305 blocks- whats the best one to use ?

Kenny Wigington · 08-18-2007, 03:50 PM

I now have a cracked 305 block. Is there any other 305 blocks that are good, for a stocker ?(I have heard that 307's sleeved down are the best to use.) I have seen a few 305 (5.0) generator motors and figured that would have to be stronger block. Anyone have a connection to Generac or Kohler ? This one cracked at the top of #5 hole.
If you have any ideas, please pass them along. I want to get going again soon !

Thanks
Kenny
kwigracing@yahoo.com

REGGIE WINKLES · 08-19-2007, 09:52 AM

Kenny, I use an early 305 block (2-piece rear seal) in my stocker. I have the block filled
with Hard-Blok and have never had any problems with cracks. I am curious as to why the
block would crack up there at the top. Did your block have any core shift? I have heard
GM has a "Bow-Tie" 305 block but, I have never seen one. If this is the first incident with
cracking I'd say you just got a bad core. That's my two cents worth.

Reggie Winkles
4102 J/Stick

FED 387 · 08-19-2007, 10:34 AM

Kenny--GM did offer 2 blocks for the 305CI------A stock version of the block part#-10066098 & a Bowtie block part# -10051181(casting # 10051182)--The Bowtie block is machined for a 1 piece rear main seal and if you need a 2 piece seal you will need cshaft seal adapter #10051118 -- I do not know if these numbers have been changed or are up to date or if either of these blocks are still available from GM..Also remember that a stock production SBC block weighs approx. 152 pounds and a Bowtie SBC block will weigh approx 183 pounds . Good luck---Comp 387

Kenny Wigington · 08-19-2007, 01:17 PM

Thanks Reggie, and Dick. I'll check into that block. Mine has hardblock in it.

greg fulk · 08-19-2007, 02:28 PM

steve is right...take a 350 4 bolt block & sleeve it down to 305....my machinest dose it..about $620.oo though.

JRyan · 08-19-2007, 03:30 PM

Kenny,

Better not use a 4-bolt 350 block as a core to sleeve, as they aren't a legal replacement for a 305 (based on a call to NHRA). The 305's were all 2-bolt and that's what NHRA wants to see IF the pan ever comes off. The best block to use if you can find one is the '68, '69 307 block. Many were cored as 350's so you end up with the very thick walls of a 350 but can use a more generally available sleeve.

Jerry

Jim Cassels · 08-19-2007, 08:59 PM

Kenny,
Jerry is giving you the correct info, they will not accept the 4 bolt block, I learned the hard way. Some run them but they are not legal.

Don quinn · 08-19-2007, 09:21 PM

The 80 corvette had a 305 4 bolt block

Kenny Wigington · 08-19-2007, 10:50 PM

Thanks guys. I do appreciate the info.

Just for the sake of asking, how much extra would a block weigh , with all sleeved ? Is it lighter than that Bowtie block, Dick and Reggie mentioned ?

Jim Cassels · 08-20-2007, 09:25 PM

Don,

08-19-2007, 09:52 AM	#2
REGGIE WINKLES Member Join Date: Jun 2007 Location: St. Augustine, Fla. Posts: 229 Likes: 558 Liked 39 Times in 9 Posts	Re: 305 blocks- whats the best one to use ? Kenny, I use an early 305 block (2-piece rear seal) in my stocker. I have the block filled with Hard-Blok and have never had any problems with cracks. I am curious as to why the block would crack up there at the top. Did your block have any core shift? I have heard GM has a "Bow-Tie" 305 block but, I have never seen one. If this is the first incident with cracking I'd say you just got a bad core. That's my two cents worth. Reggie Winkles 4102 J/Stick

08-19-2007, 10:34 AM	#3
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,409 Likes: 505 Liked 329 Times in 177 Posts	Re: 305 blocks- whats the best one to use ? Kenny--GM did offer 2 blocks for the 305CI------A stock version of the block part#-10066098 & a Bowtie block part# -10051181(casting # 10051182)--The Bowtie block is machined for a 1 piece rear main seal and if you need a 2 piece seal you will need cshaft seal adapter #10051118 -- I do not know if these numbers have been changed or are up to date or if either of these blocks are still available from GM..Also remember that a stock production SBC block weighs approx. 152 pounds and a Bowtie SBC block will weigh approx 183 pounds . Good luck---Comp 387

08-19-2007, 01:17 PM	#4
Kenny Wigington Senior Member Join Date: Sep 2004 Location: Cumming,Ga. USA Posts: 967 Likes: 36 Liked 60 Times in 12 Posts	Re: 305 blocks- whats the best one to use ? Thanks Reggie, and Dick. I'll check into that block. Mine has hardblock in it. __________________ 2894 STK

08-19-2007, 03:30 PM	#6
JRyan Senior Member Join Date: Apr 2003 Location: Aberdeen SD Posts: 645 Likes: 30 Liked 112 Times in 31 Posts	Re: 305 blocks- whats the best one to use ? Kenny, Better not use a 4-bolt 350 block as a core to sleeve, as they aren't a legal replacement for a 305 (based on a call to NHRA). The 305's were all 2-bolt and that's what NHRA wants to see IF the pan ever comes off. The best block to use if you can find one is the '68, '69 307 block. Many were cored as 350's so you end up with the very thick walls of a 350 but can use a more generally available sleeve. Jerry

08-19-2007, 08:59 PM	#7
Jim Cassels Junior Member Join Date: Nov 2002 Location: Cairo, Ga. Posts: 90 Likes: 2 Liked 0 Times in 0 Posts	Re: 305 blocks- whats the best one to use ? Kenny, Jerry is giving you the correct info, they will not accept the 4 bolt block, I learned the hard way. Some run them but they are not legal.

08-18-2007, 03:50 PM	#1
Kenny Wigington Senior Member Join Date: Sep 2004 Location: Cumming,Ga. USA Posts: 967 Likes: 36 Liked 60 Times in 12 Posts	305 blocks- whats the best one to use ? I now have a cracked 305 block. Is there any other 305 blocks that are good, for a stocker ?(I have heard that 307's sleeved down are the best to use.) I have seen a few 305 (5.0) generator motors and figured that would have to be stronger block. Anyone have a connection to Generac or Kohler ? This one cracked at the top of #5 hole. If you have any ideas, please pass them along. I want to get going again soon ! Thanks Kenny kwigracing@yahoo.com __________________ 2894 STK Last edited by Kenny Wigington; 08-18-2007 at 05:52 PM.

08-19-2007, 02:28 PM	#5
greg fulk VIP Member Join Date: Jan 2003 Location: jackson Posts: 1,165 Likes: 0 Liked 5 Times in 3 Posts	Re: 305 blocks- whats the best one to use ? steve is right...take a 350 4 bolt block & sleeve it down to 305....my machinest dose it..about $620.oo though. __________________ Greg Fulk 308 308X P/SA "ALL AMERICAN"

08-19-2007, 09:21 PM	#8
Don quinn Junior Member Join Date: Dec 2002 Posts: 2 Likes: 0 Liked 0 Times in 0 Posts	Re: 305 blocks- whats the best one to use ? The 80 corvette had a 305 4 bolt block

08-19-2007, 10:50 PM	#9
Kenny Wigington Senior Member Join Date: Sep 2004 Location: Cumming,Ga. USA Posts: 967 Likes: 36 Liked 60 Times in 12 Posts	Re: 305 blocks- whats the best one to use ? Thanks guys. I do appreciate the info. Just for the sake of asking, how much extra would a block weigh , with all sleeved ? Is it lighter than that Bowtie block, Dick and Reggie mentioned ? __________________ 2894 STK Last edited by Kenny Wigington; 08-19-2007 at 10:52 PM.

08-20-2007, 09:25 PM	#10
Jim Cassels Junior Member Join Date: Nov 2002 Location: Cairo, Ga. Posts: 90 Likes: 2 Liked 0 Times in 0 Posts	Re: 305 blocks- whats the best one to use ? Don,