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Old 10-08-2015, 10:52 AM
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Swirl port heads. Keep or sell?

I have some freshly rebuilt 191 chevy swirl port TBI heads that I'm planning on using for my engine build. I've heard these are terrible heads, but most of the time the people that say this have never used them. I've also heard that they pull hard to 5000 rpm or more. This 350 will be going into a pickup so I don't really need to scream past 5000 or 5500 rpm.

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Old 10-08-2015, 11:49 AM
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Originally Posted by EragonSuperH View Post
I have some freshly rebuilt 191 chevy swirl port TBI heads that I'm planning on using for my engine build. I've heard these are terrible heads, but most of the time the people that say this have never used them. I've also heard that they pull hard to 5000 rpm or more. This 350 will be going into a pickup so I don't really need to scream past 5000 or 5500 rpm.
They don't even get past 400-4500 RPM, they hit that and it's like having a governer on the engne.

Since port flow is limited they do respond to more cam duration but are pretty insensitve to lifts beyond .4 inch. The 191 head is the low compression version of these heads. This comes from direct experience can't speak for what you've heard. Unless you're building a low RPM grunt motor for a working truck these are not going to get you much performance. They are highly resistant to porting techniques, it would be useful to reduce the swirl vane but there isn't much meat in the casting, you get into the coolant jackets long before the vane is usefully reduced.

If you're looking for high RPMs and better horsepower that comes at those RPMs then you need to look for different heads. I put them up for sale on Ebay or Craig's List or see if you can trade them to a shop for a set of L31 Vortecs or other modern head. The L31's are a bolt on 30-50 horsepower over any older head, the power range depending on cam thus the range. And that's out of the box without any porting. These can be found inexpensivly as rebuilt as well as new and there are many aftermarket copies in aluminum or iron many of which use conventional intake bolts as well as the unique Vortec bolt pattern.

The Swirl Port heads also have a unique bolt pattern the angle of the bolts at the plenum was changed from meeting the head at a 90 degree to a 70 degree angle. If you end up using these any manifold you buy need to have that accommodation or include a modification kit, something to watch for. The larger chambered (76cc versus 64cc of the 193 head) need to be used with a flat top piston to get the compression up.

Bogie
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Old 10-08-2015, 03:25 PM
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They are a great cylinder head for what they were designed for which was a truck.. If your towing or hauling, their off idle torque is perfect.. If your drag racing, they are scrap iron..

I had a 1995 k1500 and it was about as perfect as a truck engine as it could be, and it was a 305.
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Old 10-08-2015, 03:54 PM
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We used them on a dished piston 350 we installed in my nephews 51 bus Coupe, along with a built Powerglide, a 2500 RPM stall converter, and 4.88:1 Positraction in a 56 housing/axles. I was "told" they came off a 305 "Vortec". The car is a sort of "street gasser". I've heard the same, "they're only good to 4500 RPM", but they were handy at the time with only 14K, take off miles on them. The engine will rev easily to 6000 RPM without hesitation, and pulls solid all the way. I'm NOT saying they're a great head, but they're not as bad as a lot of guys say they are. I've also heard that removing the "ramp" from them does absolutely nothing to improve on their performance. I think for low end torque, use in a light car, used with low gearing, or for use in a truck, they're fine. junior stocker
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Old 10-08-2015, 04:34 PM
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Originally Posted by junior stocker View Post
We used them on a dished piston 350 we installed in my nephews 51 bus Coupe, along with a built Powerglide, a 2500 RPM stall converter, and 4.88:1 Positraction in a 56 housing/axles. I was "told" they came off a 305 "Vortec". The car is a sort of "street gasser". I've heard the same, "they're only good to 4500 RPM", but they were handy at the time with only 14K, take off miles on them. The engine will rev easily to 6000 RPM without hesitation, and pulls solid all the way. I'm NOT saying they're a great head, but they're not as bad as a lot of guys say they are. I've also heard that removing the "ramp" from them does absolutely nothing to improve on their performance. I think for low end torque, use in a light car, used with low gearing, or for use in a truck, they're fine. junior stocker
Do those Vortec 305 rpo L30 heads have 6 or 4 intake bolt holes? If they have 4 intake bolts they are true 1996-2002 Vortec 305 heads. They do have that "swirl ramp" just like the TBI heads do.

The Vortec 305 L30 was rated at [email protected]/285 lb/ft [email protected]
The truck TBI 350;s were rated at 200-210hp and 300 lb/ft torque, so those Vortec 305 heads aren't that bad comparatively.

The L30 Vortec 305 heads with have the 059 or 520 last 3 digits of the casting number.

peace
Hog
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Old 10-08-2015, 05:18 PM
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Originally Posted by oldbogie View Post
They don't even get past 400-4500 RPM, they hit that and it's like having a governer on the engne.

Since port flow is limited they do respond to more cam duration but are pretty insensitve to lifts beyond .4 inch. The 191 head is the low compression version of these heads. This comes from direct experience can't speak for what you've heard. Unless you're building a low RPM grunt motor for a working truck these are not going to get you much performance. They are highly resistant to porting techniques, it would be useful to reduce the swirl vane but there isn't much meat in the casting, you get into the coolant jackets long before the vane is usefully reduced.

If you're looking for high RPMs and better horsepower that comes at those RPMs then you need to look for different heads. I put them up for sale on Ebay or Craig's List or see if you can trade them to a shop for a set of L31 Vortecs or other modern head. The L31's are a bolt on 30-50 horsepower over any older head, the power range depending on cam thus the range. And that's out of the box without any porting. These can be found inexpensivly as rebuilt as well as new and there are many aftermarket copies in aluminum or iron many of which use conventional intake bolts as well as the unique Vortec bolt pattern.

The Swirl Port heads also have a unique bolt pattern the angle of the bolts at the plenum was changed from meeting the head at a 90 degree to a 70 degree angle. If you end up using these any manifold you buy need to have that accommodation or include a modification kit, something to watch for. The larger chambered (76cc versus 64cc of the 193 head) need to be used with a flat top piston to get the compression up.

Bogie
Will I be able to pull 330 hp and 414 lb/ft torque out of them? I found some flow numbers from a guy called Dyno Don on a different site and plugged them into a dyno program along with my other specs and this is what I got for max hp and torque. I've heard multiple times that if you plug flow numbers in, the program is pretty accurate.
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Old 10-08-2015, 05:36 PM
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Originally Posted by EragonSuperH View Post
Will I be able to pull 330 hp and 414 lb/ft torque out of them? I found some flow numbers from a guy called Dyno Don on a different site and plugged them into a dyno program along with my other specs and this is what I got for max hp and torque. I've heard multiple times that if you plug flow numbers in, the program is pretty accurate.
Honestly, no I don't think you can make those #'s.Unless you do alot of work.What flow #'s did you plug in?
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Old 10-08-2015, 05:46 PM
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Originally Posted by junior stocker View Post
We used them on a dished piston 350 we installed in my nephews 51 bus Coupe, along with a built Powerglide, a 2500 RPM stall converter, and 4.88:1 Positraction in a 56 housing/axles. I was "told" they came off a 305 "Vortec". The car is a sort of "street gasser". I've heard the same, "they're only good to 4500 RPM", but they were handy at the time with only 14K, take off miles on them. The engine will rev easily to 6000 RPM without hesitation, and pulls solid all the way. I'm NOT saying they're a great head, but they're not as bad as a lot of guys say they are. I've also heard that removing the "ramp" from them does absolutely nothing to improve on their performance. I think for low end torque, use in a light car, used with low gearing, or for use in a truck, they're fine. junior stocker
The L30/305 Vortec head is a great head for an OEM iron head.There is no comparison to a TBI swirl port head.They do have the ramp, tho it's not as restrictive as the swirl ports.The difference is in the ports themselves.The chamber is not as efficient as it's big brother, the L31, but, it's about the next best thing in OEM iron.These heads can flow 220 cfm in stock form with 1.84/1.5 valves.They also make a great upgrade for 283 & 307's..
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Old 10-08-2015, 06:09 PM
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Originally Posted by Hogg View Post
Do those Vortec 305 rpo L30 heads have 6 or 4 intake bolt holes? If they have 4 intake bolts they are true 1996-2002 Vortec 305 heads. They do have that "swirl ramp" just like the TBI heads do.

The Vortec 305 L30 was rated at [email protected]/285 lb/ft [email protected]
The truck TBI 350;s were rated at 200-210hp and 300 lb/ft torque, so those Vortec 305 heads aren't that bad comparatively.

The L30 Vortec 305 heads with have the 059 or 520 last 3 digits of the casting number.

peace
Hog
These came off of one of Chevrolet's "305 Vortec engine" equipped trucks. The engine IS NOT a true VORTEC HEAD equipped engine, they just call it "Vortec". It gets confusing why they do/did that. They are six bolts per side with the center two being at a "different" angle, requiring a manifold designed for them, or with the adapters supplied with some intakes. We made our own "adapters" to make up for the angle differences using an old Weiand intake. I'd pull a valve cover to get the casting numbers, but it has those darned silicone, valve cover gaskets, and they're a bear to get the covers/gaskets on without them slipping out of place. There was someone on the board here a few years back that did a "real life test" of these style heads, and he had very good results; far better than anyone would have expected. Like I said, I'm NOT pushing these heads, just saying they're not at all that bad; there are worse, but there are far better heads. junior stocker.
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Old 10-08-2015, 06:33 PM
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There's a guy from Tennessee here that does work with these heads.You can get an idea of what it takes by his videos on YouTube.Search for "Headbytes Porting".
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Old 10-08-2015, 08:18 PM
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The L30/305 Vortec head is a great head for an OEM iron head.There is no comparison to a TBI swirl port head.They do have the ramp, tho it's not as restrictive as the swirl ports.The difference is in the ports themselves.The chamber is not as efficient as it's big brother, the L31, but, it's about the next best thing in OEM iron.These heads can flow 220 cfm in stock form with 1.84/1.5 valves.They also make a great upgrade for 283 & 307's..
Do you think the L30 Vortec heads would be worth running on a mild 327? I'll have the set off of my current '98 truck engine once I swap it out for the 350.
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Old 10-08-2015, 08:24 PM
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Honestly, no I don't think you can make those #'s.Unless you do alot of work.What flow #'s did you plug in?
174 int. @450 500 and 550 lift 146 exh. @ same lifts
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Old 10-08-2015, 09:12 PM
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Do you think the L30 Vortec heads would be worth running on a mild 327? I'll have the set off of my current '98 truck engine once I swap it out for the 350.
Yes.You will need to choose parts wisely to be mindful of compression.The chambers are 58cc.A flat top piston would put you at approx. 10.3:1 on a standard 4" bore.
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Old 10-09-2015, 06:56 AM
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174 int. @450 500 and 550 lift 146 exh. @ same lifts
Those #'s look about rite.They also are your best clue as to why they get a bad name as far as performance.The flow hits a wall after .450 lift.Without port work,there is no improvement.What ever gets made,has to be made by 4500 rpm,maybe slightly more with a bigger cam. 330 HP...Maybe...in a perfect world with a perfect setup,but,i doubt it. 414 ft/lb of torque...I don't think so.
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Old 10-09-2015, 03:02 PM
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There's a guy from Tennessee here that does work with these heads.You can get an idea of what it takes by his videos on YouTube.Search for "Headbytes Porting".
BE CAREFUL with this guy. Google "Headbytes Porting"some people have never gotten their heads back for many months!
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