Thread: Building a 454

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I have an original numbers matching 74 Corvette LS-4 I will be rebuilding. When I bought the car, three valves were stuck and subsequently broke their corresponding pushrods. I tore the motor apart and found the pieces in the oil pan.

I have never built a motor before, so with a few books, I have started reading. I believe the block is already bored .030 over, if it is ok, I will leave it alone. I am getting the block ready to be tanked.

It is tore apart and all the freeze plugs and oil gallery plugs removed. I will have it tanked, magnafluxed, and mic'd. It is a 2 bolt main, I was thinking about using studs instead of bolts to make it a little stronger, so it will probably get line honed.

My plan is to squeeze as much HP out of the motor, while leaving the external original. Yes I'm going to use the Rochester carb and the stock heads, intake, and exhaust manifolds. I also would like the motor to not need any external vacuum while running pump gas.

Am I being to ambitious? Once I get the initial inspection of the block and know what I need to do, I will start the work. Any suggestions, or words of wisdom are appreciated.

Todd

You won't learn any younger, I can guarantee that! Plenty of good motor guys on here, I always use a book as well, several out there and I follow them religously. Welcome also

Don't do anything else until you have your complete build on paper and run it past us hooligans. I've seen lots of guys start washing the block and buying parts, then end up with the wrong combination.

The first point I would make is that you need to build the right squish/quench into the motor if it will operate on pump gas and that may involve cutting the block decks, so don't wash the block yet.

You're going to use cast iron heads, so that will limit static compression ratio to no more than 9.5:1 in order to prevent detonation on pump fuel. Aluminum heads will control detonation up to 10.5:1, with all else being right.

You will need to measure the block deck height and the stack of parts that you intend to use. For instance, the stock block deck height of a 454 is 9.800". That's measured from the centerline of the main bearing bore to the deck where the heads bolt on. The stack of parts that GM originally used in that motor are:
2.000" crank radius (4.000" stroke)
6.135" rod length
1.640" piston compression height
These 3 values add to 9.775", leaving the crown of the piston down in the bore by 0.025" with the piston at top dead center if the block deck height is actually 9.800" (don't bet on it). When GM built the motor, they used thin steel shim gaskets (about 0.020" thick) to set the squish. Adding the piston deck height of 0.025" and the head gasket thickness of 0.020", you come away with a squish figure of 0.045". (right on the money). You can do the same thing on your rebuild if you find the piston deck height to be close to 0.025", but you need to do the measuring of your parts and the block deck height.

Some fellows like to take a cut on the block decks to insure they are flat and the same distance from the crank centerline on all four corners of the block. The other reason for cutting the decks would be to use aluminum heads. You can't use the thin steel shim gaskets with an aluminum head because of the difference in thermal growth and shrinkage between the iron block and the aluminum heads. The aluminum heads need a cushion to prevent cracking, so you would cut the block decks to maybe "zero deck" and use a thicker composition gasket that would have some "give" to it. Zero deck means that if your stack of parts is 9.775", then you would cut the block decks to a new block deck height of 9.775" and use a 0.035" to 0.045" thickness gasket.

This would be one way of finding the block deck height, measure with a 12" caliper and add the radius of the main bearing bore....
http://jamisonequipment.com/sites/de...s/BHM-24-1.gif

Measure piston compression height by hooking one jaw of your caliper on the top side of the wrist pin bore and the other jaw on the piston crown, then adding the radius of the pin hole.
http://jamisonequipment.com/sites/de...s/BHM-24-1.gif

So, measure your parts stack and your block deck height and let's see where we're at.

.

I think that you are telling us a lot when you say you want the externals to be the stock components. Carb, heads, exhaust manifolds etc. So tell us what your goals really are for this sleeper motor? You can spend huge money having the stock head castings worked, but if you are going to use the Rochester carb and stock exhaust you will be wasting the money IMO. If you cannot get the fuel/air in and you cannot get it out where are you headed?

oringinal numbers matching 1974 LS4-----------$$$$$$$$$$$$$$$$$$$$$

Originally Posted by twolaneblacktop

I think that you are telling us a lot when you say you want the externals to be the stock components. Carb, heads, exhaust manifolds etc. So tell us what your goals really are for this sleeper motor? You can spend huge money having the stock head castings worked, but if you are going to use the Rochester carb and stock exhaust you will be wasting the money IMO. If you cannot get the fuel/air in and you cannot get it out where are you headed?

The 1974 454 in the Corvette came with an 850cfm Quadrajet. Properly setup it will be fine. Compression and camshaft are where the horsepower will be found.

Not a big deal, but TriDaddy/Todd logged off 15 minutes after he posted, and has not been back so he's not read anything posted here.