Guest Anonymous Posted November 23, 2001 Share Posted November 23, 2001 Need help on how to change valve springs with heads on motor and in the car. Also how critical is measuring seat preasure and shimming etc. Cam is HYD CC 292. Valves seem to float past 6000. Quote Link to comment Share on other sites More sharing options...
DavyZ Posted November 23, 2001 Share Posted November 23, 2001 Most auto parts places like Summit and Nothern Auto Parts sell tools for taking off springs with the heads & everything still on the car. The main problem you will face is keeping the valve up in the head while you change out the spring. Remember that when you take pressure off of the spring and take out the keeper, etc, the valuve will just want to drop into the head because nothing will be holding it up at that point. I think the easiest way to keep it "afloat" iswith compressed air blown into the cylinder thru the spark plug hole. If you don't have the fitting to do this, get it from the above mentioned places; they should carry it. Good luck. Davy Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 23, 2001 Share Posted November 23, 2001 Yup, it works. I did it on a AMC motor once, put in the fitting and air'ed it up. It went to bottom dead center and held the valves up. You do have to be careful and not bump the valve to much when your taking the spring off, it is possible for it to slide out if it breaks the seal and the pressure falls off. Once pressurized you use a fulcrum type compressor and remove the keepers and springs etc. Its a good time to do valve seals while your there as well, they get brittle, crack and you get added blowby. Just a suggestion. I've also heard about people putting rope in the cylinder to stuff the chamber and then going for it, but putting something other than a sparkplug in that hole just feels wrong for me, but it seems like it would work to me. but I'd still use the compressed air. Regards, Lone Quote Link to comment Share on other sites More sharing options...
John Scott Posted November 23, 2001 Share Posted November 23, 2001 Compressed air is the way to go. Fittings avail. from auto part stores. Once under pressure. Give the valve stem a couple of light raps with a leather or other soft compound hammer to loosen the valve stem retainer. Rope works, but the risk is having it tangle in the cylinder and having to pull the head anyway. Been there done that JS Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted November 23, 2001 Share Posted November 23, 2001 Your cam will have a rec'd spring range for it. If you already have the springs then they'll have their own reccomended install height for which they have a spec'd pressure. You should only have to measure the install height. (if springs aren't new I'd have them tested...cheap insurance that paid off for me before). Cutting a piece of coat hanger wire to proper length for install height once you have it figured out is a handy measurement method. I prefer the 'overhead' KD tools compact spring compressor, can work on most any head and you don't need 'fulcrum' room. Bit of wrist work that might tire you after 16 but that's wrenching;^) Once spring is off I always twist a stiff piece of wire around the valve retainer groove just in case it wants to drop (yes, even with compressed air hooked up) [FWIW, even with assembled heads on my bench and swapping springs the valves never wanted to drop but can't hurt to be careful] Be sure to seat new valve seats down fully. As well on some of my retainers it took a swift smack of a real hammer to break their 'bond'. It's like a drumset, some sound dull and they're not 'bonded' the 'tinks' are bonded and need a swifter smack(or vice versa, it'll be obvious), an angular blow with your hammer is more likely to break that bond....done this a few times now. good luck PS A couple of those extremely handy small rare earth magnets on the tip of needle nose visegrips (or any magnet, but re magnets are v. strong) work great for grabbing the retainers/valve locks (can't recall term?) out once your valve spring is compressed far enough. I hate chasing potential lost parts.....replacing valve locks is always a good thing as well... Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 25, 2001 Share Posted November 25, 2001 Yes, thank you Ross. You will need the correct spring tension required for your cam, You cam card should tell you what spring tension is required, make sure you are using the correct spring or risk flattening out the lobes of your cam, pushing through your spring boss (on alluminum heads) or pushing through a keeper. And if you are using new springs you MUST use new valve keepers (or keys, Ross ), DO NOT reuse the old keepers with new springs. They are weak, your new springs are strong, and quite frankly, at $0.50 a piece, can you really affor to take that chance? PS. Shims are used to "dail in" the correct spring tension. In our shop we had a couple different procedures where shims were necessary. After an econo valve job (old springs and valves are reused, no hard seats, no surface, just clean and grind) BTW, I would NEVER reccomend this, but if its what the customer wants, you shut your mouth and do it, right? Well, shut your mouth just AFTER you explain that we won't warranty their heads with used parts...)Anyway, if old springs were reused we would add "booster shims" (60 thousanths)under all valve springs to raise the tension back to factory specs. (two reasons; used springs have lost some of their tension, and grinding valves and seats will raise "install height" by allowing the valve to sit deeper into the seat.) Next, after a professional valve job we used new springs, we would add smaller shims (30 thousanths) under the intake valve springs only (because of the raised install height of the intake, not the exhaust because new "hard seats" will be added and ground to factory height). And for a high performance application, an install hieght reading would be taken for every individual valve, and any combination of 60, 30, and 10 thousanths shims would be used to get as close as possible to the exact spring tension required... (That used to be my job, eciting, huh?) Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 25, 2001 Share Posted November 25, 2001 Thanks for the input. The motor is pretty new 3 years old with less than 1,000 miles. I dont trust the SOG that buit it now based on what has happened to to his other victims. The motoer seems to float at over 6,000. I suspect that the springs are bad. I ordered a new correct spring set for the CC 292 cam from Scoggin Dickey this week. I assume that this will be ok without the shims? The heads are old and have most likely had their fair share of valve jobs. Could this have lessened the tension and be causing my valve float? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 25, 2001 Share Posted November 25, 2001 Well, my intitial reaction was "yes, if they've had thier fair share of valve jobs, you need shims" But let me back up, for a minute. The best way to determine if you need shims is to set it up by installed height, on the bench. It's your call, If you want to know how to do it, let me know. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 26, 2001 Share Posted November 26, 2001 Thanks Vahan, One other question... I seem to remember reading somwhere that valve springs should be treated to a hot oil bath in the oven prior to install. Is this so I can remember where I read it or when. Quote Link to comment Share on other sites More sharing options...
pparaska Posted November 26, 2001 Share Posted November 26, 2001 Ross and Ara wrote a nice book here, but I'll try to answer a few more questions: Cooking Springs? Probably not a bad idea. Hot oil can be flamable though . I've also heard you should cycle new valve springs about ten times before reading their stiffness, etc. on a spring tester. Tavia makes a cheap spring tested that you can use in a big vise or drill press. It works o.k., but is kind of "sticky". About $60. Maybe not a bad option. I'm not too sure about the kind that you us one the head with a torque wrench, etc. The ones they use in the machine shops are expensive - even used! I agree that you should measure the retainer to spring seat height and compare it to the installed height the springs are speced at. If the valves are sunk much, this dimension might well be larger than the installed height of the springs and the seat and open pressures will be lower than spec. (not sure who'll be reading this, so I'll elaborate a bit) A snap gage and dial cailper is good enough to measure this, but there's a nice tool that goes where a spring would be that measures it directly. Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted December 1, 2001 Share Posted December 1, 2001 This might sound really mickey mouse... but i heard that you can stuff nylon rope into chamber thru the spark plugs holes... just stuff it so that it holds the valve up.. make sure the string or rope dosent break with oil or loses fibers... I think the compressed air is probably better... but just another idea... Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 2, 2001 Share Posted December 2, 2001 I got my new springs today. I will go ahead and order new locks as well. Since yall say this is needed. I pulled my valve covers and checked the old springs installed height. It was over 1.85 with a shim. Accourding to comp cams it should be 1.74 for my set up. I guess this is why my valves are floating and motor will not rev beyond 6300 rpms. I am certain that it is losing power far less rpms too. Could the valves be sunk that far? And if my measurements are correct will shimming be enough to correct the problem. Car still runs low 12 with a best of 11.95 at 113mph. 355 6 inch rods 10.25 :1.00 292 heads ported and polished 292 Cam 501. lift vic jr. 750 dp MSD 1 3/4 headers 3.90 rear end T350 trans 3000 stall Weight w/ driver 3005 What can I expect when the set up is right? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 10, 2001 Share Posted December 10, 2001 Thanks for all of the help. I changed springs and had to add an avg of .120 shims to each valve spring to get the proper installed height. The worse was .195 too high. Car now revs and pulls to 7000. Quote Link to comment Share on other sites More sharing options...
DavyZ Posted December 10, 2001 Share Posted December 10, 2001 Good to hear! Davy Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted December 11, 2001 Share Posted December 11, 2001 Hrm, you broke a rocker right? Out on the track? You might want to double check that valve and make sure you didn't get and coil bind just in case. Would be most uncool to do that again and maybe wind up dropping a valve Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 11, 2001 Share Posted December 11, 2001 I will tripple check it. Thanks for the help that makes good sense. Quote Link to comment Share on other sites More sharing options...
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