Thinking about a sleeper...
 

I'm pondering building a stock-looking engine that makes good power but starts and drives well. Assuming a good 455 short block, what would be a reasonably power goal with iron heads, intake and stock manifolds? I have a good running Q Jet and won a 1972 intake on eBay for $9.99. I'm thinking ported 6X-8 heads, ported intake and whatever cam ends up being correct. I'm also thinking the manifolds would hold me back?

I built one for a '68 400 GTO. Took the stock YS and put a Butler forged rotating assembly in it with 15 cc dish pistons to make a 10.0 CR 461 with the stock iron heads that I street ported and used the OF HR cam with RA exhaust manifolds and stock intake/carb. Open the hood and it looks factory stock but works well.

Any power guesstimates? I assume a factory intake and Q Jet should support 450ish? No idea about exhaust manifolds or ram air castings.

I think it makes 480-490 Hp based on dyno testing by SD on a similar motor, depends on the head flow. Car has a TH400 and a JH Conti converter with 3.55 gears.

That's a good read. I wish they'd tested the 455 with logs. I'm curious as to what level HP starts dropping off with logs.

After reading about Jim Hand's 455 with 400 big valve heads, I pretty much copied what he had done back in the late 1990s.

http://www.pontiacstreetperformance....ld455jh99.html

I have 1971 #96 heads with Ram Air III manifolds and a Holley 750, but everything else is about the same. My car does what you said...makes good power, starts and drives well (on 93 pump gas).

May as well go with a 4.5" stroker, for more low end torque, while maintaining a smooth "sleeper" idle. With the correct, modified parts, including a roller cam, one of these should make 500hp + and maybe 600ft lbs of torque ?--and do it all below 5000rpm.

SMI can build you a monster Q-jet, to match the power level. They advertise 'em up to 900cfm.

Can squeeze a little more out of it by going with more compression. But, to do that, you'll need more octane, either thru a mixture of race gas, Torco octane booster, or E-85.

https://www.amazon.com/Torco-Acceler.../dp/B004ZO3VN0

But, with this kind of torque, you'll need to beef up everything behind the engine.

The guys who build the stock appearing, small street tire, type cars, have all sorts of tricks you can use. They do all kinds of porting to stock logs, and everything else that can be hogged out to increase performance. They also know all the tricks to hooking the power to the ground, with hard narrow street tires. The ET's they are running are unbelievable.

http://www.fastraces.org/

https://www.facebook.com/FASTRacingSeries/

So, if you can tap into some of the tricks they use, you can more easily reach your goals. There are probably some guys who post on this site who can share some of these tricks with you. :)

You could have a stock appearing engine..with a set of headers...nobody would care about the headers becuz everybody has them.With our engines you really can't see them...I'd say depending on budget..500 hp is easy

To me a 'sleeper' is more about how the car looks and sounds.

Anything you want can be hiding under the hood if the car looks somewhat sedate and has a nicely-muffled exhaust.

If you're out doing a little stoplight to stoplight fun, who sees under the hood anyway?

This was a fun little sleeper, 455 with Tri-Power, essentially stock but still had enough power to surprise a lot of cars that challenged it.

http://i137.photobucket.com/albums/q...4/DSC00839.jpg

I found a local person who was in the middle of a Firebird project who will consider selling just the engine parts for a reasonable price. I have concerns, however... The parts include:

- 557 block machined
- Butler stroker assembly: cast crank, Eagle SIR rods, Mahle pistons, file fit rings, flex plate
- 274 camshaft
- roller rockers
- Performer intake
- D port E heads, ported
- BOP mains and oil pan seals

My concerns are:
1. Don't know anything about the machine work
2. 557 block
3. SIR rods
4. Press pin rods, no going back
5. The heads were purchased bare but are now assembled... which means they would have required a valve job
6. Quality of port work
7. If it's a XE cam, Cliff will hate me

I'd pass on that not so desireable pile of engine parts.

I out of that pile of parts if the Crank and the heads heads can be had for 1600 bucks then go for it, and this assumes that the Crank passes a mag test that the seller does first !

My thoughts on a sleeper engine. 4.5 stroke, for 488-495 cubic inches. Ported 6X-8's and ported iron intake from sdperformance, Hydraulic roller similar to the OF grind, Ram Air manifolds. compression around 9.5.
Look totally stock, but make 500 horsepower, if not more. Huge low end torque.

The larger 4.5 stroke engine will be sensitive to under-flowing cylinder heads. Something to consider with the use of iron heads, If so keep the RPM down. To illustrate, grab a bicycle tire pump some time, and first try to operate it as quickly as you can. Then, slow down the pumping action. You will notice that it is far easier to move the pump handle slowly.

Of interest, Dave Bisschop on the subject of a 4.5 stroke...

Having actually built a number of identical combo's with the only change being the stroke, I can tell you with 100% certainty that in each case the engines made more hp and torque with the 4.5" stroke vs. the 4.25" stroke running the same bore, same head cfm (iron as well as aluminum), same compression ratio's and the same cams, headers etc.

This doesn't mean I recommend everyone go to the 4.5" stroke as the gains when looking at it from hp per ci shows the efficiency is no doubt going down. The biggest difference is the low rpm torque increase with the longer arm which can make things more difficult to get the power to the ground and will be harder on drive-train parts as well, but in a heavy moderately geared street car that is set-up well it sure can work well too. From a longevity standpoint it's uncertain in the long run how well these engines will last with the additional side loading on the lower part of the cylinder walls, but so far we haven't really seen any issues, but I think the key there is too keep the rpm's down, which kind of happens automatically with all things being "equal".

To me if the car is set-up 100% to compliment the engine combination then the performance difference will most likely be little to none at the drag strip. The shorter stroke engine would need more rear gear (multiply the power) and will operate at higher rpm. I look at Lisa's 65 GTO racecar, the car weighed 3580lbs with driver and would run 10.20's @ 129-130mph all day long on a foot brake. The 413ci 670 headed engine only made 611hp and 545lb/ft of torque on the SF902 dyno we use for all our testing. If you run those numbers through most HP by ET/MPH/Weight calculators you come up with a much higher hp number than the engine actually produced, but the key was it had a 5000ish stall and 5.13 gears (31" tall tire) which perfectly complimented the power curve the engine had, it took years of tweaking and tuning to get it there, but it shows you that getting the entire drive-train combination right can and will make a huge difference on performance at the track.

Without a doubt for a street/strip car it's easier to get the longer stroke engines to work well at the track as they are much more forgiving on gearing and converter stall, but having way too much low end torque won't do you much good if you can't get it to the ground either, so choose wisely, personally I feel the 4.250" stroke is plenty for most of these combo's.

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Except for the block, everything is new with receipts. I could install it all on an older block (sans the intake). The heads turned out to be lightly gasket matched... not butchered in any way. That only leaves me with two questions:

1. Quality of the valve job
2. How much HP can these rods handle?

What are your goals? Streetability? Ultimate HP? Budget friendly?

Jay DeLaigle had his '74 TA running in the 10s, looking completely stock with iron d-port heads and log manifolds. BUT… that car was a max effort car, with a lot of time and $$$ in it and it wasn't exactly street friendly- very high compression, requiring expensive race gas to run.

On the other end of the spectrum is my '69 LeMans- again totally stock looking with mildly ported d-ports, log manifolds, untouched '69 intake, stock Q-jet, etc. Has 9.5:1 compression runs on pump gas, runs right at the thermostat, can drive it anywhere- mild and docile, but runs mid 12s at 4050 lb. race weight.

400 hp is easy, 500 is do-able- above that is possible but you're going to be giving up drivability.

https://scontent-atl3-1.xx.fbcdn.net...f5&oe=582904AA

Out of all those parts, the heads are maybe worth getting. Quality of work on the heads is of course in question here.

Performer intake doesn't belong, cast stroker cranks aren't known for reliability, press-fit rods and pistons I stay away from now. Who knows if another 'good block' will bore/clean up for that piston set.

Cam is almost certain to be an XE274, not desireble to me.

In the long run you might just be money ahead by picking the new components you really want, rather than sifting through a bunch of somewhat questionable stuff to try to make a good 'bargain engine'.

Good luck with it.

http://www.sdperformance.com/moreTech.php?newsID=39

here is an article Dave did a few years back testing just what you are looking for.