droptop z

Just wondering if any of you guys could help me out, I'm hoping to do a cam swap in the near future. My question is, when I change the valve springs, can it be done while the heads are installed on the block or do the heads have to be removed? I was just wondering 'cause a friend of mine told me "you know your gonna have to pull your heads to change those springs".

Jazsun

You dont have to pull that heads, thatd be a huge waste of time. Get the comp cams valve spring compressor which you operator w/ a ratchet and it does 2 springs at once. Ive taken all my springs off 3 times, and the comp cams one did it 5x's faster. You could get it done in less then 2 hours with it. All you need to do is figure out which cylinder is at top dead center and follow the fireing order and rotate the crank shaft accordinly depending on which cylinder you are doing. just incase a valve falls it it will stop because the piston is at tdc.

HardcoreRM125

It helps too to use a compressor fitting that screws into the spark plug hole. Run about 50-60 PSI. Just enouigh to hold the valves up incase your pulley mark is off or something happens ( You screw it up ) Heads stay ON car for this. Although with them off the car id imagine they could all be changed and put ot the correct install height in about a half hour if that?

Dont use a valve spring compressor you need to wind down. You will thank yourself later for not using one

rskrause

You could change the springs with the heads on and the motor in the car. But just changing the springs is not the proper way to set up heads. The installed height needs to be checked/adjusted to the correct specification. And unless the heads are fresh, removing them is a good excuse for a valve job.

Rich

BlackScreaminMachine

My thought exactly, installed hight is critical. On spring may need a 0.010" shim while another may need 0.030" shim. If you go beyond 0.030" then there is an in adeqate spring. Since there is so much that can go wrong, its not that hard to remove and install a head. People just tend to be lazy and want to race the car

96speed

Taking the heads off is a real pita. You can easily mic each spring with the heads on the car. You cannot get them perfect, but you can get them within, say, .015" of eachother.

There is no good reason to get a valve job with stock heads, unless they are "jacked up." Sorry, but a $150-300 job in machine work is unneccessary for a cam swap. You have to look at the whole picture, not just the "ideal
picture, IMO.

Ryan

HardcoreRM125

And I have to argue the installed hieght thing. Mine were all the same. Only one cylinder was off and it was off by .04 ... On a stock set up, they are relatively close. Dont get me wrong, I would never do it without checking, and shimming where needed. Just saying, they can be VERY close to each other and MOST dont need shimming.

FormulaW66

so your saying to do this with out the compressed air? and when the valve falls it will hit the top of the piston and you can still grab the valve stem and pull it back up??? about how far does it drop if the cylender is at TDC

Dansean1

They say you can do the job with the piston at TDC, but its risky. Compressed air is the best. You KNOW for for sure the valves wont fall down.

Someone said the wind down type of valve spring compressor is not good in comparison to the ratcheting type, why?
Im about to change my springs to LT4 valve springs in less than a month.

SS RRR

Using compressed air is a real pain in the *** since the hose just doesn't want to bend the way it needs to go. I've tried it, but I fear that I'd cross thread it and screw myself. I've had great success with just getting 1/4" dia nylon rope and stuffing into each cylinder and turning engine over until it stops. I can't see how you could just use the piston at TDC to get the springs off since there's so much play due to the piston valve reliefs.
A traditional spring compressor is the worst. Especially with dual springs and having to fight w/ the cowl for the back cylinders. The CC spring compressor is pricey, but if you don't want to be frustrated to the point of stabbing a wrench into your throat it may be worth the money.

sssalah

I have a Crane cam compressor that does 2 springs at a time, didn't know that Comp made one also, but that tool is a real saver especially for the cylinders under the coil area and where daul springs are used. Also I always put the pistons at TDC and never use compressued air, the valve would hit the piston with a good length of the stem still extended.

Stoopalini

There is no risk whatsoever doing the springs with the piston at TDC. The valve falls a very small amount (1/2" or so?) and then rests on the top of the piston. Read Shoebox's Valve Spring Swap Article and use the tips & tricks he has there to find TDC for each cylinder as you change the springs out. It's actually very easy to do with the right tools.

Good luck getting an air fitting into the spark plug holes. Whoever suggested that on an F-body LT1 probably hasn't done a a spring change on one before. I used an air fitting on my old '87 full size Jimmy, and it was nice; but I couldn't imagine doing that on my '96 Z.

I used the Proform Spring Compressor and it worked great. Only problem with it, is that it can tend to angle the spring on compression if you're not watching it closely.

Also, there is no problem micing and shimming the install height with the heads on the car. When I installed my 1.7 Scorpion rockers, I also installed the Comp Cams Beehive 918 springs. I chose an install height of ~1.75 and had to shim 7 of the 16 springs. 6 of them used 0.015 shims, and one needed a 0.030 shim. So don't assume the factory install/machining job is going to be right on.

Thomas.

Javier97Z28

We use the spring compressor that some dude on ls1tech.com sells... real basic piece of metal, but it does the trick. It's like one of those old crowbar looking tools, but cut in half to fit under the cowl and bolts onto the rocker stud to compress the spring.

We always use the TDC method, since we're usually doing it with a cam install we have the timing cover off and watch the dots. Valve stay up enough and if the seals are good they will hold the valve up when you pull them up.

I can barely get a compression tester onto an LT1 f-body with headers, and forget the tool to fill the cylinders with air, found that to be impossible...

wrd1972

I did not shim any of the LT4 springs when I installed them with the heads still on the engine. I was told I would be fine, now I am hearing otherwise.

What is the worse that can happen. My engine is running very strong.

FormulaW66

can you explain this alittle more.