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Discussion Starter #1
So, as the title says I have a 1969 Caprice, it has a 350 that is all stock (other than the carb). I have seen a lot of things about swapping heads over, and I am already aware that Id have to get a different intake to go from the carb to the injected Vortec heads, but is this even possible to do on a 69' 350. I haven't seen anything dealing with a motor as old as this one, only 75 and newer. Plus if I did do this what would be the actual gains of the head swap? How much of a power increase should there be? This is my first project car and I have enough knowledge to get myself into trouble, but not enough to get back out of it, so any help is apricated.

Thanks!
 

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You need to pry the valve covers off to get the head casting numbers as there were pretty good heads being used back in 69.

This gets into the change of accessory brackets bolting to the front faces of heads and 69 is in this swap period where Chevy was leaving in machined on their ends heads behind and going to heads with machined ends. This is all about accessory mounting. All of these heads will fore and or backdate with the correct brackets to hang the accessories on.

The usefulness of L31, Vortec or any post 1995 modern head whether GM or aftermarket has a lot to do with cam timing and compression. Note your 69 probably already has a decent compression ratio but here you and we need the details that can be gleened from casting numbers and if still visible the engine ID numbers which will be on the block pad just above and behind the right side coolant pump block attachment. This be on your left when standing in front of the vehicle. From these it can be deduced what option this engine is.

There are a lot of mix and matches that work and a lot that don’t so do not go crazy and buy anything till we know where you are starting from. A for instance is your 69 heads use a cast integral push rod guide and unguided rocker arms. As the L31 Vortec head was used for production it does not have insitu push rod guides and uses self-guiding rockers. Now the L31 head can be modified to use guided push rods with the installation of screw in rocker studs which anchor sheet metal push rod guides. This being an example of changes that you will discover crossing production years.

Another is the L31 Vortec changes the intake bolt pattern from 6 bolts per side at 45 degrees to the intake, to 4 bolts to a side straight down which requires a matching intake manifold. An advantage to aftermarket performance heads is they are finished to accept the pre-vortec and the vortec bolt patterns. So there are to point out once again a bunch of differences that you need to know about so parts from here and there can be connected. It’s doable, everything is out there but you have to be careful and we are here to help you through this maze.

So come here with questions, as usual the only dumb question is the one you didn’t ask.

Bogie
 

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For what it is worth, GM Vortec heads are the best head GM ever made. But they need machine work to have any lift over .450. Plus they are notorious for cracking between the valves. For the time, money, and parts needed, you would be much better, and save money, to buy aftermarket heads.

If you’re stuck on using vortec heads, they’re pretty much a bolt on. There are plenty of how to’s and info on google.
 

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One reason Vortecs are used so often on the 70’s 350 engines is that many have about 8.1-8.5 factory compression, and Vortecs with 64cc chambers raise it about a point. If you use .026 head gaskets you can raise it a little more than that. I assume a real ‘69 vintage 350 probably has factory compression more like 9.1-9.5.

Bruce
 

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Discussion Starter #6
You need to pry the valve covers off to get the head casting numbers as there were pretty good heads being used back in 69.

This gets into the change of accessory brackets bolting to the front faces of heads and 69 is in this swap period where Chevy was leaving in machined on their ends heads behind and going to heads with machined ends. This is all about accessory mounting. All of these heads will fore and or backdate with the correct brackets to hang the accessories on.

The usefulness of L31, Vortec or any post 1995 modern head whether GM or aftermarket has a lot to do with cam timing and compression. Note your 69 probably already has a decent compression ratio but here you and we need the details that can be gleened from casting numbers and if still visible the engine ID numbers which will be on the block pad just above and behind the right side coolant pump block attachment. This be on your left when standing in front of the vehicle. From these it can be deduced what option this engine is.

There are a lot of mix and matches that work and a lot that don’t so do not go crazy and buy anything till we know where you are starting from. A for instance is your 69 heads use a cast integral push rod guide and unguided rocker arms. As the L31 Vortec head was used for production it does not have insitu push rod guides and uses self-guiding rockers. Now the L31 head can be modified to use guided push rods with the installation of screw in rocker studs which anchor sheet metal push rod guides. This being an example of changes that you will discover crossing production years.

Another is the L31 Vortec changes the intake bolt pattern from 6 bolts per side at 45 degrees to the intake, to 4 bolts to a side straight down which requires a matching intake manifold. An advantage to aftermarket performance heads is they are finished to accept the pre-vortec and the vortec bolt patterns. So there are to point out once again a bunch of differences that you need to know about so parts from here and there can be connected. It’s doable, everything is out there but you have to be careful and we are here to help you through this maze.

So come here with questions, as usual the only dumb question is the one you didn’t ask.

Bogie
Its a matching numbers, all stock 350 that came with 300hp from the factory, I'm in the process of moving currently so the car isn't where I am staying right now or I'd get you more details about the motor. And I know the heads were decent but I though I might be able to push out a little more power with Vortec heads over the stock ones. My end goal for this car is an overpowered cruiser, hp between somewhere 400-500 and 450+ lbs of torque. I had planned on doing the heads and cam and seeing where that landed me then go from there with more extensive upgrading.
 

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stock heads will get you no where near 500 hp. Thats not a little more, thats a lot more. Vortecs can get you into the low 420s for hp. To get 500 hp you will probably need 205 cc profilers or better with a solid roller cam, 11:1, single plane, 850 cfm carb, 1 3/4" long tube headers with all the supporting parts,,,
 

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Discussion Starter #8
stock heads will get you no where near 500 hp. Thats not a little more, thats a lot more. Vortecs can get you into the low 420s for hp. To get 500 hp you will probably need 205 cc profilers or better with a solid roller cam, 11:1, single plane, 850 cfm carb, 1 3/4" long tube headers with all the supporting parts,,,
To me torque is more important than hp, as long as its above 400hp (and doesn't grenade itself) I'll be pretty happy with it, and I'm already guessing I'm going to be swapping out my auto 3 speed transmission as well with the power boost
 

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You are going to make more hp than torque because you will be building a 6,000 rpm peak power engine.
440 hp and 420 torque with budget after market heads or vortec heads and a really well matched parts list,,,
 

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All I can say is, I love my iron Vortecs on my 350 street engine. Planned my build around them, so I'm using a Vortec-specific intake with a mild cam (.462/.469 lift) and 625 cfm Demon carb; flat top pistons. Great torque and responsiveness up to 5,500 RPM. Not a race motor, but suits me fine!
 

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Basically the recipe for a 380 hp and similar amount of torque on a 350 includes the following.
  • L31, Vortec heads with factory pistons
  • a Comp XE268H cam and kit, needless to say the upper valve guides of these heads need to be trimmed down for the lift
  • 1.5 ratio rockers on 3/8ths studs
  • an Edelbrock Performer RPM intake
  • a 650 to 800 cfm carburetor or self leaning EFI
  • 1-5/8ths long tube headers.

This can be pushed into the low 400s of torque and hp by simply adding more cam or putting some effort into the heads. The disadvantage of more cam is that cams which time similar to the XE268H are typically as far as you can push a stock stall converter. So this is a decision point that incurs pulling the tranny and putting money into the converter if not also including a rebuild and hop up of the slush box while you’re there.

Starting from the 380 hp build going to the low 400’s can be achieved with the following:
  • a moderate port clean up, the L31 head is already pretty good so just some deburring and streamlining is about all that is needed.
  • installing 7/16th studs will stiffen up the valve train too insure the engine can rev higher
  • using 1.6 rockers provides a faster opening profile with a bit more peak lift which is very useful with modern fuels as this allows building greater cylinder compression pressure without going to a longer duration cam and the resultant effect of lowering bottom end power as an expense of top end gains. This gets into a ton of engine theory that is a long discussion in itself so I’ll pass for now.
  • The exhaust system is starting to get twitchy at 400 horses which is likely to want 1-3/4 ID tubes.

This is about the limit with L31 Vortec heads without a lot more cam and professional porting. For aftermarket aluminum heads there is another 20 to 40 horses hiding in this build that they can exploit depending on who’s head your budget can support.

If you’re building a new bottom end then the use of flat top or D dish pistons are good for another 15 to 20 foot pounds and horsepower’s as they offer a better burn than factory round dish pistons. Flat tops will be looking at larger 74ish cc modern chambered aftermarket heads. These retain the shapes of the modern Ricardo chamber just adding volume, they are not to be confused based on chamber volume with old fashion open chamber SMOG heads. The use of D dish pistons offers the squish/quench and wet flow characteristics of a flat top piston while addressing the max compression ratio limits of smaller chamber heads on modern octane limited pump fuel. Aluminum heads really need the block to be decked or raised compression height pistons to be used to optimize the squish/quench clearance. Aluminum is more forgiving on this clearance so going wider than optimum is safe but doesn’t use the head as well as it can be used. The issue vis-a-vis an iron head is in gasket thickness combined with the factory piston crown to deck clearance of .025 inch. It is generally conceded that about .035 to .040 inch of clearance for the squish/quench step of the head’s chamber is well optimized. But the softer aluminum needs a composite gasket the thinnest being about .026 inch which when combined with the factory piston to deck clearance is .051 inch. Where with iron you can use a .015 or .019 steel shim gasket to get the s/q clearance down to .040 to .044 inch. Aluminum transfers heat faster than iron so it’s big advantage is detonation suppression which allows more compression than iron so to take advantage of this characteristic it is useful to press the squish/quench clearance and the overall compression ratio harder than is practical with iron heads. So this is some of the stuff if your looking for big torque and power numbers that you need to consider before ordering parts and deciding on machine operations.

If you need a new crank it is just as cost effective to build a 383 stroker, this will broaden the smile on your face. There are a lot of ways to slice this pie as well so stay in contact if you consider this option.

In summary you can go from a very stable 400 to 430 horse 350 with an easy to build motor very streetable motor or of course go wilder and or bigger. But 400 horse 350’s these days are not difficult to achieve. 450-500 is getting into the more exotic builds on a 350 but are doable.

Bogie
 

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Discussion Starter #12
Basically the recipe for a 380 hp and similar amount of torque on a 350 includes the following.
  • L31, Vortec heads with factory pistons
  • a Comp XE268H cam and kit, needless to say the upper valve guides of these heads need to be trimmed down for the lift
  • 1.5 ratio rockers on 3/8ths studs
  • an Edelbrock Performer RPM intake
  • a 650 to 800 cfm carburetor or self leaning EFI
  • 1-5/8ths long tube headers.

This can be pushed into the low 400s of torque and hp by simply adding more cam or putting some effort into the heads. The disadvantage of more cam is that cams which time similar to the XE268H are typically as far as you can push a stock stall converter. So this is a decision point that incurs pulling the tranny and putting money into the converter if not also including a rebuild and hop up of the slush box while you’re there.

Starting from the 380 hp build going to the low 400’s can be achieved with the following:
  • a moderate port clean up, the L31 head is already pretty good so just some deburring and streamlining is about all that is needed.
  • installing 7/16th studs will stiffen up the valve train too insure the engine can rev higher
  • using 1.6 rockers provides a faster opening profile with a bit more peak lift which is very useful with modern fuels as this allows building greater cylinder compression pressure without going to a longer duration cam and the resultant effect of lowering bottom end power as an expense of top end gains. This gets into a ton of engine theory that is a long discussion in itself so I’ll pass for now.
  • The exhaust system is starting to get twitchy at 400 horses which is likely to want 1-3/4 ID tubes.

This is about the limit with L31 Vortec heads without a lot more cam and professional porting. For aftermarket aluminum heads there is another 20 to 40 horses hiding in this build that they can exploit depending on who’s head your budget can support.

If you’re building a new bottom end then the use of flat top or D dish pistons are good for another 15 to 20 foot pounds and horsepower’s as they offer a better burn than factory round dish pistons. Flat tops will be looking at larger 74ish cc modern chambered aftermarket heads. These retain the shapes of the modern Ricardo chamber just adding volume, they are not to be confused based on chamber volume with old fashion open chamber SMOG heads. The use of D dish pistons offers the squish/quench and wet flow characteristics of a flat top piston while addressing the max compression ratio limits of smaller chamber heads on modern octane limited pump fuel. Aluminum heads really need the block to be decked or raised compression height pistons to be used to optimize the squish/quench clearance. Aluminum is more forgiving on this clearance so going wider than optimum is safe but doesn’t use the head as well as it can be used. The issue vis-a-vis an iron head is in gasket thickness combined with the factory piston crown to deck clearance of .025 inch. It is generally conceded that about .035 to .040 inch of clearance for the squish/quench step of the head’s chamber is well optimized. But the softer aluminum needs a composite gasket the thinnest being about .026 inch which when combined with the factory piston to deck clearance is .051 inch. Where with iron you can use a .015 or .019 steel shim gasket to get the s/q clearance down to .040 to .044 inch. Aluminum transfers heat faster than iron so it’s big advantage is detonation suppression which allows more compression than iron so to take advantage of this characteristic it is useful to press the squish/quench clearance and the overall compression ratio harder than is practical with iron heads. So this is some of the stuff if your looking for big torque and power numbers that you need to consider before ordering parts and deciding on machine operations.

If you need a new crank it is just as cost effective to build a 383 stroker, this will broaden the smile on your face. There are a lot of ways to slice this pie as well so stay in contact if you consider this option.

In summary you can go from a very stable 400 to 430 horse 350 with an easy to build motor very streetable motor or of course go wilder and or bigger. But 400 horse 350’s these days are not difficult to achieve. 450-500 is getting into the more exotic builds on a 350 but are doable.

Bogie
Ok, so a lot of that went over my head, but I'm starting to realize its a little more complicated than just slapping heads and a cam in it and calling it a day. I'm planning on doing most of this myself in my garage if possible, and as "cost effective" as I can. So its sounding like (without dumping a ton of cash into it) lower 400s is do-able but much more than that is going to start getting expensive. What roughly should I set aside for a budget?
 

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1969 350 300hp is a pretty decent place to start, it'll havew flat top pistons and 1.94" valve closed chamber("fuelie") heads on it, which you could sell to partially finance the better head swap.

What is the head casting number of the heads on the motor right now??
They could be woth anywhere from $200-500 to sell off depending on who the buyer is and what numbers you have.

Take that, put it with another $700 or so and buy a set of budget aluminum heads, such as FLo-Tek or ProMaxx Maxx series in the 180-190cc runner volume catagory.
Add a cam, lifters, timing set, pushrods, rocker arms, headbolts w/washers, and the necessary intake manifold and headers.

If you are not going to upgrade to hydraulic roller cam and lifters, then I would run a small tight lash oval track type cam.
Have yourself a decent 460-475 hp 450 ft.lbs with a 2200--5500 rpm power band yet still be hanging strong if you need to run it up to a 6000 rpm redline.
Something reminiscent of the 1970 Corvette /Camaro LT-1 350 but a modern grind.

Shop careful and you could do it for around $2k, but figure $3k if you need a new carb and distributor too
 

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The 300 horse 350 for 1969 cam with the high compression 64 cc heads. It uses the same cam ending in part number 929 as the lower rated 255hp 350, same iron intake and same carb which original would be a Qjet. These heads if yours is a real 300 horse should be Camel Humps with 1.94 and 1.5 inch valves with the casting number ending in 041, 186, 291 or 462. The 250 and 255 hp versions used 76cc open chamber heads with the 250 using a 2bbl carb.

The cam times very close to the 250ish horse 350 L31, Vortec but that is a roller and the power is SAE net where your 300 horse 350 is rated at SAE gross. Best I can say about this engine is it was underrated by Chevy calling the peak power earlier in the rev range than where it really peaks. This motor from my experience when fresh will deliver an honest 325 at the crankshaft. GM did this same trick on the DZ 302 rating it at 290 hp. Before you dressed it to racing it would wind way higher and pound out numbers like 340. Once you stiffened up the rocker studs, added some Harlen-Sharp roller rockers and better valve springs you could wind those things up around 360- 370 hp without breaking a sweat. Taking the gloves off for a big big cam and a lot of porting you can bang on the 400 hp door pretty hard.

These are high compression heads depending on a dish or flat top piston the advertised SCR ran from 10 to 11.5, so I don’t expect this thing was happy with today’s gas. These heads would not have hardened exhaust seats unless somebody on a rebuild put inserts into them. So a modern head would be more compatible with today’s unleaded fuels and modern high swirl heads will be happier with the 91 to 93 octane premium available at the pump. The high swirl chambers of modern heads make the fuel act as if the octane was 4 or 5 points higher for iron heads and aluminum will act like 8 to 9 points higher.

Cam is important for the head change, more cam the more power the L31 and other modern heads produce. With the cam you have I expect that there would not be a significant power change.

In general with your 300 hp cam I’d expect stock iron Vortecs to pump up the torque by 20 ft pounds and do that a couple hundred RPM sooner. The horsepower should see about 25 more and should hold about 200 revs higher than your current head. Pinging on the L31 head with a better cam with moderate porting and beefing up the studs, rocker ratio and the use of a full roller rocker you could expect the torque to peak about 50 ft pounds higher and power about 40 ponies higher. These are not quite as good gains as starting from SMOG heads simply because the dual quench head is not as bad as factory open chamber heads.

Bogie
 
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