My old man is a master machinist and mechanic and has been building sbc race engines along time my first memories are handing him wrenches and helping while he was building race engines for late model dirt cars. In late 80s early 90s he was making 700hp sbc engines. So I’m lucky to have someone a lot like yourself who’s forgot more then it seems I can consume😂

My skilled friend always asked if we had tried to port a "Trapezoidal" type intake port. I was embarrassed to ask him what he was talking about. Looking at your intake profile I now know what he was alluding to....Stupid idiot I was. He is a guy who is well know by some people for making high HP...ported the cylinder heads for the Factory Yamaha MotoX team for several years. Thanks for sharing your knowledge. I own most of your books.😃

Clicked on this this video and I said to myself "Oh, an hour long power tech 10 (10 means 10 minutes long) video. I'll probably take a brake half way through and do something else." DV then proceeds to keep me riveted through the hole video and I'm not even a Chevy guy! Can't wait for DV to do a seminar! Sign me up!

That you give THIS amount of expertise, for free… Is astounding.. Thanks David-

I love seeing factory heads do work.

Love your last name! You must get this all the time, but I’ll say it here again, it sounds like a wizard. Mr. Vizard, you are definitely a physics application wizard! ❤

Rock and roll : Mick Jagger Basketball: Michael Jordan Internal combustion engine: David Vizard Thank DV ! Long may you rein sir !!

Thanks for the content David l'm looking forward to see what you do with the 318 Mopar. 🇺🇸

Very cool - cause it’s factory heads:) Thank you Sir David Vizard…

David this video reminded me of the articles you wrote in Popular Hot Rodding in the early to mid ‘80s on porting these head castings (and prepping the block) for a budget bracket racing engine. I used this article for a friends 355 with the 291 head castings back then. I see that as expected over the last 30+ years you have made new refinements to get the most from these heads but the main modifications are still very similar

Have you ever given thought to partnering with a foundry to make a David Vizard designed cylinder head?

Thank you for the teaching Mr vizard you are the best

This is a master class in head technology.

I LIKE YOUR VIDEOS BECAUSE I'M OLD SCHOOL. THANK YOU VERY MUCH.

Another GREAT example of what hundreds of hour's learning on the flow bench & dyno will teach ya. It's funny how many are still tunnel visioned on BIGGER is Better. You have Majority in disbelief just due to the 1.94 valve. Port volecity too many never take into effect... Thanks for sharing as always my friend!

I had a set of those 186 heads on my 350 cu. in. Chevy in the 70's ported by Kay Sissel with 194 intakes , that engine was a power house, thank you David enjoyed the schooling.

im so glad i saw this video i have a set of 186 ,maybe time for porting school😃

550 hp on a 302 is impressive. Surprising potential in those old castings, definitely improved upon with years of R&D.

I can’t wait to see what you do to the 318 heads. I keep trying to see if you post anything yet. I think it will be big with a pro like you chopping at the heads getting the big numbers out of the motor. Thank you D V .

It is amazing the amount of time you have put in grinding iron heads. It is really cool that you are old school enough you had to port iron. I have done some sets myself and stopped years ago due to the amount of time it takes versus doing an aluminum set.

So 2.02-1.6 valves in a set of double hump heads actually hurts flow, yet every machinist out there says to put them in. What David shown us here makes sense. I've also done every mistake he said not to do. Lol live an learn.

This video is awesome. David is definitely a master at his craft. Amazing how he made a 50 year old casting relevant!

David, there was a lot of work and time in what you have accomplished, thank you...

Excellent video Mr Vizard! Everything in this video pertains to every SBC I own😉

Best video I've ever seen on porting and flow. 👍👍

I'm happy that you made the Chevy 302 the subject around those 186 casting numbers those engines came with those castings anyway I'm a big fan of the 302 Chevy and many think that it's a waist of time building them but in reality they can run circles around a lot of engines in the quarter mile drag strip if properly built and in a good chassis car. Those engines were quite common in modified production and in the alphabetical lower classes which had even smaller engines, generally they all were capable of turning 9,000 to 11,000 rpms . If you could find some of those 90s videos from Rockingham with Brett Kepner the tower announcer at one of those super rod events, super rod is IHRAs modified production like NHRAs modified production you will see the times those cars ran some had to carry weight depending on the cubic inches and many were running high 9s to low 10s and I'm very familiar with those Lola T-70s and they came equipped with the 302 engine for the five litre class and that's pretty Ironic, because they couldn't sell a lot of those 302s in the Camaro in 69, 70, 71 and so on so those engines had to go somewhere and many ended up in the Lola's and in the South African CanAm muscle cars so they are still out there just somewhere else, I'd like to see you do more work with a 302 engine we all know that the 383 is trending today and anyone can build one even GM markets a crate engine, Jegs, Summit, Competition products and everyone else let's see you build a small cube Chevy or even a Clever or Windsor 289, or 302 and twist them on the Dyno and let's see what they can put out in today's era in performance parts

Awesome video. Thanks for sharing your knowledge. I've got a set of these 3927186 . I'll be 70 in couple months I'm having as much fun with these heads now as I did 50 years ago. Back then most people didn't have a clue when I'd talk about porting.. Anyway keep bringing it David 👍 gotta love old iron. Keep em on the road.

There is so much that I can apply to my 50yo cast iron 4-banger with known exhaust port problems, similar to the old Pontiac and Chev 6-pot port issues. Time to get a practice head, some flow balls and start from there. Thanks David.

Straightforward explanation of complex subject material. 👍Thanks DV

Excellent content, looking forward to Richard Holdeners Omni 4 banger and UTG’s / Unity Motorsports Garage 318 build as well . Keep up the good work.

Those were the heads to have back in the 70s but my first real set of good performance heads was a cast iron set of Lee Shepard 202 angel plug heads I had a solid lift high winding small block in a 67 camaro that picked up 4 tenths in the quarter mile in 1977 I payed $500 for them from a guy I knew who had a pair on his dragster. That was the most expensive part on my car and I pulled the heads off when I sold the car and put them on my 331 I had in my nova. I love street racing back then.... your friend from Louisiana Rick 427

Love the content. Will admitted I just getting up to speed. I'm building a mopar 5.9 for a 98 Zj limited. Want to keep it iron and get all I can out of it. Lots to learn from your shows

You know what no channel talks about heat

Wow, I can now improve my porting technique. Thanks for sharing.

Great content David, very helpful stuff

thanks dave another great porting show

Spectacular demonstration and explanation.

You are the man David, thanks for sharing your knowledge 💯👍

Wow, I have heard the name Vizard but now I know why! Such a clear and concise explanation and really made me feel confident about some of my guesswork which has been somewhat clued in by the late David Ijams in regards to port velocity and shrouding. I’m only building mild street truck engines and I have questioned running a smaller intake valve on a 1093 open chamber head and this is just enlightening to say the least. I’m probably not going to do that $$ but where I thought I was only going to focus on exhaust ports and valve face may be revised. Total noob machinist here 🥳🤣

I love these videos, makes me want to scrounge up some old heads and get the die grinder out.

I'd like to see the comparison of the factory port vs the one you ported . Thanks for all the knowledge of porting .

Great content I have a set of those heads did something like what you just showed on porting and had them on a sbc 383 with a 1107 summit cam pickup half a second on the quarter mile. Was very pleased with the results.

I'm blown away that you achieved those results! Fantastic job!!

thank you sir. you are a master of your skills and have blown my mind with info... I'll be processing this for a while... Thanks again...

I have everyone of your books Dave, Great work is never done, Thanks a MILLION>

Great job very good information.keep up the good work. Thank you 😊

...still learning.... Thank you very much 👍🏻👍🏻

This was an excellent session ,thank you David from all us poor boy hotrodders,,,!!!

Great information. Wish I had time for porting

I'm surprised there is no mention of the 462 heads. they have a similar chamber to the 186.

Thanks once again David!!

Awesome content

I truly appreciate this video. I’m building a 55 Chevy 2 dr post. I have been thinking about which of my blocks and heads I want to run. I have a 350/010 block with TRW .30 over. I have a 327 large journal in an 010 block I was thinking about building a 331 from. I also have a 283 setting under a shelf I’ve been waiting to build. I have a slew of heads including a couple sets of power pack heads (896s). I have several other sbc heads I am going to go through tomorrow and see what’s in there. Now your video really has me rethinking things. I’m disassembling the 327 right now and inspecting it. The heads that are on it are 032s. I’m not going to the drag strip in the 55 but I want it to haul tail if I can say it that way. Thank you sir for the great information!

Thank you for sharing your knowledge!

Hey DV, so good to see another video! One thing I didn't see you mention however, I thought I'd bring up... ...whenever I am going to work on any old engine part, I am a firm believer in chasing EVERY threaded hole before any other machine work is done, and before cleaning. Learned behavior... I found that if I didn't do it first, it got left until the very last. After everything was done, and I was going to assemble it. Which means, I had to take a lot of care to not get any chips in anything (and not infrequently had to take things back apart for cleaning afterwards) You probably already know this (and probably do it and just didn't document it on video), since you've been doing this stuff since before I was born - but mention it in hopes it will save somebody else a little bit of hair pulling on some project...

David Hobbs the bad ass road racing master!

The charts are pretty, question is, what cam specs are needed to take advantage of them.

Thank you Mr. Vizard!

Thank you for this.

great video thank you david

Huge Hobbs fan!!! F1 isn't the same without him.

I mean if the old casting has the ability to match the new geometry there is no reason it can't make the same power. the engine doesn't care when it was made.

Enjoy your content so very much. Would love to know what you'd do to a Alloy LS1 5.7L head

David is the man

Professor David 'the humiliator' Vizard. Specialty; machining stock production passenger car cylinder heads & using them to outperform the best cylinder heads the aftermarket high performance boys can design & build. The David Vizard motto; "If you can design & build it I can better it!"

First time subscriber I think this is a wonderful learning channel appreciate your advice and insight on cylinder heads that I am very interested in do you have anything on LS heads that I can learn

With all the chamber cutting, how much has the volume increased, hence the compression ratio dropped?

What product do you use for the port molding?

Got it 👍thanks again

I loved your video and your explanations. I'm from Quebec and I want to modify a 283 SB CHEVY with a crank of 350, 6.125 rods and original heads # 520 of 283. Make a video on these heads and their possibility of modification would be very appreciated. I want to keep the look of the 283 even if I'm going to have 340 cubic inches.

If I had the cash and the time I'd like to drop a 4 inch crank in a 318 and build a long runner crossram intake to see how much low rpm torque I could get.

Great Informationen next time i will work for better radius on fast flow side to the Chamber

also, one of my late friends had an "open wheeled" "winged modified dirt track car and with a destroked 302, he won the feature and you could hear his motor on the track no matter where it was, over the others.... his tattle tail tachometer read 9,200 rpms!!!

Thank You .

WOW! That's a lot to think on. Nicely done. Any quick thoughts on roots blown head work? These would be 2V 351C heads we're working with. Where do you spend time and money? Thank you David. All the best!

Very informative and interesting when porting cylinder heads do you ever change the way you port a head, for instance, Cam Duration lift lobe separation RPMs what you're using it for etc... Just Curious about that GODSPEED and Thank You for your wisdom

Love this kind of content! I would like to know how my IOP program can tell me if an exhaust port needs more bias as in the case shown here? Thanks for another great job!

Hi David ive got a set of BBC 702 castings. these are closed chamber bathtub style chambers (96cc ) If i do the same mods to the exh side quench area, blend and clean up the bowls , do a 3 angle valve job and some port work on the roof side, i should see atleast a 30-50 ft lb of improvement in the low end?

Hi David,I appreciate the hands on knowledge you share with us on KZfaq, I am grateful.One question for you:Would exhaust flow better if the valve face had a convex shape to assist in directing the exhaust flow directly to the circumference of the valve?Just thinking.Thx David and looking forward to your reply

David, if you were to put that head on an empty, upside down block, and look down the cylinder, would it be advantageous to have absolutely no overhang of the chamber over the cylinder edge adjacent to the exhaust valve?

Was glued to the tv watching this one! Thank you again David for such a brilliant comprehensive review

I learned from this

Did you polish the water jacket side of the crack-prone area to stress relieve it?

Just imagine if Mr. David Vizard forged/casted his own line of cylinder heads and intake manifolds? The performance/racing world would be a better place.

One thing I noticed is that a lot of the older sbc heads have alot more meat in them to hog out , like vortec heads flow better than double hump heads out of the box but when ported you get better flow out of double humps I believe when I weighed them the vortecs were 10 pounds lighter .

Thank you for. your great videos. But something goes not my brain, why do you leave the dog leg in. the exhaust port? Doesnt it hurt the flow? Marco

So if the plan is a racing engine that will be pushed hard, would it be worth it to get a set of 186 castings? Or would it be more economical to clean up an aftermarket set?

Would love to see the results with the same head treatment on a 400 cubic in Chevy.060 over 10:1 compression with 770 cfm holley on Performer intake. Hydraulic flat tappet limit approx 6000 rpm.

I am goone port like you Show hear Tanks four yor tricks hear👍👏⛄️🎄👍

David vizard ive watched this video serveral times very imformative but i have to ask. What is the benefit of lets say a 416 casting small chamber for compression with a 1.72/1.50 valves. Using your techniques and using the stock valves would port velocity play a roll in power production without chamber modification except maybe on the exhaust side to benefit flow at the .250 lift mark so the flow goes in the port instead of over the valve.

How much chamber Cc will you lose when unshording the valves?

I have a set of 1965 FE heads . I have 2.04 intake and 1.6exhaust that flow 278cfm at .500 and 205 at .500 and they never backed up leveled off just from using your books. How does the abeviated intake port of the FE. 394 ci 503 hp 496 ft lbs. effect the flow. To me no more than I did I am happy, but I wish I knew how much more it really flows with the equal amount of port length that is on the intake manifold under the valve cover. I have done the same heads with 2.09/1.65 valves on a 426 ci FE and it did 596 hp at 7100,538 ft lbs at 4800. Can you postulate the rough difference. Those had radically different cams. But it did surprise me.

May i ask if these same pricipals apply to big block chrysler 915 closed chamber heads since they are very simular ?

With low comp and .475" lift rule we made 580ish hp in ihra class 360 Mopar in the late 90's. Gezz with all this info we would have made 1000hp. 😆

will these 186 castings work on a 2 bbl class motor 355 cuin 10 to 1 cr

What do you use to mold a port ??

The 426 ci engine flowed 302@ .600 with the iron 65 heads and 224@.600 The cam was .600 with the 1.76 rockers

I have a set of 040 head are they similar to 186 heads they have no accessory holes

have you done any thing with sbc 461x heads

do you have the air flow number for those heads