Thread: SBC 350 build

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Originally Posted by Bowtiepickups

I've decided I will bite for the extra few dollars and added security and go with a retro fit hydraulic roller cam.

I think you'll find that the best deal going on a retro roller will be from Howard's Cams, about 500 bucks for the cam and lifters. Most of their stuff is ground on a 112 degree lobe separation angle. You can install the centerline anywhere you want to though, when you are degreeing the cam in the block. Advancing it 2 or 4 degrees will add to the bottom end while detracting from top end performance. Retarding it 2 or 4 degrees will add to the top end and sacrifice some of the bottom end grunt. If you have to advance or retard more than 4 degrees to get where you want to be, then you have installed the wrong cam. Speaking of degreeing the cam, here is a tutorial that you should study until you know it by heart...
http://www.iskycams.com/camshaft.php

You might want to consider starting with a roller block. If you could find a good L31 short block with the roller lifters, dogbones and spider and the lifters were in good shape, you could be money ahead by not having to buy lifters, just buy the cam that will work for your combination and SCR. The added benefit would be the one-piece seal, as opposed to the two-piece seal in the earlier blocks like you have. If you don't do everything just right on assembly, the two-piece seal will leak and there's nothing worse than to get a motor together and running and find that you have a leak at the rear seal.

Originally Posted by Bowtiepickups

Should I get self aligning rockers or ones that use guide plates? The self aligning are only a couple bucks more than ones that use guide plates on summit.

The cheapest way to do it would be to pin the studs and use rail rockers. To use conventional rockers, you would have to remove the studs, mill down the pad on the head by the thickness of the guide plates, then drill and tap for screw-in studs with guide plates. Something has to keep the rocker tip centered over the valve stem tip, either a rail rocker or guide plates that keep the pushrod centered, which keeps the rocker centered. I don't think I would want to use rail rockers with a wild camshaft, but with what you are considering building (probably less than 0.525" valve lift), I would be ok with rails.

You'll have to determine if it is worth it to install roller rockers or use conventional stamped stockers. The advantages of rollers would be less friction generated, thus, less heat in the oil and the fact that they would be a true 1.5 ratio. Stockers will normally check less ratio than the engineers specified, sometimes as little as 1.4 according to some fellows, so you would not be getting the full valve lift that the camshaft was designed to produce. The downside is the cost and the fact that the rollers are not as durable as stamped steel rockers. Some fellows have experienced them coming apart and scattering little roller bearings throughout the motor. If you do run rollers, it's a good idea to epoxy some brass screen material over the oil return holes to catch the rollers before they go to the pan. Some might slip past and go down the pushrod holes, but hey, you do the best you can with what you have to work with. The screening can also catch shrapnel from fragged springs or retainers.

I searched around for the best price on Scorpions for you, seems like they have taken a giant leap in price since the last time I looked. Some ebay vendors are asking 300 bucks for a set. Anyway, the part number for a narrow-body (to fit inside the L31 valve cover), self-aligning, 1.5:1 ratio set of 16 is SCP1035. Mountain shows them as SCP1035-1 for 270 bucks. Click the blue oval that says "Update Price"....
http://www.mountainperformanceonline..._p/scp1035.htm

Originally Posted by Bowtiepickups

Assuming my deck height is stock and stays the same with the KB pistons, I worked out a 9.57:1 compression ratio with 0.015 fel pro gaskets using summit's compression calculator.

OK, first I want to make sure you learn the proper terminology. There is "block deck height", which is the measurment from the centerline of the main bearing bore to the flat deck of the block where the heads bolt on and is usually around 9.025" on a virgin block. Then there is "piston deck height", which is the measurement from the piston crown to the flat deck of the block where the heads bolt on with the piston at top dead center and will usually be from zero to 0.050", with an average of maybe 0.035". I know you will hear fellows say just "deck height" without specifying which one they mean and most of the time, in that case, they will be talking about the measurement from the centerline of the main bearing bore to the block deck. But I want to teach you properly, so whenever someone says "deck height", ask them whether they are talking about block deck height or piston deck height. They might look at you like you have two heads, but they are the ignorant ones if they don't know the difference. Now, as you know, ignorance can be cured by teaching and learning. On the other hand, stupidity goes all the way to the bone and is terminal.

To do the thing right, you would first align hone (or align bore if the register is way out of whack) the main bearing bore in the block. This will take out material between the centerline of the bearing bore and the centerline of the camshaft bore. If enough material is removed so that the timing chain will be sloppy, there are timing sets that are a little shorter to take up the slack. Then you would measure the block deck height. Normally, you will find that there is a fairly large discrepancy from one end of the block to the other. Sometimes the machinist at the factory did not get the register cleaned out of all the chips from the previous block and the block decks will be machined uphill/downhill. I personally have seen 0.014" on a 429 Ford block and I'm sure Pat McCarthy and Jerry Clayton have seen worse than that, as many engines as they have built. When you deck the block to bring it back to square, that's when you measure all the components (rod journal throw, rod length and piston compression height) in order to set your piston deck height according to the gasket you plan to use so you can set the squish between 0.035" and 0.045".

If you think about it, you can see where the intake manifold would not sit on the heads properly if the deck was tilted uphill/downhill. I think sometimes that is what makes an internal vacuum leak happen. This is where the outside of the intake manifold is pinched pretty well at the cylinder heads, but on the other end of the port, on the crankcase side where you can't see it, the gasket may not be squeezed and the intake ports are pulling in not only air from the carburetor, but also oily air from the crankcase. This can make you nuts if you don't know about it, because no amount of spraying a combustible material such as propane around the intake manifold will find an INTERNAL vacuum leak.

Now, another good reason to deck the block and maybe even take a skim cut on the heads is if you are going to use a shim gasket. You mentioned using a 0.015" gasket. That's a shim gasket, not a composition gasket. While a composition gasket will tolerate some wavy action on the deck and heads, a shim gasket is not as tolerant. Both the decks and the heads need to be pretty flat and smooth to insure that the motor won't spit out the shim. Just be aware.