I read a few places online that the summit vortecs aren't considered a performance head but a stock replacement. All stock vortec heads are setup for a roller cam, correct? And the tech at summit told me the summit heads are springed for a flat tappet? How are they a stock replacement head then?

 

As far as flow numbers go each head would be a little different, the only way to get the same flow from each head would be if they were CNC heads. Far as I know all Vortec heads are stock replacement, they just flow better than most ome heads. They could be used for roller or flat tappet, but that depends on how much lift each cam has. Most people use different springs cause their using a more aggressive cam. A few years ago I ordered new GM Vortec heads from Summit. I pulled all the springs off, pulled all the studs out, did a pocket port job an cleaned up the ports of casting flash, install screw in studs an replaced the springs with Crane spring & retainer kit p/n 10309-1. Reused all the valves, keepers, seals. One thing to know is the heads is where HP is made. If it wasn't for the fact that just the head gaskets cost me 100.00, I would of taken them off an ported them more.

 

contact Scoggin Dickey
ask same questions.
SS,racers shop castings as castings are not consistant.

 

so if a cylinder head flow numbers vary from head to head due to castings how much could they differ?

 

That I don't know, maybe theirs someone who's spend a lot of time flowing heads on here.

 

From what I've heard the Summit Vortecs are a replacement head for a Vortec engine.Bolt patterns,ports,etc,but the chambers are not as efficient in design as the GM Vortecs.

 

The vortecs were a great oem head 20 years ago. You can get a much better head now. If you get them for free or dirt cheap then they do well, not worth putting any money into though. Btw they'll all need springs to match your cam and oem ones will need guide work. They may also need a valve job.

 

I'll bite, so what's better for the money now? Or heck, better for close to the money (honestly, I'm not sure that I think that vortecs are better for the money than a lot of other things, the different intake pattern makes them $$$ unless you just want to run a carb intake on them... FI, the cost difference starts climbing, fast).

 

At first I thought vortecs haven't been around 20 years.

Then I frowned.

Damn , time keeps going.

 

Well, it's a little less than 20 years, but close enough to show how dated they are.

 

yes they are just a few years from being twenty years old but the gm vortecs still fall into the best bang for the buck category. I don't think anyone has ever said money aside they would still run a set of factory gm vortecs but when it comes to budget builds they are still a well sought after head

 

As long as you're buying matching rockers, intake, have money for machine work, and don't mind them cracking... Yea they're a real bargain.

I did a few sets of them and they were good back in the day. They're not worth the cost now. They've gone the way of camel humps.

 

Its been 14 years since Vortecs were used in a 1/2 ton SUV/truck, 11 years since 1/2 ton vans usage. Marine usage not sure if they are still used by GM, still available on the Ramjet 350 and HT383 engines.

What heads are currently as good as an OEM Vortec that you can currently buy? Their low lift numbers were killer.

The new for 2014 Fastburn heads at 210cc and teh small and large port Vortec Bowties are good as well. Costs do add up when you factor in, a full rebuild, retainers, springs, screw in studs, drilling for 1.6:1 rockers etc etc etc.

peace
Hog

 

it's been eighteen years since 96 when gm put the vortec head into production.

 

What's missing in this is the combustion effeciency of the Vortec combustion chamber. Everybody is caught up in flow numbers but that's half or less of the problem of getting power out of the cylinder.

The visual differences between a highy efficient chamber and an almost efficient chamber are very subtle but the power resulting from doing the chamber right and doing it almost right is very significant. The Vortec chamber and it's even better relatives to be found in the aluminum LT1 and LT4, and Fast Burn heads are very correct; you see this again in the SB2 head combustion chamber layout. This layout is classic Ricardo and has been understood since the 1930's, just seldom used because it was patented and Sir Harry demanded a royality to use it, Ford did on the original Y blocks but discontinued it after the 1954 model year, then brought it back on the 1960 high performance 352 FE block for a year than dropped it again. Now it's in vouge and everybody is makeing a version that fits their basic original design and tooling. The people who get the closest is GM, SBC-Gen I and II, and the Ford Windsor; all of these started with a chamber that very similar but not so similar to the Ricardo that they violated his patents and evoked royality payments. The small block Chrysler like so many used a very open chamber a configuration dictated by spark plug location which make it difficult to incorportate all of the Ricardo chamber features but the modern Magnum head comes very close and is very potent.

Key elements you're looking for in a chamber is pushing the spark plug as close to the bore center as the valves will permit with a wedge chamber, a bit of favoring the exhaust valve side does help with detonation/preignition control as well as keeping the plug from becoming fuel soaked by the intake blast and unmixed fuel streams that could flow over the tip. This location also allows the plug to locate a little deeper toward the bore center. A tight valve pocket, flying in the face of those who open the chamber up on the bore side is the SB2 and SB2.2 chamber which is extremely tight but also shallow and the engine uses extreme lift at the valve to overcome bore side flow issues which is something you can't easily overcome with a 23 degree head.

The basic Vortec chamber provides a relief between the valve and the spark plug to guide the mixture into the chamber and start the remix of fuel to air process while engaging the beginning of the swirl action. This chamber also furnishes the dual quench pattern of the older performance heads which is ued to concentrate the mixture into the valve pocket and in front of the spark plug which improves the initiation of the ignition event and speeds the burn which reduces the need for excessive spark advance and reduces the exposure to detonation causing events.

There is a beak that extends between the exhaust and intake valves which is used to provide mixture guidance during overlap which reduces the loss of fresh mixture out the exhaust during this period resulting in more of what you pay for doing work through the crankshaft rather than going out the exhaust unused.

So these features are things you want to see in the combustion chamber of any head you buy:

- Double quench

- Spark plug to the bore center as much as possible as allowed by the valve's location.

- A beak extending from the far side squish/quench step between the valves.

I've included a file with a picture of a Fast Burn in aluminum I stole from somewhere and a comparison picture of a cast iron Vortec to an older Dual Quench that Cobalt included in a blog he did a long time ago to give you an idea of the differences that are often easy to overlook but provide substantial power differences. So when someone says they're selling a Vortec style head, have them show you the chamber. There are many older designs on the market that proport to be Vortec chambered that are not quite complete design wise.

Bogie

 

Its stupid question day for me........on the summit vortecs the combustion chamber is in the picture below. There are no provisions to move the spark plug as close as possible to the center of the bore but could a longer reach spark plug be used to get closer to the center of the bore? Or would the spark plug just not survive? Laugh......I am. I am just unsure of the outcome of this and would like to know.

 

This is one of those chambers that show most of the characteristics, a little different but mostly there. you'll see how the plug is inside or at least adjacent to a line drawn from the tangents of the intake and exhaust valves, this is pretty close to as good as it gets with this type head I haven't pulled numbers on this head but have on the 190 cc port aluminum ProComp which has a very similar chamber. On the dyno with the ProComps track power to the L31 Vortec very well with a common bottom end. Being aluminum they could use more compresson and maybe 15-20 degrees hotter coolant as this would probably show even better power.

My tested flow for the 190 cc port head:

.1 68/55
.2 127/99
.3 177/135
.4 222/159
.5 250/170
.6 263/176

You will note compared to the Summit or L31 Vortec there's a hole at .3 inch lift on the intake but at .5 lift it really comes on and continues the gain into .6 inch lift. This is be a good head with a fast and high cam or with 1.6 to even 1.7 rockers on an SBC. The exhaust is rather weak at low lifts, has a very good mid to half inch lift flow then curves over for less of a gain by .6 inch.

So though I don't have any hands-on test data with the Summit; looking at an extrapolation from the Pro-Comp suggests that the Summit will be close to the Pro Comp thus close to the L31 Vortec as well. The L31 does take a bit of crutching to get into the 400 horse category, it does take port clean up and 1.6 rockers in and ex with a flat top piston and .040 squish/quench clearance to get them to hit 400 plus a few horses test after test after test. The Pro-Comp will do it without port clean up but only requires a 1.6 rocker on the intake this is with the well documented by the hot rod press Comp XE268H cam. Compare the Comp Cams web site test with SR heads which are chambered and ported as the earlier Chevy small chamber head, where this head is done around 350 horses.

Bogie

 

and what are your thoughts on the combustion chamber itself? I understand what Bogie is saying about the spark plug location and have never heard this until now but after looking at combustion chambers of various cylinder heads i definitely see what he is talking about......thanks Bogie.

 

looking at the spark plug location on the summit vortec it would be further away from the center of the bore than the gm vortec, correct? And it would create lesser of a better burn like you had stated earlier when you posted the pic of the older gm head vs the vortec head.

the pictures are in order: GM Small Port Bowtie Vortec, ProMaxx Performance Vortec, GM Vortec, Summit Vortec

I imagine the promaxx vortecs were designed to copy the Small Port Bowtie Vortecs

Bowtie http://www.summitracing.com/parts/nal-25534421/overview/
ProMaxx http://www.summitracing.com/parts/pmx-2151/overview/
GM http://www.summitracing.com/parts/nal-12558060/overview/
Summit http://www.summitracing.com/parts/sum-151124/overview/

 

Here's a ProComp NKB-200 chamber which is pretty close to the earlier 190 head I've tested. You'll see this is quite similar to the Promaxx chamber. Keep in mind that pictures can be a bit deceiving because of how camera angle kind of parallaxes the view.

Bogie

 

Great info. bogie. I always learn something from your post.

 

So I happened to be coming by one of the Summit Racing stores. I decided to stop in and check out their cast iron "Vortec" replacement head. They happened to have one on display. They are definitely nice clean castings but..............i was rather dissapointed in them. I'm not saying they are a bad cylinder head but they are not a "Vortec" head in my book. They are just a replacement head for the vortec engine. They are EXACTLY the same casting as their double hump replicas except they will bolt to a vortec manifold. Looks like they ran an endmill into the intake runners to raise them to match the vortec manifold closer but they are not a raised intake runner, they are just raised at the entrance.

These two cylinder heads are exactly the same castings http://www.summitracing.com/search/...50/cylinder-head-material/cast-iron?SortBy=BestKeywordMatch&SortOrder=Ascending

Looking both cylinder heads over though they are nice clean castings.



On the AFR cylinder heads I noticed that the intake and exhaust runners had what I would say are ribs through the entire runner. Are these heads finished like this? Or did summit just buy them un cnc'd for their display models?

 

I just talked to the customer service at summit. He says they are not the same castings but besides the entrance of the intake runner and the bolt pattern for the intake manifold they look pretty dang close

I could be wrong on this but I don't think I am.

Carson: Hi, my name is Carson. How may I help you?
Craig: hi, i have been looking at you two cast iron summit brand chevrolet 5.7 cylinder heads
Carson: HI Craig. What are the part numbers and what is your question on them?
Craig: I have been looking around online and have read that the castings are the same just the bolt pattern is different
Craig: SUM-152123
Craig: SUM-151124
Carson: No, Those are two different heads and they are not cast the same or anything.
Craig: looking at the pictures of the vortecs it looks like they just ran an endmill or something into the intake runners to raise them to match up to the raised runners of the vortec intake manifold. It just doesn't look like they were casted with a raised runner i guess?
Carson: I show they are not the same casting as I have mentioned.
Craig: would you happen to have flow numbers for each cylinder head. I'm interested in the vortecs but if the double humps flow better i might go that route>
Carson: SUM-152123 (double humps)
Intake 210 cfm @ .500" lift w 28 in. water
Exhaust 138 cfm @ .500" lift w 28 in. water

SUM-151124 (vortecs)
Intake flow: 232 cfm @ .500 in. lift / 28 in. H2O
Exhaust flow: 138 cfm @ .500 in. lift / 28 in. H2O
Carson: Is there anything else I can help you with today?
Craig: okay, i don't mean to be a pita but do you have the .400 lift numbers?
Carson: Those are the only flow numbers I have on those heads unfortunately.
Craig: okay, i guess that will be all then. Thank you for your time
Carson: No problem, have a great day.
Carson: We appreciate your business.
Thank you,
Summit Racing Equipment
Carson has disconnected.

I guess looking at the specs on summits webpage they are different size runners and combustion chambers. The combustion chambers on both heads are identical in shape and design, this I am sure of.