Opinion on dyno results
07-30-2019, 03:24 AM
#11
Numbers look about right though. Typical is 330 or so but a lot of variables here.
Next step is cutting the heads to bump compression. 1cc for every .006" cut.
07-30-2019, 04:58 AM
#12
Not sure I nor any published dyno agree with this statement unless you just meant 853? The 706/862 heads have been proven to show highest peak numbers in stock form from any factory head, no? I digress....
Numbers look about right though. Typical is 330 or so but a lot of variables here.
Next step is cutting the heads to bump compression. 1cc for every .006" cut.
Numbers look about right though. Typical is 330 or so but a lot of variables here.
Next step is cutting the heads to bump compression. 1cc for every .006" cut.
the 706/862 and the 243/799 heads are close in terms of performance but above .500 lift is where the 243s start to pull away, both being stock the 243/799 are the best flowing heads for sub 4.00" Bores, also the 706 heads are prone to crack so I wouldnt spend any money on them....if OP is deadset on staying N/A I would change the heads and upgrade to TBSS intake...used 243s are cheap these days, they already have the bigger valves, flow better, just get them milled to maintain or bump compression...would prob come out cheaper than having the 706s ported and the bigger valves installed
07-30-2019, 06:30 AM
#13
More flow doesn't equal more power. If there is too much flow, port velocity slows down and it starts hurting performance.
I pulled my CNC 317s off in lieu of 706 heads cleaned up. Off idle performance is better, mid-range is better and top end feels better.
Whatever possible flow I hurt with putting the 706s on, I gained that and then some with the added compression on my 370.
This is what @Drspencer is talking about: http://www.superchevy.com/how-to/eng...nder-head-test .
If you're boosted, the ball game changes.
I pulled my CNC 317s off in lieu of 706 heads cleaned up. Off idle performance is better, mid-range is better and top end feels better.
Whatever possible flow I hurt with putting the 706s on, I gained that and then some with the added compression on my 370.
This is what @Drspencer is talking about: http://www.superchevy.com/how-to/eng...nder-head-test .
If you're boosted, the ball game changes.
07-30-2019, 12:15 PM
#14
706 casting has proven to make the best midrange and usable power in these 4.8/5.3's even vs the 243/799 with the BTR or truck cam's. Have a set of 862's cleaned up with a valve job and you'll make some good power. throw some 4.10's in it. Cam is small in general, but nice for a daily truck.
07-30-2019, 04:08 PM
#15
More flow doesn't equal more power. If there is too much flow, port velocity slows down and it starts hurting performance.
I pulled my CNC 317s off in lieu of 706 heads cleaned up. Off idle performance is better, mid-range is better and top end feels better.
Whatever possible flow I hurt with putting the 706s on, I gained that and then some with the added compression on my 370.
This is what @Drspencer is talking about: http://www.superchevy.com/how-to/eng...nder-head-test .
If you're boosted, the ball game changes.
I pulled my CNC 317s off in lieu of 706 heads cleaned up. Off idle performance is better, mid-range is better and top end feels better.
Whatever possible flow I hurt with putting the 706s on, I gained that and then some with the added compression on my 370.
This is what @Drspencer is talking about: http://www.superchevy.com/how-to/eng...nder-head-test .
If you're boosted, the ball game changes.
Interesting Article...but I still think some 243s milled to 60CC chambers would make a little more power. Like you mention the reason you gained power from switching over to the 706s is the compression bump not becasue they are better heads. If the 706s were GMs best Cathedral heads why didnt they use them on the 5.3 HO (L33) or LS6 and LS2 or the Gen IV 4.8/5.3s?
Last edited by 01FormulaTA; 07-30-2019 at 04:13 PM.
07-30-2019, 05:17 PM
#17
TECH Junkie
My question is for a larger engine such as a 6.0 or larger could the small intake keep up. I forget what cu in yours is Jessie? Either way it looks like the ticket for a bone stock head for a 5.3 or smaller at least not boosted. When I bought a forged 6.0 for turbo from HKE in Houston, Erik spec'd CNC ported 317's 72cc for a low cost head. Patriot stg. 2's with 2.055, 1.57 as I recall. I was going for 6's but a jackass tuner effed it up. Miss typed 26 deg. timing instead of 16 deg. Tmi again Jessie 
07-30-2019, 08:15 PM
#18
My question is for a larger engine such as a 6.0 or larger could the small intake keep up. I forget what cu in yours is Jessie? Either way it looks like the ticket for a bone stock head for a 5.3 or smaller at least not boosted. When I bought a forged 6.0 for turbo from HKE in Houston, Erik spec'd CNC ported 317's 72cc for a low cost head. Patriot stg. 2's with 2.055, 1.57 as I recall. I was going for 6's but a jackass tuner effed it up. Miss typed 26 deg. timing instead of 16 deg. Tmi again Jessie
My engine started out as a TMS 370 longblock.
I opted for the CNC 317 heads which was a $750 up charge.
About a year later, after reading until I was blue in the face, I picked up some clean 706s and swapped them with ls3 headgaskets.
Best move I ever made.
07-31-2019, 06:02 AM
#19
Couple more. Really waiting on Super Chevy or Richard Holdener to do a back to back, no speculation on same combustion chamber size 243 vs 862.. I'll keep saving $300 on cores by using 862 heads...lol
Let's Talk Torque: LS Truck Upgrades - CPG Nation
http://www.superchevy.com/how-to/eng...t-under-boost/
Let's Talk Torque: LS Truck Upgrades - CPG Nation
http://www.superchevy.com/how-to/eng...t-under-boost/
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