Chevy 305 engine

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m (→Overview: changed 350 to 305 in the first line)
 
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**2.100" rod
 
**2.100" rod
 
**2.45” main
 
**2.45” main
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 +
==305 SBC block casting numbers==
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{|class="wikitable"   
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|-
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! '''Casting Number''' !! '''Year'''!!!!''' Casting Number'''!! '''Year'''
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|-
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|'''355909''' || 1976-'85 ||||'''14010231''' || 1978-'86   
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|-
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|'''361979''' || 1976-'79 ||||'''14016381''' || 1980-'84   
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|-
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|'''460776''' || 1976-'79 ||||'''14016383''' || 1978-'88   
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|-
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|'''460777''' || 1976-'79 ||||'''14049047'''  || 1978-'86   
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|-
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|'''460778''' || 1978-'79 ||||'''14088551''' || 1986-'92   
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|-
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|'''581671''' || 1976-'85 ||||'''14093627''' || 1988-'94 
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|-
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|'''14010201''' || 1980-'84 ||||'''14094766''' || 1988-'94 
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|-
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|'''14010202''' || 1980-'84 ||||'''14102058''' || 1987-'88 
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|-
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|'''14010203''' || 1980-'84 
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|}
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==305 RPO codes==
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*LE9 (LF3 CA), 160 HP/235 TQ, K10, 1981-'86
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*LG9 2bbl, 130 HP/240 TQ, K10, 1981
 +
*LO3, TBI, 170 HP/260 TQ, V10, 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.
 +
 
 +
In 1996 the 305 got different heads and induction system.
  
 
==Cost==
 
==Cost==
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==Cylinder heads==
 
==Cylinder heads==
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The chamber volume is less than the 5.7L heads, around 55cc to 58cc depending on the casting. Like any head the chamber volume has to be measured to know for sure what the volume is. The biggest 305 intake valve valve is 1.84".
+
The chamber volume is less than the 5.7L heads, around 55cc to 58cc depending on the casting. Like any head the chamber volume has to be measured to know for sure what the volume is. The biggest production 305 intake valve is 1.84". The largest practical intake valve size is a 1.94", and the chambers need to be unshrouded for these to flow their best. In cases where there is no problem losing a little compression ratio, the cylinder bores can be slightly notched (like was done with some Pontiac and BBC engines, to name two) to help the intake flow.  
  
−
===Pre Vortec heads===
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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.
−
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.
+
  
−
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.  
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===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 same swirl port type heads for TBI applications, again same as the 350.
  
−
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.  
+
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.  
  
−
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.  
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====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.
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*'''14014416''' Another common 305 head for performance use. 1980-'86 "HO" heads. Nominal 58cc combustion chamber volume, 1.84" x 1.50" valves.  
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*'''14022601''' 1979-'86 These also respond well to porting and 1.94" intake valves. <br>
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{{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.
  
−
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.
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====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.  
  
−
===Porting===
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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".
−
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.  
+
 
 +
Unshrouding the intake valves needs to be done if larger valves are used.
  
 
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.  
  
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====305 heads to avoid====
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===Vortec heads===
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Casting number 450 and possibly 434 castings are the 2 bbl heads, and have 1.72" intake valves.
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====L31 5.7L 350 heads====
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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 ===
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−
The casting number 12558059 Vortec L30 5.0L head is quite a bit different than the L31 5.7L Vortec heads. While the Vortec L31 5.7L heads have a totally new intake port with a raised short-turn radius and raised roofs, the L30 5.0L Vortec heads are somewhat of a carry over. The L30 Vortec heads use the same intake bolt pattern as the L31 5.7L Vortec heads, but share few other similarities with them.
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====L30 5.0L 305 heads====
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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).  
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{|
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|[[File:L31 305 VORTEC HEAD CASTING ID.jpg|thumb|center|350px|305 Vortec L30 casting ID]]
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|[[File:305 VORTEC CHAMBER CN 059.jpg|thumb|middle|200px|305 Vortec L30 casting number 12558059 chamber]]
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|}
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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"/>
  
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The 305 Vortec heads have a spark plug location similar to the swirl port head, and a similar combustion chamber shape as well. This chamber 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.
+
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 1996 the RPO L30 305 got different heads than were previously used. These heads featured revised intake bolt pattern and a small swirl vane in the intake port. Unfortunately the '96-up 305 Vortec heads did not get the same type combustion chamber as the 350 Vortec. They used self-aligning rocker arms and the same center bolt valve covers like used since '87.
+
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.
  
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===Swirl-inducing vane===
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=====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.
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−
[[File:Tbi swirl port vane.jpg|thumb|left|300px|TBI swirl port vane]]
 
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<br style="clear:both"/>
 
−
 
 
{|
 
{|
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|[[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]]
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|[[File:305 VORTEC CHAMBER CN 059.jpg|thumb|center|240px|305 Vortec L30 casting number 12558059 chamber]]
 
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|[[File:L31 305 VORTEC HEAD CASTING ID.jpg|thumb|center|350px|305 Vortec L30 casting ID]]
 
 
|}
 
|}
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=====L30 Vortec head flow=====
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{|style="color:black; cellpadding="5" cellspacing="0" border="1"
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!bgcolor="#DDDFFF"|Lift (in.) !!bgcolor="#DDDFFF"|Intake (CFM) !!bgcolor="#DDDFFF"|Exhaust (CFM)
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|-
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| align="center" |0.100 || align="center" |68 || align="center" |47
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|-bgcolor="#F1F1F1"
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| align="center" |0.200 || align="center" |128 || align="center" |103
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|-
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| align="center" |0.300 || align="center" |179 || align="center" |138
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|-bgcolor="#F1F1F1"
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| align="center" |0.400 || align="center" |205 || align="center" |152
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|-
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| align="center" |0.500 || align="center" |221 || align="center" |163
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|-
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|}
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;Source<nowiki>:</nowiki> [http://users.erols.com/srweiss/tablehdc.htm#Chevy Stan Weiss flow chart]
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=====305 Vortec donor vehicles=====
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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:
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*1996-2002 Chevrolet Express/GMC Savana full-size vans
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*1996-1999 Chevrolet/GMC C/K full-size trucks
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*1996-1999 Chevrolet Suburban/GMC Suburban full-size long wheelbase SUVs
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*1996-1999 Chevrolet Tahoe/GMC Yukon full-size short wheelbase SUVs
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 +
===305 heads to avoid===
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*'''376450''' have 1.72" intake valves
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*'''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.
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*'''14102187''' Swirl port heads used on some 305 TBI engines
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*'''10110810''' 1986-'91 swirl port
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 +
===Aftermarket 305 heads===
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*[http://www.trickflow.com/search.asp?N=400098+4294952110+4294934453+115+4294952012&autoview=sku Trick Flow Super 23 175 cylinder heads], 175cc intake port, 56cc nominal combustion chamber volume, 1.94" intake x 1.5" exhaust valves
 +
*World SR Torquer 305 (discontinued)
  
 
==Block preparation==
 
==Block preparation==
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==Pistons==
 
==Pistons==
−
Use the same guidelines as you would for a SBC 350 for selecting the type of piston. Cast are fine for engines that won't see nitrous or boost, forged if it will. There are those who say using cast pistons and nitrous/boost is acceptable. And it is- providing the tune is spot on and the engine never sees detonation. If it does, the cast pistons will be the first thing to fail, and when they go they usually damage the bore and possibly the cylinder head as well.
+
Use the same guidelines as you would for a SBC 350 for selecting the type of piston. Cast are fine for engines that won't see nitrous or boost, forged if it will. There are those who say using cast pistons and nitrous/boost is acceptable. And it is- providing the tune is spot on and the engine never sees detonation. If it does, the cast pistons will be the first thing to fail, and when they go they usually damage the bore and possibly the cylinder head as well. This is because cast and hypereutectic aluminum alloys are brittle and when they fail they tend to shatter into many pieces, where a forging will generally stay in one piece, with pinched ring lands or depressed crowns, etc.
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 +
The worst possible piston design if a dished piston is needed is a round dish with a 45 degree chamfer around the outer edge. That leaves a scant 1/2" band on the top of the piston to provide the quench effect, and that's just not enough.
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 +
[[File:Round dish sbc piston.jpg]]
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 +
 
 +
A much better choice if a dished piston is needed is a reverse dome or D-cup type piston (the one below is for a SBC 383 stroker).
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 +
[[File:KB P-N 135 SBC 383 PISTON.jpg]]
  
 
==Intakes==
 
==Intakes==
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1987-'95 heads use straight center bolts
 
1987-'95 heads use straight center bolts
 
1996-'02 heads use the Vortec bolt pattern
 
1996-'02 heads use the Vortec bolt pattern
−
Also see '''[[Intakes]]'''
+
Also see '''[[Intake manifold]]'''
  
 
==Car Craft 305 build-up==  
 
==Car Craft 305 build-up==  

Latest revision as of 12:30, 3 July 2016

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