307 heads: what can you tell me? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bigcarguy · 09-02-2002, 11:03 PM

Ok, I've been going through this in my mind and I just need some more numbers to help me. I want to work on the heads on my truck and am considering three options, the cheaper the better. Option 1:Port the stock 307 heads and put swirreled valves and new springs. Option 2:Port 77 305 2bbl heads and the valve/spring thing. Option 3:get World Products Torquer S/R 305s. Keeping in mind that I'll have headers and a new cam in when I get ready to assemble. Now I can do the first two for less than half the price of option 3. Since I'm a poor college student, the first two options are the ones I'm leaning towards the most. But I need to know as much as I can about the 305 heads as well as the 307 heads. I need to know valve size, combustion chamber size, flow numbers if anyone knows, etc. If no one knows then maybe someone could point me in the right direction to finding out. Like I said, the Torquer S/R's are a last ditch option, so I'd really like to know which of the first two options would be best. Thanks.

Longhorn Man · 09-02-2002, 11:07 PM

1. 307 heads...I dunno.
2. 305 heads...you don't want to. Been there, done that. They will choke the crap out of your engine.
3. If you can do it, these will be awsome.

You thought about Vortecs?

bigcarguy · 09-02-2002, 11:19 PM

Well, hadn't really thought of Vortecs because of the small size of my engine(307). That actually might be a good idea. I know where I can get a pair that are drilled for early style intakes for just under $600. They may be worth it, though. Would there be anything other than center bolt valve covers that I'd need to invest in when I get Vortecs? Also, what kind of compression ratio would I be looking at with 64cc combustion chambers?

Longhorn Man · 09-02-2002, 11:23 PM

I know car craft had to mill them for a 305...no idea other than that.
If you get some that are drilled for the old intake, all you should need is the new guided rockers, and the centerbolt valve covers.

bigcarguy · 09-02-2002, 11:31 PM

What's the difference between guided rockers and regular rockers? I was thinking of going with roller rockers anyway, would there be a special kind I'd need?

bigcarguy · 09-03-2002, 12:58 AM

Ok, I haven't checked my casting number on my heads yet, but from what I can tell from this site: http://www.camaro1stgeneration.com/c...dcastings.html my heads should have around 70cc combustion chambers. What kind of compression ratio could I possibly be looking at with 64cc chambers? I believe stock compression is 8.5:1, but I have nothing to back that up(man I need a manual).

*Fast68Chevy* · 09-03-2002, 02:00 AM

depends on what engie you put the heads on and what year engine, different years and applications of same size engines can have different pistons to work with heads with different combustion chambers volumes to achieve compression ratio goal of GM at that time. different pistons were used o soem, some with deeper or ore or less reliefs, or less or more head height, etc etc. some engines were 8.0 some were 8.3 some were 8.5 and sem were 9.6 and some were 9.0 and some were 9.5

the L69 305HO(factory 350 Vette camshaft- the 190 horse 305) were 9.5 CR and the LG4 305 of same year(base 4bbl 305)were 8.5, for comparison purposes

most 8.5 CR engines had 75 or 76cc heads,. there were both, the there were 70 and 58 and another one,

changing valves sizs or thickening seats or milling down head deck gasket surface etc will affect volume of the combustion chamber and therefore the CR of the engine.,

could go on forever, there are aways HUGE discussions over this and everything else at places like thirdgen and chevytalk and so on and so forth.,

head work is $$$$$ to have done, personally id just find a set of good/better ready to run heads of some kind- older or later- even if you have to get a different intake, i have found a set good stock 1990 350 TBI heads i am getting tommorrow for use on a '85 350 bottom end that i have here that i want to have ready to run, only 'cuz can get them alot cheaper than any caveman{carbureted) heads (ones that that arent completely worn out and needing rebuild, guides, seats valves, etc)

even stil cheaper even after intake purchase in order to be able to use carburetion, if not cheaper, then damned close

good luck

09-02-2002, 11:03 PM	#1
bigcarguy Finally a Bulldawg Join Date: Apr 2001 Location: Athens, Georgia Posts: 220	307 heads: what can you tell me? Ok, I've been going through this in my mind and I just need some more numbers to help me. I want to work on the heads on my truck and am considering three options, the cheaper the better. Option 1:Port the stock 307 heads and put swirreled valves and new springs. Option 2:Port 77 305 2bbl heads and the valve/spring thing. Option 3:get World Products Torquer S/R 305s. Keeping in mind that I'll have headers and a new cam in when I get ready to assemble. Now I can do the first two for less than half the price of option 3. Since I'm a poor college student, the first two options are the ones I'm leaning towards the most. But I need to know as much as I can about the 305 heads as well as the 307 heads. I need to know valve size, combustion chamber size, flow numbers if anyone knows, etc. If no one knows then maybe someone could point me in the right direction to finding out. Like I said, the Torquer S/R's are a last ditch option, so I'd really like to know which of the first two options would be best. Thanks. __________________ Ah yes, the college life. School all morning, work all night, study when ya can. Uh...

09-02-2002, 11:19 PM	#3
bigcarguy Finally a Bulldawg Join Date: Apr 2001 Location: Athens, Georgia Posts: 220	Well, hadn't really thought of Vortecs because of the small size of my engine(307). That actually might be a good idea. I know where I can get a pair that are drilled for early style intakes for just under $600. They may be worth it, though. Would there be anything other than center bolt valve covers that I'd need to invest in when I get Vortecs? Also, what kind of compression ratio would I be looking at with 64cc combustion chambers? __________________ Ah yes, the college life. School all morning, work all night, study when ya can. Uh...

09-02-2002, 11:31 PM	#5
bigcarguy Finally a Bulldawg Join Date: Apr 2001 Location: Athens, Georgia Posts: 220	What's the difference between guided rockers and regular rockers? I was thinking of going with roller rockers anyway, would there be a special kind I'd need? __________________ Ah yes, the college life. School all morning, work all night, study when ya can. Uh...

09-03-2002, 12:58 AM	#6
bigcarguy Finally a Bulldawg Join Date: Apr 2001 Location: Athens, Georgia Posts: 220	Ok, I haven't checked my casting number on my heads yet, but from what I can tell from this site: http://www.camaro1stgeneration.com/c...dcastings.html my heads should have around 70cc combustion chambers. What kind of compression ratio could I possibly be looking at with 64cc chambers? I believe stock compression is 8.5:1, but I have nothing to back that up(man I need a manual). __________________ Ah yes, the college life. School all morning, work all night, study when ya can. Uh...

09-02-2002, 11:07 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	1. 307 heads...I dunno. 2. 305 heads...you don't want to. Been there, done that. They will choke the crap out of your engine. 3. If you can do it, these will be awsome. You thought about Vortecs?

09-02-2002, 11:23 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	I know car craft had to mill them for a 305...no idea other than that. If you get some that are drilled for the old intake, all you should need is the new guided rockers, and the centerbolt valve covers.

09-03-2002, 02:00 AM	#7
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	depends on what engie you put the heads on and what year engine, different years and applications of same size engines can have different pistons to work with heads with different combustion chambers volumes to achieve compression ratio goal of GM at that time. different pistons were used o soem, some with deeper or ore or less reliefs, or less or more head height, etc etc. some engines were 8.0 some were 8.3 some were 8.5 and sem were 9.6 and some were 9.0 and some were 9.5 the L69 305HO(factory 350 Vette camshaft- the 190 horse 305) were 9.5 CR and the LG4 305 of same year(base 4bbl 305)were 8.5, for comparison purposes most 8.5 CR engines had 75 or 76cc heads,. there were both, the there were 70 and 58 and another one, changing valves sizs or thickening seats or milling down head deck gasket surface etc will affect volume of the combustion chamber and therefore the CR of the engine., could go on forever, there are aways HUGE discussions over this and everything else at places like thirdgen and chevytalk and so on and so forth., head work is $$$$$ to have done, personally id just find a set of good/better ready to run heads of some kind- older or later- even if you have to get a different intake, i have found a set good stock 1990 350 TBI heads i am getting tommorrow for use on a '85 350 bottom end that i have here that i want to have ready to run, only 'cuz can get them alot cheaper than any caveman{carbureted) heads (ones that that arent completely worn out and needing rebuild, guides, seats valves, etc) even stil cheaper even after intake purchase in order to be able to use carburetion, if not cheaper, then damned close good luck



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