The "Sneaky 500 HP" motor

Torque at 2000 rpm is really never a problem with any 455 based buildup.

OD transmissions with a lockup converter, and low numerical gears would be the only time there was a concern here, and since I did just do such a car, with a similar camshaft, I can tell you that there is no issue driving around at low speeds, with the trans in 4th and the converter locked up, with that 435ci BBB and 3.08 gears. It was still plenty strong, even down at about 1800 rpm.

I don't test engines at that low an rpm on the dyno.. it is very hard on them.. It's exactly like taking a 4 speed car, putting a 10,000 lbs trailer behind it, and accelerating in 4th at WOT.

Hope that answers your question.

 

Jim,

Thanks for sharing this with us. I have often thought that using a 118 cam would work better for turbo apps for the same reasons. I could run a longer duration and not have the reversion issues. What do you think?

 

Yes, your correct.. just keep the overlap low, when your juggling duration specs around.

JW

 

Well damn. That's good stuff. Sounds like there's no performance downside to a setup like that. Well done.:beers2:

 

Jim on your sneaky 500 setup what kind of timing curve were you able to run? Peace, Mike D.

 

He is in Ohio at BPG.

My experience with his stuuff is that 34 degrees total is tops on a street engine.

 

Jim,
I'm curious about the good idle and vacuum you got from the apt 800 qjet.
What size are the brass idle tubes, and air bleeds? Float level?
Also, .073 jets? smaller than stock STG 1 .075 ??

....eventually do a sticky on a basic 450-500HP APT qjet project when you get time?

 

just wondering about an update on the dual 4 iron head build your working on thanx jamie

 

The motor is now secure in her moorings.

 

Looking Good !! :TU:

 

Jim, how do you think a similar build would work out on a SBB?

 

Marc,

It's important to remember that this motor, with different cam timing, and a different intake and carb is easily capable of 575-600 HP..

the point of this one was to build 500 HP, but do it in a way that it's idle or physical appearance didn't give it away..

The 350 really doesn't have heads capable of that kind of non boosted HP, so you really can't give anything back..

I think the sneaky 350 is the boosted stuff (turbo or SuperCharger) that is out there.. just don't open the hood.. LOL.. :TU:

JW

 

Hi Jim, If you were to build the 290H cammed engine today, would you still use the 118 lobe centers? Looked today at the TA site and they list a 290H with 112 lobe centers. Also how easy would it be to tune a Holley 1050cfm 3 barrel carb on a ported SP1 with the 290H on 118 lobe centers camshaft? Also would the sneaky engine run on 87 octane fuel/ Thanks, Bruce in Alaska.

 

:Smarty: Sweet Logic JW..... I love it!...now I just have to go rob a bank to pay for it, but will be in touch when ready to move forward. :3gears:

 

Bruce,

It all depends on what the customer wants.. if he is after max performance, then I would use the 112 lobe center cam. If he wants to idle up next to somebody and not have the cam lope give it away, then I would certainly run the wider lobe center stuff..

Generally speaking, the better a motor runs at idle and lower rpm, the easier the carb tuning is.

If you believe all the theory on Dynamic compression ratios, then yes, it should run on 87 octane. While DCR certainly will affect lower and mid range compression pressures, there is some disagreement in biz about it's actual affect at higher rpm. Simply because at higher engine speeds, there is less time for the camshaft timing to affect cylinder filling.

Consider a typically BBB with that 290H/112 cam.. lumpy at idle, but smooth at silk at 3500 rpm.

All you have changed is time.

JW

 

Jim, I'm still trying to wrap my head around cam variables and effects. But thinking about this combination, what about this cam kills the dynamic compression so much?

Comparing it to my current cam, TA_C118, the 290H has an extra 10* of duration on the intake (while removing 11* from the exhaust, but I have iron heads), I would think that is it, but I want to make sure I'm seeing the whole story. =) I'm looking at possibly getting some TA Aluminum heads in June and possibly changing cams at the same time.

Thanks for any info.

290H-238* Duration
C118-228* Duration

 

Have to be careful with this, it's one of those "it depends" statements that confuses people so much regarding Dynamic Compression.

At high rpm, there can be so much inertia of the intake charge that it continues to flow into the cylinder past the open intake valve even after the piston is coming up from BDC. This is the benefit of a late closing event. It hurts power at lower rpms because there's not enough air/fuel interia and the piston pushes it back into the intake manifold.

This is why a lot of people get into trouble relying on the DCR calculation thinking they can get away with more SCR running a big cam...they can to an extent, but if they get carried away they risk detonation at high rpm due to the very nature of the excellent cylinder filling, the whole reason to run a big cam to begin with.

Good stuff here:

http://www.e30m3project.com/e30m3performance/myths/more_myths1/comp_ratio/comp_ratio2.htm

Devon

 

Thanks for the links guys. I've read some on dynamic compression before. The thing that shocks me about this build is getting down to 6.5, as opposed to in the mid-7's or so.

Another question I was thinking of is does the LSA effect it the dynamic compression? Such as going from the 118 to 112 LSA?