Author Topic: Rear wheel horsepower & compression ratio  (Read 3590 times)

Offline Fleet 500

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Rear wheel horsepower & compression ratio
« on: October 16, 2007 - 06:41:05 PM »
On another message board, someone is claiming that the actual ("mechanical") compression ratio of '60s muscle car engines was well below the advertised figure. He claims that the highest c.r.'s were barely above 10.0:1. I find this hard to believe.

He also claims that the strongest of the '60s muscle car engines put out "barely 200 hp" at the rear wheels.

Has anyone here checked the actual compression on their Mopar engine and/or measured the rear wheel horsepower?
Link is here:
http://www.ultimatecarpage.com/forum/american-cars/33343-actual-horsepower-60s-70s-muscle-cars-8.html
(Post # 119)




Offline GoodysGotaCuda

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Re: Rear wheel horsepower & compression ratio
« Reply #1 on: October 16, 2007 - 06:47:30 PM »
He wanna line his wonder vette up to a 'stock' hemi dart? or barracuda? :D Newer cars only have 30 some-odd years of technology stuffed into them. Perfect tune, no matter the conditions, variable valve timing, multi-valve heads, overhead cam, variable intake runners, awesome flowing stock cylinder heads, more efficient drivelines that eat up less power......Oh and the cost of things have gone up a few bucks.

So yea, they do lay down more power per cube. As they should.

As far as "Strongest of the 60s muscle cars" at 200rwhp....yea....okay.. :blah:
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Offline KellysCuda aircard

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Re: Rear wheel horsepower & compression ratio
« Reply #2 on: October 16, 2007 - 06:53:36 PM »
Lots of the older cars had CR of closer to 11-1

Offline 72hemi

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Re: Rear wheel horsepower & compression ratio
« Reply #3 on: October 16, 2007 - 06:58:49 PM »
Some were as high as 13 to 1.
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Offline MEK-Dangerfield

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Re: Rear wheel horsepower & compression ratio
« Reply #4 on: October 16, 2007 - 07:19:25 PM »
If you have a compression ratio of 10:1 or better, you are doing a little better than 200HP with a big block V-8.   :grinyes:


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Offline Fleet 500

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Re: Rear wheel horsepower & compression ratio
« Reply #5 on: October 16, 2007 - 07:47:37 PM »
The poster was claiming that the "actual" compression ratio of '60s muscle car engines was much lower than the advertised cr. Meaning actually measuring the cr yourself. But I don't buy it. I don't see how the actual cr of, say, a 340 (10.5:1 advertised) is lower than 10.0:1.

nivvy

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Re: Rear wheel horsepower & compression ratio
« Reply #6 on: October 16, 2007 - 10:13:21 PM »
well with the gas back then mattered...look up the specs on a pontiac 400.... 10.75 to 1 compression...I really dont think compression ratio was a selling point back then...

This is all I have to say is yea technology is better today but

600HP IN THE 60'S IS THE SAME AS 600HP TODAY!!! any way you build it!

YOU CAN ONLY DO SO MUCH ON THE STREET!


the kids come running up the alley everytime I fire up the big bad dodge... and there Generation X.... Muscle cars will ALWAYS rule!

Gross HP
NET HP
Rear Whell HP
 :blah: :blah: :blah: :blah: :blah:
Timeslip is the true measure of a man/woman :working:



I love eating up chassis dyno racers  :burnout:
« Last Edit: October 16, 2007 - 10:19:00 PM by StrOkEr »

Offline Chryco Psycho

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Re: Rear wheel horsepower & compression ratio
« Reply #7 on: October 16, 2007 - 11:21:38 PM »
most flat top pistons with open chamber heads cannot reach the 10:1 ratio advertised even with the piston zero decked which never happened so basically I agree
 as for 200 RWHP it depends what dyno is tested with HP is an ambigous # at best , most of the modified engine I have built have been in the 275-340 RWHP range so most will surpass 200 RWHP but in reality unmodified 383& 340s have trouble surpassing 200 RWHP 

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Mopar Noob

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Re: Rear wheel horsepower & compression ratio
« Reply #8 on: October 17, 2007 - 01:28:07 AM »
This seems like a good place to bring this up... I think I may have brought it up before but here goes again...

I really cant remember what the show was but I saw something on the SPEED channel there they tested the top engine from each company in the 60's and 70's...

The top Ford engine which was rated at something like 400hp back in the day rated on the show at 600hp
The 426 HEMI which was rated at 425 back then got rated at 800hp on the show...

I'm not 100% sure what their standards were but that sounds pretty good to me...

Offline NoMope Greg

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Re: Rear wheel horsepower & compression ratio
« Reply #9 on: October 17, 2007 - 02:05:34 AM »
I remember seeing that show.  It was on "American Muscle Car."  The numbers weren't quite that high, though they were higher than the advertised hp from the factories at the time.  I do recall that the Hemi did make the most power and that the big block Chebby wasn't even close.  Kinda like on the drag strip... :roflsmiley:

Anyone else ever notice that no one ever seemed to make much more than 425hp?  I think the most I've ever seen for factory advertised was the 430 hp Max Wedge 426 of '63(?).
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Mopar Noob

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Re: Rear wheel horsepower & compression ratio
« Reply #10 on: October 17, 2007 - 02:42:02 AM »
Yea my numbers may be a bit off but I know they were way up there...

What would it cost to get a modern car going fast...

Now what would it cost to find those extra horses and that speed in an old muscle car?

Again I don't know all the numbers but I know I have to sell my soul any time my "modern" car needs anything at all...  :dunno:

Offline Fleet 500

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Re: Rear wheel horsepower & compression ratio
« Reply #11 on: October 17, 2007 - 04:06:21 AM »
From what I've read through the years, the "425 hp" 426-Hemi made a minimum 470 gross hp.
The "375 hp" 440-4 bbl made more like 410 hp and the "275 hp" 340 was about 320 hp.

nivvy

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Re: Rear wheel horsepower & compression ratio
« Reply #12 on: October 17, 2007 - 05:42:56 AM »
They advertised gross HP not net HP which numbers fell off but really who cares about numbers....the timeslip is what matters  :cooldancing:  :burnout:

Offline HP2

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Re: Rear wheel horsepower & compression ratio
« Reply #13 on: October 17, 2007 - 07:15:00 AM »
I didn't go read the linked thread, but based on the original post here, I'll say the guy is somewhat correct. BUT..it also depends on what combination you are talking about.

The engines built in the day all showed advertised, gross values. Yes there were a lot of advertised 10+ to 1 engines, for static ratios. Dynamic cranking ratios were likely all less. Horsepower figures were also gross numbers at the crank, in ideal conditions, with no accessories. Install a 335 horse engine in a car and subtract 35% of its output for accessories and drive line and yes, your down around the 200 mark, plus or minus some depending on the actual configuration.

Now, there were still some killer combinations from the day that were far and above the 200-250 mark. However, not every muscle car from the day was Hemi car or a shotgun Ford or LS Chevy. By far, the majority of muscle cars were just average big blocks. At least for a few months and the new owners started tinkering with them.

The engine shoot out show mentioned here also isn't accurate. The builders of that Hemi have admitted it wasn't exactly a stock unit, but rather a FAST style set up. I love mopars as much as hte next guy, but a 700 HP STOCK Hemi? Sorry, don't buy it.

So look at your time slip at your next trip to the track. Your mph figure will tell you pretty closely how much horsepower is at your wheels. E.T. is how well the combination of engine and chassis are working together. This is why you see some combos that do lay down big mph, but don't have the fastest e.t.

Offline Pistol Gripper

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Re: Rear wheel horsepower & compression ratio
« Reply #14 on: October 17, 2007 - 07:20:37 AM »
 :roflsmiley: :rofl: :roflsmiley: :rofl: :roflsmiley: :rofl: :roflsmiley: :rofl:

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