Built 2V and 4V 400 dyno's suprisingly similar.
#31
12-06-2010, 04:54 AM
Posting Guru
#32
12-06-2010, 03:02 PM
I've been comparing data from built up 400's with 2V and 4V heads, and although I'm only working with a few sets of data that I've been able to dig up on this site and others (would love anyone else's dynos), I've been very suprised so far with what I'm seeing.
Pretty standard 400 builds (CR 9.5-10, 4 barrel, straight up timing, free flowing exhaust, moderate cam and springs) with both 2V and 4V heads offer suprisingly similar power through most of the rpm range.
In the engines I've looked at, the 4V heads seem to offer about 20% more peak HP, and peak about 1500 RPMs higher than a 2V head. (Slightly less difference than I had expected)
What really suprised me though, is that the 2V heads peaked at only around 10% more TQ, and only about 500 RPMs earlier than the 4Vs! The 4V torque curve also shadowed just 50 ft/lb or so under the 2V one all the way down to 1500 rpm, where I ran out of data points.
Like I said, these are built examples of these engines, not stock, but since anyone who is considering the 4V option is likely going to be going through their whole engine anyway, I think it's a fair arguement that a 4V headed engine is a better option even in our heavy trucks for all but the most extreme applications.
Support? Arguments? More dynos?
AleX
Pretty standard 400 builds (CR 9.5-10, 4 barrel, straight up timing, free flowing exhaust, moderate cam and springs) with both 2V and 4V heads offer suprisingly similar power through most of the rpm range.
In the engines I've looked at, the 4V heads seem to offer about 20% more peak HP, and peak about 1500 RPMs higher than a 2V head. (Slightly less difference than I had expected)
What really suprised me though, is that the 2V heads peaked at only around 10% more TQ, and only about 500 RPMs earlier than the 4Vs! The 4V torque curve also shadowed just 50 ft/lb or so under the 2V one all the way down to 1500 rpm, where I ran out of data points.
Like I said, these are built examples of these engines, not stock, but since anyone who is considering the 4V option is likely going to be going through their whole engine anyway, I think it's a fair arguement that a 4V headed engine is a better option even in our heavy trucks for all but the most extreme applications.
Support? Arguments? More dynos?
AleX
351M/408, Tmeyer 400 pistons, Comp 255DEH, Edelbrock 400 intake and 600cfm carb, OEM 2v heads, Long tube headers 1 5/8" x 2.5", OEM distributor
#33
12-06-2010, 04:26 PM
Thanks, I have a 4V 408 going in RIGHT NOW, and I'm hoping to have the truck driving by the weekend, so we will see!
Great numbers though smokey, I'd love to be able to get mine dyno'd, and I love that torque! Mine dyno simmed to a peak TQ of about 460, and to help it actually get there, I've swapped in a few more low end oriented components, but we won't know until I get moving. I'm excited to have my truck back at all, but if this thing can't take off anymore I'm going to kick myself.
Great numbers though smokey, I'd love to be able to get mine dyno'd, and I love that torque! Mine dyno simmed to a peak TQ of about 460, and to help it actually get there, I've swapped in a few more low end oriented components, but we won't know until I get moving. I'm excited to have my truck back at all, but if this thing can't take off anymore I'm going to kick myself.
#34
12-06-2010, 05:59 PM
Thanks, I have a 4V 408 going in RIGHT NOW, and I'm hoping to have the truck driving by the weekend, so we will see!
Great numbers though smokey, I'd love to be able to get mine dyno'd, and I love that torque! Mine dyno simmed to a peak TQ of about 460, and to help it actually get there, I've swapped in a few more low end oriented components, but we won't know until I get moving. I'm excited to have my truck back at all, but if this thing can't take off anymore I'm going to kick myself.
Great numbers though smokey, I'd love to be able to get mine dyno'd, and I love that torque! Mine dyno simmed to a peak TQ of about 460, and to help it actually get there, I've swapped in a few more low end oriented components, but we won't know until I get moving. I'm excited to have my truck back at all, but if this thing can't take off anymore I'm going to kick myself.
Keep us up to date with your engine.
#35
12-29-2010, 05:31 PM
#36
02-14-2017, 08:10 PM
#38
02-21-2017, 12:28 AM
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I have a dilemma.
I have a 400m, has 268H cam, straight up timing, headers, HEI dizzy, edelbrock 400 intake, 670 holley, fresh STOCK pistons .030 over and stock rebuilt 2V C open chamber heads. Runs like a dream but leaves me wanting.
I have on the shelf; a set of 4V 351C CJ open chamber heads and a set of 4V N-code closed chamber heads. As well as 2 other sets of 351C 2V heads.
I am wondering where to go with what i got. Do I....
1. Put the N code closed chamber heads on my current bottom end and get the spacers, intake, 4v headers.
2. Get the tmeyer pistons and stay with my current heads (maybe port them a little)
3. Get the tmeyer pistons and put on the 351C CJ open heads, spacers, intake, 4v headers.
opinions?
I have a 400m, has 268H cam, straight up timing, headers, HEI dizzy, edelbrock 400 intake, 670 holley, fresh STOCK pistons .030 over and stock rebuilt 2V C open chamber heads. Runs like a dream but leaves me wanting.
I have on the shelf; a set of 4V 351C CJ open chamber heads and a set of 4V N-code closed chamber heads. As well as 2 other sets of 351C 2V heads.
I am wondering where to go with what i got. Do I....
1. Put the N code closed chamber heads on my current bottom end and get the spacers, intake, 4v headers.
2. Get the tmeyer pistons and stay with my current heads (maybe port them a little)
3. Get the tmeyer pistons and put on the 351C CJ open heads, spacers, intake, 4v headers.
opinions?
#39
02-21-2017, 09:07 AM
Mountain Pass
Where exactly do you want to go on #268h? Theyre ok to about 5000 but nose over little past 5200 i ran a Bracket MasterII 536/567 293dur 112 lsa at 8.7 compression on spray and drove it daily w mild lope. Wanting more so going to Howards 238101-09. Open heads should be fun. Closed heads w TMI pistons i would recommend better gas and no spray (will try it anyway w aussie heads) just a question of what are you using it for most?
#40
02-21-2017, 10:54 AM
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Where exactly do you want to go on #268h? Theyre ok to about 5000 but nose over little past 5200 i ran a Bracket MasterII 536/567 293dur 112 lsa at 8.7 compression on spray and drove it daily w mild lope. Wanting more so going to Howards 238101-09. Open heads should be fun. Closed heads w TMI pistons i would recommend better gas and no spray (will try it anyway w aussie heads) just a question of what are you using it for most?
I have more blocks, I could do another short block with a different cam option and different heads. Just looking for info on which heads people have used.
The closed chambers with Tmeyers I think would put me up in the 12:1+ range. I'd have to get some race fuel?
I'm wondering if anyone has put the closed chambers on factory pistons and want kinda difference they've made?
#41
02-21-2017, 11:03 AM
Mountain Pass
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