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Discussion Starter · #1 · (Edited)
Hey

i have a smog 77 sbc (010 block 4 bolt main ,for now its stock internally, quadrajet 4 barrel carb, 882 heads.

I took off the smog pump and the accessories then replaced the exhaust manifolds with midlength headers to a y pipe the duals after

All trans rebuilt th350 ,i dont have any specs on it so im gonna assume its near oem


So right now im looking to get to in the neighborhood of 300 hp from 170 it came rated at

I currently have but not installed a 1406 edelbrock cfm carb and a ZZ4 chevy performance aluminum intake .

Id like to figure out which way to go n a mild set of heads and a decent cam ,i dont need anything special .



Ive also been told i can “wake the car up “ with some adjusting the timing of the cam? Is that true or bs?

Thanks for your time
 

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The thing about sbc engines is that you really need to change the heads and pistons bumping up the compression to make them breath better. Most factory heads have horrible exhaust valves so that leaves you looking to the aftermarket or your local machine shop to install larger valves.
Then you can install a cam and rocker setup to make some power.

But the thing is that with a SBC the power per dollar is pretty low. You need to go through and replace a majority of the engine to make it reliable. Around 300hp you can get away just running a better flowing exhaust, idle to 3500rpm intake, and a 650ish cfm carb. You can play with your timing and install different head gaskets/mill the head true. But those are more reliablity things then power things and the goal should be to keep this under $500.

I have bought four 383/350's with dart heads carb to pan running engines for $900 to $1200 each at this point. The heads alone are worth $600 the cam and pistons are around another $400 especially if it is a 383. Sometimes you get a roller cam. But the majority are flat. These engine still come around if you keep an eye out. But as you can imagine fewer people are building them so there are less around.

If I wanted to run a 300-350hp SBC then I would start telling people I have cash in hand and let them come to me ready to sell that engine they have $1500-$2000 into(more if they had a shop build it) for $1000.

This worked great for me till around 2002 when the LS engines started really hitting the junk yards. I would find tons of cheap low power TBI engines so I moved onto those. Occasionally I would find a built SBC. But it was usually from someone doing a LS swap. At this point I only play with LS and TBI because as I said before the carb SBC needs alot replaced to touch a factory 5.3 and the ones you do find are often two or 3 times what a TBI 5.7 will cost.


If you want to keep the 350 in there just stay away from the rabbit hole or you will be another guy who has $1500-$2000 into a engine only making 330hp who sells it for $1000 when you do a LS swap.
If it only makes 280hp then oh well. Drive it while saving up/looking out for another engine that is already built that someone wants to swap out.
 

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Discussion Starter · #3 ·
@cerial thanks for your response. Seems a reasonable way to go about it. I prefer to build my own engine. Its in an impala and ive touched everything else in the car except for the engine block itself.

I have a 5.3 ls already but im sticking to the 350 for various reasons But mainly because i like the sound of glasspacks behind it . Im looking for a truck i can race also so thats when ill start with ls stuff
The thing about sbc engines is that you really need to change the heads and pistons bumping up the compression to make them breath better. Most factory heads have horrible exhaust valves so that leaves you looking to the aftermarket or your local machine shop to install larger valves.
Then you can install a cam and rocker setup to make some power.

But the thing is that with a SBC the power per dollar is pretty low. You need to go through and replace a majority of the engine to make it reliable. Around 300hp you can get away just running a better flowing exhaust, idle to 3500rpm intake, and a 650ish cfm carb. You can play with your timing and install different head gaskets/mill the head true. But those are more reliablity things then power things and the goal should be to keep this under $500.

I have bought four 383/350's with dart heads carb to pan running engines for $900 to $1200 each at this point. The heads alone are worth $600 the cam and pistons are around another $400 especially if it is a 383. Sometimes you get a roller cam. But the majority are flat. These engine still come around if you keep an eye out. But as you can imagine fewer people are building them so there are less around.

If I wanted to run a 300-350hp SBC then I would start telling people I have cash in hand and let them come to me ready to sell that engine they have $1500-$2000 into(more if they had a shop build it) for $1000.

This worked great for me till around 2002 when the LS engines started really hitting the junk yards. I would find tons of cheap low power TBI engines so I moved onto those. Occasionally I would find a built SBC. But it was usually from someone doing a LS swap. At this point I only play with LS and TBI because as I said before the carb SBC needs alot replaced to touch a factory 5.3 and the ones you do find are often two or 3 times what a TBI 5.7 will cost.


If you want to keep the 350 in there just stay away from the rabbit hole or you will be another guy who has $1500-$2000 into a engine only making 330hp who sells it for $1000 when you do a LS swap.
If it only makes 280hp then oh well. Drive it while saving up/looking out for another engine that is already built that someone wants to swap out.
 

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I don't know your budget.
But below is a good video on the good/bad factory heads.

Mind you most of them still need hardened guides to run todays fuel.

Now some guys are reasonable with what they charge and some guys will want $800 for what I would have sold for $100 to $150.

But the deals are out. Same deal when upgrading most guys dont care or loose money on the old parts. So if you know what to look for you can save some cash getting "performance" heads on a budget.

Now they are not going to be as good as aftermarket. The technology and heads are just better. But if you can pick up a set of heads that already had the valve seats done and will give you a bump in compression for $400 vs some aftermarket ones that will run you lets say $1000 more. That is going to let you use that cash in other areas like the suspension, steering, brakes, etc.


 

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Discussion Starter · #5 ·
I don't know your budget.
But below is a good video on the good/bad factory heads.

Mind you most of them still need hardened guides to run todays fuel.

Now some guys are reasonable with what they charge and some guys will want $800 for what I would have sold for $100 to $150.

But the deals are out. Same deal when upgrading most guys dont care or loose money on the old parts. So if you know what to look for you can save some cash getting "performance" heads on a budget.

Now they are not going to be as good as aftermarket. The technology and heads are just better. But if you can pick up a set of heads that already had the valve seats done and will give you a bump in compression for $400 vs some aftermarket ones that will run you lets say $1000 more. That is going to let you use that cash in other areas like the suspension, steering, brakes, etc.


My budget is 1500 for heads

i have my eye on these at the moment,i am open to other aftermarket options

 

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Every SBC head that GM produced is prone to cracking . If you cut the seats more than a couple times , let alone put in bigger valves , you may as well replace seats . when you're done , you'll have heads with poor flowing runners ,& crappy combusrtion chambers &small ports that are still prone to cracking pieces , that you'll have more in than if you'd bought new aluminum heads ! . At the 300 HP level , stock Chevy crank and rods will last just fine , the shape of the top ,of the piston & the resulting compression ratio sucks .a set of 345np pistons @ $100 & rings , $700 for a set of aluminium heads , $125 cam & lifters & necessary additional parts wi!l build you a reliable , 300+ HP cruise , not a 7000 rpm racer , just a cruiser .
 

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Most important on these old smoggers is head’s. These are low compression, lazy burning head’s intended to reduce NOx emissions by cooling and slowing the burn. You want 64 cc chambered head’s with heart shaped combustion chambers. Since you already bought an intake that takes the conventional intake to head bolt pattern you can’t use the GM L31 Vortec head as it uses a different intake bolt pattern. This unless you are willing to buy a different intake this requires the use of the late 1960’s through 71 GM dual quench head’s or going to the aftermarket where there are many and better choices in iron or aluminum. Without a head change everything else you’re doing is just messing around on the edges.

Now you can get 300 horses with the heads you have but it takes a lot of cam and more compression where the engine has no efficiency so you throw a lot of fuel at it for what it gives back in power and such cams are not happy on the street and are likely to need a higher stall converter.

If your not going to replace pistons and you're not going to mill the block deck to insure its flat then you really need to consider using a composite head gasket to get enough compliance to the surface that it seals up. In this case it probably doesn’t matter much whether you use an aluminum or iron head as for either you can use a .028 inch composite gasket which nets with the typical SBC piston being .025 inch in the bore at TDC the squish/quench clearance between the rim of the piston and the step of the combustion chamber is .053 inch where .040 is about the optimum but without decking the block or using a raised compression height piston you can’t get there from here. Still when you consider that GM uses a .047 thick gasket for a gap of .072 you’ve gained on squish/quench and got some more compression out of the deal, not racer optimized but a bunch improved. If your going deep to replace all the guts and do proper machining then I’d recommend a different set of steps and parts

For a budget build basically an Ebay set of import head’s is just fine into about a 420 horse build.

The cam in the 77 is the old 929 hydraulic flat tappet it is good for 300 horses on a higher compression 350. It gets a little hard to recommend cams simply because as you start messing around one gets excited that if they can get 300 horsepower then 400 is just in sight and that takes a little difference in selection. An example a Comp XE262H builds a nice 330 horse engine but the XE268H builds into the 400’s and while it is at the upper limit of stock stall converters it will work with them without much pain to the driver.

Then if you’re going to open the motor up and it needs a crank you can put together a budget 383 for about the same cost as a 350 rebuild. So there are a lot of possibilities before you spend money on parts. Some parts like head’s can carry through several engine builds.

Without changing the head’s or cam there isn’t a lot to be gained by playing with the timing because the compression is so low and the combustion chambers so crappy the burn doesn’t really respond much to timing changes without at least getting the compression up. The other big problem with these open chamber head’s is they quickly go into detonation. One of the big reasons for modern heart shaped chambers is they are very detonation resistant. The subtle changes of shapes in their chamber shapes allows the chamber to act as if the fuel has a 4 to 6 higher octane than it tested for as marked on the pump. This allows for more compression and higher burn temps which make for more power.

Headers, nothing like long primaries, they build mid range torque and top end power. Shorties often cut torque but gain way up on the top end where a daily driver seldom operates, mid lengths are something of a mixed bag they sometimes improve mid range torque and do offer top end gains. So far as I’m concerned the jury is out on H versus X pipes different builds net different results about the time everybody moves to X pipes somebody comes along with an H pipe that meets and raises the stakes. For sound I like the mellow rumble of H pipes over the screech of X pipes.

The one thing you can say about the 882 head is it is the best of the worst head’s and is sought after by guys racing in the lower classes where open chamber 76cc head’s are rules required.

We need to talk your real goals if you don’t want to stop at 300 horses and your budget and time availability. Example if this is a daily driver that can’t be down longer than a weekend.

Bogie
 

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The "quick and dirty" version. If you're planning to keep the block and rotating assembly as is, in an Impala, stock torque converter, assuming mild gear ratio and using the intake/carburetor combo you have:

Flotek 180 cc heads (64cc chambers to bump up compression)
Lunati 250 Voodoo flat tappet cam/lifters (could consider the 256 Voodoo)
Measure for pushrods, new stamped rockers and balls

It should have you in the the neighborhood of 300 hp at the crank, with enough left over to get a blue box Transgo shift kit for the TH350, within the 1500 budget you mentioned for the heads.

This is just one way to get it done. If you get into changing parts in the rotating assembly, machine work, etc...obviously, there would be better plans. The Flotek heads have the exhaust ports raised by .125" (1/8th) and I'm not sure if that would cause a problem with the existing exhaust.

In the 70's the manufacturers changed the way they rated horsepower. They went from crankshaft (gross) to rear wheel (net). I think the rating on the '77 engine would be rear wheel. If you're thinking 300 rear wheel (net) horsepower, the parts listed above won't get you there.
 

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Discussion Starter · #10 ·
Most important on these old smoggers is head’s. These are low compression, lazy burning head’s intended to reduce NOx emissions by cooling and slowing the burn. You want 64 cc chambered head’s with heart shaped combustion chambers. Since you already bought an intake that takes the conventional intake to head bolt pattern you can’t use the GM L31 Vortec head as it uses a different intake bolt pattern. This unless you are willing to buy a different intake this requires the use of the late 1960’s through 71 GM dual quench head’s or going to the aftermarket where there are many and better choices in iron or aluminum. Without a head change everything else you’re doing is just messing around on the edges.

Now you can get 300 horses with the heads you have but it takes a lot of cam and more compression where the engine has no efficiency so you throw a lot of fuel at it for what it gives back in power and such cams are not happy on the street and are likely to need a higher stall converter.

If your not going to replace pistons and you're not going to mill the block deck to insure its flat then you really need to consider using a composite head gasket to get enough compliance to the surface that it seals up. In this case it probably doesn’t matter much whether you use an aluminum or iron head as for either you can use a .028 inch composite gasket which nets with the typical SBC piston being .025 inch in the bore at TDC the squish/quench clearance between the rim of the piston and the step of the combustion chamber is .053 inch where .040 is about the optimum but without decking the block or using a raised compression height piston you can’t get there from here. Still when you consider that GM uses a .047 thick gasket for a gap of .072 you’ve gained on squish/quench and got some more compression out of the deal, not racer optimized but a bunch improved. If your going deep to replace all the guts and do proper machining then I’d recommend a different set of steps and parts

For a budget build basically an Ebay set of import head’s is just fine into about a 420 horse build.

The cam in the 77 is the old 929 hydraulic flat tappet it is good for 300 horses on a higher compression 350. It gets a little hard to recommend cams simply because as you start messing around one gets excited that if they can get 300 horsepower then 400 is just in sight and that takes a little difference in selection. An example a Comp XE262H builds a nice 330 horse engine but the XE268H builds into the 400’s and while it is at the upper limit of stock stall converters it will work with them without much pain to the driver.

Then if you’re going to open the motor up and it needs a crank you can put together a budget 383 for about the same cost as a 350 rebuild. So there are a lot of possibilities before you spend money on parts. Some parts like head’s can carry through several engine builds.

Without changing the head’s or cam there isn’t a lot to be gained by playing with the timing because the compression is so low and the combustion chambers so crappy the burn doesn’t really respond much to timing changes without at least getting the compression up. The other big problem with these open chamber head’s is they quickly go into detonation. One of the big reasons for modern heart shaped chambers is they are very detonation resistant. The subtle changes of shapes in their chamber shapes allows the chamber to act as if the fuel has a 4 to 6 higher octane than it tested for as marked on the pump. This allows for more compression and higher burn temps which make for more power.

Headers, nothing like long primaries, they build mid range torque and top end power. Shorties often cut torque but gain way up on the top end where a daily driver seldom operates, mid lengths are something of a mixed bag they sometimes improve mid range torque and do offer top end gains. So far as I’m concerned the jury is out on H versus X pipes different builds net different results about the time everybody moves to X pipes somebody comes along with an H pipe that meets and raises the stakes. For sound I like the mellow rumble of H pipes over the screech of X pipes.

The one thing you can say about the 882 head is it is the best of the worst head’s and is sought after by guys racing in the lower classes where open chamber 76cc head’s are rules required.

We need to talk your real goals if you don’t want to stop at 300 horses and your budget and time availability. Example if this is a daily driver that can’t be down longer than a weekend.

Bogie
Thank you thank man ,i now have an idea of what direction of where i want to go. I will say that im not planning to change anything on the bottom end of the engine but i will invest in a set of heads and cam (aftermarket for this) ill do some research on that cam you mentioned.


my goals for this is just for cruising because im gonna do my racing stuff with another vehicle so if i get to 300hp with this ill call it a day.
 

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Discussion Starter · #12 ·
The "quick and dirty" version. If you're planning to keep the block and rotating assembly as is, in an Impala, stock torque converter, assuming mild gear ratio and using the intake/carburetor combo you have:

Flotek 180 cc heads (64cc chambers to bump up compression)
Lunati 250 Voodoo flat tappet cam/lifters (could consider the 256 Voodoo)
Measure for pushrods, new stamped rockers and balls

It should have you in the the neighborhood of 300 hp at the crank, with enough left over to get a blue box Transgo shift kit for the TH350, within the 1500 budget you mentioned for the heads.

This is just one way to get it done. If you get into changing parts in the rotating assembly, machine work, etc...obviously, there would be better plans. The Flotek heads have the exhaust ports raised by .125" (1/8th) and I'm not sure if that would cause a problem with the existing exhaust.

In the 70's the manufacturers changed the way they rated horsepower. They went from crankshaft (gross) to rear wheel (net). I think the rating on the '77 engine would be rear wheel. If you're thinking 300 rear wheel (net) horsepower, the parts listed above won't get you there.
forgot to mention im running 3.08 gears in the rear.


and now that i have some suggestions for cam and heads ill add that to the list of the parts to research before i make a decision. Thank you for your help
 

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With 3.08 gear and a 3 speed auto, I would go with something around a Comp XE262, the XE268 will make more power but feel pretty soggy off the line. Everyone makes cams around those sizes, just look up the specs. I ran the comp HE268 with 3.08's in my vette with Brodix IK heads and it was fine mid range but below about 2500RPM is was pretty slugish. Sometimes less is better. With headers, heads, and intake, it should be over 300 HP and have a good launch.
 

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Discussion Starter · #15 ·
With 3.08 gear and a 3 speed auto, I would go with something around a Comp XE262, the XE268 will make more power but feel pretty soggy off the line. Everyone makes cams around those sizes, just look up the specs. I ran the comp HE268 with 3.08's in my vette with Brodix IK heads and it was fine mid range but below about 2500RPM is was pretty slugish. Sometimes less is better. With headers, heads, and intake, it should be over 300 HP and have a good launch.
Is this it here?

 

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Thanks man,they seem to have a smooth idle sound looking at videos on yt and thats what im looking for.
I think the summit brand cam 1065 is pretty close for a little lower cost. Just get good lifters if you can, others may be able to comment on the best way to go right now. You will also need hardened pushrods and rockers for the new heads.
 
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