No problem at all. The 454 block must be a Mark IV (pre 1990 I believe).

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von '69 300 Dlx SS TC #15 ACES #1575
My '69 SS

 

What would the resulting HP be, assuming everything else stock LS6? I'm guessing this combo would be meaner than 454 heads..

 

Do you have the casting #'s handy? Are they oval or square port? Big block head casting #'s fit a wide range of applications,example being that several motors with different HP ratings used the same castings...

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1970 Chevelle SS396/M21/4.10 My 70 SS396
Engine pic
1970 Chevelle SS454My 70 SS454
1968 Oldsmobile Cutlass convertible
1982 Oldsmobile Cutlass 350 Olds,TH350(daily driver)
Chris Corwel,TC Member 785

 

No casting numbers specifically, but thought if my 454 block with 427 heads would be a better combo for performance, I'd look to get a set of 427 heads....

I've got '291 square port heads on there now.

 

I just replaced a set of aluminum 427 heads with the correct LS6 heads on my LS6 car and really see no noticeable difference in power,,wat I did notice was when I took the Aluminum high rise intake off and replaced it with the correct LS6 intake,,lost sum of its zip,,if U know wat I mean,,,

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<LI> ACES Charter member # 0073 <LI>TEAM CHEVELLE # GOLD 009
<LI> 70 triple Black LS-6 SS 4 speed car / 70 Cortez silver L34 SS 4 speed car
www.members.home.net/northern/bowties

 

JoenAnne, dang folks, just get a 427 in there and have some 7 grand fun!

But seriously folks, it'd be the configuration of the head rather that it was a 427 head. Is it an aluminun rect port head, iron oval, closed/open, etc...

Common wisdom seems to indicate that oval ports would be a better match for your useage. So a set of 68/9 (open chamber) 400hp 427 heads might be right.

BTW, 427 and 454 share the same blocks and bore dia.

[This message has been edited by 427L88 (edited 05-21-2001).]

 

uh oh...there must be something wrong, my 454 will go 7 grand

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Bob West
Monett,Mo.
1972 Malibu .030 over 454
350 turbo-3.73's
10.71@96.12 1000ft.track
8.20@85 mph 1/8th mile

 

I have a 75-83 car and truck 454 in a 69 chevelle with 66-67 396/427 oval port closed chamber heads with 109cc runners. This car runs very strong. I was told that these heads actually produce power in the lower RPM range which is different than the 454 heads which produce their power the higher RPM range (5000 and above).

 

IIRC most 427's came with closed chamber heads with varying chamber sizes. All large oval port with rectangular ports on the 425 and 435 hp versions

One thing to watch out for is if the 454 has domed pistons, you will need to make sure if they are compatible with the 427 heads. A good example: A 76 stock 454 with open chamber heads and 8:1 compression, domed open chamber type pistons were installed to bump the compression to 9.5:1. You install a set of closed chamber 427 heads, the pistons contact the combustion chambers, ouch.

If flattops are there you should have no problems. In fact that is an easier way to improve the comp ratio in a smogger 454

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Frank W
Forgotten Chevelles Rule
74 Laguna S-3 454 soon, 350 sooner 3.42 Posi
90 LX 5.0 Daily driver
Homepagehttp://www.chevellepages.com/folingo
Club Page clubs.hemmings.com/bearingburners