690 horsepower pump gas "true" street engine
 

I came across a post on Facebook in regards to a gentelman inquiring about building a 690 horsepower, 93 octane pump gas, street engine. Using a factory block around 460 CID. This engine needs to have street friendly characteristics so the wife, mother-in-law and girlfriend ;) can run it to the grocery store if needed. Not getting much worthwhile input over there (accept for a guy who explained how to do it, but his own personal attempt came up around one hundred horsepower shy) and get some input, ideas and details from anyone that has done it, come close or thought about it.

I don’t have time for science fiction....

I do not think any stock block engine that makes 700 HP could use a converter than is street friendly.
Maybe if you had the perfect high end set of heads, intake and use electronic fuel injection where you could get it done with a small enough cam ?
Or put a turbo on a RAIV cam, done !

It needs to be naturally aspirated. The converter could be worked around by using a switch pitch.

you cannot do this with a 535, much less a stock block.

i am no engine builder, definitely no expert,but i think 460 cubes is big enough.heads is where i would think would be the deciding factor. its definitely a tall order. probably take 12.1 comp, a cam with right spec. maybe 390 cfm port flow? i only jumped in because i want to learn.

you would need a cam so big you would have very little idle vacuum. forced induction is the only way to accomplish this.

either that or you have to really stretch the definition of "street friendly."

if i really wanted to pull this off, first i would go hydroboost to get rid of the power brake issue. then a wide ratio six speed manual so i have a really steep first gear. big hydraulic roller with light retainers and beehive springs. maybe wide port edelbrocks and a victor? and a chassis that allows headers with big primaries. get the newer chambers to help with octane requirements. and a 4781 with a manual choke. all the cool kids have manual chokes!

4032 pistons instead of 2618, too!

A 535 could do it with ease, no replacement for displacement. But a 461 would be tricky i think, it can make the power but just how street friendly will it be.

and a light car would make the lack of low end less bothersome.

that's about 1.3 hp per CID, or about the same as a 600 hp 461. i don't think most wives and girlfriends would think a 600 hp 461 has good street characteristics!

Our 461 makes 610hp and is very street friendly. Power brakes, tighet'ish converter and 3.42 gears. Really is very street friendly

what heads you running?what compression?

I have seen aftermarket blocks achieve 675 to 700 hp/tq and be street friendly get in and drive engines with EFI. Now running one myself. But man would be something to get a stock block to those numbers. Like the OP said, to 600hp it is doable, but to 700 would take some real voodoo magic I feel.

Get an MR1 or IA2 block if wanting a 700 streetable horse and torque build that will last.

The turbo stuff was just a joke.

I think it would be tough. But, if someone found the perfect 455 block and bored it over .100 like Ken at PPR used to do, stroked to 4.25, 12-1 with perfect cam. Lots of lift and around .260-265 @ .050 , 2.25 valve 400cfm High Ports that have been wide ported or the like E head, have Marcella make a tuned port EFI intake with all the sensors and bells and whistles, custom 2" headers with high end merge collectors, . thin metric rings with V pump, trick oil pan with big kick out and scrapper..... maybe they could do it.
Put the biggest cam you can that is street-able. Might take a few tries with cam.
Might need aluminum rods pushing the CR that high.

This formula has been scoffed at, but here it is anyway for entertainment value...

Air Flow Research developed a formula based on air flow. It predicts a normally aspirated engine's horsepower potential based on intake-system airflow. But note, and important, according to AFR they state it is based on the net cfm airflow delivered at the valve thru the carb, intake manifold and cylinder head. Not the cylinder head cfm flow itself. The formula.....

Horsepower = 0.25714 x cfm at 28" x number of cylinders

There are some caveats involved. Actually reaching the predicted power level requires the engine to have the right compression, the right cam, a tuned exhaust, and a nonrestrictive carb and intake manifold. The combined lift generated by the cam lobe and rocker arm should equal the observed lift on the flow bench needed to achieve the desired intake port flow, plus a good exhaust port flow. Etc, etc.

335 cfm equals 689 hp.

Again, keep in mind that 335 is air flow delivered to the valve.


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Mine makes close to 600hp and drives smooth, you don't know the power is there until you step on it.
A larger cu inch engine could achieve the goal.

Steve,
That is a good middle of the road estimate. Did AFR ever say what CR they based that on? I would think a true street engine would need more like 360 + CFM. Just like xxx MPH @ zzzz weight will take qqq HP. The answer is not the same for a Firebird and a mini van. :D

Stan