Q&A

Ask Away! with Jeff Smith: How Much Power Can I Make By Adding Ported Vortec Heads to My SBC Engine?

proper spark plug reach

Make sure the spark plug is not too short. This photo shows what happens when a too-short 0.460-inch reach spark plug is used in a Vortec head. Note how the electrode is absolutely buried inside the spark plug mounting threads. You can barely see the ground electrode. This absolutely kills combustion efficiency. (Image/Jeff Smithi)

You did a tech answer around two years ago which was about adding a set of Vortec heads to a small-block Chevy. How much of a horsepower gain could you expect from porting these heads using the cam and everything? — R.B.

Jeff Smith: We wrote about Vortec heads in 2016, and that article spawned this question.

The original answer was related to modifying the heads to accept more valve lift.

Stock Vortec heads are limited to 0.425- to maybe 0.450-inch lift. The details on how to increase the retainer-to-seal clearance can be found in the article and comments here:

[READ: Ask Away! with Jeff Smith: Blueprint for a Budget Small Block Chevy Build]

Our original answer combined the Chevrolet Hot cam with a set of these Vortec heads. Our estimate then and now is around 350-375 horsepower.

Your question relates to porting the Vortec heads to improve the flow, which is a great idea. The Vortec heads offer great intake port flow despite the rather small 1.94-inch valves.

Where you can gain substantially more power is by concentrating on the exhaust side of the head.

The Vortec heads are much like other stock small-block heads in that the intake port flows fairly well, but higher rpm power is limited by a weak exhaust port. Based on information from different cylinder head porters, they feel that you could pick up an easy 20-25 hp by modifying the exhaust side just in the area directly under the exhaust valve seat.

This is often called pocket porting and the area just below the 45-degree valve seat is where you can gain the greatest airflow improvement for the least amount of effort.

We pocket-ported a set of stock iron small-block Chevy heads a long time ago with direction from a good friend – Rod Sokoloski – who passed away in 2013. Rod worked for Edelbrock for a long time and was the company’s resident cylinder head guru. He showed me how to perform a simple pocket-porting effort on both the intake and exhaust side.

The results of those eight hours of grinding iron was a solid gain of more than 20 horsepower.

We flowed the heads before and after, and the improvements were mostly on the exhaust side.

Rod attributed the jump in horsepower to the flow increases we generated on the exhaust side. He said if the engine had gained more torque, that would have revealed an improvement on the intake side but since we saw only minimal gains in torque, he said the exhaust side improvements were mainly responsible for the horsepower increase.

So while we’re running your engine on our theoretical dyno, if you could find a cylinder head porter who is still willing to grind on cast iron (it’s nasty work and takes much longer than working on aluminum), we will venture a guesstimate that with a mildly pocket-ported set of Vortec heads and that GM Hot cam on a 355 cubic-inch small-block Chevy with 9:1 compression, an Edelbrock Performer RPM intake manifold, and a set of long-tube headers that combination could make 400 hp and maybe a touch more.

That may not sound like much compared to today’s big-power LS and Chrysler Hemi engines, but it’s pretty good power for a somewhat dated small-block Chevy with production iron heads!

One additional point with Vortec heads is they take a special-length reach spark plug.

The reach is defined as the length of the threaded portion of the spark plug. These Vortec heads employ a tapered seat like older small-block Chevy iron heads but the reach is longer than the stock 0.460-inch iron small-block. The Vortecs use a mid-length 0.708-inch reach with a tapered seat versus the more typical 0.750-inch gasketed plugs used in performance cylinder heads.

If you mistakenly use the typical 0.460-inch reach plugs that are commonly used in small-block Chevys, this buries the active end of the plug inside the threaded portion of the head. The engine will run poorly and not respond to tuning. So be sure to use the proper spark plug application. A stock heat range plug would be a set of Autolite 605 plugs or an ACDelco R44LTS6.

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14 Comments

  1. So how would I go about learning to pocket port my heads? I’m going to be running almost the exact same set up. I’m doing as much of the work myself as is realistic. And what kind of tools will I need to do this properly?

    • Daniel Ring says:

      David Vizard has excellent information on all aspects of doing your own porting in his books on building and modifying small block chevys.

  2. Jeff Smith says:

    Jim, I’ll try to make this brief. The best thing would be to look up pocket porting on the internet to see some examples. Keeping this really simple, what you are trying to do is to carefully blend the short turn side of the port where it transitions into the valve seat. In production heads there is generally a really bad bump or sharp edge that disrupts flow. This sounds really easy but it’s really hard to not go overboard. Removing too much material can actually hurt flow. The best tool is an actual porting electric motor and a couple of porting cutters. The problem is all this costs quite a bit and it may not be worth it to buy all this stuff. You might be able to find a friend with some of these tools who is willing to let you borrow them. I did a story for Hot Rod back in the 1980’s that might be online (not sure) that goes through the procedure. Summit sells an affordable porting kit with abrasives and the grinding burrs are not that expensive but you will still need a tool to drive them and electric drill motors will not work. The key is to work slowly and not hog out the port but work very carefully. In my first attempt, I spent 8 hours on two small-block Chevy heads but the gain in power was worth it- we made another 25 hp with just that change – but I had access to professional tools. I might be a good idea to practice first on a dead cylinder head to get the feel for it. One key is to avoid hitting the valve seats with the grinder – if you do, then that port will require a kiss with a valve seat grinder/cutter. You can do it if you are willing to put in the time. Just remember – less is more!

  3. carl v weaver says:

    So with stock vortec head’s and 450 lift cam my baseline would be roughly?

  4. Larry Simmons says:

    I have a 97 Chevrolet pickup truck with a 5. 7 L Vortec with 255 horsepower what can I do to get more horsepower on a budget

  5. mike Dilligaf says:

    i am modifying my intake to add a M-90 Eaton super charger i am attempting to lenghten the lines on the spyder. inj i believe a ecm can make a blower operate flawless Any input is very appreciated i need my yukon to pull like a clydsdale weighing in at 11k with a load of gold ore your insight to pocket porting is bitchen

  6. Mike sorenson says:

    Jeff I have a Yukon 1998 I mine for gold average weight 11.000 lb my vortec can’t get out of it’s way it spun a rod bearing what is your opinion on a ls4-v conversion I value your opinion thank you

  7. Roy Fauquher says:

    Anyone looking for some performance aftermarket aluminum heads small block 350 s big block small block Ford feel free to contact me

  8. I’ve made 460 hp and 480 torque on a 9.5 383 with porTed 062’s and 503 and 450 on a 355,good heads but for my customers it’s cheaperto buy aluminum,the 383 ran 11.35 @3200lbs

  9. 1993 5.7 vortec with port and polished heads especially the exhaust side. .513 comp cams thumpr cam air gap intake edlebrock 650 carb shorty headers. Any idea what my horsepower will be at? Id like to get 400 out of it. Switched to hydraulic roller instead of flat tappet, new springs pushrods everything is new down to main bearings.

  10. ron hamilton says:

    i am going to put built vortex heads on my 1977 sbc 350ci engine and the vortex heads have had the guilds turned down and have had the stock springs put back on then i am not sure of how big of and camshaft as far as lift i can go so i am also putting on a new timing chain and self aligning roller valve guilds edelbrock airgap performance intake manifold and headers not to sure of the tipe of headers i will be using at this point i would like to go with a camshaft with around a 0.489 max lift and a duration of 226/236 give or take and have a 2200 to 2400 custom built stall also for it and have 373 posi 10 bolt 8.5 rear end and 215 15inch on the back and 205 15inch on the front and my 1950 gmc truck has been lowered 2 inchs in the front and 1.5 in the rear and is about 3700lbs please help me out with this i need to no what camshaft i should be using and what intake and headers i shouls be using and what kind of compression will i be at and hp and tork thanks for any help Ron

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