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400 small block build

12K views 49 replies 18 participants last post by  crystalbluevib  
#1 ·
I have a chevy 400 block and crank with a set of 64cc vortec heads. im in the process of beginning my build. I am shooting for 450hp to 500hp. I would like to run it on high grade pump gas and i need to know the best pistons for this application.
 
#2 ·
mlmcmahan42 said:
I have a chevy 400 block and crank with a set of 64cc vortec heads. im in the process of beginning my build. I am shooting for 450hp to 500hp. I would like to run it on high grade pump gas and i need to know the best pistons for this application.
A street 400SBC that runs on 92 octane pump gas needs a dished piston when using a 64cc cylinder head.

The dish can be a standard type dish, but preferably a "D"-shaped dish that will take more advantage of the quench areas of the Vortec heads.

Depending on the 'quench' (piston to head) distance, the dish will prolly end up in the 18cc to 22cc range.

An example is the KB pistons like shown. Again, depending on the clearances, the CR would be around 9.75- 9.8:1.
 
#3 ·
I have basically the same combination as you are considering. I doubt you can get to 450-500HP with those heads. Desktop Dyno estimates mine at close to 375 HP and 435 lb.ft torque.

I have a Comp extreme cam and a RPM performer, 750 Edelbrock carb. I also have 5.7 rods. The pistons in the previous post.

The engine is a torque monster and pulls very well through 5000RPM. After that it flattens out, I suspect the heads just won't flow any more.

I will be trying a Holley 750DP next year to see if it runs better, but I suspect the heads are the limiting factor.
 
#5 ·
ap72 said:
If you spend about an hour on each port cleaning it up those Vortecs can get you to your goal pretty easily. You can pick up 30hp just by doing a good job cleaning up your castings.
Although you are correct about picking up HP by a little port work. You still have small valves and small runners. These heads work very well to 5000RPM and maybe a bit further with the right combination. But I think it's hard to get 450-500HP when restricted to about 5000RPM. Put on a better set of heads and a cam to match and I think the 400 will do what you want. You better have a good bottom end also.

That's just my opinion. There are a lot of guys on this board that have used Vortecs that have flowed them and know exactly what they will do and won't do.

All I did to my Vortec 060 heads was opened the bowls up under the seat, contoured the valve guides, installed screw in studs, and guide seals. Mine do exactly what I thought they would do. In the 400 they make tons of low to mid range torque and it pretty much goes up to 5000 or a bit more. I have the rev limiter on 6000 and shift light on 5000.

In a 3600# S10 extended cab the first time out, it ran a 8.39 @80 in the 1/8. It was my first time on a drag strip in 30 years and my son's first time. We made every mistake except fall out of the truck.

Anyway good luck with your build.
 
#9 ·
if i were you i would use the same heads that you have and just do some work to them. bore the intake valves out to a 2.02. then port match your runners with a good intake. then do some porting and polishing to the intake and heads and you will be able to flow just as good as any out of the box race head from summit or jegs.
then for the pistons it all depends on what you want to do with it. if you want some thing that doesn't have to run on 94 octane just to run ok then i would go with a dished hperetuertic aluminum. but if you dont care about the gas prices then i would go with a flat top hyperetuertic aluminum. then your compression would go from 10.5:1 up to 11.5:1. the dished would run you at like 8.9:1 or so.
 
#13 ·
TroyBoy said:
My apologies. :drunk: I re-read all 7 pages of the original post,lol.Memories not what it used to be. :rolleyes:
Its perfectly fine, I'm still relatively young and my memory ain't what it used to be.

I really like the Vortec heads for street build where you want good throttle response and don't mind having a limit of about 475 (450 is more common though) as cast on a 350 or about 575 with a full port job and large valves on a 400. If you're serious about going beyond 500hp then other heads make more sense from both a performance and cost stand point.

They are a great head for the street but they are not a "cure all" as many people claim them to be, like everything else they have a specific application that they do well in and going outside of that is just going to be a exercise in futility.
 
#14 ·
Thanks for all the help guys. I really appreciate it. I have two more questions. Is it true the 400SBC was always a two bolt main? I was told they never made a four bolt block and the conversion kits offered today actually weaken the block? And also how extreme of a cam would be best? Im wanting it to be a bad street car and mild drag car.
 
#15 ·
ap72 said:
if you're looking for max hp I'd just run the 6" rods.
longer rods are much to do about nothing.

the only reason to use even 5.7 inch rods is for a wider piston selection.

a 6 inch rod just adds complexity and cost for no reason what so ever. I guess it feels good to say "I got 6 inch rods" but that is about it. But you can say that anyways since you one can see inside your engine.
 
#16 ·
mlmcmahan42 said:
Is it true the 400SBC was always a two bolt main? I was told they never made a four bolt block and the conversion kits offered today actually weaken the block?
Not true.

In fact, in the beginning, all GM made was 4-bolt 400's!

Later, they went to 2-bolt blocks, which when converted to a splayed cap 4-bolt configuration, is said to be stronger than a factory 4-bolt.

Some even go as far as to say they prefer a 2-bolt over a 4-bolt, splayed caps or not.
 
#17 ·
That, and on enignes where you have a relatively small runner volume (say 180cc's for ported 062 Vortecs) on a larger displacement (400ci) the longer rods will produce more power.

True, the difference will only be about 3-5% but on a 500hp engine that's around 20hp.

Joe Sherman tells me he sees a 30hp gain on a 383 by going to longer rods every time. "Everytime" Is a pretty convincing argument. Also, if you just plot it out short rods for low end and long rods for top end makes sense, circle track guys have known that for years.
 
#19 ·
rods

ap72 said:
That, and on enignes where you have a relatively small runner volume (say 180cc's for ported 062 Vortecs) on a larger displacement (400ci) the longer rods will produce more power.

True, the difference will only be about 3-5% but on a 500hp engine that's around 20hp.

Joe Sherman tells me he sees a 30hp gain on a 383 by going to longer rods every time. "Everytime" Is a pretty convincing argument. Also, if you just plot it out short rods for low end and long rods for top end makes sense, circle track guys have known that for years.

Did you ever stop to think that Joe Sherman might be wrong??? I can find you 10 other well know builders that will tell you long rods make no difference.

It sure would be nice to have people post first hand info about these type of arguments instead of what someone else told them.

Years ago I made an offer of $500 to anyone that can prove this long rod deal to me with A-B-A testing. I still have my $500..

I have built 383's with the 5.56,5.7 and 6.0 rods and as a trend they all made the same power. I never seen a 30 hp difference from any of them. I sure do wish I had the resources to do the A-B-A testing and put this old theory to rest. Or find someone that did the A-B-A testing and proved it to be true.

BTW I seen that statement by Joe and I think he only ever built one 383 with a 5.7 rod, lost 30 hp and decided that is was the rods fault and never built another one with 5.7 rods. What he didn't do was change that motor to a 6.0 rod engine to see if his 30 hp came back and why. There for it's a flawed theory.

A few years back I built what were almost twin 406 street engines. 1 was a 5.7 rod, 1 was a 6.0 rod. I don't have time to type the entire story, but I promise you if you would have been there during the teardown you would re-think 6.0" rods in a street engine.


Keith
 
#20 ·
454C10 said:
Did you actaully read that? There was no argument made that I could see, just that they felt it didn't matter. Njo solid reasoning, just taht there are differen lengths and they all connect a piston to a crank... Duh!

Plot the piston acceleration rates against the cam timing, and contemplate how a larger runner may affect the airflow in relation to the piston acceleration rates. Keep in mind what you're shooting for in relation to your maximum air velocity and when it might peak.

Its really not that hard to see if you just plot it all out.
 
#21 ·
rods

ap72 said:
Did you actaully read that? There was no argument made that I could see, just that they felt it didn't matter. Njo solid reasoning, just taht there are differen lengths and they all connect a piston to a crank... Duh!

Plot the piston acceleration rates against the cam timing, and contemplate how a larger runner may affect the airflow in relation to the piston acceleration rates. Keep in mind what you're shooting for in relation to your maximum air velocity and when it might peak.

Its really not that hard to see if you just plot it all out.

The maximum difference In piston location any place in the cycle between a 5.7 and 6.0 rod is like .023" Since you all ready calculated it out tell us where that difference is...

Also we don't race graphs, we race cars. Sometime what shows on a graph makes zero difference in HP.


Keith
 
#25 ·
ap72 said:
if you're looking for max hp I'd just run the 6" rods.
ap, you knew dam good and well what this post would result in. Are you taking on the mantle of a flamer now? :mwink:

I recall the late Smoky Yunick saying in Circle Track, IIRC, to build a RACE engine w/as long of a rod that was practical. That is as close to an actual endorsement as I've ever heard from an engine builder extraordinaire, one way or the other. And genius though he was, he's not infallible, either. Likely on the facing page was an ad from Carrillo! lol

That is, other than the same old deal, "short helps in the opposite way that a long rod does", i.e., if one helped the bottom end, the other favored the top end. That sort of thing, where there's a trade off either way. And I suspect that's the actual case, if there is any actual measurable difference AT ALL.
 
#26 ·
mlmcmahan42 said:
Thanks for all the help guys. I really appreciate it. I have two more questions. Is it true the 400SBC was always a two bolt main? I was told they never made a four bolt block and the conversion kits offered today actually weaken the block? And also how extreme of a cam would be best? Im wanting it to be a bad street car and mild drag car.
They did make both styles 2 and 4. From what i have read the 4 bolt version is weaker due to the 400 having larger main journals which makes the bolts closer to the pan rails. Splayed caps is always stronger than the conventional 4 bolt but you need to machine for the caps and then do a line bore which always costs $$$$$.

On the rod length subject. On paper it makes perfect sense. The pin is higher so the rod angle is less so less force exerted on the side walls, but have never seen a dyno show that it makes more power.