KJL

Usually when I look at dyno runs the HP value is always higher than than the TQ value. My numbers are opposite. What would cause that that to happen? Seeing Paul's dyno numbers has made me rethink my components. Back when I built this engine, there was not a lot of data or advice to be had from manufactures regarding large displacement small block applications. I basically selected all my components based on technical information available at the time and a program called Dyno 2000. I am sure there are better programs out there today.

Revi

It all depends on what you build, exhaust, etc. Most "stock" vehicles will have a higher TQ reading compared to HP.

My "stock" 70 L-46 engine dyno numbers - 341hp/387tq, chassis dyno numbers - 245hp/305tq.

cv67

x 2

KJL

Thanks for the input but was wondering if this is indicative of flow restriction somewhere in the system, heads, exhaust etc. I understand this is a fairly broad question but am hoping I might get some insight as to possible causes.

REELAV8R

Seems like a cam of smaller duration would limit your RPM potential.

Since HP is RPM dependent for a given displacement then If you limit the cam duration and thereby the effeciency at a higher RPM you also limit the HP for that engine.

Other flow restrictions could do the same.
I think anything that reduces the RPM and flow potential will also reduce the HP potential for a given set up.

Diesels have monstorous torque with relatively low HP numbers due to their RPM limitations.

StraubTech

What is your bore stroke combo?

What size header do you have?

We have no problem putting 1 7/8" headers on a BBC 427, but some think putting them on a 427 SBC is too big when in fact the SBC 427 4.125 x 4" stroke is a bigger engine due to piston speed than a BBC 427.

We think 245cc head is a large head for a SBC 427, when the general regularly put 320cc heads on its BBC 427.

KJL

4.125 x4.0"
AFR 210cc heads
1-3/4 headers through Flowmaster Supper 40's

How the heck do you bold on 1-7/8" headers?? I can barely get a wrench around my stud nuts.

diehrd

1 7/8 headers on a small block look stepped so you can get the bolts in

roscobbc

With the smaller bore diameter of small block engine - valve diameters will be smaller than same capacity big block engine. This will ultimately restrict high rev flow of the big capacity small block Theoretically and perhaps illogically to some will this mean that a big capacity small block will potentially have a higher TQ vs HP than same capacity big block at lower rpm's purely because the big block will be built to maximise flow benefits of larger valves, probably maximising TQ and HP at a far higher rpm than the equivalent capacity small block. So in capacity terms does this now mean that rather than 'less being more' - this now mean 'less is actually less'

BKbroiler

Back to the HP vs torque issue - HP is calculated from ft lb torque by the formula HP = (rpm X ft lb) / 5252. So if the ft lb torque peak occurs at less than 5,252 rpm, peak HP will be less than peak torque. So if the torque peak, say 400 ft lb, occurs at 5,000 rpm, the peak HP is (5,000 X 400) / 5252 = 381 HP. If the same torque peak occurs at 5,500 rpm, the HP is 419 HP. So, raising the peak torque rpm point has a big effect on peak HP.

scottyp99

Torque is a measured force. Horsepower is a number calculated using torque and rpm. So, the higher the rpm number is, the higher the horsepower number will be, at the same torque value. Have you ever noticed that torque and horsepower always cross-over at 5252 rpm? Torque is always a higher number than horsepower below 5252 rpm, and horsepower is always higher than torque above 5252 rpm. It's because of the math used to calculate horsepower.

Scott

StraubTech

Your head choice will limit the rpm of the engine. Your combo is more demanding on induction and exhaust then a BBC 427 due to piston speed. GM put a minimum of a 253cc head on its 427 factory engine.

The 210cc head and its MCSA will allow the engine to make peak somewhere below 6000 rpm. You can cam the engine to make more peak power but the powerband will narrow and it will be peaky.

These are not Small Blocks anymore. They are Morphed Mouses that have BBC demands. The supporting cast members like oil pan area, header size and intake MCSA is all needed.

I posted a year ago about short stroke big bore engines putting less demand on supporting cast member but able to still make very good useable power.

Your engine makes good power, BUT there is more left in it. Going to a customer 2" pan rail kickout pan in a SBC 4" stroke engine is 20HP. Putting a set of 1 7/8" headers on it will net 10 to 15HP, BUT all of this at what cost. A good fabbed pan and set of custom headers can run you $2K. Is it worth 30HP to spend $2K. For some yes, for some no.

REELAV8R

More duration on the cam will move that peak torque up the RPM range. More lift on the cam can also allow better breathing at higher RPM. Given the rest of your specs it sounds like the cam may be causing your issue. Could try retarding it a bit to get the peak torque to occur later. could also try higher lift RR if piston to valve clearance allows it.
what CFM carb is on it? Intake configuration good for unrestricted flow?
Just off the cuff guesses.

StraubTech

I'll disagree with you although this is what we have been led to believe for years. I've shortened duration and changed the valve events and made torque higher. By doing this you can control the velocity in the ports and maximize the time they are at peak before they stall out.

I've proven this time and time again with small camshafts going in engines where larger cams were taken out. I would never have made this statement 15 years ago as I believed what I was taught...put a bigger cam in it and it will make more power.

I know I am in very small group with this thinking but I have plenty of customers to back it up.

KJL

I am not sure what a custom 2" pan rail kickout pan is. I have a 7 quart capacity oil pan on there now and some windage baffle plates installed.

The AFR site recommends at least a 220 cc for 427's. Back when I purchased the 210cc heads, the 220's I think required shaft rockers etc. They no long do, however, 227 and up sizes require shaft mount rockers or offset rockers and offset stud girdles. I love the AFR's but those would not be cheap. The exhaust ports are also a tad higher. This caused an interference with the driver side floor pan. Unfortunately the Hooker collector flange is only inched away from the floor pan and attempting to transition the 2/5" around the floor plan seems to not be possible or certainly easily done. Perhaps other brands might drop lower. At this point I would consider an upgrade. I could probably get some decent money for the slightly used components.

StraubTech

A 2" kickout is at the pan rail where the pan bolts to the block. It would extend the entire side of the pan except for a starter notch to the passenger side of the car. This is the "shut down" area for windage. This added area is needed as when you increase stroke you increase windage in the crankcase. The general designed the OEM oil pan/crank case area for a max of 3.75" stroke.

You've got a stout engine. To make more power you are correct new head and bigger headers would be needed. Now if you wanted to make more power but higher up and keep the same heads and headers then a piston and crank swap to a shorter stroke would be the better choice. The shorter stroke put less demand on the parts, BUT will allow the engine to rpm higher thus giving you more calculated HP due to rpm.

StraubTech

https://www.google.com/search?q=Kick...ml%3B400%3B300

This is a kickout pan. Not a sump kickout but a pan rail kickout.

REELAV8R

That sounds believable to me and I can't disagree. I was looking for a solution that didn't involve a major change from what was in the car currently.
If that is what the op is looking to do then improving the effeciency of the flow to cylinders without increasing the duration of the cam is a win win type of scenario. I just don't know if he's looking to go that far to achieve that goal.

Based on the idea that filling the cylinder to greatest capacity for a given intake event is the solution to more power, one way to do that is to hold the valve open longer or open it more for better cylinder filling thereby delaying the the inevitable decline in cylinder filling as RPM increases.
Not opening the valve longer or more would require a port that can flow better and/or faster past the valve to improve cylinder filling.
So I agree. If that can be achieved without increasing the duration then by all means do it.
As you pointed out however there is a limit to the speed of the flow.

StraubTech

And I agree for what it would cost to gain 35 to 50RWHP for the OP, me personally, I would not spend the money. But hey they don't hook Uhaul trailers to hearses so part of me does say enjoy it. I didn't need the last Colt .45 I bought but I WANTED IT!!!

bluedawg

So the flow numbers of the op's 210's versus the flow of the heads on a stock gm 427". With out looking them up I'd say that the 210's actually flow more at less rpm. Now then I could be wrong. If I were building a 427" sbc I'd go with a 235cc afr but if I were building a bbc I'd go 265 to 295cc.