421 cube pulling truck engine

General engine tech -- Drag Racing to Circle Track

Moderator: Team

JoePorting
Guru
Guru
Posts: 2997
Joined: Mon Jun 14, 2010 3:16 pm
Location: Lake Elizabeth, CA

Re: 421 cube pulling truck engine

Post by JoePorting »

Sounds like a nice engine build except for the heads. I'd think the heads would limit the power to around 600 hp. If you want 750 hp, you'd have to upgrade to a head with a 2.20" intake valve like in a Brodix 18C head or a Dart 9 degree head. My experience with welding up the pushrod pinch area is that it's a waste of time. The bottle neck is the small intake valve and the shallow intake bowl. If the rules demand an iron head, then I guess there's not too many good options.

One idea is to change the valve sizes from 2.08/1.6 to 2.20/1.5 if the larger intake will fit the head gasket (valve spacing issues). Or maybe 2.15/1.55 is another option. But even then power will only improve by 20/30 hp at best.
Joe Facciano
randy331
Guru
Guru
Posts: 3337
Joined: Mon Dec 04, 2006 7:30 pm
Location: N.W. MO.

Re: 421 cube pulling truck engine

Post by randy331 »

JoePorting wrote: Sat Jan 27, 2018 6:29 pm Sounds like a nice engine build except for the heads. I'd think the heads would limit the power to around 600 hp.
That would be very disappointing to go to all this expense and work adding cubes, compression, etc, only to loose 30 HP over the 355 that was in it last year.

JoePorting wrote: Sat Jan 27, 2018 6:29 pm One idea is to change the valve sizes from 2.08/1.6 to 2.20/1.5 if the larger intake will fit the head gasket (valve spacing issues). Or maybe 2.15/1.55 is another option. But even then power will only improve by 20/30 hp at best.
Since the 355 only had a 2.05" valve, and this set of heads have 2.08" valve, is it at least possible this engine won't loose power over the 355 ?

Randy
Keith Morganstein
Guru
Guru
Posts: 5566
Joined: Sun Feb 19, 2006 10:19 am
Location: MA

Re: 421 cube pulling truck engine

Post by Keith Morganstein »

randy331 wrote: Sat Jan 27, 2018 7:34 pm
JoePorting wrote: Sat Jan 27, 2018 6:29 pm Sounds like a nice engine build except for the heads. I'd think the heads would limit the power to around 600 hp.
That would be very disappointing to go to all this expense and work adding cubes, compression, etc, only to loose 30 HP over the 355 that was in it last year.

JoePorting wrote: Sat Jan 27, 2018 6:29 pm One idea is to change the valve sizes from 2.08/1.6 to 2.20/1.5 if the larger intake will fit the head gasket (valve spacing issues). Or maybe 2.15/1.55 is another option. But even then power will only improve by 20/30 hp at best.
Since the 355 only had a 2.05" valve, and this set of heads have 2.08" valve, is it at least possible this engine won't loose power over the 355 ?

Randy
Surely more than 600 HP can be made with a 2.08" valve. 2.6" CSA, 240 CFM port.
Automotive Machining, cylinder head rebuilding, engine building. Can't seem to quit #-o
randy331
Guru
Guru
Posts: 3337
Joined: Mon Dec 04, 2006 7:30 pm
Location: N.W. MO.

Re: 421 cube pulling truck engine

Post by randy331 »

Keith Morganstein wrote: Sun Jan 28, 2018 5:02 am Surely more than 600 HP can be made with a 2.08" valve. 2.6" CSA, 240 CFM port.
The heads for the 421 are in the 315-317 cfm range, so it will need to make 2.38 HP/cfm to meet my 750 HP goal. That's doable.

With 2.6 in csa it will need to make 750/2.6 = 288 HP per inch of csa. That's doable.

If I can make 1.45 pounds of TQ/cubes at 5800 ish rpm that will be 610 TQ. And hold on to %90 of that TQ till 7200 that will be 753 HP.
My calcs for port size/csa puts the 5800 rpm and 7200 rpm for peak tq and peak HP right in line with past results, and 1.45 pounds/cubes is certainly within reason for a build like this on Q16 fuel. Our emc 353 made 1.44 LBs/cube under much more limited rules.

Other calcs seem within reason to make 750 HP out of this build.

1.78 HP/cube don't seem out of line for this type of build.

But,.. maybe all that counts is intake valve size ? :?: :D

Randy
RevTheory
Guru
Guru
Posts: 5646
Joined: Thu Sep 04, 2014 6:45 am
Location:

Re: 421 cube pulling truck engine

Post by RevTheory »

If you're willing to share, what are you doing to calculate your target peak torque rpm?
Keith Morganstein
Guru
Guru
Posts: 5566
Joined: Sun Feb 19, 2006 10:19 am
Location: MA

Re: 421 cube pulling truck engine

Post by Keith Morganstein »

randy331 wrote: Sun Jan 28, 2018 11:17 am
Keith Morganstein wrote: Sun Jan 28, 2018 5:02 am Surely more than 600 HP can be made with a 2.08" valve. 2.6" CSA, 240 CFM port.
The heads for the 421 are in the 315-317 cfm range, so it will need to make 2.38 HP/cfm to meet my 750 HP goal. That's doable.

With 2.6 in csa it will need to make 750/2.6 = 288 HP per inch of csa. That's doable.

Randy
Typo, I meant to write 240 CC port, (not 240 CFM)

And yes I think your goals are achievable.
Automotive Machining, cylinder head rebuilding, engine building. Can't seem to quit #-o
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: 421 cube pulling truck engine

Post by CGT »

randy331 wrote: Sun Jan 28, 2018 11:17 am With 2.6 in csa it will need to make 750/2.6 = 288 HP per inch of csa. That's doable
randy331 wrote: Sun Jan 28, 2018 11:17 am so it will need to make 2.38 HP/cfm to meet my 750 HP goal. That's doable.
Considering that particular set of heads prior to your new recent rework made over 2hp per cfm(290 cfm) on a 10.5:1 357 with a hyd roller. I think its very doable.
steve316
Expert
Expert
Posts: 630
Joined: Fri Apr 13, 2007 10:06 pm
Location: St.Joseph,mo.

Re: 421 cube pulling truck engine

Post by steve316 »

On this type of build I think your are being conservative on your estimates.I think your torque will be in the 1.5 to 1.52 range; and HP in the 1.85 to 1.9 range. The spread between peak tq & peak hp will depend on min csa and max csa in the intake track. JMO; looks good to me =D>
user-17438

Re: 421 cube pulling truck engine

Post by user-17438 »

JoePorting wrote: Sat Jan 27, 2018 6:29 pm Sounds like a nice engine build except for the heads. I'd think the heads would limit the power to around 600 hp. If you want 750 hp, you'd have to upgrade to a head with a 2.20" intake valve like in a Brodix 18C head or a Dart 9 degree head. My experience with welding up the pushrod pinch area is that it's a waste of time. The bottle neck is the small intake valve and the shallow intake bowl. If the rules demand an iron head, then I guess there's not too many good options.

One idea is to change the valve sizes from 2.08/1.6 to 2.20/1.5 if the larger intake will fit the head gasket (valve spacing issues). Or maybe 2.15/1.55 is another option. But even then power will only improve by 20/30 hp at best.
Lol.. a 2.200 valve can move over 450cfm of air. I think the 2.080 is small as I would prefer a 2.100. But not a 2.200. You couldnt get the port large enough to require that big of a valve. Nor the combustion chamber shape, approach from the short turn. Etc. There is more to making hp than throwing the biggest valve in it and the most cfm.
randy331
Guru
Guru
Posts: 3337
Joined: Mon Dec 04, 2006 7:30 pm
Location: N.W. MO.

Re: 421 cube pulling truck engine

Post by randy331 »

MTENGINES wrote: Mon Jan 29, 2018 9:26 pm But not a 2.200. You couldnt get the port large enough to require that big of a valve.
So you don't go along with the put the largest valve that will fit in every head theory ?
You seem to imply that the valve should be sized according to port CSA, and I think so too.
MTENGINES wrote: Mon Jan 29, 2018 9:26 pm There is more to making hp than throwing the biggest valve in it and the most cfm.
Not to some.

Randy
proheader
Pro
Pro
Posts: 346
Joined: Thu Dec 14, 2006 5:40 pm
Location:
Contact:

Re: 421 cube pulling truck engine

Post by proheader »

IMAG0249.jpg
Plenty of 4-2-1 headers in Missouri..
You do not have the required permissions to view the files attached to this post.
In-Tech
Vendor
Posts: 2812
Joined: Wed Apr 21, 2010 4:35 am
Location: Fresno, CA

Re: 421 cube pulling truck engine

Post by In-Tech »

I really like the headers, not so sure on that dropped valve though. :shock: [-o< :mrgreen: And where is the o2 bung? :wink:
Heat is energy, energy is horsepower...but you gotta control the heat.
-Carl
proheader
Pro
Pro
Posts: 346
Joined: Thu Dec 14, 2006 5:40 pm
Location:
Contact:

Re: 421 cube pulling truck engine

Post by proheader »

O2 bung is down on the inside of the collector... 74-92 squarebody fenderwell headers
Keith Morganstein
Guru
Guru
Posts: 5566
Joined: Sun Feb 19, 2006 10:19 am
Location: MA

Re: 421 cube pulling truck engine

Post by Keith Morganstein »

proheader wrote: Thu Feb 01, 2018 6:25 am IMAG0249.jpg

Plenty of 4-2-1 headers in Missouri..
Now I have! Missouri is the “show me” state after all!
Automotive Machining, cylinder head rebuilding, engine building. Can't seem to quit #-o
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: 421 cube pulling truck engine

Post by CGT »

Any updates? Head flowz? Short block flowz? Perfect cam flowz? :?
Locked