I finally got my 427 (L-36) rebuilt rather than going the crate motor route. I used one of the best racing shops locally. They do a lot of big blocks for pro dragsters, boats, as well as street cars,etc.

Basically a stock .060 over 427/390 hp (L-36), now 439 c i, from a 1969 ragtop. Stock oval port heads, treated to a mild port on the exhaust side, with hardened seats added. Factory low rise alum. intake, Hooker 1 & 7/8" headers. A Comp Cams 270 Magnum hydraulic flat tappet cam. Crower stainless steel roller rockers, a "Sean Murphy Induction" built Quadrajet fine tuned on the dyno yesterday ( it was too rich out of the box and leaning it out added 25 hp).

Full rebuild including decking the block, overbore to .060, plate honed,etc. Balanced and blueprinted.

This shop is known for finding horsepower and I was pleasantly surprised by the numbers. This is from the owner of the shop on the phone, I don't have the graphs in front of me yet:

Peak hp is 456 @ 5100rpm

Peak torque is 536 @ 3600 rpm

Holds to a very flat power curve and still makes 437 hp @5700.

Does not want to run past 5800 rpm. Which is expected due to the heads and intake limitations.

Overall, much better than expected.

That's all I've got for now.

Regards, Mark
:flag :chevy


[Modified by marky mark, 1:15 PM 4/29/2004]

 

Are those results from an engine dyno, or chassis dyno?

 

Chassis dyno, sorry. They break in the motor, then fine tune the fuel/air mixture, set timing to optimum, then do a couple of pulls. This is before they install the motor in the car. Cost is an additional $400.

I'm figuring rear wheel numbers in the range of 355 hp and 425 tq. Which would be fine with me.

Thanks, Mark

 

Impressive numbers. It sounds like you had it done on an engine dyno. Chassis dynos give the rear wheel HP and are measured with the engine in the car spinning the rear tires. An engine dyno is just the engine on a stand.

 

:thumbs: Sounds like a healthy big block :yesnod: You'll have fun cruising with that baby :steering:

 

Imressive #'s man, congrats :cheers:

 

Mark!!! (Please start the Twilight Zone music now! ) :lol:
I also have an L36 engine... (in my 68 vert)

and..... my ebay name is Mrktymark !!!! :eek:

but it gets better...... My wife's last name is Hemphill !! :shocked:

Anyway, nice numbers! Do you know what the actual jetting of your Qjet is? I think the last time I messed with mine (Edelbrock 1901 Qjet) I put in 73 jets.

I have no idea if my internals are stock. I don't know if the engine was rebuilt in the past. Several have commented that my idle is a bit "lumpy". I have limited myself to carb tuning, distributor/timing setup, and headers/exhaust, but it sure would be nice to have the whole thing rebuilt to squeeze out an extra 100 hp or so! :) MJ


[Modified by MNJack, 9:12 AM 4/29/2004]

 

nice!! :cheers: :cheers:

 

I'm just about ready to do similar mods to my 454. It is encouraging to see you results. :thumbs:

 

Your rebuild is similar to mine (cam etc.), although I did not have to punch mine out any further. I think yours is producing better power than mine, though. I wish I had some porting work done on those heads.

Congrats on the power.

 

It sounds like you engine builder did a great job for you!

I added a 454 crank to mine. I switched from the Q-jet/stock manifold to Holley/torkerII and gained 30 HP. I used Merlin heads. The price was about the same or maybe even less for the new heads versus making the old heads flow as well.

Even though I have more cubic inces I don't have much more power. You should be thrilled :)

It'll be fun to drive.

~Jay

 

Those are good numbers. It sounds like you have a nice little power plant on your hands. It will be great to get that back in the car.

 

Thanks for the info. My rebuild is very similar to yours. I never dyno'd mine so now I have an idea what to expect. Sometime in the future I may put it on a chassis dyno to dial in the carb.

 

MNJack,

That's some wild coincidences!

Good luck on your car.

Engine builder said secret to getting more power is to make sure they plate hone block. Not many shops here have plates for big block's, although some have them for small blocks. Of course, this guys been doing it for so long I think that has something to do with it as well.

Here's what it (Quadrajet) came back from Sean Murphy with. Although I still have to ask what the engine builder did to "lean it out" :

Jet:74
Rod:49M
Sec:BG

This is not a 60's vintage carb but one from the late 70's early 80's. Originally purchased as a Stage II Quadrajet from the Carb Shop in Calif.

Thanks, Mark

 

I would guess that a 454 will make 50 or so more hp and torque than a 427. So, your engine would be in the high 400 range for hp and close to 600 tq if I am correct.

Have read many dyno sheets on this Forum and some seem inflated as mine might be.

Re: this builder-I can't verify their dyno's calibration,etc. So, have to take them at their word. But, their reputation is solid and they do build a lot of high performance motors so I tend to think it is accurate. But, who knows for sure?

Thanks, Mark

 

I think every brand of Dyno is different. You can look in my signiture, there is dyno chat from the engine dyno. I think mine was 495HP @ 5600, and 540TQ @ 3500 or so.

I had my car chassis dynoed on a Dynojet and it was 404HP, then a few weeks later I had it tuned on a Superflow and it was only 368 after tuning. I asked why there was such a difference, and he didn't know, but said there was an option to use a Dynojet correction factor.

So In my case the Superflow engine Dyno was 495, and the Superflow chassis was 368. That is a litte more than 25% Drivetrain loss.

368 isn't a huge number to brag about....but it is enough power to scare the crap out of my passengers :D ......and me somtimes :eek:

~Jay

 

Thanks Jay,

Good point about the different dynos.

Also, I remember reading a thread on here about the disappointing net numbers (chassis vs engine dyno numbers) people were getting and that it had to do with the exhaust differences on the dyno vs real world exh pipes, & mufflers.

Thanks, Mark