440 Block and Dyno HP Question

[wsr1961]

I have a '71 440 six-pack (clone) with a "crate" engine that I figured out is a 1970 maniford for the 3 Holleys and a 1974 440 block. The heads are Edelbrock Performer RPMs with 82cc chambers, it has headers an alegedly a decent street cam. It seems to run well.

I had it dyno'ed and the HP came back at 192. Torque was in the mid to high three hundreds, I think. I expected the engine had less than the 500 advertised HP, but with the heads and headers I would think it would have better numbers than the 390 gross HP of a real six pack. I suspect the net HP from the dyno transalates into about 220 HP gross.

Car shop guy says cylinder compression is fine and engine runs good, but that I need an older block to get the HP up. Actually, he wants to to give up my life savings for a new stroker block. He mentioned how HP went down in the mid 1970s. It is my understanding that changes made to heads, carbs, cams etc., dropped the HP ratings, in addition to the transition from gross to net numbers. I think a '74 block might have cast shaft and connectors, but should run just as well as a 1970 block unless or until you go high RPM and sling a cast rod. AM I right in that the basic block should not be causing my HP drop off, and that they are either hussling me or don;t have their facts straight?

I have also had some prior experience with bad dyno numbers in another shop where they didn;t really know what they were doing. I had a supercharged 5.7 liter estimated at 320 rear wheel HP when I know it was well above that number.

So, it my 1974 block/pistons/bore/stroke putting less to the wheels than a 1970 set-up? I don;t think it should.

 

[moparleo]

The problem is that you are guessing about the short block internals. You need to know the static Compression ratio. The specs on the cam. Any head mods, rocker ratio, carb jetting etc... Any of these things can have a big affect on your hp/torque numbers.. Unless you open her up and check things for your self it is just a guessing game.

 

[TC_Cuda]

I have to agree with moparleo its all just a guess without good hard info... but I would like to take a guess anyway

I had a 78 440 which I believe has the same specs as your 74 440.
What I found is that the true compression was a miserable 7.2 to 1 as at the time Mopar tolerance's were pretty big during this time.
So if your engine is stock or rebuilt stock, then even with the head you true compression is probably 8 to 1 at best,
also if your dyno run was on a chassis dyno then, I have always counted on a loss of at least 125hp when on a chassis dyno
so that would put you over 300hp and that's not bad for what I assume is a stock 74 440 with some parts bolted on
and with some tuning I bet you could get more.

please remember this is just my 2 cents

TC_Cuda

 

[IQ52]

Wow, It could take six days to straighten out this can of worms. 1st, yes it is quite possible that your engine could be making less than the 1970 model and I suspect it is.

I suspect you didn't completely understand exactly what the "car shop guy" was saying and perhaps there might be a tiny bit of hustle, but I would have had to been privy to the entire conversation.

The year block isn't the cause of the power drop off, but the engine internals will contribute to the loss. The 1970 and 1974 440s have exactly the same rod forgings.

A well designed pump gas 440 6-Pack could be putting out 200 horsepower more, as this one does, than a stock 1969-70 6-Pack. 550+TQ/590+HP



Jim La Roy
La Roy Engines
Challis, ID

 

[Chryco Psycho]

HP is just a number , it depends what dyno is used & how it is measured .
I always used a Mustang dyno , it was very versatile , it could test steady cruise as week as full throttle pulls , but it always tested 15% lower than a Dyno Jet with the same engine .
I built 2 identical 71 440+6 Challengers , i ported the heads & tuned both engines but the short block & cam on 1 were built & picked by me , the second 1 was built by another person . The second one pulled 210 RWHP , the one I built , made 320 RWHP on the same dyno . Both were breathing through iron exhaust manifolds [ported] of course with TTi 2.5" exhaust .
BTW 320 RWHP is a lot more than 395 gross factory HP @ the Crank

 

[moper]

"Wow, It could take six days to straighten out this can of worms. 1st, yes it is quite possible that your engine could be making less than the 1970 model and I suspect it is.
I suspect you didn't completely understand exactly what the "car shop guy" was saying and perhaps there might be a tiny bit of hustle, but I would have had to been privy to the entire conversation.
The year block isn't the cause of the power drop off, but the engine internals will contribute to the loss. The 1970 and 1974 440s have exactly the same rod forgings.
A well designed pump gas 440 6-Pack could be putting out 200 horsepower more, as this one does, than a stock 1969-70 6-Pack. 550+TQ/590+HP"

"HP is just a number , it depends what dyno is used & how it is measured ."

These. You have placed faith in a shop that does not have your best interests in mind. Your engine might be down on power. It's been my experience that performance is relative to the level of ignorance of the parties involved. Sometimes a more experienced set of eyes and hands is required.
The dyno could be way off. Dynos are tools that are manipulated by their operators as part of their use. They are not gospel. All 440 blocks are virtually identical, from '65 castings to '78. There are differences in metallurgy (although all Mopar stuff is good material) and there are evolutions in the accuracy of the casting processes. But all Mopars suffer from some casting flaws like core shift that can make some blocks better than others, but it's on an individual basis - not a year of casting number. Only by inspection and sonic testing is one found to be better than another, regardless of the year. The wrong tune up can cost you 100hp and yet it will still run. Other assembly or parts choice issues could exist. The block is more than likely just fine.
As an example, I pulled a 77 440 from a New Yorker, stuck a moderate hydraulic cam in it, valve springs to match it, an iron '70 6bbl setup, and cheapie headers. In an E body that would run 12.40s on Dunlop GT Qualifiers, and I drove it daily for 2 years. It was low compression, and ran pump "whatever" fuel.

 

[Steve340]

The compression while cranking will need to be around 175 psi.
If it is say 120 psi the engine will run good but it could make less power than stock.
Matching the cam, compression ratio and cylinder heads is the answer.
I agree with Moper be wary of the shop.
A decent engine guy would be giving you the answers not smoke and mirrors.