Some help with a 400

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justthatguy

justthatguy

Josh(69 Valiant)
Joined
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Hey guys, I've not posted here in a while, but I have a question I think you can help me with.

I'm looking at building a 400 I have and I'll go ahead and say it's not going into an A body, a C body is the target for this one, so, my question might be a bit unique in this circumstance. Have no fear, however, my A body will get a small block and that's a work in progress.

My question is, lots of guys build these for horsepower, what about torque? The obvious answer is a stroker, but I'm not in stroker money territory. I'm in the new pistons/top end territory. This is a industrial engine I believe(motorhome? I have no idea I haven't actually looked at it in years) I was thinking something like the kb 1274 or the 240 piston(recommended by Hot Rod, who built a 400 I'm basing this on), the Edelbrock E streets (84 cc, 2.10 intake, 1.81 exhaust), and maybe something around this:
COMP Cams Thumpr Hydraulic Flat Tappet Cam and Lifter Kits K21-601-5
for a cam selection, puts my usable rpm range right around cruising speed on the highway. I'll probably use a performer rpm intake because everyone else does. It must run on pump gas and I'm not looking for ridiculous compression, a street engine that could pull if it needed to, really. If I like it in a C, I would probably put the same thing in an A, in the future of course.

It's not technically an A but for those of us that like torque, what do you guys think of this combination? I'm still a bit new to big blocks, and to engine building in general, so bear this in mind before you flame me.
 
I’m not exactly a fan of the thumper line but I have an idea for you to watch. Check out the engine masters episode of the 383 MoPar vs the 383 Chevy and watch the MoPars torque line from start to finish.
That’s my 2 cents.
 
rumblefish360 said:
I’m not exactly a fan of the thumper line but I have an idea for you to watch. Check out the engine masters episode of the 383 MoPar vs the 383 Chevy and watch the MoPars torque line from start to finish.
That’s my 2 cents.
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They made all the old episodes private. I'll be damned if I pay money to watch guys horsing around with their toys when I can go do it in my garage for free!
 
You can build a 451 for the same money as a 400.
 
Ottmundr said:
They made all the old episodes private. I'll be damned if I pay money to watch guys horsing around with their toys when I can go do it in my garage for free!
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I have to sallow some pride and say I subscribed to MTOD because Steve Dulcich is my hero but I just now rewatched that episode and wow that thing made torque, if they did that with a 383 and 906s I'd have to do better with more cubes and better heads. He's got more lift on his cam it sounded like, .05. I can't argue with that powerband either, that was flat as a pancake until 5500.
 
I used this is my Dakota with 400. Grind number XE268H. I certainly wish I could have built a 451 for the 1500$ or so I have into the 400. I have not had her over 6k, but it feels like she is still pulling there
FEA85672-C6D4-42DB-A0BA-573C00EDEA75.png
 
A stock stroke 400 with good pistons (9.5 or so on the compression) and a set of Trick Flow 240 heads would wake up most any car. Keep the compression below 10:1, use the TF heads and everything else should fall into place. You'll need headers to fit the angled spark plugs and you'll want to keep the camshaft fairly mild. A Performer RPM is a decent intake to use but keep the carb on the small size. Maybe a 600 cfm Edelbrock carb or something along those lines. The cam and the carb don't need to be very big if you have good heads and the correct compression.
 
Wouldn’t higher compression produce more torque?
But I suppose running a short duration cam that doesn’t bleed off much cylinder pressure you can’t go as high on the static side...
 
twayne24365 said:
Wouldn’t higher compression produce more torque?
But I suppose running a short duration cam that doesn’t bleed off much cylinder pressure you can’t go as high on the static side...
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The problem with higher compression is octane requirements. If you want to run pump premium you'll need to keep the compression below 10:1. IMO, considering the crappy gas at the pumps I would keep it below 9.5:1 and that might be pushing it. You can take some timing out to make up for not enough octane (to a degree) but you lose more power by doing that than having a lower compression ratio to begin with.
 
My 383 is currently being built by a well experienced man. This will be a "restoration" with some changes. When done , I will drive it, so the builder is lowering the compression from 10 to 1 down to 9.5 to 1 to compensate for the bad gas, and am using a roller cam and rockers to compensate for the poor oils. These are things to consider when building a modern engine.
 
younggun2.0 said:
Why is 10:1 the limit? Detonation?
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Yes
91/93 octane is really only good for so much cylinder pressure. (Dynamic compression)There are fellas here, myself included, that run the best pump swill with ratios of 11-1. (I do) The trick is to bleed off compression with a big cam. This is the give and take catch 22 of pump gas.

Being the car is a big heavy car with the wish of cruising, it makes very good sense to be a bit prudent and conservative on what your doing for added performance. Lower compression and a smaller cam is the start.

Depending on the cars weight, gear ratio etc.... a 9.0-1 is where I’d start.

twayne24365 said:
Wouldn’t higher compression produce more torque?
But I suppose running a short duration cam that doesn’t bleed off much cylinder pressure you can’t go as high on the static side...
Click to expand...
Yes! The extra compression, it would make more power but a heavier car with cruising in mind it can do very well without. Between the cars weight, lower than best acceleration gears, the added power from compression is an issue with pump gas.
 
rumblefish360 said:
Yes
91/93 octane is really only good for so much cylinder pressure. (Dynamic compression)There are fellas here, myself included, that run the best pump swill with ratios of 11-1. (I do) The trick is to bleed off compression with a big cam. This is the give and take catch 22 of pump gas.

Being the car is a big heavy car with the wish of cruising, it makes very good sense to be a bit prudent and conservative on what your doing for added performance. Lower compression and a smaller cam is the start.

Depending on the cars weight, gear ratio etc.... a 9.0-1 is where I’d start.


Yes! The extra compression, it would make more power but a heavier car with cruising in mind it can do very well without. Between the cars weight, lower than best acceleration gears, the added power from compression is an issue with pump gas.
Click to expand...

Exactly what I was thinking, 9 or 9 and a half. With a moderate cam, I should be right around 450 to 460 on the torque with my head size and runner volume if I can pick a piston (I can't to save my life)
 
RustyRatRod said:
400 block, stock 440 crank and plenty of people make off the shelf pistons.
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I had heard that when you use a 440 crank you grind the hard metal off for the offset and it weakens the crank. Never looked much into it however, would I use the 400 rods or the 440 rods? Sounds expensive for machine work.
 
justthatguy said:
I had heard that when you use a 440 crank you grind the hard metal off for the offset and it weakens the crank. Never looked much into it however, would I use the 400 rods or the 440 rods? Sounds expensive for machine work.
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This method has been done for decades without issue. There is truth to what you wrote only because the reduced size of the journals, however it has been show that the crank still holds plenty of power and life. The modified 440 cranks properly machines is no weaker than the 400 crank and it actually should be better.

justthatguy said:
Exactly what I was thinking, 9 or 9 and a half. With a moderate cam, I should be right around 450 to 460 on the torque with my head size and runner volume if I can pick a piston (I can't to save my life)
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Speak with your machinist. It’s the best and easiest way to get the ball rolling when you don’t know for sure.
Otherwise, you need
To know what ratio you want, need and what is an acceptable amount above/below your need.

You’ll also need to know the cylinder head cc amount, the head gasket to be used & the blocks deck height to know where the piston will sit so these numbers can be calculated for a compression ratio with a given piston and it’s height from the pins centerline. And that’s the tough part. Where does the slug sit in the cylinder?!?!?!

Need a machinist for this? LOL
I do unless I have some knowledge on what I already have.
 
justthatguy said:
I had heard that when you use a 440 crank you grind the hard metal off for the offset and it weakens the crank. Never looked much into it however, would I use the 400 rods or the 440 rods? Sounds expensive for machine work.
Click to expand...

You "heard" wrong. Build what you want to. Andy is right, though. A 400 with 3K dollars worth of heads will haul ***.
 
Fresh rings and bearings, mill the smogger heads .060" on the deck and .072" on the intake face, Comp 275DEH cam, Comp #911 springs, Hedman shorty E-body headers (THEY FIT) and a Performer RPM intake if you have the budget. Enjoy!
 
justthatguy said:
I had heard that when you use a 440 crank you grind the hard metal off for the offset and it weakens the crank. Never looked much into it however, would I use the 400 rods or the 440 rods? Sounds expensive for machine work.
Click to expand...
I am not going to let this one slide. I had a factory 440 forged crank turned down to 400 main size and took .125" in radius off the counter weights. I used a 6.76 H-beam 440 length rod and a Ross forged piston. Wound it to 7,200 rpm where it was making 787 HP on 91 octane pump gas. It is now de-tuned to 580 HP and running in the shop truck. No, I think the factory 440 forged crank will hold up just fine.
 
That's why I ask those more experienced than I about such things.

I found a 70 chrysler newport with a 383 ailing from a spun bearing, I'm assuming it has good 906 heads and I do have a 440 crank too so this might be the easiest stroker ever. I might even have some 440 pistons or I might have some used 400 flattops I can get a hold of.

This thing should haul *** to be a road bound aircraft carrier.
 
My machinist says that the old Mopar steel cranks are hard just about all the way though, not sure about the cast stuff. So offset grind or grind a 440 crank to fit in your 400 all you want....

On the dyno my 383 makes 400 HP @5200 and 436 ft/lbs of torque @4300 with over 400 ft/lbs from 3000-5200 with a modest 264/272, 217/225 @ .050 with .544 lift custom hydraulic roller with 1.6 rockers and basically stock 906 heads.

So with the cam you have chosen, with the Eddy heads should really make some good HP and torque. I'd say 450 HP and 485 ft/lbs torque. Stroke it to 451 and you would have even more.

Garth
 
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