Bowtie Vortecs (merged threads)

Looks like we'll be seeing the new Bowtie Vortecs arriving at the end of the month for a future article in Chevy High Performance Magazine. One of the issues I brought up was that these new heads feature a raised runner design that may pose a problem mating up to my existing Vortec manifold. GMPP says they'll send the proper manifold, gaskets, hardware, and everything else. And I thought just getting the heads would be cool! At least you won't have to wait until the story comes out to find out what the outcome was. I'll just post here as things progress. I'm still curious about the d-port exhaust runners and how they'll mate to the hedmans that alot of us run for headers.Stay tuned- Dale

Well- these new Bow-Tie Vortecs are beginning to show their evil side. I guess that's why this is all one big test or experiment. After the head bolt issue, I thought we were home free, but alas, problems arise again. And with first generation Nova's, this may be a big one. I've stopped dead in my tracks. It seems that the machined exhaust head surface is milled at a slightly different angle then standard, as it has "flared out" my hedman hedders (mind you they're only 1 1/2" primaries) to a point where they come into major contact with things that had 1/8th to 1/4 inch before. I've some ideas to remedy this, but I don't care for any of them. It just should not have to be this way! Frustration is starting, and we all know that's the time to walk away from it for awhile. :confused: Dale

Awe man! What a PITA!!! If I dont have to work Saturday Im gonna head up your way and help you out. Ill even bring my BFH just in case! ;)

Makes me wonder what's going on with this whole thing. I'm wondering if these were some initial pre-production pieces. First, chamber volume was not as specified, second, intake and exhaust port runner volumes were not as specified in catalogs, third, head bolt alignment problems with a couple, and now, exhaust side machined surfaces not matching up to production tolerances. Leaves me with a head being scratched. :confused:

That sucks. Its really odd that the castings or milling of the surfaces would be any different than any of the standard SBC pieces. I would definately be on the phone with your supplier trying to figure out what the problem is. These heads should be little more than just a bolt on affair and not much of an "experement" really. Heres hopin you figure it out. Let us know how it goes. Good luck.

Kasey

I wonder if the angle the exhaust surface is off is the same as the angle the headbolt holes were off.

Before you spend time getting the headers to fit, verify the intake surfaces are not off as well. It would be a crying shame to have to angle mill the intake and run really thick gaskets.

I've come this far, so for now there won't be any turning back. All this that's been going on will make for some good reading in CHP when it hits the stands.The heads came directly from GM Racing Division, so I'm trying to get some answers in the next few days. Only two bolt holes were slightly out of whack, but this "off angle" exhaust machine surface is inherent to both heads.Intakes all line up perfect,so angle milling will just create more problems I'm thinking.But in the mean time, until we get some more information through GM, We are going to try to get hedman hedders to send out an identical set to what's on the car now, only not ceramic coated. My theory is to make "pie cuts" of only a degree or so out of the bottoms of each primary tube, then squeeze it back together and weld up. That way, I'll butch these up and get the car back running to make the next set of dyno runs to show if all this was worth it or not. My gut tells me that I'm only having this problem due to the fact that we drive early Nova's,which have very small confined spaces to run headers to begin with. Camaro's, Chevelle's and other cars have bigger engine compartments and would hopefully not have an issue with this problem. BUT, we are. What I'm also trying to do is respectfully inform GM that what they have now is not what it's supposed to be. It may be a small amount, but it's enough to throw a big wrench in the gears. Boy, I'd love to have a detailed set of drawings on these heads?

It's very possible that the first batch of heads were incorrectly machined. I would contact GM racing and tell them the problem. They may want them back to check.

Hey Dale, I have my old set of Hedman's Ill donate to you if you want. Let me know...

I read that these heads are good for vortec or standard intake manifolds - would that universal fit have any thing to do with changing the exhaust side?

Chuck- it should not have anything to do with it. Paul- you are correct.I'm curently awaiting a call from one of the GM Racing's project managers. I sent an e-mail through Scoggin-Dickey (whom orchestrated most of this with GM) and got an immediate response. Seems they may have grabbed a set not destined for use. Hmmn? We'll know more as the day unfolds.

You will hit the giant brick wall with GMPP, their "leader" is so self-protective that no info will get past him to R&D or the production staff unless it is complementary to him, and the products he states have no problems at all.

He posts on chevytalk.org, and getting any useable info from him is just plain next to impossible, but, he emphatically states that their products are dead on correct and it has to be some other aftermarket parts being the cause of any and all issues.

I don't remember his name or username on CT, but he shouldn't be hard to find there. He is the head protector of all things GMPP mis-machined.

Well, I did receive call backs from one of their senior engineers,and they are interested in whats been happening. The guy I talked with was familiar with what I've been doing with these heads. He informed me that they were indeed pulled straight from production inventory, and was most concerned about the head bolt hole alignment issues. Asked alot about what we did to remedy it. Then he dropped the bomb. This new head is actually a "marriage" of the best parts from two different heads, the Vortec truck head and the aluminum fast burn head. They designed this head three years ago, so they were going to pull up drawings or diagrams to see the difference's.So there are two different design elements involved. I missed his second call back in the afternoon with some numbers, but will most likely hook up on Monday morning. Still trying to keep the faith, but this is not a true bolt on after all?

"Gary" was the guy's name, never a problem with GMPP products always the aftermarket stuff that didn't fit. Real defensive on the GMPP stuff, even when proven he was covering something up.

It takes a bunch of lack of engineering to get a small block head NOT to fit, they've only been around for what....50 YEARS, now.

AFR, Brodix, other heads are available.

Input is always appreciated! ;)

And the plot thickens!
Mike

I put the word out I'm gonna cut into some headers, and a few people have come through. NOGO has stepped up with a donor set and another good friend has given me a beautiful new set of three quarter length Hookers from a Chevelle part number to try and squeeze around. Maybe we'll stumble on a good alternative that'll cross over with small modifications??? Thanks, guys for stepping up. Looking for an old set of Hooker headers in a Nova part number if anyone would maybe want to get rid of for a good price? (62-67)

Is the problem the angle of the exhaust face of the head? Can you measure the angle with an angle finder? I wouldn't cut up headers if the problem is mis machining issue or a design issue.

Paul- I just spent some time with their engineers and the answers I've been given are very disappointing- they've failed to let people know (this through the catalog and various suppliers including GM dealerships) that they have relocated the exhaust surface .250". Thats ALOT to move something and not let anyone know. I felt (and I told them) that this will have a huge impact on the consumer that will put forth the funds for a set of "bolt on" heads only to find out that the exhaust system will not even come close to being able to be installed. This is such a big design change that other GM model cars will experience clearance issues as well. I won't bore anyone with the specific's of why the changes were made, but nevertheless, they are what they are. I'm waiting on a call back from a header manufacture that tells us they do have a part number that will fit, but I'm skeptical. They still are very upset about the head bolt alignment issues, and wanted production numbers off the heads. Gee- I'm wondering how many people have already purchased these heads through suppliers like Jegs and others only to find out that Pandora's box has been opened? :(

Actually you wouldn't bore me with those details AND you'd be doing a great service to others considering these heads. So the ports are raised 1/4" and that's why the bolt holes don't line up? Does this mean the collectors are closer to the floor pan by an equal amount or am I missing something?

From what I can remember of our conversations, the changes were made to incorporate the d-port design of the GM Fastburn aluminum head, and also to facilitate better coolant flow around the exhaust ports.When we had the new heads on the bench next to the old one's for photo purposes, I only measured from the top of the valve cover gasket machined surface down to the exhaust bolt hole, when I should have been measuring from the deck up to the holes.I think if this would have happened, we would have seen the problem sooner. I put a protractor (manual, not digital) on the head sufaces after the new heads were in, and compared them to the old head which I had mocked up on the bench, and while these measurements came out close, I could not validate them as being accurate, there were just too many variables.The raising .250" still cannot explain this "flaring out" as I call it of the headers.Theoretically, the raising of the ports should only correspond to raising the header closer to the floorboard of the car, but this does not hold true, so I'm assuming when he told me they moved the face .250" he was referring to top to bottom exhaust side of the head as a whole (?). I was assured that we would be sent more technical data (I'm hoping for a good diagram?) that would help in explaining things for the article. But at this point, GM's position is its a header fitment issue. :( Some background on the heads: They're concept for these heads was to replace the Bowtie 492 castings that are still being produced, although the tooling for these heads is flat worn out. They have a very high scrappage rate currently. So this new design will carry on into the future for santioning bodies of racing to use these in their "spec" classes. In flow testing, these babies outflow everything else GM has to offer out of the box.What we are trying to show is that these heads can and (hopefully when this is all said and done)will prove to be a great street/strip performance head. On a set of headers that reportedly will fit our early Novas: Hedman makes a d-port configured header for them, but they do not sell them under the Hedman name.Apparently somebody else, whether it be one of the big name mail orders or whomever, let me know if there is someone out there who has a header that looks awfully close to hedman, and should have a 1 5/8th's inch primary but still be able to cover the d-port. Hedmans stance is that they are trying to figure a way to market this header and still not step on their clients toes whom they supply this header to. Does this make any sense? In a way I see it, but their logic seems slightly flawed to me, as if supply is needed Hedman gets to make more of these headers anyways, so all win. We get a header that fits, Client sells more headers, Hedman gets to make more headers! So for now, I need to come up with an alternative plan to make a header fit with these new heads. Guess I can always throw the stock manifolds back on, but that just defeats the whole pupose. It's also way to easy- us grease monkey's always gotta do things the hard way!

Hmm, very interesting. I think Pace Chevrolet has the exclusive on D-port Hedman headers.

Btw, I would have put the heads on a surface plate or any flat surface and measured the angle of the exhaust face and campared to regular heads.

My guess is GMPP is intending these heads for racing not street/strip and assuming the racers will build custom headers or the aftermarket will eventually step up to the plate.

Hi,

This is very interesting stuff.


I have milled the exhaust side of sbc heads to correct the angle, on angle milled heads, and I have also milled (this also requires ex bolt hole modifications) the ex side to improve flow on some heads.

I know this isn't the issue here, and I would not want to change the ex angle on the head because it may help flow, but if you you have room could you add an a angled spacer to bring the header back to the proper angle?


If the header flange is thick enough could it be milled to correct the angle?


I agree that this a bear for a" bolt on "application.

Good Luck.

Jeff

I just the copy of this month's write- up on the heads in Super Chevy Magazine.Since all testing was done on a engine dyno- they've yet to encounter our problems.Still, even with a 350 they flowed well. Tomorrow I'm going to try my luck at relieving the headers of their alignment stress. I found a guy local who gently abraded away the ceramic coating around the header ports. I'll try and document this so in the future if anyone tries to tackle it, they'll have some useful info. Dale

Well- looks like the driver side is done. It really does not look too bad for a slice and dice. What I'm trying to do with it now that I know it'll work is to try and open up the header port as much as I can to better fit to the contours of the d-port. I cannot get an exact match, but I can get within a 1/16th inch all the way around. Good enough? How important is it to port match on the exhaust side. I recall somewhere reading that the gains are not all that significant?

Im not sure about the port matching question, but i have to say your definately takin one for the nova team by stickin with this project and seein it through. This is a lot of hassle for a "bolt on" project. I hope it all works out. IM anxiously awaiting the results. Good luck.

Kasey

Im not sure about the port matching question, but i have to say your definately takin one for the nova team by stickin with this project and seein it through. This is a lot of hassle for a "bolt on" project. I hope it all works out. IM anxiously awaiting the results. Good luck.

Kasey

Ill second that! If you want me to come over and help you out Saturday let me know...

Teddisnoke:
Can you post pictures of the mismatch and the mods? It will be helpful if we can see what your are describing.

I took pictures today, but not until after I had already welded up the primaries. But with them, I'm sure you'll get the idea of what had to be done. I STILL FEEL that GM does not understand what had to be done to get it to work. It is such a subtle, minute change.After I made the cuts along the tops of each header tube almost all the way through to the bottom, after installing them in the engine bay tightening all header bolts down, it only amounted to about two more sawblade thickness's 1/16th inch (?), then I just filled in the gap with a mig welder and ground down anything that came into the inside during the welding. It is so small an amount at the flange, but way down at the other end at the collector, it amounted to about 3/8th's inch. So- it looks like at this point, that hurdle is done. Tomorrow, things get buttoned up and fingers will be crossed. I would be able to send these photo's to someone if they wanted to see, or maybe someone might host them? Ironically- on a side note, the collectors came no further up against the bottom of the car, as GM said would most likely happen due to the raised port design. Go figure!

Send me the pixs, as moderator I can post them

Speaking strictly as a machinist here...the exhaust flange face angle would be the least critical of the numerous machining parameters of this new head. Having said that, the exhaust face machining TOLERANCES (i.e. the + or - machining angle specs) are probably rather liberal. IF, for instance, the new heads were machined toward one end of the tolerance spec (thus angling the headers ends OUT at the bottom) and your old head machined to the other extreme (but still with-in tolerance) that in it's self would lead to your dilemma as far as two separate assemblies not locating them selves at the EXACT same location. Who knows! Maybe the new heads are fine, and your OLD heads (from which you based your clearance from) are the real culprit. ;)

In a lesser probability...the manifold GASKETS that you used COULD be manufactured at a slight angle or compressed unevenly for that matter.

Even the smallest amount of improper angle at the head "bolt up" location will significantly effect the header outlet position due to the relative distance involved and multiplied error.

Well- I never thought I'd be able say this, but close the door on the Old Vortec Saga! We just got back awhile ago from some extensive "seat of the pants" testing with the new Bowtie Vortec big port heads and its gonna be hard to wipe the ear to ear grin from off my face!!!!!!! :D :D :D :D :D I know that this type of testing is not very accurate, or maybe its due to the fact that it all is working after what we had to do, but regardless, it feels very good. Biggest thing I notice is the heads ability to make the 406 want to rev quicker. Could it be the lighter valvetrain components? Hollow intakes along with sodium exhaust valves and lightweight retainers may help. I also went from 64 cc Vortecs to a "as measured" 62 cc. Slightly more "pop" there.We never had to touch the idle circuit screws, and set timing pretty much where we've always had it at 11-12 initial with 33-34 total all in by 2,600 rpm. In timing, we did notice some erratic jumps in the increase in rpm's possibly due to the distributor needing a dab of grease around the springs. But all in all, so far so good. I'll try and have some eighth mile passes in next Thurs. night before we pack up and head to SEMA. :) Dale

OK Guys... here's Dales shots of the two heads... first one is Vortec... second is of Bowtie... 1/4 difference...

Thanks Dale :)

http://i7.photobucket.com/albums/y258/64Flyer/DSC01222.jpg

http://i7.photobucket.com/albums/y258/64Flyer/DSC01223.jpg

Thanks, John. Crude measurement, but you will get the idea about where the change lies in the difference between these two heads. Its a small amount at the top where the header attaches to the head, but down by the collector, its swings like a pendulum.

no biggie Dale, always glad ta help :)

nothing like some instant payback on all that work. :D
sounds like you had some well deserved fun.

The new 206CC runner Vortec is just an awesome head for the 406. The older Vortec @ 170CC does make it a 406 a TQ monster, but the difference between the old Vortec's 239CFM, and new Vortec's 263CFM turns a 406 into a TQ and HP monster.

You found that the 406 wanted to rev a lot more?

Well, its not that (it) wanted to rev more, its because you were making more HP at a higher RPM due to uncorking the restrictive runner/head, and YOU just didn't want to lift because it was still makin HP at a higher RPM. hehehehhe

You woke up the beast by letting in air :D :D

You got that right.Actually, the runners now measure out at 215 cc on the intake port and 84 cc's on the exhaust.GM had to revise the numbers,as when the catalog was released, the heads were not in production yet, so there are a few changes made .

Good job!! :) It's nice to have those positive results after all that hard work and it sounded like hard work. Sounded like this experiment was maybe for one of the mags? Are we gonna see a write up on this in something soon?

Will be very interested in the 1/8 and dyno results. Good luck. :)

After chassis dyno and dragstrip testing with these new GM big port heads, we gained an average of 11hp and 17 lbs ft. throughout the entire range on the Dyno jet . And this is with (up until last night at the dragstrip) no jetting or timing changes. Strictly a head swap. We saw a high point of 20 hp in 4,000-4,500 rpm range. Last nights runs at the track were met with a new e.t. and mph (7.628 at 92 mph)with all belts and fans running.The flow numbers from the old Vortecs were higher than bone stockers on the flowbench due to a mild chamber cleanup and some light porting on the short side radius exhaust, so jumping from bone stock to these new heads will see even better numbers. So far, with the exception of the exhaust side fitment issue, I'm very happy with them, and look forward to the next series of dyno pulls and strip time with the new single plane manifold. We'll keep posting results, as Nova People "need to know" these things!!!!!! :) Dale

How much did those heads cost you? according to my new Super Chevy GM designed these to be a cheap alternative to all the current al aftermarket heads, and they are $700 assembled, but they seem to be $1000 everywhere I look.

He didn't pay for them. He works for a magazine and this is a test. I'm not sure but it may be the mag you mentioned.

How much did those heads cost you? according to my new Super Chevy GM designed these to be a cheap alternative to all the current al aftermarket heads, and they are $700 assembled, but they seem to be $1000 everywhere I look.


Heck if thats the case then I would just go with a set of AFR ot TFS heads for the same price if not a couple hundred more. The whole point behind the vortec's was they were cheap, plentifull, and made killer power for stock castings. In the end they still weigh a ton compared to aluminum heads and have all the other drawbacks of iron heads.

That being said if these were selling for say $500 a set complete then I might consider them an alternative to aluminum castings for budget racers.

First, let me say I do not work for any magazine's. I'm just a regular guy with a Nova that got his pic of his car in CHP and happened to be in the right place at the right time to hear a conversation, and I took the liberty to chime in. I met some of the editors and photographers through a welding job I did on an altered wheelbase Nova, and thay found out I was a Nova-haulic as well. Soon thereafter, opportunities came my way, some of which I turned down,and some I'm still scratching my head on (as in the Fairmont Funny).I turned down the testing of the Performance Online suspension parts for an article, because I could not stomach someone else driving my beloved car through a slalom course beating the tar outta it. But when this GM deal came my way, as I had a set of Vortec's already, I jumped on it. I've tried to keep my car as pure GM as possible, this is just the next step. Its alot of work, swapping parts around, I ain't gettin paid a dime and I think I'm doing a service of sorts to the street machine and 'strip community to show how these heads will do. I think what is cool is we have so much out there to choose from, there's something right for everyone. On pricing, there are two versions out now, I don't know if there is a price difference between the two. Dale

First, let me say I do not work for any magazine's. I'm just a regular guy with a Nova that got his pic of his car in CHP and happened to be in the right place at the right time to hear a conversation, and I took the liberty to chime in. Thanks for clarifyong that. I apologize...I misunderstood.

Still cool stuff though! :D

LOL. Mario- I think its best we leave our stock suspensions be, after you and your spindle woes and me with, well, lets say stock is cool. Those heads were good today for a 12.12 @114 mph compared to a best 1/4 mile of 12.39 @112 mph. Todays pass was at 2000 ft. on a hot day, and the other was at Carlsbad (near sea level) A good day at a track with cooler conditions and no wind would hopefully produce an 11 second run.

Anyone running GM Vortec Bowtie small port heads part#25534421? Im building a 383 and its time to choose what heads to use.
They seem to flow pretty well, and accept up to .530 lift
Around $490 each complete.
Please look at the numbers and tell me what you think.

Flow Numbers intake:
SMALL-PORT HEAD
Lift CFM
0.100 67
0.200 136
0.300 182
0.400 223
0.500 251
0.600 240
0.700 240

Any info would be appreciated!

A-M
__________________

I did a set of these for a customer in September and the flow numbers out of the box were:

Intake
.200 123.3
.300 181
.400 222
.500 241.5
.600 241.5
Since the port stalled at .500 lift I didnt go to .700
Flow @ 28" 4.00 Bore and Radiused Inlet Guide

Exhaust
.200 121
.300 148.8
.400 155.6
.500 156.5
.600 157.8
Flow @ 28" No Exhaust tube


http://i4.photobucket.com/albums/y108/Alloy-UFS-/Bowtie-VortecChamber9-15-052.jpg

Flow after. I had to rape the chamber around the spark plug to clear the piston. Short block was assembled.

Intake
.200 145.5
.300 206.7
.400 246.6
.500 262.3
.600 273
.700 276
Flow @ 28" 4.00 Bore. Radiused inlet guide

Exhaust
.200 128
.300 176
.400 203
.500 216
.600 221
.700 224.6
Flow @ 28" w/o Tube
http://i4.photobucket.com/albums/y108/Alloy-UFS-/Bowtie-Vortec9-15-053.jpg
One issue with the exhaust is the center line of the port is not the center line of the bolt pattern. I think an 1.625" header will leave the top of the port uncovered.

Thanks alot for your help guys!
The thing is that Ive sold my Vortec L31s and looking for new heads. Ive found out that its better to do some research BEFORE the purchase... Ive been looking at both AFR 180-195 and Brodix Race Rites 180, then I stumbled on these Bowtie Vortecs from GM.

I dont mind buying alu heads, not at all! Im looking for a 23 deg bolt on alternative that makes good torque for the street but also some brutal power on higher end. I thought the Bowties were a sweet deal, but after reading posts about holes that dont line up, headders that wont fit etc etc I guess there are better options out there!

Please let me know what heads you think would be the best bang for the buck?

Chevy 383
SRP -16 dish that would give app. 9.7-9.8CR with 64cc chambers
Isky Mega Hyd 274 flat tappet camshaft/lifters

Matt

I'd try the AFR CNC series heads. Article in latest Chevy High Performance (http://chevyhiperformance.com/tech/engines_drivetrain/cams_heads_valvetrain/0601ch_head/)had me impressed with quality and flow. 260 cfm on the 180 but a whopping 240 cfm at only .400 lift. Cost is a reasonable $700-1000 each.
Hand porting any head to that level would be much more expensive and not as good.
Lot's of options available so they can build them custom to your application. Call AFR for specific recommendations.

looks like im late to the converstion, but is it even worth getting the bowtie to put on a: 350, Crane duration 284/292 lift .509/.528, at 10:1 compression

Assembled small-port PN# 25534421 and
Assembled large-port PN# 25534431.
Bare heads are also available.
The GM PN for the bare 185cc Bowtie Vortec is: 25534371
PN for the bare 175cc port Bowtie is 25534351

Scoggin-Dickey performance heads page (http://www.sdpc2000.com/catalog/3129/GM-Performance-Parts-Cylinder-Heads.htm)

Super Chevy Article on Bowtie Vortec's (http://www.superchevy.com/technical/engines_drivetrain/cams_heads_valvetrain/0511sc_vortec/)