GTO1

For what it's worth if you only are planning to hit 6000 rpm and want to max out on torque, here is what my 427 setup has been since I upgraded my short block .

I've been using AFR 205s that Tony Mamo ported for me along with a 90 mm Fast and NW TB. Those heads flow as follows which, except for .600, has better numbers than both versions of the AFR 210 untouched heads:

Lift Intake Exhaust
.200 154 132
.300 216 190
.400 268 222
.500 296 238
.550 305 ---
.600 302 247

... and definitely more torque with these smaller heads.


The attached dyno graph shows 490.16 rwhp 479.01 and as my signature shows I've run 10.954 @ 123.58 NA with this combination.

To the OP...so if my results, which may or may not be typical, is in the ballpark of the results that you would see as acceptable then don't fear going to a smaller cc head if your plans stop here.

Now on the other hand, if you are going to want to achieve more in the long term then go big now and call it a day. In my case I've just gone back to Mamo and am currently installing his ported MMS 265 LS7 heads along with a 103mm MSD Atomic intake and 105mm Holly EFI TB. The flow rate of these heads is a major jump from my previous ones:

Lift Intake Exhaust
.200 160 123
.300 232 181
.400 300 226
.500 351 247
.600 387 260
.650 396 265
.700 404 268
.750 410 271

Neil B

I'm not sure what Tony Mamo does to those heads, but any kind of real port work typically adds 10-20cc to the runner volume. So your 205 heads probably measure closer to 215-220cc after Tony's magic. I wouldn't be scared to port a bigger port on a 427. Those are big block-sized cubic inches.

gkull

His heads were sold as 195 cc and porting brought up the cc to 205. they have nice CFM for lift numbers......

Tony has not worked at AFR for years.

This is my opinion on porting. It might cost you up to $1000 these days. You are money ahead to just buy modern CNC ported heads of the next cc size up and or also just run higher lifting cams. I'm pro high lifts.

Neil B

195cc ported up to 205cc makes sense. Thanks. Years ago, I bought a set of Canfield 195's that ended up at 218cc after CNC porting. I agree on just buying the slightly larger CNC'd heads if they are available for your application. Even with the CNC heads, you can usually run your finger along the short side radius and feel enough of a ridge for a little hand-dressing.

gkull

If I was building a mild 427 and using dished pistons these are the heads I would buy because they don't need the super shaft rocker setups and they have good flow. You just need to figure out the total compression with your setup.

https://www.summitracing.com/parts/afr-1103/overview/

cv67

neil look up mamomotorsports....hes is doing up some of his own stuff that sets the bar higher than the comp ports...real nice stuff.

MotorHead

You are building a 427ci small block with a 4 in. crank. Not sure if anything has changed but when I built my 427ci the World Products Motown block was the only non exotic block that would handle a 4 in. crank with no clearancing.

The block comes with all five mains being 4 bolt with the inner three splayed. I paid extra to have the billet steel caps. It is pretty much bullet roof.



I went with AFR 227ci heads port matched to a Vic Jr intake, I would not use conventional valve train as the 60/40 split will put the intake rocker on a bad angle. It can be done but is no recommended.



Next mall base circle cam will need to be used along with "stroker" rods which are clearanced on the shoulder closest to the cam. You can see this in the rod below, the bottom shoulder has been milled down.





Another pic of the T&D Shaft rockers showing the intake valve rocker is moved over, in my opinion a conventional rocker would be on a unacceptable angle.



So in closing, the more power you make then both HP and Torque go up making the ol wive's tale of increasing torque and reducing HP with smaller heads not hold water. Take a look at the Engine Masters video on Ytube which they did a test on this.

My CR is 10.6 to one with a 248/254 dur. cam with .670 lift allowing the engine to make over 600HP. And yeas I can tool around town at 2000RPM and the engine runs smooth and does not overheat.

Hope that answers some of your questions.

drwet

I contacted Dart using the 'Contact Us' link on their website. Much to my surprise they got right back to me. (I am getting used to companies ignoring my enquiries. Nothing from Comp Cams or RHS.) Dart tells me they have redesigned the coolant passages on their SHP block so that it is not necessary to drill the steam holes in the head. Thought I would pass this along.

cooper9811

Yep, same thing I was told...

pauldana

https://www.corvetteforum.com/forums...ort-block.html


NEW ENGINE SPECS 650HP

My 427 build from the bottom up:
Dart SHP block
Milodon 7qt road race oil pan
Milodon diamond stripper windage tray
Calis Dragon Slayer Crank
Skat H-beam's
Probe racing pistons 11:1 forged
AFR competition ported 220 heads w/titanium keepers and locks
AFR plastic single plain titan intake manifold
Sportsman XFI 2.0 fuel injection system by FAST..
MSD full ignition with crank trigger
Kooks 1 7/8 ceramic headers
3" duel mandrel bend exhaust with X-pipe custom made by D&C design... my son Danny:-)
Borla mufflers
march pulley system
22 lb steel billet flywheel
McCloud twin disk clutch
Fluidamper 6 1/4" HB
Custom Cold Air Intake by me:-) D&C design
Custom cam by Strub 611/592 244/248 109 Sep
Morel reto hydraulic lifters
Crain gold race RR's
TKO 600 transmission
SUPER 10 rear end built by trackdog2
18" custom built 2 piece centerline wheels
Willwood big brake system all around
hydroboost braking
rac-n-pinion steering
550 springs up front, 360 composite in back with all Bilstin sport shocks and front and rear sway bars
3" HD Dewitts radiator
DELTA PAG brushless fan w/D&C custom fan shroud
Dewitts 3" heavy duty radiator

bmans vette

Hi,
Nice list.
Debating the cost of a 406 vs a 427 build and was wondering if you could share how much just the 427 engine build was?

Txs
Bman (Dennis)

pauldana

over $12,000

fule injection was over $2,500
Calis crank was over $2,500


First Dyno after being build was about 525hp at rear wheels.. 200 miles on engine
Second Dyno run after new EFI and brake in 550hp at rear wheels

And i have power from 2000rpm to near 7000...

gkull

Paul has some of the highest level of dyno verified powe levels I never did dyno times I live at 4700 feet and have less access

I was also not ever worried about the power level

I went for 11.7 CR and big cam and heads the cost is also up there if I didn't have all these parts for a n/a motor a smarter person would build a dart block with a super charged 400 or 415

Paul said $12000 for the motor. What is behind it costs about the same. When you get up over 600 hp you have to have super clutches and transmissions and rear ends. Don't forget the roll cage and safety equipment with monster tires

bmans vette

Thanks George.

I have a beefed up T56 and a Super 10 4.11 diff to hook it up with.
Complete 1350 rear axle setup, 3 1/2" half shafts, offset TAs, & safety loops.
Debating whether to go TKO600 instead.
No roll cage yet.

Txs again
Dennis

pauldana

The TKO 600, which I run, is rated for 600tq, but new seems to handle as much as 1000tq,,, but over time as the steel is hit, it will not do 1000hp, and will let loose with more that 700tq hitting it all the time..
This is my understanding in my research. This of course can me mitigated somewhat by tires that slip/spin

bmans vette

Txs Paul.....

Now if money was no object...right?
That always tends to be the final determining factor.

MotorHead

Pretty much everything that was wrong with the OEM 400ci block was a dressed with the Motown block.

For example here you can see the bulges on the outside of every cylinder to increase coolant flow so the block runs relatively cool. No need to drill steam holes.

bmans vette

How does a Dart SHP 400 match up to a Motown?
Txs
Dennis

cooper9811

I cant give you a complete comparision as I have no experience with the Motown, but here are the SHP block features:

* Priority main oiling system
* Siamese cylinder bores with extra-thick walls
* Extra thick decks to ensure reliable head gasket seal
* Blind head bolt holes (don't go through water jacket)
* Scalloped water jacket walls for improved flow around cylinders for better cooling
* Clearance for 3.75 in. stroke with steel rods
* Splayed outer bolts on middle main bearing caps
* Provisions for OE stock roller lifters and cams
* All OE bolt holes starter, clutch ball, etc.
* Uses 1981 to 1985 stock style oil pan and passenger side dipstick
* Uses stocked stamped steel timing cover

From my own mild build,I can also add:

* Minor clearancing was needed for a 4" stroke
* I am able to use standard base circle cam with a 4" stroke (I have to call out that I am using forged crank and H-beam rods from Ohio Crankshaft; these are probably designed to allow standard cam, so not sure if that still holds true for all other crank/rods on the market).

Hope that helps.

bmans vette

Txs Jim.
I can read specs from the mfg but real experience from a user of one helps a lot.
Dennis