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and yet dyno tests readily available comparing back-to-back head testing on the exact same engine with no other changes show the 706's make MORE HP and MORE TORQUE in the average daily driver RPM ranges than both the 799 and 243 heads. Even though flow benches show that the 799/243's outflow the 706's number wise, the dyno shows that the 706's (below 6000 RPM I think??) make more HP and more torque..
I've sold off the 243's I have and am about to remove the 799's I have on my 6.2 in favor of a set of ported and polished 706's.
The ports in the 243/799 castings are much better than the other cathedral port castings. Most of the difference is in the short turn, where the floor is taller and the radius is more ideal for high airspeeds.[/QUOTE]
and yet dyno tests readily available comparing back-to-back head testing on the exact same engine with no other changes show the 706's make MORE HP and MORE TORQUE in the average daily driver RPM ranges than both the 799 and 243 heads. Even though flow benches show that the 799/243's outflow the 706's number wise, the dyno shows that the 706's (below 6000 RPM I think??) make more HP and more torque..
I've sold off the 243's I have and am about to remove the 799's I have on my 6.2 in favor of a set of ported and polished 706's.
[/QUOTE]
True for stock application the 706 have the lowest cc so highest compression even tho they don't flow as much. Flow doesn't always mean power but for my 806 I wanna make the most power I can with the best flow possible to get as close to 100% volumetric efficiency as I can (I know not possible without boost). 706 heads always scare me tho because I'd say about 7/10 times we get a set of them at least one is cracked. 862s don't crack as much (not never) but freeze plugs have become a problem.
Too much flow? Not enough compression or vice versa?
So for stage 2 of my top end build what do you guys think about this. Bronze guides, Ls3 seats, ls3 stainless valves, lt1 springs with stainless retainers, low lift cam (about 550) with longer duration (235ish?), send them out to get a really good port polish job (maybe frankenstein), and unshroud around intake valves. but the problem is I can't unshroud too much because of the material for the spark plugs threads and and ls3 seat and valve would be really close to the fire ring or heck I just thought would hit the cylinder right like any ls3 head or would it? IF it clears the cylinder what would you say to welding up the spark plugs hole and redrilling and tapping it so it comes in from the exhaust side (if you're looking at it from the combustion chamber) and if I do unshroud a lot then my compression drops so then can I weld extra aluminum in the chamber where it won't disturb flow but help compression? Sorry if this is too much for efficiency I just get curious and excited then ideas start growing wether good or bad haha😅
So for stage 2 of my top end build what do you guys think about this. Bronze guides, Ls3 seats, ls3 stainless valves, lt1 springs with stainless retainers, low lift cam (about 550) with longer duration (235ish?), send them out to get a really good port polish job (maybe frankenstein), and unshroud around intake valves.
I think the 2.165” intake valve is a little too big for a 3.898” LS1 bore, but it fits. Since you’re doing all that work already, you may want to consider turning the intake valves down a little but, maybe like 2.100”?
Originally Posted by 5point_rx7
the problem is I can't unshroud too much because of the material for the spark plugs threads and and ls3 seat and valve would be really close to the fire ring or heck I just thought would hit the cylinder right like any ls3 head or would it? IF it clears the cylinder what would you say to welding up the spark plugs hole and redrilling and tapping it so it comes in from the exhaust side (if you're looking at it from the combustion chamber) and if I do unshroud a lot then my compression drops so then can I weld extra aluminum in the chamber where it won't disturb flow but help compression? Sorry if this is too much for efficiency I just get curious and excited then ideas start growing wether good or bad haha😅
You won’t need to do all that. I put full size LS3 intake valves in a 5.3l heads years ago and it was pretty straightforward. I have a set of 799’s with new seats installed without the valvejob too. I’ll try to find some pics this evening.
So I just cc the heads and stock they cc at 68 so my plan is to add material and make the chamber ls3 style and unshroud it a lot like how performance heads are done
So I just cc the heads and stock they cc at 68 so my plan is to add material and make the chamber ls3 style and unshroud it a lot like how performance heads are done
Sadly no I'm gonna attempt it myself by hand and just cc the chambers afterwards. I'm pretty much just going to copy and paste what brodix did on a set of lsx heads we have at my shop. Left is my 806, middle is an ls3 head, and right is a cnc ported brodix lsx head. So I plan to add material behind the spark plug hole and if needed by the intake seat to the left on the picture. Then cc hopefully around 63 and finally unshroud like the brodix heads and hopefully hit 64 cc.
The LS-3 Combustion Chamber shape was made for a NASCAR race engine by Hendrick Motorsports.
I too have welded/"filled in" combustion chambers on earlier LS heads adding Squish Pads on the sparkplug side.
This squish pad will "center" the pressure direction of the gases to the center of the chamber.
The intake valve side "welding" will help pressure recovery after the fuel/air enters the cylinder AND help keep fuel off the cylinder walls.
and yet dyno tests readily available comparing back-to-back head testing on the exact same engine with no other changes show the 706's make MORE HP and MORE TORQUE in the average daily driver RPM ranges than both the 799 and 243 heads. Even though flow benches show that the 799/243's outflow the 706's number wise, the dyno shows that the 706's (below 6000 RPM I think??) make more HP and more torque..
I've sold off the 243's I have and am about to remove the 799's I have on my 6.2 in favor of a set of ported and polished 706's.
More compression is gonna make more down low, that's not shocking.
Mill the 243's and they will hang with the 706's down low, or out perform them, and then run away from them as air flow demands increase. LIKE PUTTING THEM ON A 6.2 FOR EXAMPLE.
Putting 706's on a 6.2 versus 243's would be a poor choice IMO. I would mill the 243's and run a .040-.045 headgasket and kill the 706's in every single way.
Couple the above with a really nice valve job on the 243's and they'll make the 706's look like trash.
I Have a set but I am curious how much maybe I can make a second set or a few if possible.
make me a fair offer I'll bag all of it independently and mark bags with valve train specific locations so it can be reassembled as removed. From a90 k car driven and maintained by a retired guy.
I know shipping for heads is like 125 alone. I'm sure I could bundle if interested all came off my 98 camaro z28
But you could have all of it rockers lifters trays rods cam covers bolts I also have
8 ngk tr55 3186 plugs with 3k miles
2 rear oxy sensors 3k miles a
slp lid
brand new set of TSP head bolts
Brand new 100mm specter maf housing with a new ls3 style maf
Pcm 98 camaro
Stock maf with elbow
4 corner Steam vent line and bolts
stock Power steering pulley
Steering wheel with airbag
Stock air box
Graphite dash pad
2.73 gear and pinion
probably going to put it all up on market place eventually you can text if you want specific picture ect it's all pretty great condition.
I'm just building the car so just took it all off in last 2 weeks. My number 3203343113
08-24-2021, 05:35 PM
