Dyno a 7.5:1 400? Sure, why not?

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IQ52

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So ya want a 400 for your company 2whl drive pickup that the employees will drive daily and you don't want it to be a hot rod. Huh..........

So we keep the stock 2bbl Holley and cast iron 2bbl intake. Let's deck the block to square it up, bore it .030" over and hone the cylinders with a deck plate. Use cast aluminum replacement pistons and balance the rotating assembly. 346 heads with 2.14/1.81 valves, hardened exhaust seats and enough porting to get, 250 cfm @ .500" lift. Use a Summit 6400 camshaft and 'takeoff' 440 Source valves springs set up at 120# IH and 240# @ .450" lift. Comp 10 degree retainers and locks. Stock rocker assembly and TrickFlow 3/8 pushrods to get the correct lifter preload. Recurve the stock distributor, use the dyno headers and spin the 400 up on the dyno.

RPM.................TQ/HP

2500...............351/167
2600...............350/173
2700...............355/183
2800...............367/195
2900...............371/205 peak torque
3000...............368/210
3100...............369/218
3200...............366/223
3300...............367/231
3400...............361/234
3500...............359/239
3600...............360/247
3700...............354/249
3800...............351/254
3900...............343/255
4000...............337/256
4100...............329/257
4200...............325/260
4300...............326/267
4400...............323/270
4500...............322/276
4600...............307/269
4700...............318/285 peak horsepower
4800...............308/281
4900...............302/281
5000...............297/283

What if there was enough spare time to install a 383 Holley Street Dominator intake and a 950 Quick Fuel carburetor? What if just that change? Let's start the at 2800 RPM and pull the little 400 to 5300 RPM.

2800...............346/184
2900...............347/192
3000...............359/205
3100...............374/221
3200...............376/229
3300...............383/240
3400...............391/253
3500...............396/264
3600...............397/272 peak torque
3700...............395/278
3800...............392/283
3900...............397/295
4000...............397/302
4100...............397/310
4200...............390/312
4300...............388/318
4400...............377/316
4500...............374/321
4600...............375/329
4700...............380/340
4800...............382/349
4900...............380/355
5000...............368/351
5100...............371/361 peak horsepower
5200...............362/358
5300...............345/348

7.515:1 compression? 85 octane? You betcha!
 
IQ52 said:
So ya want a 400 for your company 2whl drive pickup that the employees will drive daily and you don't want it to be a hot rod. Huh..........

So we keep the stock 2bbl Holley and cast iron 2bbl intake. Let's deck the block to square it up, bore it .030" over and hone the cylinders with a deck plate. Use cast aluminum replacement pistons and balance the rotating assembly. 346 heads with 2.14/1.81 valves, hardened exhaust seats and enough porting to get, 250 cfm @ .500" lift. Use a Summit 6400 camshaft and 'takeoff' 440 Source valves springs set up at 120# IH and 240# @ .450" lift. Comp 10 degree retainers and locks. Stock rocker assembly and TrickFlow 3/8 pushrods to get the correct lifter preload. Recurve the stock distributor, use the dyno headers and spin the 400 up on the dyno.

RPM.................TQ/HP

2500...............351/167
2600...............350/173
2700...............355/183
2800...............367/195
2900...............371/205 peak torque
3000...............368/210
3100...............369/218
3200...............366/223
3300...............367/231
3400...............361/234
3500...............359/239
3600...............360/247
3700...............354/249
3800...............351/254
3900...............343/255
4000...............337/256
4100...............329/257
4200...............325/260
4300...............326/267
4400...............323/270
4500...............322/276
4600...............307/269
4700...............318/285 peak horsepower
4800...............308/281
4900...............302/281
5000...............297/283

What if there was enough spare time to install a 383 Holley Street Dominator intake and a 950 Quick Fuel carburetor? What if just that change? Let's start the at 2800 RPM and pull the little 400 to 5300 RPM.

2800...............346/184
2900...............347/192
3000...............359/205
3100...............374/221
3200...............376/229
3300...............383/240
3400...............391/253
3500...............396/264
3600...............397/272 peak torque
3700...............395/278
3800...............392/283
3900...............397/295
4000...............397/302
4100...............397/310
4200...............390/312
4300...............388/318
4400...............377/316
4500...............374/321
4600...............375/329
4700...............380/340
4800...............382/349
4900...............380/355
5000...............368/351
5100...............371/361 peak horsepower
5200...............362/358
5300...............345/348

7.515:1 compression? 85 octane? You betcha!
Click to expand...

Just curious. Why a 950 carb? Is it a double pumper? What would happen with something smaller like a 750 vac secondary?
 
The 400 is the most under rated engine in the whole Mopar universe. The quickest and fastest dead stock Mopar I ever owned..and this includes Hemi and Six Packs, was a 72 Roadrunner 400 4 speed. Car had a 3:55 gear, no options and with ONLY a basic supertune ran effortless 12.80's on street tires.
True, I never came close to duplicating those numbers with another similar stock 400, but that one happy freak made me a believer.
 
IQ your work with low compression engines and the power you get is amazing. Makes me want to keep my 8.5:1 440 pistons
 
Very cool engine.....

Boy the good heads really showed up with some breathing on top...:thumbrig:
 
Well as we can see, a low compression engine can make good power. This is not new news. Back in the 70s when Detroit dropped the compression across the board it did not take long for people to discover that it was not the end of the world as far as making power and getting their car to run quick. The thing about compression is that even though it does not make a dramatic difference in power by itself, it has a big effect on the attitude of the engine. I've said this before and I'll say it again. Take two identical cars, one with 8.5 to 1 and one with 10.5 to 1 being the only difference and drive both of them. Without a doubt the 10.5 to one car will be a lot more fun to drive and will sound better also. Better throttle responce and more immediate torque also. Drag race the two cars against each other and the high compression car will probly win but only by a small margin. Now take the two c ars and start going up on the cams, identical in both and tbe high compession engine will start to shine brighter. Just an opinion.
 
Doosterfy said:
Just curious. Why a 950 carb? Is it a double pumper? What would happen with something smaller like a 750 vac secondary?
Click to expand...

Don't own a 750 vacuum secondary. The Q950 double pumper is my go to dyno carb. Works great for breaking in an engine because of it's reliability. The reason bigger carburetors haven't worked on smaller engines in the past is because they don't pull enough signal strength across the boosters. As boosters are developed and become more sensitive we may someday see where a 1250 Dominator can be used on a 170 ci Slant Six. Carburetors aren't necessarily too big, they are just insensitive...................like most husbands.

Doosterfy said:
Well as we can see, a low compression engine can make good power. This is not new news. Back in the 70s when Detroit dropped the compression across the board it did not take long for people to discover that it was not the end of the world as far as making power and getting their car to run quick. The thing about compression is that even though it does not make a dramatic difference in power by itself, it has a big effect on the attitude of the engine. I've said this before and I'll say it again. Take two identical cars, one with 8.5 to 1 and one with 10.5 to 1 being the only difference and drive both of them. Without a doubt the 10.5 to one car will be a lot more fun to drive and will sound better also. Better throttle responce and more immediate torque also. Drag race the two cars against each other and the high compression car will probly win but only by a small margin. Now take the two c ars and start going up on the cams, identical in both and tbe high compession engine will start to shine brighter. Just an opinion.
Click to expand...

Ah, but it is news. Most build suggestions say, "The first thing you need to do is get the compression up!"

Not a bad idea, but do you need to? Depends upon your goals. Yes I could bump only the compression on this build and make 305-320 horsepower with the 2bbl or 390-405 horsepower with the 4bbl. Then my customer has to go to premium fuel and he doesn't want to.

It's okay, we're building a 572 Hemi that will be around 11.8:1 compression and run on pump gas. It's what the customer wants......................
 
IQ52, thanks! This helps give hope to my 400.
('1978-400-727 in a '71 Duster with the same intake and Hedman B body headers)
The timing of this is perfect.


PoisonDart74 said:
High compression is overrated.
Click to expand...

Yea it is. It seems to be closer to a bragging point. The higher compression helps make that larger cam work better and it does add a good amount of HP, but the draw back of running the high (or very high) ratio can take you to high octane pump or better real quickly.

At approximately 3% more power per 1 point of compression, it can pay off in the right arena.
A lot depends on your wallet.

OldmanRick said:
Very cool engine.....

Boy the good heads really showed up with some breathing on top...:thumbrig:
Click to expand...

Air flow, that's the key. Always has been.
 
Back in the late 70's we had a printout of Direct Connections "recipes" for a bracket car. It was based on an A body (duster I think) with a 400 in it. The "recipe" for each category was spelled out in detail with part numbers for 14 sec., 13 sec, etc. with suspension mods. needed to run in that bracket. Nobody really considered the 400 a performance motor at that time.
 
dukeboy_318 said:
IQ your work with low compression engines and the power you get is amazing. Makes me want to keep my 8.5:1 440 pistons
Click to expand...

You can change pistons if ya want to, nothing wrong with that. But this will give you an idea of what you can get if you decide to keep what you have.
 
IQ52 said:
You can change pistons if ya want to, nothing wrong with that. But this will give you an idea of what you can get if you decide to keep what you have.
Click to expand...

I agree, but... That's the half of it for me. A piston change is not in the budget at all. I have to work with what I have. A very good running 400 & a 727 in a Duster.
 
IQ52 said:
Yeah, the pistons are .120" below the deck.
Click to expand...

I've been thinking for quite awhile now that there are lots of niche markets to be expolted to serve the low buck hot rod, racing enthusiasts. One part would be pistons for Mopars. We all know about the factory leaving the pistons a good .100" or more down in the hole. So the budget builder who can't afford to open up the "go to the machine shop and bore, deck, new pistons and balancing" routine is stuck with the low compression, no quench engine. I bet if someone produced low cost pistons that were .100" taller and very close to the weight of the factory piston they would sell plenty of them. OK, I admit, I realy don't like low compression. LOL. Good job IQ52, your threads are always good and educational.
 
IQ52 said:
Yeah, the pistons are .120" below the deck.
Click to expand...

I've been thinking for quite awhile now that there are lots of niche markets to be expolted to serve the low buck hot rod, racing enthusiasts. One part would be pistons for Mopars. We all know about the factory leaving the pistons a good .see100" or more down in the hole. So the budget builder who can't afford to open up the "go to the machine shop and bore, deck, new pistons and balancing" routine is stuck with the low compression, no quench engine. I bet if someone produced low cost pistons that were .100" taller and very close to the weight of the factory piston they would sell plenty of them. OK, I admit, I realy don't like low compression. LOL. Good job IQ52, your threads are always good and educational.
 
Doosterfy said:
I've been thinking for quite awhile now that there are lots of niche markets to be expolted to serve the low buck hot rod, racing enthusiasts. One part would be pistons for Mopars. We all know about the factory leaving the pistons a good .see100" or more down in the hole. So the budget builder who can't afford to open up the "go to the machine shop and bore, deck, new pistons and balancing" routine is stuck with the low compression, no quench engine. I bet if someone produced low cost pistons that were .100" taller and very close to the weight of the factory piston they would sell plenty of them. OK, I admit, I realy don't like low compression. LOL. Good job IQ52, your threads are always good and educational.
Click to expand...

Or how about rods that are .100" longer?, that would probly be cheaper and easier than pistons.
 
Mann do I suck at managing my not so smart phone. I tried to edit my post and wound up posting the same thing twice. I wish IQ52, MRL, or some of the other good Mopar engine builders were located here on Southern New England. I would use you guys for sure. The cost and hastle of shipping back and forth to far off shops makes it a problem. I hate to say it but I've had way too many problems with the engine builders in my area.
 
One of the things I've been wanting to experiment with are shims or pucks that can be attached to the piston head with taper head allen screws...positioned more or less the way gas ports are. The weight would be insignificant considering where in the assembly it is positioned, and it would open up a universe of possibilities as far as compression and more importantly quench is concerned. It sounds off the wall, but I can't see any reason why it would not work.
 
I used to mess with a VW engine I wanted to put in a homebuilt airplane. I built it with lots of stroke and 7.0-1 CR to run 87 pump gas. It was a stump puller for sure and would pull up to 5500 RPM.

Re-doing the 496 KB/B1 motor and dropping the CR to 10-1. With the 47cc chambers it will be 0.060 down in the hole with a huge dish. Gonna boost it this time and run E-85. With 10-1 should be able to rum pump swill with the gas carb and no boost.
 
rumblefish360 said:
I agree, but... That's the half of it for me. A piston change is not in the budget at all. I have to work with what I have. A very good running 400 & a 727 in a Duster.
Click to expand...

as a reference i got my results from the shop today

they dynoed my budget 400 build. 2500 for eddy top end kit (comes with a cheap hyd cam & lifters .480 ex / .495 int 300 or so duration). kb240 pistons 10:1 i cheaped out didnt bother getting another cam. 750hp carb

got 470hp i'll get the full dyno sheet friday when i'm off work i can go up there

i spent roughly $5500
i got the engine for 1000, top end kit for 2500, valvetrain 700, carb 600, block decked + balance etc. mancini water pump, some other odds n ends
 
IQ52 said:
You can change pistons if ya want to, nothing wrong with that. But this will give you an idea of what you can get if you decide to keep what you have.
Click to expand...

Ok, my concern is that I am wanting to go to eddy RPM heads at some point when I can, mainly for weight savings as well as power. Would that affect the CR enough to actually hurt the performance? I currently have regular Silvolite 1263 flat top pistons but was thinking of jumping up to 6-pack piston with valve cuts, L2335 is it?
 
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