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Old 09-01-2012, 02:29 AM
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bbc help

hey guys so the engine is out and will be taking it to a shop in a few days...the engine is a gen v 454..i am only sending the block(not the heads since i am trying to swap to large oval port) to the shop...am going to rebuild it stock; bore .030 over, grind the crank, new pistons, etc... now i want to run pump gas...doesnt matter if its premium..how do i reach my goal? what piston? last but noit least...i am planning on running the 049 or 781 mark iv heads (i am aware that i need special gaskets)..would any modifications be required for the head swap? such as rocker arms, cam bearings, valve springs or?...thanks alot guys

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Old 09-01-2012, 05:59 AM
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In general pistons with up to about a 1/4" dome will work with 119 +cc. 049-781 type heads. Pump gas @ about 10:1. Keith Black website has good descriptions and compression calculator.

Stock cam bearings are OK. Not a problem with BBC.

You will need different valve springs/retainers/locks/seals for any kind of real performance head work. 049-781 heads are great castings. But to get them to work. You need to...

First. They need 2.19/1.88 valves and related seat work. Not cheap. But if that is out of the budget, it is best to at least replace the stock valves with aftermkt stainless. One of the serious failures that BBC tends to have is dropped valves, especially stock intakes.

Make sure seats are "high" into chamber. I had a set a couple of weeks ago that the intake seats were sunk over .125 . Remember you loose flow on initial opening because of the sinking/shrouding around valve.

Next. These castings have rotators under the exhaust springs. These are trouble at high rpm. Need to be replaced with a solid spacer. Comp Cams and several others supply the correct parts.

These castings use a very short valve spring. Limiting any kind of performance cam lift. This can be remedied by.. Cheap way.. +.100 aftermkt retainers. These are only available with 10 degree locks so you will need a set of them, std height groove.
Correct way. While you are buying the stainless valves get then in +.100 long. That way you can use any higher lift spring/retainer combo. Or, old way, cut spring pockets .100 deeper.

Valve guides will neet to be shortened. If not done will smash seals/retainers at high lift. While this is being done have guide cut for .530 aftermkt positive seals.

Have the head castings milled .010" at least. This will remove years of abuse, help seal to the later block and get the chambers closer to advertised size. Most are big.

BBC are particular about pushrod length. If incorrect (which most I see are) will cause many rocker/spring/valve wear/alignment problems. BBC Pushrods are available in MANY lengths because of this. I have several hundred in stock. No valve train problems= happy customer. Stock pushrods don't cut it. Even on a lot of stockers. Use 3/8", correct length, with corresponding guide plates.

After all this work. You will think. I can get aftermkt aluminum mega flow heads for just a little more! Yup..

Thats why I sell lots of Pro Comp BBC castings.. Use quality, Manley etc. Valves and springs. They make great horsepower, last and take weight off the front end of the car.

Good luck..
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Old 09-01-2012, 06:56 AM
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If you plan to use a "RV" type cam, a cam with a smooth idle. Then limit compression to 9:1cr.

A 454 with flat tops and 781 or 049 head will make around 7.75:1 cr and 8.75:1 with a 1/8" dome.

8.75:1cr can use 87 octane with a mild cam (210 degrees at 0.050"). BBC's get 20% less mpg as compared to a SBC. So if you plan to drive it on the street then don't underestimate the value of being able to use 87 octane fuel (10% less cost which is the same as 10% more mpg).

With a cam in the 240 degrees at 0.050", you should be able to use 10:1 cr.

So cam size will have a big effect on how much compression you can get by with. Furthermore, going from 9 to 10:1 isn't worth that much more power. Maybe 2 or 3%. That would be 12hp in a 400hp build.

Figure out what cam you will use before setting up the compression ratio. I would error to the side of caution, and use lower compression if given a choice.

Due to the large surface area of the bearings, BBC's need to have tight bearing clearances to maintain oil pressure at idle when warm. I recommend 0.0015 to 0.002 on the mains and rods, and 0.0025 to 0.003 on the rear main.

Finally, when you tune a BBC, be aware that they love lots of ignition timing. 20 at idle, 40 total, and 10 more from an adjustable vacuum advance canister on manifold vacuum is a good place to start.

For a mild to moderate build, a regular RPM intake (not air gap) and a holley 750 cfm model 3310 would work well.
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Old 09-01-2012, 01:07 PM
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oohhh man i never realized it would be this much work to get it all to work..but if thats what has to be done well i have no other choice right..okay i have another question since you brought up the aluminum heads...lets say if i get me some procomp heads..will the similar process be required? All i want is a mild build..a 400-450 hp engine..an rv cam was somewhat already in my mind to install..if there was an eassy way to make 400+ horses with the peanuts i would definitely go that way since i already have them but heard it requires ALOOTTTT of porting
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Old 09-01-2012, 04:28 PM
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Aftermkt heads in general don't need any machine work. Most are set up for performance situations.

As for 400 hp 454. You can get that with mildly worked iron heads, good intake and a reasonable street cam.

Combination is the clue..
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Old 09-01-2012, 05:56 PM
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bbc help

First you should have the set of heads so you can cc the chambers. This would help when buying the pistons. If the set you get are 118cc you can get a set of KB Hypereutectic pistons. There is two to choose from KB201 have 1/16x1/16x3/16 rings, KB203 have 5/64x5/64x3/16 rings. Both have .133 domes and summit racing's price 461.95. If you get smaller chambered heads you would have to go with flat top pistons. To get a compression ratio of 9.1 the easiest way is have the block decked to .005 that way you can use the .039 compressed thickness head gasket. This will give you .044 quench which is important in using 87 octane gas. To get to 400-450 hp you need a set of aluminum heads that have good flow or a set of 781's reworked and ported. The procomps that you are talking about I don't have any knowledge about. I have read post where people have bought them bare and take them to a machine shop to have them checked and put ss valves in them.
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Old 09-02-2012, 06:45 AM
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Read this.

Cheap Big-Block Chevy Engine Build - Car Craft Magazine
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Old 09-02-2012, 10:02 AM
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BBC help

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Originally Posted by 454C10 View Post
A good article nothing fancy and peanut port heads too. This engine beats any 383 small block. Over 500 lbs of torque would work nice for a pickup or heavy sled car and under $3000.
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