Chevy 305 engine

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**2.100" rod
 
**2.100" rod
 
**2.45” main
 
**2.45” main
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 +
==Block casting numbers==
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*'''355909'''         1976-'85       
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*'''361979'''         1976-'79       
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*'''460776'''         1976-'79         
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*'''460777'''         1976-'79       
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*'''460778'''         1978-'79       
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*'''581671'''         1976-'85       
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*'''14010201'''      1980-'84
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*'''14010202'''      1980-'84
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*'''14010203'''      1980-'84   
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*'''14016381'''      1980-'84   
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*'''14010231'''      1978-'86   
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*'''14016383'''      1978-'88   
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*'''14049047'''      1978-'86   
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*'''14088551'''      1986-'92 
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*'''14093627'''      1988-'94 
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*'''14094766'''      1988-'94 
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*'''14102058'''      1987-'88 
 +
 +
==305 RPO codes==
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*LE9 (LF3 CA), 160 to 235 HP, K10, 1981-'86
 +
*LG9 2bbl, 130 to 240 HP, K10, 1981
 +
*LO3, TBI, 170 to 260 HP, C10, 1987
  
 
==Changes==
 
==Changes==
−
Like the 350, most 305's beginning in 1987 got revised block castings and machining that allowed the use of a hydraulic roller cam and lifters, along with a 1-piece rear main seal and the 72 degree intake manifold center bolt angle.
+
Like the 350, most 305's beginning in 1987 got revised block castings and machining that allowed the use of a hydraulic roller cam and lifters, along with a 1-piece rear main seal and the 72 degree intake manifold center bolt angle. Exceptions to this were the TBI truck engines, which retained a flat tappet cam.
  
−
Exceptions to this were the TBI truck engines.
+
In 1996 the 305 got different heads and induction system.
  
 
==Cost==
 
==Cost==
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{{Note1}}Just be sure the relief doesn't reach the top ring with the piston at TDC and that the relief does not go under the fire ring of the head gasket! Use a head gasket as a template on the head and block so the combustion chamber and the cylinder reliefs match and don't intrude on the fire ring of the head gasket.
 
{{Note1}}Just be sure the relief doesn't reach the top ring with the piston at TDC and that the relief does not go under the fire ring of the head gasket! Use a head gasket as a template on the head and block so the combustion chamber and the cylinder reliefs match and don't intrude on the fire ring of the head gasket.
  
−
===Pre Vortec heads===
+
===Pre-Vortec heads===
−
The heads were similar to the 350 except for having a smaller combustion chamber volume, and smaller intake valves (1.72" or 1.84", depending on the application). 305 engines even got the dreaded swirl port heads for TBI applications, again same as the 350.
+
The heads were similar to the 350 except for having a smaller combustion chamber volume, and smaller intake valves (1.72" or 1.84", depending on the application). 305 engines even got the same swirl port type heads for TBI applications, again same as the 350.
  
−
Swirl-port, pre-Vortec heads were used for all of the TBI 305s, and do not respond as good to porting and big valves as the non swirl vane heads.  
+
Swirl-port, pre-Vortec heads were used on many TBI 305 engines, and do not respond as well to porting and 1.94" intake valves as the non swirl port heads.  
  
−
A good 305 head used from about 1987-'92 has a casting number ending in '''081'''. These were supposedly used on 1987 305 engines, and all TPI 305 engines from 1987-'92. These came with 1.84" x 1.50" valves, and had a 55cc nominal, more efficient combustion chamber.  
+
====Good 305 head casting numbers====
 +
*'''14101081''' These were supposedly used on 1987 305 engines, 1987-'94 or '95, and TPI 305 engines from 1986 or '87 to 1991 or '92 (depending on the source). Sometimes called "center bolt HO" heads, referring to the valve cover attachment used on 1987-up SBC engines. While they do resemble the "real" HO heads (c/n's 601 and 416), the vehicles they were used on (1987 LG4, TPI 305 from 1987-'92, and the 1987-'88 L69 and LG4 used in the Monte Carlo) never had an HO designation. They came with 1.84" x 1.50" valves and use center bolt valve covers.
 +
*'''14014416''' Another common 305 head for performance use. 1980-'86 "HO" heads. Nominal 58cc combustion chamber volume, 1.84" x 1.50" valves.
 +
*'''14022601''' 1979-'86 These also respond well to porting and 1.94" intake valves. <br>
 +
{{Note1}}Don't confuse these heads with c/n 3910601 heads used on 1967-'68 327 engines.
 +
*'''10088113''' These are aluminum heads used on about 1988-'92 Corvettes and the ZZ4 crate engine. They have 1.94" x 1.50" valves and a 58cc chamber with angled spark plugs. They use the pre-'87 style intake bolt pattern.
  
−
The next most common 305 head for performance was the pre-'87 c/n 416 heads. Nominally 58cc combustion chamber volume, 1.84" x 1.50" valves. These two heads, as well as the c/n 601 respond well to porting and 1.94" intake valves, if the machine shop does it right rather than doing it cheap.  
+
====Porting====
 +
If you've done well practicing on a junk head, then this is worth trying. Taper all the guide bosses, except in the Vortec 350 intake ports. Ever so lightly, blend the 75-degree cuts into the ports, too.  
  
−
A performance valve job for these heads, and for milled Vortec 350 heads, starts with ordering better valves: stainless steel, 1-piece, swirl-polished, undercut-stem. You can get all 16 for $70 plus shipping. Next is to have the shop put a 30-degree back-cut on them. Then have the seats cut with standard 30/45/60 degree angles, as far out on the valves as possible. Next is the bowl hog, a 75-degree cut that goes as deep as possible without hitting the guide boss, while simultaneously narrowing the 60-degree cut to about 0.050"-0.055" The de-shrouding sweeper cut really isn't worth it. If you're doing milled Vortec 350 heads, some use 1.60" exhaust valves.
+
A 30-degree back-cut on the valves will help flow. The seats can be cut with standard 30/45/60 degree angles, as far out on the valves as possible. Next is a 75-degree cut that goes as deep as possible into the bowl, below the bottom 60-degree valve seat angle without hitting the guide boss, while simultaneously narrowing the 60-degree cut to about 0.050"-0.055".
  
−
===Porting===
+
Unshrouding the intake valves needs to be done if larger valves are used.
−
If you've done well on a junk head, then this is worth trying. Do taper all the guide bosses, except in the Vortec 350 intake ports.  Ever so lightly, blend the 75-degree cuts into the ports, too.  
+
  
 
Polishing the intake ports is not advised. Doing the chambers is good if you protect the seats. Doing the exhaust ports is great. Gasket-matching the ports isn't necessary, and for the exhausts it's not helpful, either.  
 
Polishing the intake ports is not advised. Doing the chambers is good if you protect the seats. Doing the exhaust ports is great. Gasket-matching the ports isn't necessary, and for the exhausts it's not helpful, either.  
  
−
====305 heads to avoid====
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===Vortec heads===
−
Casting number 450 and possibly 434 castings are the 2 bbl heads, and have 1.72" intake valves.
+
====L31 5.7L 350 heads====
−
 
+
The L31 5.7L Vortec head can be used on the 305. The stock combustion chambers are too large as-cast, so they need to be milled if used on a 305. More info on them can be seen at '''[[Vortec L31 cylinder head]]'''.
−
===Vortec L30 5.0 L 305 head ===
+
−
In 1996 the 305ci RPO L30 engine got different heads than were previously used. These heads featured revised intake bolt pattern and a small swirl vane in the intake port (the swirl vane is much smaller/different that what's used on the swirl port heads).  
+
====L30 5.0L 305 heads====
−
 
+
In 1996 the 305ci RPO L30 engine got different heads than were used previously. These heads featured revised intake bolt pattern and a small swirl vane in the intake port (the swirl vane is much smaller/different that what's used on the swirl port heads).  
−
Unfortunately the '96-up 305 Vortec heads did not get the same type combustion chamber design as the 350 Vortec. The 305 Vortec combustion chamber is similar to the swirl port head. This chamber design places the spark plug more towards the center of the chamber and slightly biased towards the exhaust valve, all of which are improvements over the old smog castings.
+
{|
 +
|[[File:L31 305 VORTEC HEAD CASTING ID.jpg|thumb|center|350px|305 Vortec L30 casting ID]]
 +
|[[File:305 VORTEC CHAMBER CN 059.jpg|thumb|middle|200px|305 Vortec L30 casting number 12558059 chamber]]
 +
|}
 +
Unfortunately the '96-up 305 Vortec heads did not get the same combustion chamber design (right) as the 350 Vortec heads. However, the 305 Vortec combustion chamber is similar to the swirl port head, which is an improvement over earlier heads. This chamber design places the spark plug more towards the center of the chamber and slightly biased towards the exhaust valve, all of which are improvements over the old smog castings. <br style="clear:both"/>
  
 
The L30 heads use self-aligning rocker arms and the same center bolt valve covers like used since '87. They also use the same intake bolt pattern as the L31 5.7L Vortec heads, but have a smaller chamber volume (~58cc) than the 5.7L Vortec heads. The ports are a bit smaller as well (~160-165cc).
 
The L30 heads use self-aligning rocker arms and the same center bolt valve covers like used since '87. They also use the same intake bolt pattern as the L31 5.7L Vortec heads, but have a smaller chamber volume (~58cc) than the 5.7L Vortec heads. The ports are a bit smaller as well (~160-165cc).
  
−
In addition to the 059 casting number, there is a c/n 12552520 head listed in the databases as a '96-'97-up "Vortec" head, comparable to the c/n 059 head by all appearances.
+
In addition to casting number 12558059, there is c/n 12552520 listed in the databases as a '96-'97-up "Vortec" head, comparable to the c/n 059 head by all appearances.
  
−
===Swirl-inducing vane===
+
=====Swirl-inducing vane=====
 
While the 305 Vortec head has a swirl vane in the intake port, it is ''much'' smaller than what's seen in the 5.7L swirl port heads like the c/n 191 and 193 heads.
 
While the 305 Vortec head has a swirl vane in the intake port, it is ''much'' smaller than what's seen in the 5.7L swirl port heads like the c/n 191 and 193 heads.
−
 
−
[[File:Tbi swirl port vane.jpg|thumb|left|300px|TBI swirl port vane]]
 
−
<br style="clear:both"/>
 
−
 
 
{|
 
{|
 +
|[[File:Tbi swirl port vane.jpg|thumb|left|300px|c/n 191/193 TBI swirl port vane]]
 
|[[file:305_VORTEC_SWIRL_RAMP_CN_059.jpg|thumb|center|200px|305 Vortec L30 vane]]
 
|[[file:305_VORTEC_SWIRL_RAMP_CN_059.jpg|thumb|center|200px|305 Vortec L30 vane]]
−
|[[File:305 VORTEC CHAMBER CN 059.jpg|thumb|center|240px|305 Vortec L30 casting number 12558059 chamber]]
 
−
|[[File:L31 305 VORTEC HEAD CASTING ID.jpg|thumb|center|350px|305 Vortec L30 casting ID]]
 
 
|}
 
|}
 +
 +
=====L30 Vortec head flow=====
 +
{|style="color:black; cellpadding="5" cellspacing="0" border="1" bgcolor="#FFF8DC"
 +
!bgcolor="#CCCCFF"|Lift (in.) !!bgcolor="#CCCCFF"|Intake (CFM) !!bgcolor="#CCCCFF"|Exhaust (CFM)
 +
|-
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| align="right" |0.100 || align="right" |68 || align="right" |47
 +
|-
 +
| align="right" |0.200 || align="right" |128 || align="right" |103
 +
|-
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| align="right" |0.300 || align="right" |179 || align="right" |138
 +
|-
 +
| align="right" |0.400 || align="right" |205 || align="right" |152
 +
|-
 +
| align="right" |0.500 || align="right" |221 || align="right" |163
 +
|-
 +
|}
 +
;Source<nowiki>:</nowiki> [http://users.erols.com/srweiss/tablehdc.htm#Chevy Stan Weiss flow chart]
  
−
====305 Vortec donor vehicles====
+
=====305 Vortec donor vehicles=====
 
The following list is for L31 5.7L donor vehicles. But some/all of the same vehicles may have been available w/the L30 305 engine:
 
The following list is for L31 5.7L donor vehicles. But some/all of the same vehicles may have been available w/the L30 305 engine:
 
*1996-2002 Chevrolet Express/GMC Savana full-size vans
 
*1996-2002 Chevrolet Express/GMC Savana full-size vans
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*1996-1999 Chevrolet Suburban/GMC Suburban full-size long wheelbase SUVs
 
*1996-1999 Chevrolet Suburban/GMC Suburban full-size long wheelbase SUVs
 
*1996-1999 Chevrolet Tahoe/GMC Yukon full-size short wheelbase SUVs  
 
*1996-1999 Chevrolet Tahoe/GMC Yukon full-size short wheelbase SUVs  
 +
 +
===305 heads to avoid===
 +
*'''376450''' have 1.72" intake valves
 +
*'''354434''' and others are 2 bbl heads, and have 1.72" intake valves. Best to just avoid these altogether since other, better heads are readily available.
 +
*'''14102187''' Swirl port heads used on some 305 TBI engines
 +
*'''10110810''' 1986-'91 swirl port
 +
 +
===Aftermarket 305 heads===
 +
*[http://www.trickflow.com/egnsearch.asp?N=400098+4294925232+340107+115+4294840138&autoview=sku Trick Flow Specialties Super 23], 175cc intake port, 56cc combustion chambers, 1.94" x 1.5" exhaust valves
 +
*World SR Torquer 305 (discontinued)
  
 
==Block preparation==
 
==Block preparation==

Revision as of 13:10, 13 February 2013

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