valve adjustment. help? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

aric68 · 02-23-2010, 01:44 PM

my buddy decided he wanted to adjust the valves in my 72 402. we tightened them down until we could not spin the push rod and then tightened them a 1/2 turn more. we followed a pattern we saw on line that allowed us to adjust half of them then rotate 1 turn and adjust the rest of them. well it sounds ok idling but put it into gear and it almost dies no power. whats wrong?

67vetteal · 02-23-2010, 01:48 PM

Your Valves are too tight. Back each nut uo until you hear a slight clicking sound. Then tighten just a half turn. That's 180*. Do this immediately or you may wipe out your Camshaft.

Al W.

Myself · 02-23-2010, 02:33 PM

I agree, way too tight. You only tighten until initial drag is felt while spinning the pushrod with your fingers. If you tightened until you could not spin them, you probably went a couple turns too much.

*Ticker* · 02-23-2010, 03:55 PM

Don't adjust valves with the engine running.

Unless you have a radical cam, the companion cylinder method is quick and easy. Key point is as above...the very first time you feel any drag at all is zero lash.

http://www.carcraft.com/howto/ccrp_0...aft/index.html

Phlebmaster · 02-23-2010, 04:39 PM

Quote:

Originally Posted by Ticker

Don't adjust valves with the engine running.

Unless you have a radical cam, the companion cylinder method is quick and easy. Key point is as above...the very first time you feel any drag at all is zero lash.

http://www.carcraft.com/howto/ccrp_0...aft/index.html

That is a good article. I plan on using this method next time I adjust my valves. Last time I did mine was a mess! I had oil all over the place and the smoke was unreal.

Ticker, I just noticed all of the helpful links in your signature.

aric68 · 02-23-2010, 05:12 PM

well the mechanic said the cam is gone, but it was running with an intake back fire with and acceleration before, and now it keeps trying to die when put in gear.

*Ticker* · 02-23-2010, 05:15 PM

If you tighted down the cam too much...then you'd have wiped the lobes

The backfire was likely timing and/or fuel related.

aric68 · 02-23-2010, 05:25 PM

we timed it to -9 and dialed in the carb before we ever took off the valve covers.

Wrenchbender Ret · 02-23-2010, 05:45 PM

What do you mean by "-9". You may have it timed too slow & your valves are OK. If it was popping back through the carb on accel. your mech. is probably right. You may have a bad cam. Run or turn the engine with the covers off & watch for a valve that barely opens.

aric68 · 02-23-2010, 05:52 PM

so the mechanic wants to charge me 1000 to replace the cam. how hard is it?

aric68 · 02-23-2010, 05:53 PM

i guess i mean 9 off top dead center

Phlebmaster · 02-23-2010, 05:55 PM

Quote:

Originally Posted by aric68

so the mechanic wants to charge me 1000 to replace the cam. how hard is it?

It is not that hard. I did mine with no previous experience. Buy a kit if you can and follow the install and break in instructions for your new cam.

Here is a video I made of the swap>

YouTube- 350 with Comp Cams Magnum 270H 112 LSA...

This one might give more detail of the front of the block and cam gears

YouTube- SBC Noisy Cam Gear Swap and header...

Put the engine at TDC for # 1,

Pull the distributor (after you mark it)

Then the intake

then the grill, radiator, water pump and the stuff attached, then the crank pulley/harmonic balancer, then the timing cover.

Then pull the timing gear/ chain.

Pull the fuel pump (there is a fuel pump lever actuator rod in the block)

Loosen the rocker adjuster nuts, pull the push rods, then the lifters (keeping them in order).

The cam should just slide right out. (be careful not to bung up the cam bearings)

Do the reverse to put it all back together.

*Ticker* · 02-23-2010, 06:45 PM

"off TDC" can go either before (BTDC) or after (ATDC) - 9 BTDC is reasonable, the other way - you'd get the issues you're noting or worse.

You can ABSOLUTELY do this swap on your own with a little time and basic hand tools - 4 hours or so.

I have to note...that depending on how far the cam is gone, having the metal particulate in the engine is not good

I've seen a fair number of bearing failures follow cam failures

If you're not tearing it down, then there's nothing you can do about it other than do a couple of quick oil changes (right after cam break in, and then again at 1000 miles) and hope for the best.

Phlebmaster · 02-23-2010, 06:58 PM

I almost forgot to mention........ You want to make sure you replace the lifters with the cam. It is not wise to reuse lifters unless you have them re-surfaced.

New ones are not that expensive.

Myself · 02-23-2010, 10:59 PM

If it ran any longer than a few minutes with the intake backfire, I would bet there are chunks of cam metal imbedded in your crank bearings. I would just go ahead and pull the engine and check out the bearings too. The last time I had a cam failure it totally wiped out the crank.

spinem · 02-23-2010, 11:25 PM

your supposed to tighten until the rods stop spinning, then loosen. not tighten.

James Mc · 02-23-2010, 11:31 PM

I just had a cam failure in a 350. We pulled it out and the bottom of the oil pan was full of metallic oil, So I agree, You can do some quick oil changes and hope for the Best or even better, Yank it out and rebuild it. We replaced ours with a 383 Stroker. Going to redo 350 for an S10 we have.

James Mc · 02-23-2010, 11:34 PM

Spinem
I've got an old Hanes manual that says to tighten to 0 tolerence then tighten 1/2 turn more. So if you tighten them until You just start to feel friction and tighten them 1/2 more turn they are good. Used this method many times.

Sillyoldman · 02-23-2010, 11:37 PM

My most recent cam install. Put in an Isky race cam in my 327. Yes replace your lifter rods timing chain or gears. Make certain that if you decide on a loppier cam that your heads will work with it. This was at initial start up. Not running well in video.

YouTube- 1963 CHEVY big window pickup. First time...

Almost forgot, make sure to use cam lube and prime your oil pump before you stab the rotor.

bikertim · 02-23-2010, 11:40 PM

Older big blocks are known for eating cams anyway -- 1 tip I got from a guy who knows these engines REAL well says ALWAYS use AC Delco lifters --- no matter what cam installed. Thats what i have in my 454 with ISKY cam now and works fine. Just my 2 cents --

Ditto on the metal in the crank bearings -- when my cam went flat almost 10 years ago (prior to the AC Delco lifters) I ended up spinning a main bearing after replacement. Cheaper to do now than replace a crank etc later. You could always just take a chance -- you may be ok -- but be aware it will be more expensive later! No matter what -- flush it REAL good!

02-23-2010, 01:44 PM	#1
aric68 Registered User Join Date: Mar 2009 Location: winthrop, wa. Posts: 33	valve adjustment. help? my buddy decided he wanted to adjust the valves in my 72 402. we tightened them down until we could not spin the push rod and then tightened them a 1/2 turn more. we followed a pattern we saw on line that allowed us to adjust half of them then rotate 1 turn and adjust the rest of them. well it sounds ok idling but put it into gear and it almost dies no power. whats wrong?

02-23-2010, 01:48 PM	#2
67vetteal Registered User Join Date: Apr 2008 Location: riverhead,new york Posts: 160	Re: valve adjustment. help? Your Valves are too tight. Back each nut uo until you hear a slight clicking sound. Then tighten just a half turn. That's 180*. Do this immediately or you may wipe out your Camshaft. Al W.

02-23-2010, 02:33 PM	#3
Myself Registered User Join Date: Oct 2005 Location: Northern Arkansas Posts: 1,131	Re: valve adjustment. help? I agree, way too tight. You only tighten until initial drag is felt while spinning the pushrod with your fingers. If you tightened until you could not spin them, you probably went a couple turns too much.

02-23-2010, 03:55 PM	#4
Ticker Account Suspended Join Date: Oct 2009 Location: Sammamish, WA Posts: 2,404	Re: valve adjustment. help? Don't adjust valves with the engine running. Unless you have a radical cam, the companion cylinder method is quick and easy. Key point is as above...the very first time you feel any drag at all is zero lash. http://www.carcraft.com/howto/ccrp_0...aft/index.html

02-23-2010, 05:12 PM	#6
aric68 Registered User Join Date: Mar 2009 Location: winthrop, wa. Posts: 33	Re: valve adjustment. help? well the mechanic said the cam is gone, but it was running with an intake back fire with and acceleration before, and now it keeps trying to die when put in gear.

02-23-2010, 05:15 PM	#7
Ticker Account Suspended Join Date: Oct 2009 Location: Sammamish, WA Posts: 2,404	Re: valve adjustment. help? If you tighted down the cam too much...then you'd have wiped the lobes The backfire was likely timing and/or fuel related. Last edited by Ticker; 02-23-2010 at 05:16 PM.

02-23-2010, 05:25 PM	#8
aric68 Registered User Join Date: Mar 2009 Location: winthrop, wa. Posts: 33	Re: valve adjustment. help? we timed it to -9 and dialed in the carb before we ever took off the valve covers.

02-23-2010, 05:45 PM	#9
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,207	Re: valve adjustment. help? What do you mean by "-9". You may have it timed too slow & your valves are OK. If it was popping back through the carb on accel. your mech. is probably right. You may have a bad cam. Run or turn the engine with the covers off & watch for a valve that barely opens.

02-23-2010, 05:52 PM	#10
aric68 Registered User Join Date: Mar 2009 Location: winthrop, wa. Posts: 33	Re: valve adjustment. help? so the mechanic wants to charge me 1000 to replace the cam. how hard is it?

02-23-2010, 05:53 PM	#11
aric68 Registered User Join Date: Mar 2009 Location: winthrop, wa. Posts: 33	Re: valve adjustment. help? i guess i mean 9 off top dead center

02-23-2010, 06:45 PM	#13
Ticker Account Suspended Join Date: Oct 2009 Location: Sammamish, WA Posts: 2,404	Re: valve adjustment. help? "off TDC" can go either before (BTDC) or after (ATDC) - 9 BTDC is reasonable, the other way - you'd get the issues you're noting or worse. You can ABSOLUTELY do this swap on your own with a little time and basic hand tools - 4 hours or so. I have to note...that depending on how far the cam is gone, having the metal particulate in the engine is not good I've seen a fair number of bearing failures follow cam failures If you're not tearing it down, then there's nothing you can do about it other than do a couple of quick oil changes (right after cam break in, and then again at 1000 miles) and hope for the best. Last edited by Ticker; 02-23-2010 at 06:46 PM.

02-23-2010, 06:58 PM	#14
Phlebmaster Registered User Join Date: Nov 2009 Location: Oregon City, OR Posts: 146	Re: valve adjustment. help? I almost forgot to mention........ You want to make sure you replace the lifters with the cam. It is not wise to reuse lifters unless you have them re-surfaced. New ones are not that expensive. __________________ Thanks, Aaron Life is about making dreams come true, stop dreaming and make life happen. 64 GMC Project MY_YOUTUBE_VIDEOS To keep an opened mind- speculation is devine. Assumptions always lead to a dead end! Last edited by Phlebmaster; 02-23-2010 at 06:59 PM.

02-23-2010, 10:59 PM	#15
Myself Registered User Join Date: Oct 2005 Location: Northern Arkansas Posts: 1,131	Re: valve adjustment. help? If it ran any longer than a few minutes with the intake backfire, I would bet there are chunks of cam metal imbedded in your crank bearings. I would just go ahead and pull the engine and check out the bearings too. The last time I had a cam failure it totally wiped out the crank.

02-23-2010, 11:25 PM	#16
spinem haha, ford guys... Join Date: Feb 2007 Location: Visalia, CA Posts: 576	Re: valve adjustment. help? your supposed to tighten until the rods stop spinning, then loosen. not tighten.

02-23-2010, 11:31 PM	#17
James Mc Registered User Join Date: Feb 2010 Location: Ft Gibson Posts: 3	Re: valve adjustment. help? I just had a cam failure in a 350. We pulled it out and the bottom of the oil pan was full of metallic oil, So I agree, You can do some quick oil changes and hope for the Best or even better, Yank it out and rebuild it. We replaced ours with a 383 Stroker. Going to redo 350 for an S10 we have.



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02-23-2010, 11:34 PM	#18
James Mc Registered User Join Date: Feb 2010 Location: Ft Gibson Posts: 3	Re: valve adjustment. help? Spinem I've got an old Hanes manual that says to tighten to 0 tolerence then tighten 1/2 turn more. So if you tighten them until You just start to feel friction and tighten them 1/2 more turn they are good. Used this method many times.

02-23-2010, 11:40 PM	#20
bikertim Registered User Join Date: Dec 2005 Location: gilbert arizona Posts: 48	Re: valve adjustment. help? Older big blocks are known for eating cams anyway -- 1 tip I got from a guy who knows these engines REAL well says ALWAYS use AC Delco lifters --- no matter what cam installed. Thats what i have in my 454 with ISKY cam now and works fine. Just my 2 cents -- Ditto on the metal in the crank bearings -- when my cam went flat almost 10 years ago (prior to the AC Delco lifters) I ended up spinning a main bearing after replacement. Cheaper to do now than replace a crank etc later. You could always just take a chance -- you may be ok -- but be aware it will be more expensive later! No matter what -- flush it REAL good!

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