Cam Swaps


This guide was written with the small block Chevy in mind, but most it applies to any engine. I won't cover every detail, such as removing the fan belt before removing the water pump. Things like that should be abundantly obvious once you get to it. Also, I'm going to focus on flat-tappet cams. A factory roller-cam setup will have a couple extra steps, but they'll be obvious when you get to them. Aftermarket roller cams require a few more details. If you need to know about them, my e-mail address is at the bottom of this guide.

For the first part of the cam swap process, remove the lower radiator hose and drain the coolant. Once it's all drained, remove the upper hose, radiator, water pump, and on some vehicles, the hood latch support, A/C condensor, grille, etc. This is to give adequate clearance for removing the cam from the block.

Next, read and follow the 2QuickNovas Guide to Intake Manifold Swaps. It will guide you through the removal of the carb, distributor and intake manifold.

Once you have all the obstructions out of the way, remove the harmonic balancer using a puller. Cheap pullers can be bought for about $5 at your local junk store, but dont' be surprised if they only survive one or two uses. Be careful to not damage the crank. Some pullers will try to dig into the snout and wipe out the threads.

If your engine has a mechanical fuel pump, it is driven by an eccentric on the camshaft. Remove the pump, being careful with any spilled fuel. On a Chevy, you can let the fuel pump pushrod slide down into the pump cavity. This saves you from removing the pump plate and gives ample room to slide the cam out.

In order to get the timing chain cover off, the front of the oil pan must drop about an inch. Total removal isn't necessary and is sometimes hard to do with the engine in the chassis. Loosen all the oil pan bolts and then remove the ones toward the front half of the block. Gently pry the oil pan loose from its gaskets.

Once the pan is clear of the timing cover, the cover can be removed. Don't get too rough with it when prying it loose from the gaskets. They are not very thick and you don't want to cause any leaks. Also, the cheap, chrome timing chain covers are usually junk. They don't seal well at all and are more headaches than they are worth. Just something to consider if you were thinking of adding a splash of chrome to your engine. If you are a racer and think you might be doing cam swaps or cam timing changes with any regularity, a two piece timing cover or a cover with a "window" for adjusting the cam could come in handy. There are a few really nice (but expensive) cast aluminum covers on the market that would work well.

Go ahead and remove the 3 bolts attaching the cam gear to the cam. The cam gear just pulls right off and the chain comes off with it. If you will be doing a lot of cam timing changes in the future, a Cloyes Hex-A-Just timing chain can be a real time-saver.

When installing a new cam, I suggest you use a new timing set. Definitely don't reuse a stock timing set that has nylon-coated gear teeth. I've seen the nylon break off, plug up the oil pump pickup, starve the motor for oil, spin multiple bearings and eventually break the crank. It's just not worth the risk. Therefore, you'll most likely need to remove the crank gear. A gear puller is needed for this. I have a cheapo imported puller and its worked fine for years. It was $5 at my local junk store. They can be handy for other projects as well.

Remove the valve covers if you haven't already done so. Loosen the rocker arm nuts. With stock rockers, you can just loosen them enough to allow the push rods to be removed. If you totally remove the rockers, balls, and nuts and plan on using them again, use a twist-tie to keep them together as a set. If you will be reusing your pushrods you need to make sure to get the pushrods and rocker arms back in the same place they came from to avoid unnecessary wear. Put the valve covers back on after the pushrods are removed to keep grit and dust off the valvetrain and heads.

You should be to the point of removing the lifters now. Sometimes the lifters can be hard to remove. Rotating the cam by hand to raise the lifters up usually does the trick. If you think you'll ever want to reuse the cam and lifters, be sure to keep the lifters in order. Putting used lifters on any cam lobes except the one it was orignally on is a big no-no. Do that and you'll have a flat cam in just a matter of miles. A divided box with each slot labled with the cylinder number and whether the lifter is from an exhaust or intake lobe is a good way of keeping track of the lifters.

Now there should be nothing preventing you from removing the cam. I suggest getting a long bolt and threading it in the end of the cam. The correct thread is 5/16-18. This bolt will give you a handle, which is necessary to prevent scratching the cam bearings as you remove the cam. Go slow and easy.

With the cam out, look down the cam tunnel to check the condition of the cam bearings. They usually don't wear too quickly, so most likely they'll be useable.

Your new cam should come with break-in lube. Liberly coat the lobes and fuel pump lobe. Then oil the bearing journals, thread the long bolt in the end of the cam, and slide the cam in. Again, be careful not to nick, bang, scratch or scrape the bearings. You'll get a feel for it. Once the cam is all the way in, spin it by hand to check for any tight spots or binding. It's doubtful that you'll find a problem, but it's always good to check.

Next, drive the new crank gear onto the crank snout. Be sure to oil the inside diameter of the gear and the crank to prevent galling. It's going to have to be driven onto the crank. Some people like to heat the gear and some just drive it on using a piece of pipe that will slide over the snout of the crank. If you heat it, I suggest just putting it in a pan of boiling water (add some cooking oil to prevent any flashing of rust) on the stove. This won't get it super hot by any means, therefore the gear won't be distorted. With this level of heating, you'll still have to gently drive the gear onto the crank. Be careful not to damage the gear or crank. PVC pipe has been known to work and is softer than the crank and gear so it shouldn't damage either one.

You are now ready to time the cam. Your motor should be sitting at TDC for the #1 cylinder if you followed my intake removal guide. The dot on the crank gear should be at 12 o'clock. Put the cam gear on the cam and turn it so that the dot is at 6 o'clock. Carefully remove the cam gear being sure to not rotate the cam. Put the timing chain on the cam gear. Holding the cam gear with the dot at 6 o'clock, put the chain around the bottom of the crank gear and slide the cam gear on the cam. The dots should line up vertically. If not, take it back off and try it again. You should easily be able to see if you have gotten it a tooth off.

I like to use Loctite 242 (blue-removeable) on the cam bolts. Torque them to 25 ft-lbs.

Most timing chains are marked so that when the dots are lined up on the timing set, the #6 cylinder is ready to fire. We want the engine ready to fire #1 (you could finish up the project and set the distributor ready to fire #6, but most people like to work with #1). To get the engine ready to fire #1, just turn the crank 360 degrees or one full revolution.

Put break-in lube on the bottom of the new lifters, oil the sides of them and put them in the block. They are all the same, so there are no tricks here, except that the flat side or the roller goes down against the cam, but you knew that already.

It's now time to start buttoning this thing back together and that starts with scraping gaskets. I like to do this after I've put the cam and lifters back in, as it helps keep trash out of the bottom end. Lay clean paper towels in the lifter valley, stuff some down the intake ports and in the front of the oil pan and cover the timing chain. Basically, just use common sense to keep the inside of your engine clean while scraping gaskets and sealer off the block, heads, intake, etc.

Before bolting the timing chain cover back on, check to be sure the gasket surface is clean and check to be sure the semi-circular rubber seal that mates to the oil pan is the correct one. There is a tall one and a short one, the right one for you depends on what year motor the oil pan you have came from. Compare the new ones to the old one and use the appropriate seal. Oil the timing chain thoroughly so its lubricated upon startup. Using a small amount of sealer on both sides of the gasket, install the timing chain cover and snug up the bolts. They don't require much torque at all, 6 ft-lbs will do it.

You can bolt the oil pan back up now. Hopefully the old gaskets didn't tear and you can just smear some sealer on them. The oil pan bolts get 14 ft-lbs of torque, but some people swear by only using 10-12. Once the pan is torqued, take some more sealer and cover all around it, especially around the bottom of the timing chain. Just use enough to fill in the seams.

You are now ready to put the pushrods and rockers back in. Tighten the rockers just enough to take up most of the slack in the pushrods.

Following the 2QuickNovas Guide to Intake Manifold Swaps, reinstall the intake, carb, distributor, etc. Reinstall all accessories.

To set the valves, follow the 2QuickNovas Guide to Valve Adjustment. Reinstall the valve covers using new gaskets.

Install the harmonic dampener. Do not beat it on with a hammer. Get a piece of threaded rod, screw it into the crank, oil the I.D. of the dampener and the crank snout and pull the dampener on with some heavy washers and a nut. A Torrington trust bearing from an automatic transmission makes for a good addition to this setup. Put the bearing between a large washer that sits on the dampener and a smaller washer under the nut. This will keep things from binding as you tighten down on the nut.

Bolt up the fuel pump, water pump, radiator, grille, hood latch brace, etc. The trick to installing the fuel pump is to thread a long bolt into the top hole in the front of the block to hold the pump pushrod up in position. Just lightly thread the bolt in against the pushrod while holding the pushrod up against the cam. Once the pump bolts are tight, remove the long bolt and replace it with a short one that won't hit the pushrod. Use a little thread sealer on it to help prevent oil from wicking up the threads. Unless I've gone brain-dead and forgotten something, you should be ready to fire this bad boy up. Get a friend to help watch for leaks (oil, water, fuel) and to keep the radiator topped off with coolant. The thermostat will trap air in the block and if you don't keep an eye on it, the motor could overheat during the cam break-in procedure.

Prime the carb. The distributor should be ready to send spark to the #1 plug, so set aside a half hour to break in the cam. Try to get the motor to fire immediately. Don't grind on the starter so that you don't wipe off all that cam lube you applied. Once the motor fires, bring the rpms up to 2000 and vary it from 3500 to 2000 for a half hour. DO NOT let it idle. Watch your oil pressure and water temp closely. Have your friend armed with a water hose to keep the radiator full and to spray the radiator if the engine starts running warm. After half hour, shut it down, change the oil and filter and let the engine cool down. Before driving it, check the water level again and the oil level, too.

These are the basic steps to swapping cams on a small block Chevy (or other similar engine). Once the engine has going through a few heating and cooling cycles, go back and retorque the intake manifold.

If you need further details or find any screw-ups in any of my guides, please contact me.

If you have any questions or comments please click the "Contact Craig" link and let him know.

Copyright 2008 Bruce Johnson and Craig Watson