The "Sneaky 500 HP" motor

Guys,

I had the opportunity to put together a motor for John Looney's resto project here recently. This is a full frame off deal, that John plans to drive alot. He is going for a "day 2" type of look, with a cast iron intake, Q-jet and headers.

He wanted lots of power, but with good driveablity. So I did a bit of a "research project" on it.


The point of this build was not a driveablity be damned all out HP engine. But rather, something that would easily pass as stock, with a small cam and headers. What would be a 425-450 HP motor with iron heads, and good driveablity.. Built many of those.. Also built many alum head 550-600 HP wilder street combo's.. but that is not what we were after here.


So no big manifolds, carb spacers, massive Holley HP carbs were in the cards for this one..

We were after that "does it have a cam in it?" sound, rather than that "holy crap, what is that" sound that the typical 500 HP dual plane motor has.. and after the easy to live with manners of a stock type engine.


To build it, I bought a set of TA SE STG 1 castings from Mike (TA Perf), and I treated them to my typical bowl and port work, along with the standard size TA STG 1 stainless valves- They flow 313/225 at .500.

Then I did some heavy port work to the iron 70 intake, cut the entire top out of it, and worked the limitation areas of the ports, along with a port match to the TA heads. This mod in the past has been proven to be worth about 20 HP in other stock appearing builds.


This motor, as a development type project, was actually built twice. The first shortblock used TA/SRP pistons, stock rods, and I selected the TA 288-92H cam. That's a 231/234@.050 duration stick. Used it many times before, and it's known to have a bit of valve train noise, which will in fact vary from cam to cam. This particular one was a touch noisy. This cam has a 110* LSA, and was installed at 106* ILC.

That 464 shortblock yielded 10.8-1 compression, with his 67cc head chambers, and a .040 gasket. Dynamic compression was figured at 8.22, which is right at the top of what 93 octane will fuel. Certainly detonation could occur, with too aggressive an advance curve, or a hot engine/air inlet temps.. And John is in North Carolina, so hot summers are in the cards.

This is what I would consider a max cylinder pressure engine for street use.

Here are the results of that first engine..



I have used this cam many times before, and with a dual plane, it idles at about 800-850 rpm, with 12-13" of vacuum. You definitely know it has a performance cam in it.

That was all fine and good, but I though I could do better. Make more HP, but also have a "tamer sounding" engine.

I also thought that the intake was the limiting factor, so keeping the intake valve open longer would be the key to more power. But to do that, I would have to widen the lobe center on the cam, to keep the idle quality.

So I took the heads and intake off that engine, and built him a new shortblock.. I decided to fly in the face of "conventional wisdom" and build a low cylinder pressure engine, but with enough duration to allow the engine to breath.

So I put my new 470 shortblock combo together, and chose a TA 290H cam, but had it spread out on a 118* lobe center. Static compression worked out to 10.25-1, and dynamic was all the way down to 6.5-1.

6.5-1 ??

The disciples of dynamic compression would lament that this combo wouldn't make any power. But the results were interesting. The superflow doesn't know it's not "supposed to" work.

Keep in mind the objective of this buildup... make a car perform with a 500 HP engine, but make it look and sound for all the world to see it as just a stocker with headers.. I would agree if I pumped up the static compression, I could make more power, but this was the first of this type of engine, so we kept it on the conservative side. And I beleived I could achieve my 500 HP goal.

Here's the results..



Let's study the sheets a little bit..

We trimmed the peak torque number a bit, but the bigger cam hangs onto the torque longer.. so it adds about 20 numbers to the HP figures up top. And also extends the useable HP range of the engine, from 5300 to 5600 rpm. Averages are very similar, across the power range.

The second motor is simply a better air pump, due to the bigger cam. VE number is up with the second engine, even thought it's a bigger cube motor, with the exact same heads and intake.

BMPE number is down, due to the lower static and dynamic compression ratios. Easier fuel requirments..

And this is a direct study of the fact that blocks can vary the oil pressure. This is exactly the same timing cover/oil pump, and the bearing clearances are slightly bigger on the second motor than the first.. Same oil, same oil temp, same cam bearings, same mods.. Engine block cam bearing and lifter bore sizing, and the accompanying clearances will vary oil pressure.. compare the two sheets.. Idle oil pressure is 5-8 psi higher in this engine.

Now here's the kicker.. I have spent the last couple days fine tuning the carb idle circuits and playing with timing curves. Results of that work were fantastic.. This thing idles at 700 rpm with 15" of vacuum, and sounds for all the world like a stock STG 1 motor. Hardley any cam lope, unless you slow it down to about 600 rpm. Then it sounds like it may have a 212 cam in it.. It's a completely different sounding engine than the first version. No fear of detonation, and no where near the fuel requirements.

And the valvetrain is dead silent, even under the stock STG 1 valve covers. This is due to the mild acceleration rates of the cam lobes.

Trust me.. this car is going to sneak up on a lot of folks.. no one that pulls up next to it, will have any idea it's going to scream as hard as it will.

And you will really raise some eyebrows when you drive the car up to the pumps, and put 87 octane gas in it! John will have to report back to us, but I truely beleive it will run on regular unleaded.

Cranking compression on this engine is 90 psi...

Yes, you read that right.. it spins over on the starter like it doesn't have any spark plugs in it..

Here's the buildsheet on this one

TSP 470 Shortblock:

TSP/Diamond Racing Forged pistons- 25CC conical dish, .990 pin, offset pins
Eagle H Beam BBC rods- 6.8" long
Offset ground Stock crank- rod throws widened to accomidate the BBC rods.
Stock timing cover with mods
Billet timing chain
TA Dual groove cam bearings
TA 290H cam- 238/238@.050- Actual was 239/238- Advertised- 297/297@.006(as measured)- cam ground on a 118 LSA
Cam installed at 118* ILC

The bolt ons:

TA/ARP complete bolt kit
TA/TSP STG 1 SE heads (313/225@.500)
Stock 70 Intake manifold- Fully ported and plenum worked
800 cfm q-jet (73 jets with Adj APT Primary rod setup, H hanger AU sec rods
1 7/8 Headers
Repro STG 1 valve covers
TSP mag converted Stock distrib, Taylor wires with stock routing
STG 1 fuel pump

Looks stock to me.. (ignore the open element breather and elect water pump, they are only on there for my test stand)



My next incarnation of this engine will be a true stock appearing engine- Fully ported iron heads, but built with higher static compression, and with a 1/4 inch stroker (494ci) and a bigger cam. We are going to sneak back up toward that "optimum" 8-1 dynamic compression figure, and see if we can duplicate this motors numbers, but with iron heads.. and iron exhaust manifolds!

I have a third one in the hopper, a 464 with 280cfm iron heads and dual quads, that I will be applying the same philsophy to.

They are in process now, stay tuned..

 

I know where my next engine build is going.

 

all i can say is, WOW YOU PERFORM MAGIC , going against all theory but you made it happen truly amazing! also are you selling your piston and rod combos ? if so how much? jamie_my

 

roughly what would a engine like this run, I really hope it won't break the pockets, because this is exactly what I'm looking for the 72 limited! Can I build this myself, or would you recommend a shop doing this. thanks much great job

 

Call TA and see if he has put this stuff in stock yet.. he was supposed to..

If he hasn't..

I can sell the piston and rod combo.. pistons are $759 and the rods are $429
I will caution that the key to this combo is the crank grind, make sure you have a grinder who is up to the task.. My cranks are offset ground, and indexed to insure accurate strokes and piston positions. And of course magg'ed it insure there are no cracks. The hard part of this deal is widening the rod throws correctly.

I can sell the crank also, with a fresh grind on the mains and the correct work to the rod journals.. cost is $349 exchange.. if you want to buy it outright, I have to get $100 for the crank core.

 

Shortblock is $5400 assembled
heads are $2795 assembled, ready to run
Intake porting is $400
Q-jet perf rebuild/calibration with your core is $575 (body colored and plated)
Dist is $195
Timing cover, from your good core, is $195

With assembly, misc small parts, and dyno, your looking at 10-11K for something like this.

Can you build it for less? .. sure, if you have access to a competent machine shop, as well as the skills and tools to put it all together, port the intake ect..

JW

 

good pricing, being in canada i would pay for the crank core and have you do the crank you know what has to be done to it,and shipping would eat up the core cost. is the offset grinding how your get 470 ci or are you boring more over the typical 462? sorry if that is a dumb question jamie_my

 

That's a great combo! I was thinking ahead to when I build another engine for my '70, and thought a "sneaky" stockish engine would be the way to go.

This is an engine that would have the guys at the local track scratching their heads!

 

No, not a dumb question..

The bore is 4.350,(+.038) pistons use the perfered 1/16 1/16 3/16 ring package.

Crank is offset ground to 3.95 stroke. This is the most advantageous way to fit the 2.200 rod bearing diameter these rod have.

JW

 

Ya, I am excited about it.. not because it makes some ungodly power numbers, but because it makes 500 Hp and you would swear this thing has a stock stg 1 cam in it. It's just such a mild sounding deal.. I love it.

Also very happy that my new pistons are really quiet on cold startup.. you guys with Wiseco pistons can understand where I am coming from on that..

 

"BMPE number is down" Jim what does bmpe mean and also "VE" what does that mean. dumb question but i wanted to know.

Cody

 

Brake Mean Effective Pressure (BMEP)...The definition of BMEP is: the average (mean) pressure which, if imposed on the pistons uniformly from the top to the bottom of each power stroke, would produce the measured (brake) power output. If you work through the arithmetic, you find that BMEP is simply a multiple of the torque per cubic inch of displacement. A torque output of 1.0 lb-ft per cubic inch of displacement equals a BMEP of 150.8 psi. in a four-stroke engine . For a long-life, naturally-aspirated, gasoline-fueled, two-valve-per-cylinder, pushrod engine, a BMEP over 200 PSI is difficult to achieve and requires a serious development program and very specialized components.

If you know the torque and displacement of an engine, a very practical way to calculate BMEP is:
BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci).


Volumetric Efficiency (VE)....In a four-stroke naturally aspirated engine, the theoretical maximum volume of air that each cylinder can ingest during the intake cycle is equal to the swept volume of that cylinder (0.7854 x bore x bore x stroke).

Since each cylinder has one intake stroke every two revolutions of the crankshaft, then the theoretical maximum volume of air it can ingest during each rotation of the crankshaft is equal to one-half its displacement. The actual amount of air the engine ingests compared to the theoretical maximum is called volumetric efficiency (VE). An engine operating at 100% VE is ingesting its total displacement every two crankshaft revolutions.

There is a remarkably close relationship between an engine's VE curve and its torque curve. For contemporary naturally-aspirated, two-valve-per-cylinder, pushrod engine technology, a VE over 95% is excellent, and 100% is achievable, but quite difficult. Generally, the RPM at peak VE coincides with the RPM at the torque peak. And generally, automotive engines rarely exceed 90% VE. For a known engine displacement and RPM, you can calculate the engine airflow at 100% VE, in sea-level-standard-day cubic feet per minute (scfm) as follows:

100% VE AIRFLOW (scfm) = DISPLACEMENT (ci) x RPM / 3456

 

Holy crap Cole. All that at midnight. You must be out on the road and bored!

 

VERY NICE Jim...looking forward to hearing more about the 494.

 

My question is why install the cam at 118 deg ICL? Why not advance it 4-6 deg? Sure you might loose a tad bit torque due to letting the exhaust out earlier and you may see something from putting more exh gas into the int during overlap at low speed, but I would guess you would more than make that up with the higher dynamic CR.

 

Scott,

That is something I struggled with.. Yes, your right, you can pick up DC by advancing the cam, but all my dyno sim programs showed a dramatic drop off in TQ and HP by doing that. The issue is there is only 2* of at .050 overlap.. so you start closing the exhaust valve really early by advancing the cam. Right now, the @.050 valve intake open/exhaust close events are happening right around TDC, and bear the greatest resemblance to a "standard" type configuration. As installed, the Intake open is at 1* BTDC, the Ex close is at 1* ATDC.

In example.. this cam, on a 112LC, installed at 108, will open the intake at 11* BTDC, and close the exhaust at 3*ATDC, for a total of 14* of @.050 overlap. This is typical of performance camshafts- open the intake before TDC, and close the exhaust ATDC.

I believe what would happen, if I advanced the cam, say 6*, and closed the exhaust valve earlier, would be to kill all the scavenging effect of the headers.

Quite frankly, had this motor not made the number, I would have moved the cam timing on the dyno. I may play with this in the future, by my sims have always shown the correct trend in the past, in regard to cam timing.

JW

 

Sleeper motors are the most fun hot rodding has to offer in my opinion.

I'm running a much lower HP 462" sleeper type motor in my 32 roadster.

9.0/1 CR and runs on 87 octane summer or winter, easy to start, 600 rpm idle.

A reasonable guesstimation from some of the old KB information puts it at about 400 HP.

I realize it takes a dyno to tell the tale, but I'm happy with it the way it is.

Made a few SBC powered coupes and roadsters unhappy though....

 

Reading this during lunch, and i just about choked!

I had an engine with that psi in 1 cyl, and i figured it was time for it to be overhauled.

Black magic for sure .
'
Keep the the good work Jim.

 

Sweet! Truly going Fast with Class!

- Bill

 

Those are great #s Jim, here is a pic of a SA 494 I did 3+ years ago. It was built so the owner could drive it on the street but now he has a bought 72 GS that will be used for SA and braket only so it is getting a few up-grades. It has GRP rods, JE pistions, ported intake and Ex manifolds etc. The heads have way to much time in them but work well. The big part is keeping the q-jet full of fuel on these SA engines. Here is the flow#s from the 494 iron stg1 heads.
.100) 74
.200)158
.300)233
.400)280
.500)292
.600)292
PS. If the carb for the X is still there can you suppy 2 of those PC valve cover decals in the box and add it to the bill? Thank you for the thread, it is great reading.........Chris