Will it hit 450 whp
#21
TECH Senior Member
iTrader: (4)
OP, on an honest dyno NA, with a TH400 & 9 inch, I think the car will make 365 whp or less with stock 853's heads & LS6 intake. Not being able to lock the TH400 will probably cost 25 hp or more depending on the converter. The TH400 isn't a high dyno number friendly transmission. TH400 do rock at the track and run well. It's possible if you have a tight converter and a,TH400 with light weight internals etc that I'm wrong and the combo will hit ~400 whp or so.
SRT8,
99-00 LS1 853 heads typically flow ~235 cfm on the flow benches I've seen. 265 seems very high for a stock 853 head. Maybe maybe it had a valve job or some basic porting, or someone forgot to put a spark plug in the cylinder being flowed. When a plastic intake is added the 853 will usually lose 25-50 cfm of air flow. It's very possible for the flow to be ~200-210 cfm with the typical intake in place.
Link to AI CNC details for 853/241 heads & flow data
Agreed 100%, my 416 is very responsive and rev happy.
SRT8,
99-00 LS1 853 heads typically flow ~235 cfm on the flow benches I've seen. 265 seems very high for a stock 853 head. Maybe maybe it had a valve job or some basic porting, or someone forgot to put a spark plug in the cylinder being flowed. When a plastic intake is added the 853 will usually lose 25-50 cfm of air flow. It's very possible for the flow to be ~200-210 cfm with the typical intake in place.
Link to AI CNC details for 853/241 heads & flow data
Agreed 100%, my 416 is very responsive and rev happy.
Last edited by 99 Black Bird T/A; 11-08-2018 at 06:03 PM.
#22
What part of ls3 heads will have shrouded valves with a 4.030 do people not understand? The only ls3 head that would work is small bore ls3 heads and those are $$$. A 225cc ported ls6 or trick head is the way to go. Especially with a fast and hyd roller cam when peak rpm will be 6400. Just because it "dynos" higher doesn't mean it will run better or faster.
#23
TECH Junkie
iTrader: (4)
#24
ModSquad
iTrader: (6)
What part of ls3 heads will have shrouded valves with a 4.030 do people not understand? The only ls3 head that would work is small bore ls3 heads and those are $$$. A 225cc ported ls6 or trick head is the way to go. Especially with a fast and hyd roller cam when peak rpm will be 6400. Just because it "dynos" higher doesn't mean it will run better or faster.
#25
TECH Junkie
iTrader: (4)
What part of best bang for you buck don't you understand? Do you really think that he choose the 853 heads over ported ls6 heads or trick heads because he thought the 853's were a better head? My guess he used them because that's what he had to use at that time. The shrouded valve issue is really not an issue in a case where you have shitty heads restricting power versus cheap LS3 heads shrouded valves and all!
#26
TECH Senior Member
I would think shrouded valves in a 4.030 bore is a very minor tradeoff.
#27
It is not the best bang for buck. 600 for heads, 200 for rockers, 800 for intake, rails and injectors. Or you could get 243s for 400 and use stock rockers. Ls7 lifters for 100 and have tsp port them for 750. It would run a whole lot better everywhere. It may not Dyno as high, but if we are going to argue that Dyno numbers means a faster car then we are too far gone to bother continuing.
#28
ModSquad
iTrader: (6)
It is not the best bang for buck. 600 for heads, 200 for rockers, 800 for intake, rails and injectors. Or you could get 243s for 400 and use stock rockers. Ls7 lifters for 100 and have tsp port them for 750. It would run a whole lot better everywhere. It may not Dyno as high, but if we are going to argue that Dyno numbers means a faster car then we are too far gone to bother continuing.
#29
TECH Veteran
It is not the best bang for buck. 600 for heads, 200 for rockers, 800 for intake, rails and injectors. Or you could get 243s for 400 and use stock rockers. Ls7 lifters for 100 and have tsp port them for 750. It would run a whole lot better everywhere. It may not Dyno as high, but if we are going to argue that Dyno numbers means a faster car then we are too far gone to bother continuing.
#30
Well aright then, I have already talked to numerous head pros about this because I wanted to run ls3 heads and they educated me about why I shouldn't. (402 ci) I then did hours of research to try and disprove them but couldn't. You want the smallest port with the highest port velocity needed for your given engine size and the correct port design for your desired rpm range. A small bore cathedral will give us this in this situation. Ported ls6 being great and aftermarket 225 being better. If he had an ls3 than my opinion would change. And yes a .03" difference of bore size is a big difference in the perspective of a cylinder and a valve that opens a hundred times a second. Shrouding is also a big deal.
#31
TECH Junkie
iTrader: (4)
It is not the best bang for buck. 600 for heads, 200 for rockers, 800 for intake, rails and injectors. Or you could get 243s for 400 and use stock rockers. Ls7 lifters for 100 and have tsp port them for 750. It would run a whole lot better everywhere. It may not Dyno as high, but if we are going to argue that Dyno numbers means a faster car then we are too far gone to bother continuing.
I gave $350 for low mileage ls3 heads with upgraded springs with rockers and see them stock at that price regularly. I gave $400 shipped for a new takeoff intake with injectors and throttle body included on e-bay. So $700 total. I have no idea where you're getting your information but considering those heads come on 6.0 trucks and they tow better than previous 6.0 models they certainly don't lack low end torque and if you've driven a Camaro or Vette you'd also know they don't lack top end.
#32
10 Second Club
A Stock ls6 intake will choke the **** out of a 408. Ls3 heads while not ideal for a 4.030 bore, still works good. A Stock ls3 intake kicks the ls6 intake square in the nuts. The 75mm opening of the ls6 sucks.
A stock ls3 top end is THE budget top end to beat, imo. They flow 300-320 out of the box and so does the intake, and has the CSA necessary to support cubic inches.
Are there aftermarket heads that are better well yeah duh get get your wallet ready.
stock ls3 heads are a real hotrodders casting
A stock ls3 top end is THE budget top end to beat, imo. They flow 300-320 out of the box and so does the intake, and has the CSA necessary to support cubic inches.
Are there aftermarket heads that are better well yeah duh get get your wallet ready.
stock ls3 heads are a real hotrodders casting
#33
TECH Senior Member
iTrader: (4)
Aren't the Gen IV L76 & L98 engines 4.0 bores with rectangular heads direct from GM that were installed in cars and trucks?
I think the 4 inch bore with rectangular heads might be a little tricky to cam and tighter on piston to valve clearance with big cams. Even with some shroud they will be better than the sucktacular stock 853's.
I think the 4 inch bore with rectangular heads might be a little tricky to cam and tighter on piston to valve clearance with big cams. Even with some shroud they will be better than the sucktacular stock 853's.
#34
10 Second Club
Aren't the Gen IV L76 & L98 engines 4.0 bores with rectangular heads direct from GM that were installed in cars and trucks?
I think the 4 inch bore with rectangular heads might be a little tricky to cam and tighter on piston to valve clearance with big cams. Even with some shroud they will be better than the sucktacular stock 853's.
I think the 4 inch bore with rectangular heads might be a little tricky to cam and tighter on piston to valve clearance with big cams. Even with some shroud they will be better than the sucktacular stock 853's.
#35
TECH Junkie
iTrader: (4)
Just because someone talked you out of LS3 Heads doesn't mean diddly. I have fully ported AFR cathedral heads and they flow great but at $2300 for the heads and $1300 for the port work and shipping back and forth they are hardly budget friendly. Yes they will make a lot more power than stock LS3 heads across the board but at that price they better. On the other hand I have a two other engines with stock LS3 heads that cost less than those AFR heads alone and at cost per HP the LS3 heads win hands down. If you have the budget there are better heads...that's the reason you got the answer you did...but that does not mean that it's money well spent.
#36
TECH Junkie
iTrader: (4)
A Stock ls6 intake will choke the **** out of a 408. Ls3 heads while not ideal for a 4.030 bore, still works good. A Stock ls3 intake kicks the ls6 intake square in the nuts. The 75mm opening of the ls6 sucks.
A stock ls3 top end is THE budget top end to beat, imo. They flow 300-320 out of the box and so does the intake, and has the CSA necessary to support cubic inches.
Are there aftermarket heads that are better well yeah duh get get your wallet ready.
stock ls3 heads are a real hotrodders casting
A stock ls3 top end is THE budget top end to beat, imo. They flow 300-320 out of the box and so does the intake, and has the CSA necessary to support cubic inches.
Are there aftermarket heads that are better well yeah duh get get your wallet ready.
stock ls3 heads are a real hotrodders casting
#37
TECH Veteran
iTrader: (40)
Someone needs to call GM and tell them what idiots they are, they're putting rectangle heads on 4" bore motors in the 14+ 2500 and 3500 trucks. Man if someone would just tell them the valves are shrouded maybe they could get some low end out of those heavy duty trucks that are built for towing and moving around literal tons of weight.
#38
TECH Senior Member
Someone needs to call GM and tell them what idiots they are, they're putting rectangle heads on 4" bore motors in the 14+ 2500 and 3500 trucks. Man if someone would just tell them the valves are shrouded maybe they could get some low end out of those heavy duty trucks that are built for towing and moving around literal tons of weight.