Comparing Stock LS Heads with Flow Numbers

I flow a stock 706, 862, and 317 LS Head and share the numbers.

[@michaelaxtell7391]

Great job sir. That definitely dispelled some of the myths surrounding stock LS heads. I appreciate your channel and your hard work.

[@jims261]

Show us the flow numbers on them after a mild port job something a home porter could do. Great video thanks

[@psychoholicslag4801]

I know very little about LS chevys but I know a little more now. Thanks for taking time to share.

[@patrickwendling6759]

Always love your videos .. very knowledgeable every time .. Thank you 👍🏼

[@markbuskens6070]

Thanks Eric that was a test I’ve been wanting to see,lot of talk about the 706 right now.Also talk about the 317 because of the 70 cc chamber size.I pretty sure the 317 has the same ports as an Ls6 head but not positive.I’ve seen Richard Holdener make 550 hp on a 6.0 with a 231 241 hydraulic can.He just dumped the 706 and the 862 with same cam and the 706 was 515 and the 862 like 507.this sounds about right after seeing your findings and the flow numbers.glad you test on the 4.030 bore!!!!Thank you so much🙏love your channel

[@PitBullEngines]

Thanks for the info sir. I'm a knowledge sponge. And hope to keep learning until the big nap.

[@drivinwithdrew7676]

I’d love to see how much you can make that 1.89 inch valve flow, I’m also interested in the valve shrouding between the 706s and 862s

[@bigredracer7848]

3👍's up EWR thanks for sharing this video with us all thanks again

[@bryang9158]

Thanks for all the great information 🙂

[@Artoconnell]

So many wives tales went to the bin with this test, the lowly maligned 317 head is for a mild build, a great choice. and seeing as how people all but give them away....Great Video SIr.

[@a807511]

When I built my short block I just went with flat top pistons and kept my 317's. Gives me a 10:1 CR, good flow, and I didnt have to spend any money on heads.

[@motorosso3349]

Thanks for the flow info.

[@peterbermingham1313]

From Australia and we really only see 241 and 243 cathedral ports, but I’d like to see the chambers sizes off small valve heads but stepped up to the same as a 241-243 head inlet to see if the extra comp and time would be worth it

[@mikkokuorttinen3113]

Great results, thank you! Do you happen to know, how do the cast iron 863 heads flow?

[@carlw.pfaender9208]

This is like going to college!! Lol great content.

[@drivinwithdrew7676]

Just about every ls head I’ve used has been cracked between the seats, i think they are usually just surface cracks, I always just go ahead and use them, I’ve never had a problem with it yet

[@angelo_giachetti]

I would like to see your independant flow #s of a hand ported LS 243 vs an as cast PRC 225cc head. The PRC is supposed to mimic a ported 243. Thanks for the posts. It helps when selecting mods and making a purchase.

[@BrandonSolid]

Thanks for the info.

[@b.s.adventures9421]

Interesting stuff

[@jakewade7388]

Looking forward to how you can improve them with flow results. BTW, the 706/862 was used on the 4.8 and the 5.3. The 862 and 706 are basically the same. Flow numbers should be very close to the same.

[@danielsullivan9865]

Like to see the 317 max ported with a 205 intake valve

[@bdugle1]

Just for the record, 4.8 and 5.3 both use a 3.78 or so bore. The 6.0 has a 4.00 bore while the 6.2 has the 4.065 bore. The 706/862 flow numbers were a bit disappointing on the intake. I believe the 317 heads use the 243 ports, which shows up in the flow numbers. It would be interesting to see the 243/799 heads along with these numbers. The 317s generally don’t hold up for power, even with the 706/862 heads, because of the drastically lower compression with the big chambers. LS3 heads flow lots more, may even be too big for a 6.0, even though the factory put them there in the L96 and LY6. Thanks for the test info, Eric!

[@hendo337]

I've looked into all this alot, Richard Holdner has compared all these heads on the dyno and he has always gotten better power from 706 heads than any other stock cathedral port head. I would recommend to anyone running a stock displacement LS with factory style EFI and a cam up to a TSP MS3/TFS/Elgin 238/242 use some 706s, a TBSS/NBS intake manifold and 1.75" primary headers. Especially if you have a heavier street vehicle with all the typical street vehicle luxuries. Even compared to an 0821 or 0823 rec port head a set of 706s are going to allow the use of a larger camshaft with stock pistons and you are going to have upto 20 ft/lbs in the midrange for 1500rpms vs a loss for around 500rpms near the peak of 10hp or less with the same camshaft from the tests I have seen, if you used the larger cam the 706s allow you might gain some of that power back. The only thing that might be a concern is you might need to degree your cam for the higher compression with flat tops to run 91 or 93 octane with the higher compression, if you can get e85 I am guessing you could get very creative with the added compression and really pick up some power. Certainly if you have an LQ4 6L there isn't likely a better factory head than the 706, they are very budget friendly, I have seen fresh remanned heads for $400 a set. If you have a 4.8/5.3/5.7 the 706 is definitely the best choice, with a flat top 6.0 or 6.2 there is debate out there but, I don't think a 853/241/799/243 would get you down the track any quicker and certainly wouldn't feel better on the street. The 317 head is the worst performing head at everything. Once you get into stroker engines like a 402/408/416 LS the rec ports are going to serve you better as long as your piston choice put your compression and P-V clearance where it needs to be so you can make power, the stock rec ports can't be beat in that situation n/a and on a budget. It takes a very expensive aftermarket head to perform better.

[@bobgyetvai9444]

A quick toosie roll with a 60 grit on the 862s which dont have near the cracking issues puts the 706 in the rear view mirror for flow and durability . For the 4.8 or 5.3 the 2" is also a no go . Cut the 2" down to 1.93 " for the small 3.780 bore or leave it at 1.89 is the plan there . For a 4.8 id leave it at 1.89 . Mild porting brings it to 255 to 260 cfm @ 600 lift with a better signal to that port with the shorter stroke and longer rod . Everybody passes on the 4.8 but it is the true badass of the LS family for hp per inch . Just spin it harder . Truthfully im glad thats ignored !!!

[@NightShift1320]

Do you think the 706 and 862 heads would produce more low lift swirl on the factory 3.78 bore size for which they were designed? I guess the real question is, is there a intake valve to bore size ratio that produces optimal swirl? Or maybe none of that matters

[@gregmcnamara2563]

Like anything, there’s always more to the story though. A 706 will always see more vacuum and port velocity on a 4”bore. They may not flow as much CFM, but if you can stabilise flow at higher lift, you’ll out perform a 241/243/317 head on the same bore out on track.

[@darylvoorhees2629]

Thanks for the good information. I have a set of 317 heads that I'm using on a 6.0L. Based on the flow numbers of the 317, looks like the intake flow peaks out in the .500-.550 lift range. Without modifying the heads, it seems to me that a cam with a lift in that .500 to .550 range should perform its best (putting aside the I/O durations). Am I correct in that assumption?

[@craigrowe9713]

Thanks for the data. Any chance you’ve seen the afr enforcer ls1 heads? Any better than stock?

[@timtaylor6147]

Thanks I have 3 sets of 317 LS heads One on an assembled 6 in 0 ready for boost A spare engine and a bare block and 317 heads I'm boosting so the bigger chamber means more volume of fuel to burn

[@braydenmeals9311]

If you milled the 317 down to the same chamber as the 243 would they still flow this good or would the valves shroud?

[@dondorfman3951]

I notice you use Performance Trends Software. How is that integrated with the Saenz bench? I have the Audie software but would like to use the Performance Trends software on my bench.

[@tbl8560]

Eric, 317 intake flow better due to valve size or is there something else going on in the port or chamber, swirl, etc?

[@thaddeusbarnett7707]

What if you put 2" intake valve in 706 or 862 ?

[@nathanhine286]

He Eric I have a set of Stock LS3 heads, what home tips can you give me?

[@tptrsn]

This is a really good video! So the fact that the 317s seem to always make less power than the 706 and 862s must just be down to compression then...

[@rickybellamy8191]

This right here. There's flow bench racing and then there's the real world. Every testing from Richard Holdener shows the 706 / 862 walks the 317. That's with a 5.3 or 6.0. Some testings upwards of 25hp with stronger quicker torque curves.

[@brandenmillisor1472]

Hi Eric. Great videos. Really great info. My question is. When porting stock Ls heads. What’s the purpose of removing the swirl ramp ? Seems like every ported ls head the swirl ramp is removed.

[@dennisrobinson8008]

Does swirl show out in power or torque?

[@TurbineResearch]

Thanks 🙏

[@WeingartnerRacing]

Thanks for watching.

[@johnjordan9538]

I have 706 heads on 5.3 can you use Bars gasket repair to fit the heads

[@jmack7351]

Great video, but I've seen test where 706 actually beats all the other ls heads on dyno thru entire rpm range. Why do you think that is?

[@deankay4434]

On the computer screen, you show a chart (862 heads & the larger one) that is guess is CFM on the vertical, but what are the numbers across the bottom? I can see 01, 02, 03, 04, 05 or something like that. Thanks. (Not a racer / just picking mufflers based on David Vizard testing.) DK, ASE master. Retired. Subscribed...

[@theozman38]

I just decked my 862’s 0.020 for a 6.0. So I’m guessing with a .048 gasket I’m still around 60-ish??

[@tbl8560]

Notice the notch in the 862 deck. Need to make sure to use a head gasket to accommodate for the notch.

[@Between2Turns]

Not all 862 have the notches, but good call out on it.

[@austindoud273]

Cut one of the ports like completely out the top go half way around the spring seat and back to the intake lol

[@timrayburn2461]

thanks

[@richgurley610]

Did you say the 243 is similar to the 317 ?

[@NightWrencher]

Internet ports stock 706 heads? 🤔

[@NightWrencher]

I have one I can send you if you want 👍

[@1clean35th]

Yes 317s flow more but are down on compression from their chamber size. 706s are 61cc vs 317 71cc. Compression>Flow. Atleast when talking NA.

[@garyatsma89]

706 are investment cast, 862 are sand cast, which explains the textural difference. Otherwise, they are identical.

[@michaelerrett1984]

Hi Eric, Richard Holdener raised an interesting question a while ago. When comparing SBCs and LSs with equal displacement and head flow, the LS still tends to make a lot more power. Is that a function of valve angle in a running engine? Thank you

[@WeingartnerRacing]

I haven’t seen that in my testing. When all are equal sbc vs ls they make about the same.

[@HioSSilver1999]

@@WeingartnerRacing odd....I've never seen a bolt on sbc make over 400whp. You would have to build a sbc to get there. But we've made 450+ with bolt on ls6 and ls3s.

[@WeingartnerRacing]

@@HioSSilver1999 Edelbrock sold bolt on kits for sbc for years that made 425 on a crate 5.7l with 8.5 compression motor and their heads sucked and it was a flat tappet cam.

[@HioSSilver1999]

@@WeingartnerRacing i made 451whp/423wtq at the wheels. Not the crank. Using stock heads stock cam. Hence bolt ons.....no sbc is doing that. Sure a built on can

[@WeingartnerRacing]

@@HioSSilver1999 they will if they have standard transmission or lock up converter. I have seen a 350sbc with unported double hump cast iron stock heads make 406hp to the wheels with a standard transmission and slicks. Flat tappet cam to boot.

[@jacksonbermingham2168]

im trying to get a 241 to send over and i wanna port one cylinder myself and see how i go never ported a head before. maybe get you to bench it verse standard port then donate for science of the channel

[@bobgyetvai9444]

I dont understand why junk the 317s when welding fixes that chamber ?? Its got 243 ls6 runners so why not ?? Makes no sense to me . People just dont think . The exhaust is under pressure so it WILL find its way out . Area rule it and look we got compression .

[@dalethomas9307]

706-862 mostly the same different casting process 243-799 mostly same different casting process 317 same as 243 but big chamber 72cc

[@stevenbelue5496]

Why does a 5.3 with a cam and intake make nearly 500hp with 706 heads, while a 350 with vortec heads, cam and intake can barely break 400?

[@WeingartnerRacing]

Because it doesn’t or at least any I have seen. Several claim 706 do but dyno says 400s. Not 500s. With 243 yes though.

[@stevenbelue5496]

@@WeingartnerRacing I said nearly, I guess I should've said 450+ or about 50+ hp over a vortec headed 350 with similar cam specs. And the 5.7 has more cubes. I'm relating to Holdener's videos which has no parasitic loses, open throttle and headers basically open. But from what I've seen the LS makes more power, and it doesn't look like it's just the heads, is the new design worth noticable power gains alone.

[@WeingartnerRacing]

@@stevenbelue5496 the real difference is in compression and cam timing. Usually sbc have less compression and more quench. The cam is also more tame. There are many vortec headed motors that make 450 plus in circle track.

[@markbuskens6070]

To you that comment that a 317 is the worst head I think you need to do more research.on a 6.0 they make about 30 more hp then the 706.on a 5.3 the 706 is the best

[@funfun8095]

Should have done the square port heads and you never answered which square port budget LS head is.

[@bobganshaw364]

Hes already done that. Watch the old videos.

[@unclegeorgesspeedandfeed]

This is painful to watch

[@WeingartnerRacing]

How so? I’m always up for things to help the channel.