Difference between 305 and 350 heads
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Difference between 305 and 350 heads
i have a 305tpi and i'm going to rebuild it.I can get a set of 350tpi heads for cheap.Have much of a difference is there between 305 and 350 heads should i pick up the 350 heads or not.
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You will lose compression from the larger combustion chambers, but the valves would flow more air. I don't even think it's possible to mill them enough to maintain compression, so I wouldn't bother.
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Coupla problems,...
1. The 305 heads have 58cc chambers and the 350's have 64cc chambers. Unless you get the 350 heads milled down, your compression will drop about one full point. But more importantly,...
2. The 305 heads use smaller valves to clear the 305's smaller bore. If you use the 350 heads on the 305, you will need to get the bores clearanced so that the larger valves on the 350 heads do not interfere with the 305 block.
Or you could just get a set of World Products "305 Torquer" heads, which as the name implies were designed to work with your block. They offer 58cc chambers, improved ports and most importantly: relocated valve centerlines(towards the bore center) to allow the use of larger valves(1.94/1.5). Which allows you to skip the machining necessary to accomodate 350 heads on a 305.
1. The 305 heads have 58cc chambers and the 350's have 64cc chambers. Unless you get the 350 heads milled down, your compression will drop about one full point. But more importantly,...
2. The 305 heads use smaller valves to clear the 305's smaller bore. If you use the 350 heads on the 305, you will need to get the bores clearanced so that the larger valves on the 350 heads do not interfere with the 305 block.
Or you could just get a set of World Products "305 Torquer" heads, which as the name implies were designed to work with your block. They offer 58cc chambers, improved ports and most importantly: relocated valve centerlines(towards the bore center) to allow the use of larger valves(1.94/1.5). Which allows you to skip the machining necessary to accomodate 350 heads on a 305.
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
What they said about 305 heads is true. The statements about 350 heads are a little over-simplified, though.
You've got to know exactly what 350 heads you're looking at. They came in 58cc (aluminum), 64cc, and 76cc chamber versions from the factory. Valve sizes varied from 1.72/1.50, 1.84/1.50, 1.94/1.50, and 2.02/1.60 from the factory. If you throw aftermarket in there, there's even more variables.
You can shave 64cc heads down to 58cc. Larger, probably not. Without shaving, the compression loss will practically offset the flow gains in power production. 76cc heads don't tend to be good performance heads, anyway.
You can fit 1.94/1.50 350 heads on a 305 without cylinder wall problems. 2.02/1.60 valves may not even hit, but the flow loss around the cylinder edges would again offset the larger size.
As IROC said, for a 305, the best bet is World's S/R Torquer head made specifically for the 305. Others can be made to work, but by the time you make them as good as the World's, you will have spent as much or more money.
A slightly off-topic opinion: If you need to put machine work into the block (bore, pistons), you'd be better off $'s/hp just getting a 350 to rebuild.
You've got to know exactly what 350 heads you're looking at. They came in 58cc (aluminum), 64cc, and 76cc chamber versions from the factory. Valve sizes varied from 1.72/1.50, 1.84/1.50, 1.94/1.50, and 2.02/1.60 from the factory. If you throw aftermarket in there, there's even more variables.
You can shave 64cc heads down to 58cc. Larger, probably not. Without shaving, the compression loss will practically offset the flow gains in power production. 76cc heads don't tend to be good performance heads, anyway.
You can fit 1.94/1.50 350 heads on a 305 without cylinder wall problems. 2.02/1.60 valves may not even hit, but the flow loss around the cylinder edges would again offset the larger size.
As IROC said, for a 305, the best bet is World's S/R Torquer head made specifically for the 305. Others can be made to work, but by the time you make them as good as the World's, you will have spent as much or more money.
A slightly off-topic opinion: If you need to put machine work into the block (bore, pistons), you'd be better off $'s/hp just getting a 350 to rebuild.
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did all the aluminum tpis heads come with 58cc chambers.if so can i put those on with out all the problems you mention.
and of course someone has to come out ith the get a 350 instead,i don't want a 350 i want to see what my 305 can do.
and of course someone has to come out ith the get a 350 instead,i don't want a 350 i want to see what my 305 can do.
Joined: Mar 2000
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
My apologies for running off so long, I missed the part about them being 350 "TPI" heads. Shave 'em, port 'em, convert the rocker studs to screw-in, then rebuild 'em. They'll make the 305 do a lot more.
The aluminum L98 heads are probably not the answer, though. They are 58cc on a 350 vs. 64cc in cast iron for a reason - you need more compression with aluminum to make the same power as cast iron. If you put them on a 305, you should shave them down to about 52-54cc to raise the compression sufficiently to make up for the loss of heat through the aluminum. And, they do not have the heat cross-over passages, but unless emissions is an issue for you, that won't cause too many problems. They also should be treated at least to a clean-up porting job, and when you're all done, their only advantages would be that they already have screw-in rocker studs and will weigh less.
And don't be too quick to sling mud at me about bringing up a 350 - take a closer look at my sig. I came mighty close to going that route - any hick-up at all with the LG4 shortblock, I would have headed down the 350 path.
I stand by what I said. Being different is only worth so much, and typically gets expensive. If you've got the money to pay for being "different", there is a lot you can do with a 305. 58cc aluminum heads is probably not the best place to start.
World S/R Torquer 305 heads is an excellant place to start.
You could really be different and stroke the 305 to 334. You should still use the World heads, though.
The aluminum L98 heads are probably not the answer, though. They are 58cc on a 350 vs. 64cc in cast iron for a reason - you need more compression with aluminum to make the same power as cast iron. If you put them on a 305, you should shave them down to about 52-54cc to raise the compression sufficiently to make up for the loss of heat through the aluminum. And, they do not have the heat cross-over passages, but unless emissions is an issue for you, that won't cause too many problems. They also should be treated at least to a clean-up porting job, and when you're all done, their only advantages would be that they already have screw-in rocker studs and will weigh less.
And don't be too quick to sling mud at me about bringing up a 350 - take a closer look at my sig. I came mighty close to going that route - any hick-up at all with the LG4 shortblock, I would have headed down the 350 path.
I stand by what I said. Being different is only worth so much, and typically gets expensive. If you've got the money to pay for being "different", there is a lot you can do with a 305. 58cc aluminum heads is probably not the best place to start.
World S/R Torquer 305 heads is an excellant place to start.
You could really be different and stroke the 305 to 334. You should still use the World heads, though.
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I wouldn't go with anything larger than the 1.84" intake valves. Yes, the 1.94"s will fit and maybe the 2.02"s, but you will have some pretty serious shrouding problems. Bigger valves isn't always better, you want the most freely flowing air, not just the most amount of it. If the air is flowing more freely, it will swirl in the chamber better and equate to more complete combustion.
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305 IMO cannot do much in terms of performance..or real performance....
More $$$ is needed. If you have it, then by all means go ahead.
lotsa nice 332 sbc's around but its not fun for a street car. You want torque for everyday drivin & light-to-light smokin.
I dont know about you but i like my bearings smooth....thats why i built a lower RPM motor, stroker. Lots of power down low WHEN i need it. No building up!
Good Luck though & my previous post was not meant to cause harm
More $$$ is needed. If you have it, then by all means go ahead.
lotsa nice 332 sbc's around but its not fun for a street car. You want torque for everyday drivin & light-to-light smokin.
I dont know about you but i like my bearings smooth....thats why i built a lower RPM motor, stroker. Lots of power down low WHEN i need it. No building up!
Good Luck though & my previous post was not meant to cause harm
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sorry guys,i didn't mean to sound like an *******.
I appreciate all the info.After long hard thought of debating i've decided it's in my best interest to get a 350.I allways wanted to keep the 305 and see what it could do but i just don't have all that money,with the money i have i can make a pretty darn 350.Thanks guys
I appreciate all the info.After long hard thought of debating i've decided it's in my best interest to get a 350.I allways wanted to keep the 305 and see what it could do but i just don't have all that money,with the money i have i can make a pretty darn 350.Thanks guys
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Re: Difference between 305 and 350 heads
My apologies for running off so long, I missed the part about them being 350 "TPI" heads. Shave 'em, port 'em, convert the rocker studs to screw-in, then rebuild 'em. They'll make the 305 do a lot more.
The aluminum L98 heads are probably not the answer, though. They are 58cc on a 350 vs. 64cc in cast iron for a reason - you need more compression with aluminum to make the same power as cast iron. If you put them on a 305, you should shave them down to about 52-54cc to raise the compression sufficiently to make up for the loss of heat through the aluminum. And, they do not have the heat cross-over passages, but unless emissions is an issue for you, that won't cause too many problems. They also should be treated at least to a clean-up porting job, and when you're all done, their only advantages would be that they already have screw-in rocker studs and will weigh less.
And don't be too quick to sling mud at me about bringing up a 350 - take a closer look at my sig. I came mighty close to going that route - any hick-up at all with the LG4 shortblock, I would have headed down the 350 path.
I stand by what I said. Being different is only worth so much, and typically gets expensive. If you've got the money to pay for being "different", there is a lot you can do with a 305. 58cc aluminum heads is probably not the best place to start.
World S/R Torquer 305 heads is an excellant place to start.
You could really be different and stroke the 305 to 334. You should still use the World heads, though.
The aluminum L98 heads are probably not the answer, though. They are 58cc on a 350 vs. 64cc in cast iron for a reason - you need more compression with aluminum to make the same power as cast iron. If you put them on a 305, you should shave them down to about 52-54cc to raise the compression sufficiently to make up for the loss of heat through the aluminum. And, they do not have the heat cross-over passages, but unless emissions is an issue for you, that won't cause too many problems. They also should be treated at least to a clean-up porting job, and when you're all done, their only advantages would be that they already have screw-in rocker studs and will weigh less.
And don't be too quick to sling mud at me about bringing up a 350 - take a closer look at my sig. I came mighty close to going that route - any hick-up at all with the LG4 shortblock, I would have headed down the 350 path.
I stand by what I said. Being different is only worth so much, and typically gets expensive. If you've got the money to pay for being "different", there is a lot you can do with a 305. 58cc aluminum heads is probably not the best place to start.
World S/R Torquer 305 heads is an excellant place to start.
You could really be different and stroke the 305 to 334. You should still use the World heads, though.
https://www.motortrend.com/how-to/cc...er-heads-test/
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