake valve- * Head Dia 2.160 * Stem Length 5.849 * Stem Dia .3725 * Seat Angle 30° * Sealed Power V1563 ^Ebay listing 221587715714 Intake valve (305) * Head Dia 2 * Stem Length 5-13/16 * Stem Dia .341 * Seat Angle 30° * Type Lock Grooved * TRW V2327 * RMC V3257 OEM GMC 2368098 ^ebay listing 321679596667 2474281 pn rod 478 ^eBay listing 282243468585 Con Rod Bearings 6200CP 0.020" / .50mm*Con Rod Bearings OD 3.016" ID 2.8117" Length .935" Wall Thickness .1010/.1015" ^ebay listing 321887078220 "New old stock piston set for GM 351 V6 truck engine from the 60's. *Includes 6 pistons and pins, ring set and pin clips. * 4 9/16 bore, approx 2 9/16 comp. height, approx 1 1/4 pins. * Parts are in good condition." ^ebay listing 322341673092 |
Re: Project Blown 305
Found this for ya:
"Heres a little about these motors I leared back in the mid 80's. My grand father gave me his 1965 GMC 1t 4x4 that came with the gas 351c v6. I rembered from a kid that this old truck would out pull anthing and never broke down. The old 351 was getting tired with about 200k on it so i decided to rebuild it and of coarse hop it up. So I started looking into performance imfo on these motors. That put me in contact with Babe Erson. He told me about the gas 478M motor and how with some work the big 478m v6 will easily make more tork and hp than a mildly built 454bbc. So I bougth a 478m motor from the junk yard and went to work per Babe's rec's. The first thing was to throw away the stock 4 ring pistons and masive rods that weight about the same as a complete hemi motor. I had a crank grinder turn the rod journals down to a much smaller size to fit a 426 hemi rod. I had BRC make some new lighter 3 ring pistons that also raised the cr up from 6.5 to 9.0. Engine dynamitics lightened the crankshaft alot and rebalanced every thing for me. Babe made me a special cam and all the vale train parts. I ported the heads and polished the combustion chambers myself. I also made a sheetmetal cross ram intake with 1 850cfm Q Jet carb and a set of home made 1 3/4" headers. Once I got all the tuning done on this motor it was one tork animal that would rev easily to 5.5k. It broke the transfer case right away so I put in a beffier transfer case out of a newer ford truck I think then I blow the old gmc rear end so I upgraded it to a dana 70 with posi. I also upgraded the old truck 4 speed to a newer 5 speed that could be shifted much faster. I had put big 38" tires on this truck and could smoke them in 2nd gear. It did not do to bad on fuel also at about 12 mpg fully loaded with a 10ft camper and pulling a 30ft inclosed trailer running about 65mph. I wish I know where this truck (James) is today as I would try to get him back." |
Re: Project Blown 305
**** that's awesome!
I'm hoping I can make that happen! Maybe I should contact them to see what they say about the motor and give me a better place to start maybe advice on how they were successful. I'd love to find a 478 block and crank to work with cuz that would bump the size further. |
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http://www.jalopyjournal.com/forum/t...series.153130/ Post #22 is the one. Don't mind the ignorance of the majority. lol |
Re: Project Blown 305
I have an intake for for a blower that was flame cut and needs to be welded together. PM me if interested. I was going to use it on a V-12, that is all machined, I have on the shelf, but it will need two blowers.:poke:
Atomman |
Re: Project Blown 305
Just remember that the V12 has different intake manifolds due to spacing and they will not interchange with the V6:lolsmack2:
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That is an issue with the magnum heads. Correct?
Atomman |
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No:pullinghairout: That is an issue regardless of heads:ahhhh: You simply can't use V6 intake manifolds on the V12 nor can you use V12 intake manifolds on the V6.
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Re: Project Blown 305
Found a blower off a 6-71.....might be to small though. :teehee:
https://medford.craigslist.org/pts/5946781139.html |
Re: Project Blown 305
Nice! I'm hoping my neighbor will sell me the 8v71 he has for a reasonable priced that one was pretty expensive.
If the intake is close I wouldn't mind modifying it to work I'm just curious what it looks like. |
Re: Project Blown 305
http://i1307.photobucket.com/albums/...psiwwsds6t.jpg
Thanks to Atomman I now am a little bit closer to getting this project off the ground! Now I just have to wait for it to arrive and figure out which blower I need! Very excited! |
Re: Project Blown 305
That looks fantastic:welldone:
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:thumbsup:
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Thank you, now having compared to the 6v92 my neighbor has it looks like I'm going to need an 8v71 or 8-71 minimum.
They sell adapter plates for the V style on a normal flange so I may get that since i can avoid trying to drill the angled holes myself and I can drill for a convention 8-71 and be able to swap between em. We shall see, I'd like to not have too terribly much into making a blower work since you can buy them new/used with a lot of the parts I'd need out of the box. (Front part with the snout for the pulleys, rear cover etc) |
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So here's my plan.
I found a few eBay sellers with blower parts for very reasonable prices I'll need the blower front cover, the blower rear cover, the snout, the pulleys (which I'll probably buy two to start mock up with them change later) and the adapter to go to the 8v71. So far I've purchased the adapter, this is already drilled for the angled bolts and includes studs gaskets etc. I mocked up the stuff a bit. I'm contemplating cutting off the whole water pump setup to save space and run an external pump, it wouldn't be hard as the pump is cast into the front cover and I'd just need two block off plates to cover the holes and put AN fittings up to them or a spot to clamp a hose. This would also allow me to run only the crank pulley for the alternator (too bad I didn't get the magneto lol) Turns out they sell new old stock 8v92 blowers for about 600 so I'm hoping that will bolt up the same way the 8v71 does as far as I can tell the engines underneath are the real variance not the blower itself. Here's the parts needed: http://i1307.photobucket.com/albums/...psdqwhi2oe.png http://i1307.photobucket.com/albums/...psifyzikdf.png http://i1307.photobucket.com/albums/...psdg0icmiu.png http://i1307.photobucket.com/albums/...pskufetzfi.png http://i1307.photobucket.com/albums/...pskpwkajfb.png |
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