To deck or not 454?
Thread Starter
Instructor
Joined: Jul 2015
Posts: 121
Likes: 3
From: Maryland
To deck or not 454?
I posted a few months ago about an issue I was having with my 454 swap. I had what seemed like an engine miss. I tried everything I could think of and also several suggestions to no avail. So out of frustration I pulled the engine back out and inspected everything. Turns out the rotating assembly was out of balance. Was told it was really out and should run smoothly now.
Now the question I have for the experts on this board:
Since I have the engine apart should I have the decks cut so I can get to .040 piston to head clearance?
As it is now I have .065. The pistons are .025 in the hole and am using a .040 head gasket.
The engine has the 454HO roller cam and the compression now is 8.82 to 1. If I have it zero decked I would be at 9.22 to 1.
Is it worth the $200 to deck it? Would I see much gain?
The only reason to do this would be to up the compression some.
Thanks for any advice!
Now the question I have for the experts on this board:
Since I have the engine apart should I have the decks cut so I can get to .040 piston to head clearance?
As it is now I have .065. The pistons are .025 in the hole and am using a .040 head gasket.
The engine has the 454HO roller cam and the compression now is 8.82 to 1. If I have it zero decked I would be at 9.22 to 1.
Is it worth the $200 to deck it? Would I see much gain?
The only reason to do this would be to up the compression some.
Thanks for any advice!
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
I know lots more about sbc than BBC. Ideally the 0.040" clearance is to obtain optimum "quench"
sbc can get head gasket in thin 0.015" . I don't know but perhaps there are thin gaskets for BBC?
If you have a "numbers matching" block... ALERT … and if you do plan to have it decked... BEFORE you choose a machine shop, tell the shop you must preserve the stampings on passenger side front deck.
sbc can get head gasket in thin 0.015" . I don't know but perhaps there are thin gaskets for BBC?
If you have a "numbers matching" block... ALERT … and if you do plan to have it decked... BEFORE you choose a machine shop, tell the shop you must preserve the stampings on passenger side front deck.
Race Director
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Decking is a nice to have sort of deal for what you're doing...but you could just use some .020 steel shim gaskets.
JIM
JIM
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
assume your 454 is Mark IV … you didn't say
if Mark IV, seems summit has 2 or 3 gaskets 0.020" thin steel shim … 0.045" is close enough for quench. You should see improved efficiency from more complete combustion … but the tiny compression increase ain't gonna matter.
if Mark IV, seems summit has 2 or 3 gaskets 0.020" thin steel shim … 0.045" is close enough for quench. You should see improved efficiency from more complete combustion … but the tiny compression increase ain't gonna matter.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Many folk have used thin steel shim HG. Most say no problem on aluminum … but who knows length of their study and did or didn't they inspect heads after long-term use? The issue is that the steel may cause the aluminum to "brinnel' aka leave an uneven impression or "dent" in aluminum. I suggest you ask the manufacturers.
Pro
Joined: Apr 2012
Posts: 657
Likes: 114
From: Picton NSW
I'm referencing sbc info.
Many folk have used thin steel shim HG. Most say no problem on aluminum … but who knows length of their study and did or didn't they inspect heads after long-term use? The issue is that the steel may cause the aluminum to "brinnel' aka leave an uneven impression or "dent" in aluminum. I suggest you ask the manufacturers.
Many folk have used thin steel shim HG. Most say no problem on aluminum … but who knows length of their study and did or didn't they inspect heads after long-term use? The issue is that the steel may cause the aluminum to "brinnel' aka leave an uneven impression or "dent" in aluminum. I suggest you ask the manufacturers.
bfit
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Team Owner
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From: altered state
St. Jude Donor '05
Not much, its a personal choice. Id go after it but if it meant using some crazy thin gasket to get there, no.
Any time Ive used a steel shim or copper head gasket they leak eventually. Use a real one
Any time Ive used a steel shim or copper head gasket they leak eventually. Use a real one
Race Director
Joined: Jul 2015
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From: SW Florida.
half a point is worth maybe 1.5% power increase. spend the 200 bucks here... https://paceperformance.com/i-625508...zz502-502.html HO cam too tame and sounds like a pass car. this will work with dog bone lifters, but you have tie-bar anyway. springs about the same. this is a 1hp/inch cam. the HO does 461 hp in a 502. what are you runing for heads, valves, chamber sizes? and did you cc your chambers? they are frequently off. 119 cc can really be 122 or 113. your current cam specs. https://paceperformance.com/i-625492...oller-cam.html
Last edited by derekderek; Jan 19, 2019 at 04:44 PM.
Thread Starter
Instructor
Joined: Jul 2015
Posts: 121
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From: Maryland
I am running the oval Pro Comp aluminum heads. I know they have a bad reputation but at the time its what I could get. They have 2.25 intake and 1.88 exhaust valves. The motor was bored .100 over and I did cc the heads and believe it or not they all measued at 119cc.
I just desktop dynoed the cam change or compression change and it looks like a cam change is worth about 25 horsepower and the compression change was only worth around 10 horsepower. The HO cam does sound really tame.............
I just desktop dynoed the cam change or compression change and it looks like a cam change is worth about 25 horsepower and the compression change was only worth around 10 horsepower. The HO cam does sound really tame.............
Instructor
Joined: Sep 2017
Posts: 169
Likes: 20
From: Westlake Ohio
The quench benefits of decking a bbc are worth it. The bump in compression is ancillary to the cleaner, more efficient burn. If not already done add the eyebrow notches to the top of the bores as well.
Le Mans Master
Joined: Aug 2017
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From: Cool Northern Michigan
Another thing to consider with any decking is that it will change the geometry of the valvetrain ever so slightly. This will need to be addressed with a pushrod length checking tool. If the block is milled 0.020 then often the pushrod will have to be 0.020 shorter and so forth. So you may be looking at another set of $100 pushrods.
Melting Slicks
Joined: Mar 2008
Posts: 2,666
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From: Spring Park MN
I've done a lot of testing over the years with quench. There are real bennefits to a tight quench, more efficient burn and detonation prevention as well as a crisper better running engine. I like to run the quench as tight as I can without hitting the heads. I would never even concider building an engine with a loose quench. Any increase in compression on a low compression engine will make more of an effect than on a high compression engine.
Mike
Mike
Last edited by v2racing; Jan 20, 2019 at 04:35 PM.