Question on sbc heads
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Screamin' Metal
Well-known member
When you look at your heads, theres alot to look for. ONE THING TO LOOK FOR IS A BOARD TO GO BETWEEN THE HEADS SEALING SURFACE AND THAT CINDERBLOCK THAT THE HEADS ARE SITTING ON!!!!!
Now, that being said....the only humps you really have to get excited about are the camel humps or double humps. These days....you aren't gonna find any good ones on a 305 or a 307, vintage 69-79 or 89....
I don't want to be the bearer of bad news, From what your picture shows is a set of ordinary, run-of-the-mill heads. Late model, low compression, greasy, probably in bad need of a valve job and surfacing.....
Most heads have certain things in common in performance applications. Multi carbs, single carb on alum. Hi-rise, and streamlined factory headers, you can bet it has performance heads in one form or another. Anything else would be a total waste.
I doubt seriously if theres very many 1969 motors out there that haven't been opened up and scavanged of their good parts. NOW, if you found or had a 69' 327 or 350....those first looks should be at the front of the heads.....anything else.....the odds are very much agianst ya. [P[
Now, that being said....the only humps you really have to get excited about are the camel humps or double humps. These days....you aren't gonna find any good ones on a 305 or a 307, vintage 69-79 or 89....
I don't want to be the bearer of bad news, From what your picture shows is a set of ordinary, run-of-the-mill heads. Late model, low compression, greasy, probably in bad need of a valve job and surfacing.....
Most heads have certain things in common in performance applications. Multi carbs, single carb on alum. Hi-rise, and streamlined factory headers, you can bet it has performance heads in one form or another. Anything else would be a total waste.
I doubt seriously if theres very many 1969 motors out there that haven't been opened up and scavanged of their good parts. NOW, if you found or had a 69' 327 or 350....those first looks should be at the front of the heads.....anything else.....the odds are very much agianst ya. [P[
71elcamino
Member
well i was just confused as to why the heads have the different bumps from one another, almost like they are 2 different heads. but they look the same. i had a set of 462 fuelies that i sold a few months back and i regret that. now curious, if i have the heads decked, does this lessen the chamber cc? and will it increase the compression? just curious, i havent got a clue on that kinda stuff. and yea i forgot to put a board but i wasnt that worried cuz they are nasty old heads that need to have work done on them or be replaced.
chevellelovermichael
Well-known member
casting #'s are by the rocker studs,if they are the same on each side they are a matched set, if the heads are milled, it will raise compression ratio,build/date code is also by rocker studs.example-c69,march 6th of 69 or79
Last edited:
Torch
Extremely dangerous with a torch!!!
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differences
It could have been a reman engine they were on.
They only care about function not appearances so they match heads based on valve size and combustion chamber volume.
any machine shop can open up a set of 1.94" intake heads to 2.02"
If the heads don't have at least 1.94" intake valves don't mess with them on anything bigger than a 305...waste of time... No power.
The (so called) best heads I had was a set of 283 power pack heads. they had the big valves and 58cc chambers. I sold them to a racer, they had way too much compression on a 350 for the street and pump gas.
A common misconception is that high octane = more power
Why? Marketing. They make more off the expensive stuff
You only need enough octane to keep the engine from pinging
The higher a gas's octane...the more resistant it is to burning and the higher compression it requires.
If you run high octane race gas at the track in an engine that will run on 89 octane from the pedro mart you will have slower times.
Any old stock 350 heads will get you 9-9.5:1 which is perfect for the street and the good cheap gas.
A brand new set of cheapie out of the box GM 350 vortec heads will out perform a set of ported camel hump heads. proven on the dyno.
With the non performance heads It's beneficial to go into the ports with a carbide and smooth out the casting marks and machine edges...round out the sharp turns. That makes a difference you can feel when you are really getting on it.
Good head guys can pick out and match a set of heads just by looking at them.
GM didn't see any need to spend money making everything so nice on a low power smog engine.
the way to tell is run your finger down the port. if it feels smooth leave it alone.
If you feel an edge grind it smooth.
leave the intake ports rough as cast and if you grind on them don't polish them out very smooth... the turbulence the air/fuel mix gets flowing along the cast iron results in better flow velocity in the port than if the sides are smooth. Smooth surfaces are "sticky" to air/fuel mixtures
Some of the local budget circle track guys use the better 305 castings on their claimer engines. They open them up a little and put larger valves in them.
Some small block heads have a relatively straight edge along the exhaust side where it meets the block. these are the thicker cast heads.
The heads that are scalloped around the head bolts are lightened castings and are more susceptible to cracking
cc the heads and port them to exacting volumes?
That doesn't make any difference at all on the street..only in a high rpm race engine and it's to insure every cylinder is making the max power.
Having each cylinder slightly different... or one side of the engine slightly different than the other doesn't hurt anything. they don't fight each other.
One cylinder making 35 horsepower isn't going to cause a neighboring cylinder making 40hp to make less, your just missing out on 5hp that's all.
it's still going to run good.
what do you want to spend to get it out of that one cylinder? It costs thousands to blueprint an engine to match every cylinder.
The reason racers do it so they don't miss any potential horsepower by not having everything tweaked up to the max.
If your engine builder or machine shop tells you that you should go to such an extreme on a street engine...he's selling you something he wants to do or charge you for but that you don't need.
Every trade does it. Everyone does it different, and everyone claims their way and their most expensive way is the "right way"
Some shops and race shops will lay out all this fancy race work and tell you it's the right way to do it. You have to know what each operation does and if it is necessary for how your going to use the engine.
I have found myself with street engines a good shop will check all the machined surfaces and correct them if not true within tolerances and check the parts for cracks and damage. You want a shop that can deck and align bore a block, do head work and grind cranks.
The cheapest insurance you will ever buy against blowing up an engine your going to use hard is to have arp connecting rod bolts installed when you get the rods rebuilt. and use arp bolts when assembling the engine. some of the older larger engines have good enough head bolts and main bolts they don't need replaced.
I put in a full arp bolt kit when I do a virgin smallblock.
Everything I know about engines ends at about 6,000 rpm Those fancy shops with their high dollar tweaks.. they are building v8 engines that redline like a 900 kawasaki...
I don't go that fast.
It could have been a reman engine they were on.
They only care about function not appearances so they match heads based on valve size and combustion chamber volume.
any machine shop can open up a set of 1.94" intake heads to 2.02"
If the heads don't have at least 1.94" intake valves don't mess with them on anything bigger than a 305...waste of time... No power.
The (so called) best heads I had was a set of 283 power pack heads. they had the big valves and 58cc chambers. I sold them to a racer, they had way too much compression on a 350 for the street and pump gas.
A common misconception is that high octane = more power
Why? Marketing. They make more off the expensive stuff
You only need enough octane to keep the engine from pinging
The higher a gas's octane...the more resistant it is to burning and the higher compression it requires.
If you run high octane race gas at the track in an engine that will run on 89 octane from the pedro mart you will have slower times.
Any old stock 350 heads will get you 9-9.5:1 which is perfect for the street and the good cheap gas.
A brand new set of cheapie out of the box GM 350 vortec heads will out perform a set of ported camel hump heads. proven on the dyno.
With the non performance heads It's beneficial to go into the ports with a carbide and smooth out the casting marks and machine edges...round out the sharp turns. That makes a difference you can feel when you are really getting on it.
Good head guys can pick out and match a set of heads just by looking at them.
GM didn't see any need to spend money making everything so nice on a low power smog engine.
the way to tell is run your finger down the port. if it feels smooth leave it alone.
If you feel an edge grind it smooth.
leave the intake ports rough as cast and if you grind on them don't polish them out very smooth... the turbulence the air/fuel mix gets flowing along the cast iron results in better flow velocity in the port than if the sides are smooth. Smooth surfaces are "sticky" to air/fuel mixtures
Some of the local budget circle track guys use the better 305 castings on their claimer engines. They open them up a little and put larger valves in them.
Some small block heads have a relatively straight edge along the exhaust side where it meets the block. these are the thicker cast heads.
The heads that are scalloped around the head bolts are lightened castings and are more susceptible to cracking
cc the heads and port them to exacting volumes?
That doesn't make any difference at all on the street..only in a high rpm race engine and it's to insure every cylinder is making the max power.
Having each cylinder slightly different... or one side of the engine slightly different than the other doesn't hurt anything. they don't fight each other.
One cylinder making 35 horsepower isn't going to cause a neighboring cylinder making 40hp to make less, your just missing out on 5hp that's all.
it's still going to run good.
what do you want to spend to get it out of that one cylinder? It costs thousands to blueprint an engine to match every cylinder.
The reason racers do it so they don't miss any potential horsepower by not having everything tweaked up to the max.
If your engine builder or machine shop tells you that you should go to such an extreme on a street engine...he's selling you something he wants to do or charge you for but that you don't need.
Every trade does it. Everyone does it different, and everyone claims their way and their most expensive way is the "right way"
Some shops and race shops will lay out all this fancy race work and tell you it's the right way to do it. You have to know what each operation does and if it is necessary for how your going to use the engine.
I have found myself with street engines a good shop will check all the machined surfaces and correct them if not true within tolerances and check the parts for cracks and damage. You want a shop that can deck and align bore a block, do head work and grind cranks.
The cheapest insurance you will ever buy against blowing up an engine your going to use hard is to have arp connecting rod bolts installed when you get the rods rebuilt. and use arp bolts when assembling the engine. some of the older larger engines have good enough head bolts and main bolts they don't need replaced.
I put in a full arp bolt kit when I do a virgin smallblock.
Everything I know about engines ends at about 6,000 rpm Those fancy shops with their high dollar tweaks.. they are building v8 engines that redline like a 900 kawasaki...
I don't go that fast.
Torch
Extremely dangerous with a torch!!!
- Joined
- Jul 18, 2008
- Messages
- 1,627
I don't know what the casting marks mean but look at where the heads are almost touching...thats the straight edge I was talking about. these are not the lightened heads they have good metal in them.
350/327 is a 4" bore
350 3.48" stroke
327 3.25" stroke
305 3.736" bore x 3.48" stroke
307 3.875" bore x 3.25" stroke
The 307 is a 283 block with the longer stroke crank used in the 327.
The 302 chevy was a 283 crank in a 327 block
If you want a 5 liter engine for putt putt pulling go with a 305 for the long stroke
If you want a 5 liter engine for high winding performance go with the 307
If you want more just build a 350
the larger the cylinder bore is... the larger the valves you can put in the heads and the better it will breath at high rpm's.
The 307 heads had lower compression... than a 283... that's not necessarily a bad thing. and remember high octane gas in an engine that will run on low octane gas actually hurts performance.
the lower the compression ratio...the more space you can fill with air/fuel mixture prior to combustion and again the cheaper the gas you can run.
Octane was high good back in the old leaded gas days...
307's...they had small valves...that is a bad thing if you want power.
If these heads have the valve rotators on the exhaust valves you want to eliminate them...
They were invented to keep the seats clean from the residue of leaded gas. with unleaded they will grind the valves into the head.
Manufacturers induction harden the cast iron seats in the heads. This is true...
I have read that they didn't do this after lead was added to the fuel because it wasn't needed. I can't say if that is true.
Fact is that gas wasn't always made with lead in it and the manufacturers used to harden the seats in pre-leaded fuel engines.
Many modern engines after the removal of lead from the fuel also had induction hardened seats or hardened seat inserts.
So I'm not sure if the valve recession that occurred running engines designed for leaded fuel on unleaded was due to non hardened seats or just the valve rotators but either way you look at it... rotators are bad.
I have used and had heads designed for leaded fuel like these last a very long time on unleaded just by removing the rotators and getting a stock valve grind. a 3 angle valve job opens up the flow for more power but the contact area of the valve with the head is thinner. It might not last as long as a stock grind unless you install new seats.
Screamin' Metal
Well-known member
Now, if you want to build a performance motor....you can use those heads, but they're gonna need some work. You can run them....but shop around. You might find someone thats looking for low compression heads and you might swap out....but look at what your getting.
Whatever you decide....get a check out on the heads....make sure they're not cracked, they're flat, the valves are decent size and you have decent springs.
Give it a good valvejob, have them decked, mild porting, make sure all your springs are good and equal, when you put things back together....port match things.....and as you were told.....smooth out any roughness.
Be good for a mild performance build....[P[
rainman
Rough Rodder
You wont know exactly what you've got til you check the cast #'s. Some of those heads are pretty decent performance wise if done right. Show a pic of the bottom of the heads and give us the cast numbers, then you can get more info!
liljgoneman
Well-known member
i bet if you were to spin 1 of those heads 180 degrees, you'd see that the castings are exactly the same.....
RPM
The Rat Master!
Those heads are probably the same, turn one of them around and compare the casting marks. You are looking at opposite end of those heads.
71elcamino
Member
thanx guys, i did some research, i think they are the crappiest heads ever made by chevy, the 185s. ive been thinking about using like 416s?? i was told that the 80s 305 HO heads would bring the compression to around 10:1 and with a mild cam i could get about 300 hp out of the 307. i did want to ask who knows where to get a re-ring kit(gaskets, bearings, rings, etc basic kit) for less then what summit racing charges which is like 180.
hotrod preacher
"Official RRR Chaplain"
this is the company i've used several times and never have gotten a wrong order or order messed up yet...and they're about the cheapest too!
will use them again if i ever get to build another motor....
http://www.northernautoparts.com/
will use them again if i ever get to build another motor....
http://www.northernautoparts.com/
71elcamino
Member
thanx bro. im honestly not sure what im gonna do right now. i want a project so bad but im broke and going to aircraft school. and the heads are junk so i need to get new heads, find somewhere local to have this block dipped and get a cam and kit for it. so right now its all in the air. i wish i could just find a 67-72 lwb chevy. i like those alot. i have a feeling the ratrod has been shot down. i have had no luck finding a cab locally. so i may be looking for a chevy truck. we'll see what happens
