I bought my 4 speed 74 L82 early this year.

Previous owner, a really good man on his late 60's, told me that the engine was in very good conditions and with some good improvements on it. I did not pay too much attention on them since he showed me how well was the engine running and on top of that I'm kind of newbie on these engines.

The issue is that during this time I've seen that the engine pushes quite decent, and after taking a deeper look on the top end engine this is what I found out some time ago so now I'm guessing about how many HP I'm dealing with.

- Holley Heads #12111 (made by Brodix)

- Holley Intake, Street Dominator (Intake 184cc, exhaust 68cc)

- Lunati cam (Part #10120304, previous part #07104LUN)
Street Master Hydraulic Flat Tappet Cam - Chevrolet Small Block 290/297

Product Description

Hydraulic Flat Tappet. Great street machine cam. Needs 2000-2500 RPM stall converter, headers and gearing.
Advertised Duration (Int/Exh): 290/297
Duration @ .050 (Int/Exh): 235/240
Gross Valve Lift (Int/Exh): .490/.490
LSA/ICL: 112/108
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 2600-6500
Includes: Cam Only
Part Number: 10120304
Previous Part Number: 07104LUN

- Headers: Hedman

- Holley 80457SA 600CFM


According to all this info my engine is running this kit:

https://www.summitracing.com/parts/hly-300-503-1


I have no idea about what final numbers should be. Post your guess, please!

 

My best guess is you should take it to a Dyno tune place. So many factors affect what you are asking for. As only the previous owner knows what he did with the motor, he can make the best guess. So, if you really want to know, dyno tune it.

 

no cam specs,,,, no one will have a true clue..

 

Does the engine have a lope to it while idling, or is it a smooth idle?
How much vacuum does it make at idle?
Answering those two questions we should be able to guess within 100 HP

 

I'm not that worry about accuracy to force the engine at that point, thanks for the ide though.

I was expecting to have a clue from somebody about the cam since they were sold as a kit with the rest of items.

Maybe these ones I read on other forum?

My Holley Performance catalog only knows one cylinder head,
Part# 300-522-1
-valve angle 20 deg.
-int. runner volume 184cc
-ex. runner volume 68cc
-comb. chamber vol. 68cc
-cfm flow @ .500 lift measured @ 28" H2O
-intake 223 cfm
-exhaust 173 cfm
-2.02/1.60 valves
-straight plugs
-deck thickness .500"
-exhaust port location stock
-heat crossover passage
-3/8 rocker studs
-bronze valve guides
-valve spring installed height 1,780"
-max lift .600"
-spring seat force 132 lbs

Two Systemax packages 350hp @ 4500rpm/357 ft/lbs @3500rpm
first kit p.n. 300-502 comes with Lunati cam and lifter kit
-Lunati p/n 06108LK
cam specs:
-int./ex gross lift .457" @ 1,5 rocker arm ratio
-adv. duration 268 deg.
-duration @ .050" 218 deg.
-intake valve lobe centerline 105 deg.
-lobe separation 110 deg.

second kit p/n 300-503-1 425hp @ 6150rpm 425 ft/lbs @ 4250rpm
Lunati cam and lifter kit p/n 07104LK
cam specs:
-intake valve gross lift .488" @ 1,5 rocker arm ratio
-exhaust valve gross lift .510" @ 1,5 rocker arm ratio
-int duration @ .050" 234deg.
-ex. duration @ .050" 244deg.
-intake valve lobe centerline 107deg.
-lobe separation 112deg.



Well, compare to what? According to the videos I've seen on youtube from original engines is not that that smooth but nothing crazy, just a little bit more rude sound. Quite similar to this one:

 

Take it to your local track. Find out what it's real world performance is like

Anything in the 109-112 mph would be similar to a c6 ls3 corvette

Which is ~ 430 hp

 

375-425 HP......thats my guess

 

How the muncie M21 could handle that?

I wish you were OK...because it's a huge power gain from it's original 250cv.

 

For what its worth, this is the dyno sheet I got with the top-end kit for a 78 L-48...should mention after street racing blew a bearing and ended up replacing with a 383.

Have fun with your new Vette!

 

I too have a 74. Mine was the fabled 190 hp L-48 version! After considering things and remembering a biography on Ralph Nader, I plucked that turd out and went with an LS3 in it's place!

 

If mean H.P., not even that much stock. Your compression ratio will have a big effect on power output as well as the cam and heads.

 

Me thinks the 600 holley is probably a bit small for peak hp number that it is capable of.

Find a chassis dyno and run it.It will tell you how much rwhp it is making(add 20% and you have a flywheel number)and you will find out the sir/fuel ratio and whether it is optimal or you are in danger of hurting something.

At the end of the day if it has plenty of power for YOU then drive and enjoy it.Bragging rights don't compare to smiles per mile while enjoying it.

 

Horsepower is just a number, and most people that you meet that spout off numbers are really just guessing anyway. Its also amusing when some of the guys that put their car on the dyno do actually take the car to the track and can't turn the number.

The dyno is definitely a great tuning tool, but what the car can run at the track is, in my opinion, what really matters.

PS an M21 will handle that power level without slicks.

 

 

run it at the track,who cares how much power it makes.

 

Just curiosity...it's like having a missing dad since you were born and want to know something about his life

 

BTW, can I use original valve covers with the Holley heads?

 

Well, I just found the info I was missing for the cam and the headers among the car documents and invoices:

Cam is 07104LUN:

Street Master Hydraulic Flat Tappet Cam - Chevrolet Small Block 290/297

Product Description

Hydraulic Flat Tappet. Great street machine cam. Needs 2000-2500 RPM stall converter, headers and gearing.
Advertised Duration (Int/Exh): 290/297
Duration @ .050 (Int/Exh): 235/240
Gross Valve Lift (Int/Exh): .490/.490
LSA/ICL: 112/108
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 2600-6500
Includes: Cam Only
Part Number: 10120304
Previous Part Number: 07104LUN


Headers : Hedman


It seems that the engine has a quite interesting set up.

As soon as I finish the front bumper replacement I will squeze the engine a little bit and double check it deeper.

 

You could add 1.6 rockers and get your lift over .500". But the heads determine how much power you can make. An easy calculation is multiply the intake CFM by 2.

 

he is talking about head flow CFM X2......

Did you ever get compression?