power difference between 402ci & 427ci w/same heads and cam?
08-24-2006, 03:16 PM
#41
I just did a graph overlay of the ET 265's, ET LS7's and Greg Fell's ported Gm LS7's and the factory castings kicked ***. Better mid lift and top end also. I guess the best arguement for the ET's is the ability to adjust the combustion chamber size over a very, very wide range.
08-24-2006, 03:19 PM
#42
Originally Posted by mike c.
i've been talking w/sponcers about a 427ci. LME-has a nice 427ci longblock w/gm ls7 heads reworked(ported)and a ls7 ported intake. it comes w/every thing needed to put it in a f-body. do you guys think the ET head is better then a gm ported ls7 head??? what do you guys think of the quality at LME??
08-24-2006, 08:10 PM
#43
LS1 Tech Veteran
iTrader: (1)
Join Date: Oct 2003
Location: Wichita, Ks
Posts: 1,170
Likes: 0
Received 0 Likes
on
0 Posts
In answer to the original question . . . if you use the same cam and heads on a 427 rather than a 402, you will get more low end torque, a flatter torque curve and less HP. Also, HP and torque peaks will be at a lower RPM.
Steve
Steve
08-24-2006, 08:14 PM
#44
Originally Posted by Steve Bryant
In answer to the original question . . . if you use the same cam and heads on a 427 rather than a 402, you will get more low end torque, a flatter torque curve and less HP.
08-24-2006, 08:43 PM
#45
10 Second Club
I was talking to a guy that had a dry sleeve 422 which had to be replaced (leaking sleeves) He went with a 402 figuring that it was close enough to not be much of a difference. Well he was disappointed and said the overall power curve was noticably less than the 422. He guessed 40 or so hp/tq. I am a big displacement lover and am in the midst of replacing a dry sleeve 418, I decided to go with a 427 instead of a 402.
08-25-2006, 06:21 PM
#47
Teching In
Join Date: Aug 2006
Location: Carlsbad,Ca.
Posts: 35
Likes: 0
Received 0 Likes
on
0 Posts
[QUOTE=Blue Hawk]
Simply put, you're heads will max out sooner because with a 427, you have bigger cylinders to fill in the same amount of time than a 402, but the resulting higher gas velocity will help you having a higher/flatter torque curve in the lower rpms. However, that torque curve will drop rapidly after the peak because your intake, heads, headers and exhaust (that were designed for the 402) can no longer flow enough for the needs of the bigger engine.[?QUOTE] You are 100% correct.
I'm guessing the HP & TQ would increase by 6.2189%
Simply put, you're heads will max out sooner because with a 427, you have bigger cylinders to fill in the same amount of time than a 402, but the resulting higher gas velocity will help you having a higher/flatter torque curve in the lower rpms. However, that torque curve will drop rapidly after the peak because your intake, heads, headers and exhaust (that were designed for the 402) can no longer flow enough for the needs of the bigger engine.[?QUOTE] You are 100% correct.
I'm guessing the HP & TQ would increase by 6.2189%
08-25-2006, 07:47 PM
#48
Originally Posted by 2001WS6Vert
I was talking to a guy that had a dry sleeve 422 which had to be replaced (leaking sleeves) He went with a 402 figuring that it was close enough to not be much of a difference. Well he was disappointed and said the overall power curve was noticably less than the 422. He guessed 40 or so hp/tq. I am a big displacement lover and am in the midst of replacing a dry sleeve 418, I decided to go with a 427 instead of a 402.
08-25-2006, 09:24 PM
#49
[QUOTE=11 Bravo]Going from the average results I see on here, 402's actually seem to make close to the same peak hp as 427's.QUOTE]
I think this has more to do with the fact that there aren't really a lot of combos out there running top ends that really show the potential of the 427. Intakes especially, and heads to a certain degree, may be enough to feed a 402, but not really a 427.
Of course, now we're seeing LS7 heads and intakes, so that may change.
I think this has more to do with the fact that there aren't really a lot of combos out there running top ends that really show the potential of the 427. Intakes especially, and heads to a certain degree, may be enough to feed a 402, but not really a 427.
Of course, now we're seeing LS7 heads and intakes, so that may change.
