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Compression ratio for 1966 440. Stock heads vs 452s? #273191
03/31/09 10:56 PM
03/31/09 10:56 PM
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Tri-Cities, Washington
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VITC_GTX Offline OP
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Tri-Cities, Washington
Friend has a '66 New Yorker with stock 440. Years ago one of the heads cracked (over heated) so he replaced both with a rebuilt set of 452s. After that he believes he lost quite of bit of power (seat of the pants measurement). This is the non-HP 440 from '66. First of all what heads did it come with from the factory? What cc are those heads? How far down in the hole would stock non-HP 440 pistons be in the block? Trying to guesstimate compression.

He believes that the difference between open vs closed chambered heads are the reason for his power loss. What do you think?

Re: Compression ratio for 1966 440. Stock heads vs 452s? [Re: VITC_GTX] #273192
03/31/09 11:01 PM
03/31/09 11:01 PM
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Florida STAYcation
dIc dOc Deity ! Offline
The village idiot's idiot
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That cyl head change .... would lose a TON of compression !

Head cc's ? .. some 452's can be high 80's/low 90's .... the early heads ... low to mid 70's.

Re: Compression ratio for 1966 440. Stock heads vs 452s? [Re: VITC_GTX] #273193
03/31/09 11:42 PM
03/31/09 11:42 PM
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Carstairs, Alberta, Canada
dave571 Offline
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Not sure how far in the hole the slugs were on a 66, But....

I had a non molested hp 67 440. The pistons were .065 in the hole IIRC. Then the .020 gasket and some 516's that cc'd around 79.

Comp calculator gives that just over 10:1

Switch to 452's and a felpro gasket, and you're down to just under 9:1.

So a full point of compression, but you did gain a bigger exhaust valve and bigger runners in the heads. So there is a debate unto itself there.

Realistically, the gains in a closed head are only seen when quench is present. With pistons that far in the hole, you have no quench.

A full point of compression should only cost you 3 to 4 % but I think there are some other variables here.

Some say that a closed head develops some swirl on the intake charge, that improves atomisaton.

So it could be that with the open heads, it became slugish down low due to poor atomisation of the fuel charge. Add on the slight overall power loss because of the comp loss, and it may be noticable in the pants dyno.

Re: Compression ratio for 1966 440. Stock heads vs 452s? [Re: dave571] #273194
04/01/09 01:48 AM
04/01/09 01:48 AM
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GTX MATT Offline
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Maybe the 452s had a crappy valve job...


Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
Re: Compression ratio for 1966 440. Stock heads vs 452s? [Re: GTX MATT] #273195
04/01/09 01:57 AM
04/01/09 01:57 AM
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Today? Who Knows?
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FWIW I've seen the dyno numbers & I know they say one point of compression is only 4% but that is at max output, seat of the pants that one point of compression has always felt stronger from off idle to max power...

Re: Compression ratio for 1966 440. Stock heads vs 452s? [Re: 1_WILD_RT] #273196
04/01/09 07:38 AM
04/01/09 07:38 AM
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Indiana
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Fury Fan Offline
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Also, the valves in the 452s are bigger, and the ports are bigger/higher flowing than what's in the -516 heads that were original to the '66. Adds up to lower port velocity, which probably reduces turbulence and makes for a less ideal burn.

I'd say that, coupled with the compression loss, is the reason. Assuming the -452 heads were in good condition, of course...


Parts I seek: driver doorpanel, 65 Sport Fury, prefer black, needs to be 7-8 on 10 scale, might buy set 16" x 6" Dodge truck wheel(s), from early 70s?, takes 9" dogdish - need for a research job so cheaper is better. 69-73 C-body caliper brackets and/or splashields Send a PM.
Re: Compression ratio for 1966 440. Stock heads vs 452s? [Re: Fury Fan] #273197
04/01/09 08:23 AM
04/01/09 08:23 AM
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Posts: 24,562
Brookeville, Md
Mr.Yuck Offline
Not enough dumb comments...yet
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Brookeville, Md
Quote:

Also, the valves in the 452s are bigger, and the ports are bigger/higher flowing than what's in the -516 heads that were original to the '66. Adds up to lower port velocity, which probably reduces turbulence and makes for a less ideal burn.

I'd say that, coupled with the compression loss, is the reason. Assuming the -452 heads were in good condition, of course...




yes but do you need all that flow when you are only spinning it up to 4800? The heads would help more top-end. He has lost all his low-end grunt.







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