Ad Radar
Item Posts    Sort Order

Cam bearing bore in Bow Tie block

 
L79lover
I love my Chevy Chevette!
Posts: 17
Joined: 04/12
Posted: 06/13/12 07:53 AM

I'm thinking about buying a new Bow Tie block that a local guy has for sale. He doesn't know exactly which block he has. The casting number is 10051184 which is one of the basic casting numbers for a cast iron Bow Tie block. So far I've found 8 different GM part numbers for a 3.98" bore block(I measured it). After I got home I figured out I should have measured the main bearing bore to see if it's for a 350 or 400 crank and also the cam bearing bore. I read that some of the Bow Tie blocks have 2" cam bores and require special cam bearings. I thought all small block Chevy's had the same cam bearing bore size. Do they?  

Post Reply
waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 06/14/12 08:17 AM

i see in the GM performance catalog that that block casting number was used in a BUNCH of different crank main journal and cylinder bore sizes...   there even seemed to be a PRO block that was STEEL not cast iron..   all under the bowtie label...

these are not production line blocks per say.. they are designed as race blocks... and require additional specialized components to finish..

they save the racer steps.. as they are already at the modification stage where a racer would have already spend many many dollars on just getting here with a conventional production block..


Main Bearing Housing Bore

283 journal blocks
2.4906/2.4916"

350 journal blocks
2.6406/2.6416"

400 journal blocks
2.8406/2.8416"

in the versions i saw.. they all were shown with the 2" bore cams...

there i think may have also been an raised cam centerline version also..

are there any STAMPED in numbers on the block.. perhaps on the deck surface?  

Post Reply
waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 06/14/12 08:52 AM

i think you might want to search over in circle track or stock car racing magazine on this site.. for info on bow tie block prep
some info on SOME of the various BOW TIE small blocks. as BARE blocks..

try to find the DATE code cast into the block..     to see what year it was CAST..  



   
10051181 Cast Iron Bow Tie Bare Block      
This updated design has a decidedly different appearance, but retains its original part number. New tooling procedures have significantly improved the quality and durability of this third-generation casting. This heavy-duty cast iron Bow Tie block has rough-bored 3.875" diameter cylinders, which can be bored to a maximum diameter of 4.030". This block is recommended for maximum effort competition engines. The deck surfaces are thicker than production blocks, and the head bolt holes are blind tapped to improve head gasket sealing. The main bearing bulkheads are .900" thick and the front and rear bulkheads are reinforced with strengthening ribs.
The updated design on this Bow Tie block's oil galleries now extend flush to the front and rear faces of the cylinder case and can interfere with some camshaft drive systems. Therefore, timing system clearance should be checked before engine assembly. The revised Bow Tie block has a boss below the bellhousing flange behind the #8 cylinder that can be drilled and tapped for lifter valley oil scavenging. Oil drainback holes in the lifter valley are drilled. The updated design provides more consistency in the thickness of the cylinder walls and water jackets. The cylinder bores have a nominal wall thickness of .340" at the casting parting line (measured 2" below the deck surface).  
Technical Notes: Oil dipstick hole is not drilled and the lifter holes are finish bored to production diameter .842". Two-bolt main bearing caps are installed to simplify the installation of the heavy-duty steel main caps with splayed outer bolts. Bow Tie blocks are designed for crankshafts with 2.45" diameter main bearing journals. The Bow Tie casting block P/N 10051182 is machined for a one-piece rear main bearing seal used on 1986 and later production small-block Chevrolet V8s. Crankshafts designed for two-piece rear main seals can be installed in Bow Tie blocks using crankshaft seal adapter P/N 10051118. These blocks weigh 187 lbs.
   
10051183 Cast Iron Bow Tie Bare Block (3.98" bore)      
This updated design has a decidedly different appearance, but retains its original part number. New tooling procedures have significantly improved the quality and dura-bility of this third-generation casting. This heavy-duty cast iron Bow Tie block has rough-bored 3.98" diameter cylinders, which can be bored to a maximum diameter of 4.090". This block is recommended for maximum effort competition engines. The deck surfaces are thicker than production blocks, and the head bolt holes are blind tapped to improve head gasket sealing. The main bearing bulkheads are .900" thick and the front and rear bulkheads are reinforced with strengthening ribs.
The updated design on this Bow Tie block’s oil galleries now extend flush to the front and rear faces of the cylinder case and can interfere with some camshaft drive systems. Therefore, timing system clearance should be checked before engine assembly. The revised Bow Tie block has a boss below the bellhousing flange behind the #8 cylinder that can be drilled and tapped for lifter valley oil scavenging. The outer water jacket walls have bosses to allow coolant passages to be drilled between adjacent "siamesed" cylinders. Oil drainback holes in the lifter valley are drilled. The updated design provides more consistency in the thickness of the cylinder walls and water jackets. The "siamesed" cylinder bores have a nominal wall thickness of .340" at the casting parting line (measured 2" below the deck surface).  
Technical Notes: Oil dipstick hole is not drilled and the lifter holes are finish bored to production diameter .842". 2-bolt main bearing caps are installed to simplify the installation of the heavy-duty steel main caps with splayed outer bolts. Bow Tie blocks are designed for crankshafts with 2.45" diameter main bearing journals. The Bow Tie casting block P/N 10051184 is machined for a one-piece rear main bearing seal used on 1986 and later production small- block Chevrolet V8s. Crankshafts designed for two-piece rear main seals can be installed in Bow Tie blocks using crankshaft seal adapter P/N 10051118. These blocks weigh 187 lbs.
   
10185047 350ci Bow Tie Block      
This block, which can be used for 302ci, 327ci, and 350ci engines, is the same as the cast iron Bow Tie bare block P/N 10051183, except that it has a "straight" nodular 4-bolt main bearing cap. It also features "siamesed" cylinder walls which could give it a maximum bore of 4.090". It has a crankshaft diameter of 2.45" and the newer (1986 and later) one-piece type rear main seal. It replaces the older P/N 366287 4-bolt block, the difference being the one-piece rear seal.  


   
12480047 Block, Bow-Tie Sportsman "350 Main Size"      
This iron block is fully CNC machined from the H-D 10051184 casting. It has siamesed cylinder walls, cast nodular caps, four bolts on all five main caps; the outer bolts on the three center main caps are splayed 20 degrees. Grade 8 bolts secure the caps. It features priority main oiling and 9.025" deck height. The blocks come finished bored at 3.980" and the maximum recommended bore is 4.150". This block features a two-piece rear main seal; "350" main size (2.45"). It features lifter bore heights (.842"), same as P/N 24502503.  
Technical Notes: It may be necessary to clearance top of lifter bores with some roller lifters. The block requires 2" O.D. cam bearings at all five locations (P/N 12370843 set.
   
12480049 Block, Bow-Tie Sportsman "400 Main Size"      
This iron block is fully CNC machined from the H-D 10051184 casting. It has siamesed cylinder walls, cast nodular caps, four bolts on all five main caps; the outer bolts on the three center main caps are splayed 20 degrees. Grade 8 bolts secure the caps. It features priority main oiling and 9.025" deck height. The blocks come finished bored at 3.980" and the maximum recommended bore is 4.150". This block features a two-piece rear main seal; "400" main size (2.65"). It features lifter bore heights (.842"), same as P/N 24502503.  
Technical Notes: It may be necessary to clearance top of lifter bores with some roller lifters. The block requires 2" O.D. cam bearings at all five locations (P/N 12370843 set).

24502501 Small Bore Cast Iron V8 Racing Block      
This Bow Tie bare block is intended for serious competition applications right out of the box. This block is "CNC" machined from a raw casting P/N 10051182. All traditional racing modifications are provided by the factory. The heart of this block starts with a non-siamesed cylinder case raw casting P/N 10051182 at a 3.875" bore, but can be bored to 4.030". This case is then blueprinted on the cylinder decks (9.025" deck height), front of case, rear of case, and oil pan rail surfaces as well as the head dowel locator pin locations. In addition, all galleries required for dry sump oil system operation are oversize and tapped for pipe plugs. 8620 steel bearing caps are installed on all locations on the block. The intermediate main bearing caps have the outer 7/16" diameter studs installed at a 20 degree splay, while the front bearing cap has 7/16" diameter studs on the inner locations and 3/8" diameter straight bolts on the outer locations. The rear bearing cap is a 2 stud (7/16" dia.) configuration and utilizes a two piece rear seal design adaptable to the one piece design. After installation of the steel bearing caps, the block is align bored. Use cam bearing kit P/N 12370843. They are 2.00" O.D. and 1.867" I.D.  
Technical Notes: The above bore sizes are after honing .005" from the cylinder by a professional engine builder. Special features are: Priority main oiling; Bearing cap inner bolts spread .210 to allow use of "2.65" dia. journal cranks on properly modified blocks; Sonic bore check (data provided); Enlarged cam bosses front and rear to allow use of larger bearings; Enlarged lifter bosses; Production .842" lifter bores; Early model two-piece rear main seals; Uses pre-1986 oil pans; Uses premium quality studs and 8620 20º steel splayed main bearing caps; and Billet wet sump rear main cap can be adapted to dry sump with plugs.
   
24502503 4.00" Bore Cast Iron Racing Bow Tie Bare Block      
This block is "CNC" machined from a raw casting P/N 10051184. All traditional racing modifications are provided by the factory. The heart of this block starts with a siamesed bore cylinder case at a 3.995" bore, but can be bored to 4.155". This case is then blueprinted on the cylinder decks (9.025" deck height), front of case, rear of case, and oil pan rail surfaces as well as the head dowel locator pin locations. In addition all galleries required for dry sump oil system operation are drilled and tapped for pipe. 8620 steel bearing caps are installed on all locations on the block. The intermediate main bearing caps have the outer 7/16" diameter studs installed at a 20º splay, while the front bearing cap has 7/16" diameter studs on the inner locations and 3/8" diameter straight bolts on the outer locations. The rear bearing cap is a two- stud (7/16" dia.) configuration and utilizes a two-piece rear seal design. After installation of the steel bearing caps, the block is align bored. Use cam bearing kit P/N 12370843 only.  
Technical Notes: The above bore sizes are after honing .005" from the cylinder by a professional engine builder. Special features are: Priority main oiling; Bearing cap inner bolts spread .210 to allow use of "2.65" dia. journal cranks on properly modified blocks; Sonic bore check (data provided); Enlarged cam bosses front and rear to allow use of larger bearings; Enlarged lifter bosses; Early model two-piece rear main seals; Uses pre-1986 oil pans; and Uses premium quality studs and 8620 20º steel splayed main bearing caps.
   
24502600 SB2 / SB2.2 Bare Block      
This "CNC machined" bare block uses bow tie casting P/N 10051184 and is machined identically to block P/N 24502503 except the lifter bore locations have been revised to match the SB2 or SB2.2 cylinder head.  
Technical Notes: Production blocks can be used if offset roller rockers and roller tappets are used. Must use special camshaft when using SB2 or SB2.2 cylinder heads.
   
24502650 Bow Tie CNC Racing Block "Short Deck"      
This “CNC machined” cast iron bow tie block has an deck height that starts at 8.300" and can be machined to 3.400", compared to the standard block's 9.025" deck height. This block is designed for small cubic inch engines used in drag racing, road racing, or restricted oval track racing. The factory bore on this siamesed block is 3.980" and can be bored to a maximum of 4.190" with a minimum cylinder wall thickness of .250". The camshaft has been raised up to 4.953" to use belt style timing drives. A priority main oiling system is designed into the block and significant changes in the oiling system ensure uniform lifter gallery oil feeding as well as integral lifter oil restrictors. The water pump holes are spread and a big block water pump must be used. When a 6" or larger damper is used, the pump must be raised with aluminum adapters. With the shorter deck, the pushrods must be shorter to mate with the cam and lifters. The main bearing diameters are 2.30", not the standard 2.45". The cam bearing holes are bored for roller bearings at 2.250" diameter O.D. x 1.875" I.D. This block features five steel main caps with the three center caps splayed at 20°, and the block weight is approximately 167 lbs.  
Technical Notes: This block uses the Oldsmobile Aurora V8 design bell housing with a flywheel maximum diameter of 12.25" . These blocks also use early style two-piece rear oil seals and oil pans. The lifter bosses are .220" taller than production blocks. These blocks will accept all V8 cylinder heads. The oil filter boss is a machined pad for a remote oil filter adapter — or tap for a fitting. The block uses a dry sump oil system only and has provisions for an integral lifter valley scavenge system. Oil is scavenged through a hole at the rear of the valley. This block does not have a manual fuel pump boss, but it features bosses for cylinder pressure transducers for development testing.


12480157 Block, Bow-Tie Sportsman "350 Main Size"      
This iron block is fully CNC machined from the H-D 10051184 casting. It has siamesed cylinder walls, cast nodular caps, four bolts on all five main caps; the outer bolts on the three center main caps are splayed 20 degrees. Grade 8 bolts secure the caps. It features priority main oiling and 9.025" deck height. The blocks come finished bored at 4.117" and the maximum recommended bore is 4.150". This block features a two-piece rear main seal; "350" main size (2.45"). It features lifter bore heights (.842"), same as P/N 24502503.  
Technical Notes: It may be necessary to clearance top of lifter bores with some roller lifters. The block requires 2" O.D. cam bearings at all five locations (P/N 12370843 set).
   
12480159 Block, Bow-Tie Sportsman "400 Main Size"      
This iron block is fully CNC machined from the H-D 10051184 casting. It has siamesed cylinder walls, cast nodular caps, four bolts on all five main caps; the outer bolts on the three center main caps are splayed 20 degrees. Grade 8 bolts secure the caps. It features priority main oiling and 9.025" deck height. The blocks come finished bored at 4.117" and the maximum recommended bore is 4.155". This block features a two-piece rear main seal; “400” main size (2.65"). It features lifter bore heights (.842"), same as P/N 24502503.  
Technical Notes: It may be necessary to clearance top of lifter bores with some roller lifters. The block requires 2" O.D. cam bearings at all five locations (P/N 12370843 set).  

Post Reply
L79lover
I love my Chevy Chevette!
Posts: 17
Joined: 04/12
Posted: 06/14/12 09:17 AM

Thanks for the information. I'm going to go back today and measure the main bearing bore and the cam bearing bore. I answered my own question about whether or not all SBC blocks have the same cam bearing size. I called Lunati tech dept and was told that there are 4 different size cam bearings and they make cams for all the different sizes. They charge a little more for the cams that fit in the 1.948" bearings (2" bore). I'm trying to figure about exactly which block they because so far I've found prices for these 3.98" bore blocks ranging from $1849 to $2947. They're asking $2000 OBA for their block. I can get a Dart block for about $1500 so I may offer them $1500 once I figure out what they have.  

Post Reply
pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 06/14/12 05:45 PM

Oh No offer them $1200. They can always refuse your offer! Work it that way. They go higher you go lower!!!  

Post Reply
L79lover
I love my Chevy Chevette!
Posts: 17
Joined: 04/12
Posted: 06/14/12 08:27 PM

Well it turns out this a part #2452503 block which is a good one. It's basically a race block that's already been blue printed by GM, has 4 bolt SAE 8620 steel main bearing caps held down with studs and the main bore can be bored out to 400 crank size if necesssary. The only drawbacks are that the dipstick hole hasn't been drilled and it requires special cam bearings for the 2" cam bore. I offered the guy $1500 and he said he paid $2500 for it about a year ago. We ended up agreeing on $1750 and I'm going to pick it up in the morning. The best price I could find was at Scoggins-Dickey where it's on sale for $2399 until they sale what they have in stock, after that it goes back to regular price of $2700. Even with the $2399 sale price after I pay tax and shipping it will be about $2650 so I feel like I got a pretty good deal.  

Post Reply
waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 06/14/12 08:43 PM

i was drooling over that EXACT block in the GMPP catalog...


24502503A  

Post Reply
L79lover
I love my Chevy Chevette!
Posts: 17
Joined: 04/12
Posted: 06/15/12 09:04 AM

That's the one I got and I'm exited about it. I don't usually make good deals. I bought it from a construction company that had a round and round race car they used for advertising. With the slow economy they had to sell their race car and I got their last spare part.  

Post Reply
TO TOP