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400 Small Block Build And Dyno Test

56K views 341 replies 53 participants last post by  cage2592 
#1 ·
A forum member had me build a mild 406 for his 71 Chevelle, I thought I would post some pictures. I had a very nice thick 817 production block, bore and stroke 4.155 X 3.750, with a 7/16 6 inch rod and a Mahle piston, we ended up with 10.3 compression. The cam is hyd roller, 234/238 @ .050 .560/.530 lift on a 110. We used a AFR 195 head with modifications and a performer RPM air gap intake with a 1 inch open spacer. Carb is a AED 750 CFM. We plan on testing different distributers, locked and with a timing curve. Gas will be 91 octane from 7-11. Should be a interesting build. I should mention the valve job from AFR was a disaster.
 

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#137 ·
I doubt that there is any power difference going from a GM 400 block to a Dart SHP. "MY" reason for getting the Dart SHP was that there are fewer question marks about block reliability. It has been my experience, that I have met Mr Murphy too many times...:D
 
#139 ·
You may pay the same by the time all the correct work is done and end up with a good pc like I/Mark did but I would do a SHP next time around.
Ok I went with an Iron Eagle so...
Dart blocks do need finish work to them so I don't know how accurate that price list is.
 
#141 ·
HI
Reports on sonic testing cylinder bores, GM factory blocks vs Aftermarket shows a huge difference.
Dart shp also have slightly different cooling galleries vs factory . Combined withother upgrades and the resale comparison the Dart block is more desirable . Factory 400 are only worth money if standard bore and no cracks .
 
#150 ·
The biggest problem I see with OEM 400 blocks lifter bores are not even close to blue print. If you using a flat tappet cam its not a big issue but if your using a roller cam you are dealing with direct center lines, If lifter bore placement is off it throws of you seat timing events, compression between cylinders is off and you end up with an imbalance intake and exhaust events = less power. Most guys if I do a high end build with a OEM block I will spot face the lifter bores which is a very good indicator of where the lifter bores are placed from the factory. If they are off then I bush them to standard at 800.00 of just go to .904 is most common and a lot cheaper.

This is very common when spot facing the top of the lifter bores on old GM blocks.

 
#144 ·
 
#146 ·
What do you think the compression is on the 400 in the youtube video? I would also note the baro @ Westec shows 29.19 right on the money, Westec sits at 800 feet elevation. Notice what the single plane does to the TQ (Anyone?) Thats not for me!
 
#151 ·
HI
Vortec Pro
Your cam and heads 234/238 195cc head MCSA 1.93
Video cam and heads 242/248 215cc head MCSA most likely around 2.1sq inches

Would have thought the video/west tech engine would have made more topend BUT no surprise the bottom end suffered considering cam/cylinder head /manifold
 
#155 ·
Intended use should always guide the purchase.
Daily driver with vortec heads and a small cam, pump gas, chances are an OEM block will work fine - if you can find one.
If I built a 400 for a sub-10 second quarter mile race car, I wouldn't think of anything other than an aftermarket block.

Best plan is to tell your trusted engine builder what your engine will be used for and let his experience guide him.
 
#156 ·
I've never been afraid of the production 400 block, you can't use just any that come along. We ran one for many years in a 3100 pound 9.80 car 7500 RPM through the light for years, engine is still together and running, 15 year old, I've done several 10 sec drivers with production blocks. I had a kid that worked for me in California and he had a 70 Chevelle, we built a 511 blocked 400, 12.1 compression 406 with a B&M small blower, we put a Rons injector over the blower and injected it with alcohol, this produced 9.50s @ 140 in the stock chassis Chevelle @ 3500 pounds, it did eventually split a cylinder though, thats the only failure I've had.
I'm sure injecting alcohol didn't help the pressure in the cylinder.
 
#158 ·
Yeah, the 850 carb was just a Dyno carb, I knew it wouldn't be perfect because they weren't going to optimize the carb for my build, it was goinh to have EFI from day one.
So I always figured that one wasn't quite right.

I actually am going to pull the fast EFI for a Edelbrock pro flow 4.
Part of me wants to toss it back on the dyno with that setup to see what it does.
I basically paid for Dyno time to get it close to know what my actual numbers were.
I quoted reelsalty because I was wondering what your thoughts are on my volumetric efficiency on my Dyno graph are.
It could be better but with all the extra fuel its hard to come up with a good number. You have a very good piece just need a better fuel curve to achieve your goals. Less fuel more air flow. The extra fuel displaces the air going in as you can see a good HP 600 or HP 650 would have been a good carb for your build
 
#162 ·
I got a block just sitting in my garage a 817 picked it up last yr for a friend and he ended up buying a crate 406 based off a 350 block bored and with a 3.875 crank, similar to the one David Vizzerd talks about in his book. So now I have a stock bore 400 block and no real use for it. thought about putting it back on craigslist but with all that is going on right now it is fine sitting in my heated garage.

I thought about building it with a scat 3.875 crank and scat I beam procomp rods and forged pistons, but not in my budget and no car to put it in.
 
#164 ·
Bigger bore shorter stroke;)
 
#168 ·
hi
Dyno sheets that donot have a FULLY filled out spec sheet are useless . Many have a secret camshaft LOL LOL

Basically these days because there are so many options eg heads cam type manifolds etc it is difficult to compare different cubic inch motors .

Most street motors with boosted brakes like at least 10--12 in vac
Most street cars have appropriate gearing no more than about 2800--3000rpm at 60mph .Approx 3.4---3.7 rear gear depending upon tire diameter.

400cuin
personal preference for cam shaft 230+ is common
borderline vac seems tobe 240+
Heads seem to be minimum 195cc high flow for mid range
Heads canbe upto 220cc with a little more cam /stall /rear gear
dual plain is preferred but a single plain is acceptable with only slightly more rear gear and stall
single plain gets slightly more topend 200-300 rpm but sacrifices below 4500rpm

[400cuin]
[ 400cuin 4.3 rear gear 4500 stall 227 heads 12:1 CR ][not mild ]
 
#169 ·
hi
Dyno sheets that donot have a FULLY filled out spec sheet are useless . Many have a secret camshaft LOL LOL

Basically these days because there are so many options eg heads cam type manifolds etc it is difficult to compare different cubic inch motors .

Most street motors with boosted brakes like at least 10--12 in vac
Most street cars have appropriate gearing no more than about 2800--3000rpm at 60mph .Approx 3.4---3.7 rear gear depending upon tire diameter.

400cuin
personal preference for cam shaft 230+ is common
borderline vac seems tobe 240+
Heads seem to be minimum 195cc high flow for mid range
Heads canbe upto 220cc with a little more cam /stall /rear gear
dual plain is preferred but a single plain is acceptable with only slightly more rear gear and stall
single plain gets slightly more topend 200-300 rpm but sacrifices below 4500rpm
Generalities like this are just that....generalities. It's all about getting the COMBINATION right for your build and its desired use. You still have to do your research and homework and the devil is often in the details.

And again, just b/c something is posted on YouTube, doesn't make it fact or gospel or accepted science. (I spend a LOT of time on YouTube, FWIW. You have to learn to separate fact from fiction and total BS on just about every "genre" of video that you watch.)

Like many things in life, consider the source. Almost everything ever written or published has a bias to it. You have to understand what that bias is.
 
#170 ·
Hi
The 2 videos are very different engines built by the same person dyno tested at the same business .
I accept there canbe differences between engine builders and dyno read outs. I purchase parts of the engine builder so I have no reason to disbelieve. And yes I am wise enough not to chase other peoples dyno numbers LOL LOL . Dyno sheets are good for bench racing and a rough comparison and as u say every bodies build/ end use is a little different .

But there are common threads between all the 400 cuin dyno results I have read .
 
#172 ·
HI
Vortec pro
Main issue is comparing same engine on 2 different dyno`s ..Seems to be the best comparison is on the same test equipment . Besides build differences as u have said the dyno setup is able to be influenced
.
Common points I regard as important is 1/at what rpm peaks occur 2/ general shape of curves [start of curve 2500-3000rpm and past peak hp and TQ ] 3/ vacuum
 
#173 · (Edited)
Super Flow came to my shop checked the dyno calibration, witnessed the test of one of my big blocks, the engine was pulled off the dyno put in a box and shipped to Westec, Super Flow sent their people to Westec to ck their calibration, calibration was made, my engine was unpacked and put on their dyno. Both SF 901 dyno's. 1 HP difference between the two dyno's going from 6200 feet to 800 feet elevation on a 670 HP engine. 669 HP @ Vortecpro, 700 HP @ Westec, the over lays of the graphs were exact! Don't be BSed by people telling you we don't race dyno's.....................you have to know where the numbers come from.......

https://www.chevelles.com/forums/13-performance/237951-vortecpro-505-dynoed-westech-today-9.html

On of TC all time greatest threads!
 
#174 ·
Damn that was a cast of thousands, and a lot of the new people here have never heard of them.
 
#175 ·
We have no idea how accurate White's dyno is, or even to what standard to judge their engines.

In what air was the dyno conducted? What type of test?

Compare the data provided in the screenshots.

Compare the power curves.

Compare the BSFC, Fuel A looks out of whack per power...(even if you combine A and B from Mark's engine).
 

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