The "Sneaky 500 HP" motor

I'd like to know that too, seems a lot to give up, losing 14lbft of torque more where you're probably going to use it vs. gaining 20 hp in an area you probably won't.

Your low cranking compression is not only due to the higher duration but to the much later intake valve closing. Not consistant with good throttle response either. I'll bet the second one is noticeably lazier than the first.

I'd be very interested to see the 2000-3000 numbers. not sure if you couldn't have gotten similar results by just having the first cam ground on a 112 or 114, in at the same, maybe with just a bit more exhaust duration and not made such a drastic change.

I'd rather have the higher torque down low, that's what moves a street vehicle, not hp up higher.

 

In my odd ball goal of HP vs. mpg's (see one of my threads..) I'm looking at factor's like low vacuum and cranking compression to reduce pumping losses and internal resistances while cruising (~2200rpm) and still maintaining a good peak power. If I can do that and run cheap gas, all the better! As for idle and low rpm characteristics, my "hope" is that with the megasquirt efi I can tune/crutch lower rpm undesirables with tightly controlled timing and fuel. EFI in "general" fattens up the torque curve (and average power) down low compared to a carb tuned for peak power.

(if I'm off in my assessment by all means call me on it, I'm always open to an opportunity to learn something)

 

Plenty of torque available with these BBB's... moving a little around here and there is no issue.

Trading some torque that shreds tires, vs some HP that is actually useable, has proven to be advantageous in cars built here in the past.

JW

 

This is a great answer Jim. Generalizations about which lsa is better does not take into consideration the individual vehicle. As this relates to the intake valve closing event, I have had cars that were traction limited where moving the power-band upward would have been a real plus. Conversely, I have also had cars the could have really benefited from a torque boost.

Back in the day, I advanced a cam in sluggish 1974 Corvette where the owner put a little too much cam for the compression ratio. It help noticeably. I had also retarded a cam 4 degrees in my buddies 67 Olds 442 that just would not stop pinging on pump gas. This allowed him to run a bit more timing and the car ran better all the way around.

 

Be careful about trying to lower vacuum and cranking compression to improve mpg's.

1) Fuel atomizes better as vacuum goes up. Better atomization = more efficient combustion.
2) Increased cranking compression is a direct result of increased mixture trapping by several means such as an earlier intake closing as mentioned previously. One thing an earlier intake closing can achieve is reduced overlap and unburned fuel going straight out the tailpipe. Cranking compression is also primarially affected by static compression. Running as much static compression as you can (on the given fuel grade) extracts more energy from every drop of fuel burned.

It's all a balancing act.

Just some things to think about. I spend a lot of time thinking about improving fuel economy too.

 

I just realized that what you have created is pretty a much a Miller Cycle Buick 455. Only instead of using a supercharger to make up for the pumping losses, you are using a high (for pump gas) static compression ratio.

I always wondered how well that would work in an old school engine. Very slick indeed!

 

Thanks for the answer. I expectthe heat, the fuel injectors and immediate vacuum of the near-by cylinder to suffice for atomization. I'm running 10:1 pistons, and has 135psi cranking compression (at 6500ft elevation, 80kPa).

I'm not sure I understand the "One thing an earlier intake closing can achieve is reduced overlap and unburned fuel going straight out the tailpipe." logic. I get the reduced overlap part, but not sure how it follows to unburned fuel into the exhaust. Wouldn't advancing the ignition timing along with that take care of any issue like that?

 

I'm enjoying all the talk about my motor. We got paint on the jambs today and plan on painting the car over the upcoming 3 day weekend. With any luck I will have the car at BG in Oct. We'll see how it does in the quarter then. If it runs in the 12's and looks and sounds stock, I'll be happy.

 

I just read my last post and find it amusing since it was several months ago and we're still not finished, but.......After two years sitting silent, we fired the motor today. I don't know why I am amzed but it was completely uneventful. After wiring up the MSD box, plumbing or plugging vacumn lines and plumbing water and tranny lines, we poured a little gas in the carb and she fired right up, idled nicely, no excitement at all. I had a little leak on one of the transmission coolant lines, tightened the fitting and that quit. Oil pressure was great, no spittin or sputterin, awesome. Thanks JW! It sounds so good through the headers I hate to put the mufflers on it.

 

It's amazing somtimes when something just "works"... Stuff never just "works" without a bunch of troubleshooting..

Nice..

 

Hi Jim

Great work and engine. Now im building mine up . Your cam is very impressive and i looking for something simular. I would like a cam thats run great in idle 650-750rpm like yours. My SCR is 10.5:1 and with a TA212 Cam i have a DCR 8.5 <--- heating and Detonation Problems... I want lowering the dcr to get more Hp and a lower risk to get detionations...

Where i can buy a cam like yours?


Thanks

Robert

 

You could try retarding your current cam a few degrees

 

This is a good idea. I had done this on a friends car and it solved his detonation and hard starting problems.

 

I have a TA212 and a stock from a 72 455 wich i should take?

 

A great read 15 years later. I saw John shared pics of his car on the v8buick facebook group page last week.

 

JW

im interested in the manifold you cut the top out of , do

have picture you could post

 

Wow, this thread brings back memories..

Sure, I have one in the shop that I can take a picture of, but it basically looks like a Performer/B4B plenum, with the divider cut down, when you mill out the top of the stock intake.

JW

 

Thanks Jim , please excuse my messy query, technology and I were having a disagreement and I think I got done . I have seen various versions of cut down dividers , I was wondering how much of the plenum you actually removed for this build. Cheers