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Sbc 400 vs 415 vs 427?

General engine tech -- Drag Racing to Circle Track

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Mikej26
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Sbc 400 vs 415 vs 427?

Post by Mikej26 »

Looking to build a new short block soon and seeing as I need to get a new block and rotating assembly anyhow I’ve decided to go with a Dart SHP block and a 4.125” bore. Going from there I’m undecided on which direction to head regarding stroke. Plan is pump gas compatible street strip deal. I don’t put many miles on the car in a year so I’m tolerant of it being a bit more race than cruiser. What I want is a robust short block that’s reliable that might be overkill for my current top end (ported profiler 195’ and Holley 300-110 with AED 950HO), but will be something I can grow into with future upgrades.

So for the money and with the above in mind what stroke would be the best bang for the buck with the least downsides, 3.75”, 3.85” or 4”?

All things being equal is the power difference dramatic or minor?

Pros and cons of each?
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Re: Sbc 400 vs 415 vs 427?

Post by prairiehotrodder »

i'm pretty sure dart does not recommend bigger than 3.875 in the SHP block but many have done it.
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Re: Sbc 400 vs 415 vs 427?

Post by steve316 »

I would go dart shp block, with 3.875 stroke with small rod journals ( 2.000) and compstar rods as they clear standard base circle cam with no modifications to rods or block.
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Re: Sbc 400 vs 415 vs 427?

Post by Mikej26 »

Ok, I’m seeing that the 4” stroke might be less ideal with cam clearance as well as needing to add clearance in the block etc. so now comparing the 3.75” to the 3.85” stroke, is the difference that significant?

I’m sure I can get great power out of the 3.75” stroke. I’m just trying to avoid the inevitable “Dammit, I wonder if I should’ve gone bigger?” feeling a year from now lol
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Re: Sbc 400 vs 415 vs 427?

Post by Mikej26 »

BLOCKMAN wrote: Tue Jan 14, 2020 7:16 pm
Mikej26 wrote: Tue Jan 14, 2020 6:01 pm Looking to build a new short block soon and seeing as I need to get a new block and rotating assembly anyhow I’ve decided to go with a Dart SHP block and a 4.125” bore. Going from there I’m undecided on which direction to head regarding stroke. Plan is pump gas compatible street strip deal. I don’t put many miles on the car in a year so I’m tolerant of it being a bit more race than cruiser. What I want is a robust short block that’s reliable that might be overkill for my current top end (ported profiler 195’ and Holley 300-110 with AED 950HO), but will be something I can grow into with future upgrades.

So for the money and with the above in mind what stroke would be the best bang for the buck with the least downsides, 3.75”, 3.85” or 4”?

All things being equal is the power difference dramatic or minor?

Pros and cons of each?
I am not a fan of a 4.0 stroke in a non-raised cam tunnel unless you spend the extra money on the Callies XD rods. Other then that I put a 421 recipe out there years ago. It seem to have taken off and has been duplicated many time. Have a new build coming only change with be the AFR 1112 heads and going to use a different intake. The builds I have been doing been using the Callies Compstar rods and and a .420 lobe and a 1 inch base circle and have gone to the .904 lifters to reduce lifter pressure angle.
https://www.chevelles.com/forums/13-per ... sults.html
I believe that’s pretty much the type of build I want to do. What compression ratio did you land at with the 75cc chambers? Did you use a flat top or a small dished piston?
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Re: Sbc 400 vs 415 vs 427?

Post by n2omike »

I don't think there's a whole lot to gain by going over 406ci using standard 23 degree heads with the intake ports in the stock location. If you went 18 degree, or even a 23 degree head with the pushrods moved further apart... you'd better be able to take advantage of the extra displacement. These heads are out there, but require expensive shaft rockers. If those are in the budget, step it on up. AFR makes their 227, 235, etc with this arrangement. I'm sure others do as well.

You could always just switch to Ford. Problem solved. :mrgreen:
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Re: Sbc 400 vs 415 vs 427?

Post by Mikej26 »

BLOCKMAN wrote: Tue Jan 14, 2020 8:38 pm
Mikej26 wrote: Tue Jan 14, 2020 7:59 pm
BLOCKMAN wrote: Tue Jan 14, 2020 7:16 pm

I am not a fan of a 4.0 stroke in a non-raised cam tunnel unless you spend the extra money on the Callies XD rods. Other then that I put a 421 recipe out there years ago. It seem to have taken off and has been duplicated many time. Have a new build coming only change with be the AFR 1112 heads and going to use a different intake. The builds I have been doing been using the Callies Compstar rods and and a .420 lobe and a 1 inch base circle and have gone to the .904 lifters to reduce lifter pressure angle.
https://www.chevelles.com/forums/13-per ... sults.html
I believe that’s pretty much the type of build I want to do. What compression ratio did you land at with the 75cc chambers? Did you use a flat top or a small dished piston?
Photo Bucket is have problems for some reason, The compression is 10:3 used the Mahle Power Pack Flat top pistons.

Here is a copy of the dyno sheet
https://flic.kr/p/2if9dPA
Man, that would be perfect. Wasn’t expecting it to be that stout with only 10.3:1 comp. Great power with a conservative rpm that doesn’t threaten durability. Could easily be stepped up further with a smaller combustion chamber for a compression increase etc. I think this settles it, will go this direction with the short block and use my current heads, cam, intake etc as a starter. Will likely fall short of your build, but it seems I will have all of the room to grow with this short block as I will likely ever need.
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Re: Sbc 400 vs 415 vs 427?

Post by econo racer »

I do not think you will get much results going to more stroke unless your car is heavy. If heavy I would build as big a SBC as your budget allows. :D
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Re: Sbc 400 vs 415 vs 427?

Post by Mikej26 »

econo racer wrote: Wed Jan 15, 2020 5:09 am I do not think you will get much results going to more stroke unless your car is heavy. If heavy I would build as big a SBC as your budget allows. :D
Un-lightened 65 Malibu SS. Does that qualify as heavy?
My thinking is that with the extra torque I won’t need as steep of a gear and it will have better street manners with the extra cubes unless I go really big on the cam.

But I am curious if I would be losing much by sticking to the 3.75” stroke vs the 3.875”.

If I built something comparable to the build Blockman posted above and the only difference was a slight decrease in stroke to 3.75”. What neighbored would the power level be in?
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Re: Sbc 400 vs 415 vs 427?

Post by CGT »

Mikej26 wrote: Wed Jan 15, 2020 11:27 am Un-lightened 65 Malibu SS.
I got one of those too. Got any pics of yours?
Mikej26 wrote: Wed Jan 15, 2020 11:27 am But I am curious if I would be losing much by sticking to the 3.75” stroke vs the 3.875”.
The engine posted makes 1.35 tq per cube, pretty typical result for those kind of parts. That's gonna follow the difference in cubes pretty directly. 421 to 406 is gonna lose about 20lbs roughly using the same parts.
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Re: Sbc 400 vs 415 vs 427?

Post by n2omike »

You said you had ported Profiler 195 cylinder heads. The build BLOCKMAN is referring to, used AFR 220's.

I originally said going much over 400ci was approaching the law of diminishing returns without going to a head that spreads the pushrods for bigger ports. That depends on your application. If you're going all out with big compression and a solid roller spinning 7000+ rpm, it's easy to run out of cylinder head with the stock pushrod locations. If you're not worried about making power over 7k rpm, going bigger is just fine... as was shown in BLOCKMAN's recipe.

You mentioned wanting to leave room to 'grow' in the future. You can build a decent 421+ with your existing heads... Just build it as a GOOD combination for the RPM it will be best suited for. If you get the bug to make bigger power through rpm in the future, you can always save your pennies for bigger/better heads, and truly take advantage of the extra displacement.
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Re: Sbc 400 vs 415 vs 427?

Post by Mikej26 »

n2omike wrote: Wed Jan 15, 2020 12:15 pm You said you had ported Profiler 195 cylinder heads. The build BLOCKMAN is referring to, used AFR 220's.

I originally said going much over 400ci was approaching the law of diminishing returns without going to a head that spreads the pushrods for bigger ports. That depends on your application. If you're going all out with big compression and a solid roller spinning 7000+ rpm, it's easy to run out of cylinder head with the stock pushrod locations. If you're not worried about making power over 7k rpm, going bigger is just fine... as was shown in BLOCKMAN's recipe.

You mentioned wanting to leave room to 'grow' in the future. You can build a decent 421+ with your existing heads... Just build it as a GOOD combination for the RPM it will be best suited for. If you get the bug to make bigger power through rpm in the future, you can always save your pennies for bigger/better heads, and truly take advantage of the extra displacement.
That’s right inline with my thinking. I’m guessing that my existing heads will have it running out of steam before 6000 rpm. But I’m thinking it’ll still out perform my current setup that is a 360 ci shortblock. Then as you say, I can save for some bigger heads and so forth down the road. My room to grow involves high end parts like shaft rockers etc. it’s just time and money right? Lol

Current 360 is 10.8:1 cleaned up/ported profiler 195’s in the neighborhood of 205cc (only 2.02” intakes though) hydraulic roller Isky/Johnson hpx needless lifters, 240/244 @.050 .576/.558 on 109lsa installed at 105 icl with T&D shaft rockers 1.6/1.5, port matched Holley 300-110 and an AED 950HO(really an 830cfm).

Would literally transfer everything over to the new short block for the time being and then go from there. Not sure how down on power I’d be. Curious if any could ballpark that for me from experience.
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Re: Sbc 400 vs 415 vs 427?

Post by rfoll »

I had a decent top end already and purchased a Dart built flat top 415. The pistons were supposed to be .015 in the hole and were in fact .025. This necessitated using a .027" mls head gasket to reduce quench to something reasonable. With a 70 cc chamber head, static compression came out to 10.3:1. My heads flow about 260 at .600" lift, and I'm pretty sure they are all done by 6500 rpm. It will pull to 6900 crossing the finish line, but the big cube small block needs good heads. You will need more cam than you have to turn 6000 rpm. The bigger engine will be faster, and it will be turning more rpm at the finish line. My first go around with a 406 was a full second faster than my 355. At 3500 Lbs with me in the car I am running 10.90 @122 mph.
So much to do, so little time...
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Re: Sbc 400 vs 415 vs 427?

Post by prairiehotrodder »

i have an experience doing what you mention that i am still trying to understand Mikej26.

I helped along a friends engine :

stock block 383 with AFR 227 CNC heads, T&D shaft rockers, flat top icon pistons, 11 - 1 CR, comp solid roller (12-863-9) 263 / 272 .648/.648 108 AFR titan plastic intake, 850 quick fuel carb, 1.75" headers. Most people would say that it was a too big head deal but the intent was to gather good parts (we already had the 383 short block) and eventually put a bigger bottom end under it. The car ran 10.60's with this combo.

last winter we did that.

purchased from Steve Scmidt a 423 short block ( Dart little M block (not shp) with 4.165' bore, 3.875" stroke, domed JE pistons (13.3 CR) and transfered the heads, cam , intake and headers to this new motor. Also added a 1050 CFM carb (QFT with 4150 base). We expected 100 hp. In truth we got about 40. The car has gone 10.30. Still trying to figure out what happened.

Brian
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Re: Sbc 400 vs 415 vs 427?

Post by Mikej26 »

prairiehotrodder wrote: Wed Jan 15, 2020 2:41 pm i have an experience doing what you mention that i am still trying to understand Mikej26.

I helped along a friends engine :

stock block 383 with AFR 227 CNC heads, T&D shaft rockers, flat top icon pistons, 11 - 1 CR, comp solid roller (12-863-9) 263 / 272 .648/.648 108 AFR titan plastic intake, 850 quick fuel carb, 1.75" headers. Most people would say that it was a too big head deal but the intent was to gather good parts (we already had the 383 short block) and eventually put a bigger bottom end under it. The car ran 10.60's with this combo.

last winter we did that.

purchased from Steve Scmidt a 423 short block ( Dart little M block (not shp) with 4.165' bore, 3.875" stroke, domed JE pistons (13.3 CR) and transfered the heads, cam , intake and headers to this new motor. Also added a 1050 CFM carb (QFT with 4150 base). We expected 100 hp. In truth we got about 40. The car has gone 10.30. Still trying to figure out what happened.

Brian

That’s a head scratcher, I would’ve expected more than 40 hp out of 40 extra cubes and 2 points of compression as well. Do you think the engine is really not realizing the power increase or could it be the case that it’s just not making it to the ground?

Driving through the converter?

Maybe it now needs less gear?

I have a buddy with a 427 ls3 powered Rambler. He added a 250 shot of NOS and didn’t see much improvement at the track. His buddy put it on a chassis dyno and from that that decided on a different torque converter. That change took nearly a full second off of his 1/8th mile et
Last edited by Mikej26 on Wed Jan 15, 2020 3:59 pm, edited 1 time in total.
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