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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: josh0325 on September 06, 2017, 07:43:00 pm
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Hey guys, I need a little help as I'm confused about timing my new engine. I know that Initial timing should be something simple but it's got me frustrated. Before initial fire up I set the TDC mark on the balancer on the timing pointer 10 degrees btdc, then I dropped the dizzy in on #1.is this okay, or should I have set the TDC mark on O and used the distributor to set initial timing. Would this result in late valve timing??? Please help, I do not want to mess this engine up.
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Distributor position has zero effect on valve timing. Valve timing is controlled by the rotational position of the camshaft in relation to the crankshaft. That relationship is fixed by the timing chain. As long as the timing chain was installed correctly and the cam was properly timed during assembly of the short block, valve timing is fine. If you stabbed the distributor one tooth advanced, the vacuum advance may not be in the optimum position once the timing is properly set using a timing light - meaning the vacuum advance may interfere with other components in proximity.
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Make sure #1 piston is at tdc on it's compression stroke. Mark your distributor on the base dead center below #1 on the cap. Set your balancer mark at 10 degree btdc as indicated on your timing cover. Measure 2 1/4 inches to the right of your initial mark on the dist and mark. Looking down into the engine take a long screwdriver and turn the oil pump tang to line up with # 5 intake valve. Turn the rotor to line up over your second mark. Slide the distributor down into the block and it should fully seat with the rotor contact directly over your initial mark at # 1 on the dist. Take off the rotor. Turn the dist to match the triangle on the shaft to the closet triangle on the base and tighten up the dist to the block. This should allow the engine to readily start. When it warms up and you can get a steady idle, plug the vacuum port from the carb to the dist, attach your timing light to #1 and set it at your desired timing. I set my 454 @ 10 degree btdc. Some folks like to set it higher but in my experience while it makes it run better it makes starting it harder after its at running temp. My 454 runs like a scalded dog and starts with a click of the starter hot or cold.
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Thanks for the heads up, I was pretty sure I had it where it needed to be, it starts right up, and it idles like a popcorn maker. But, when I hook up my vacuum gauge for carb adjustment it flutters in the red, and it reads incorrect valve timing, intake manifold leak. Intake and carb do not respond to carb cleaner sprayed around base of carb or around the intake.Pretty sure cam was installed correctly, and straight up as well. Has me puzzled
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Well if it sounds like a popcorn maker then you wouldn't expect to see solid vacuum gauge readings. Is it a stock cam? What is the base timing set at?
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cam is not stock. Advertised duration .296/.296 . Duration at .050 is .238/.238, lift is .542/.542. was just worried because vacuum gauge connected to full manifold vacuum at intake says late valve timing, leaking intake etc. Checked the intake and its fine, don't understand about late valve timing.
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Base timing is set at 12 degrees initial, and 36 degrees all in by 3000
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cam is not stock. Advertised duration .296/.296 . Duration at .050 is .238/.238, lift is .542/.542.
^^^^ This is the low vacuum reading....
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Yeah if your valves are properly adjusted and with that cam you shouldn't be looking at a vacuum gauge at idle.
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Lol...that's what I kinda thought, just ticks me off a little bit, because the cam manufacturer tech told me it would operate mybrakes just fine. Also said I wouldn't need a stall converter since it's decent cubic inch engine. I appreciate all of the help from everyone. This is the biggest cam I've ever used, and this is third time I've had to pull the engine and had it built. Wife is ready to put a slug in the truck. Is there a gtbing I could do to help vacuum quality??? I suck at tuning...
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So is your problem lack of vacuum for your brake booster? I run much more aggressive cams than that without issue.
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Yes, it feels like it had manual brakes. I tried eliminating outside sources of vacuum issues. Plugged off all vacuum ports at intake for brake booster, and modulator for trans. Still same reading. Tried to post a video of engine running, but says document too large when I try to post. Gauge is reading fluttering needle between 5 and 10 in hg. Gauge indicates late valve timing, leak at intake or leak at heat riser. I don't have a heat riser, and I don't know how to eliminate intake as the issue. When I spray starter fluid around intake the tan just blows it away, and I cannot efficiently reach the rear due to firewall and dizzy. I'm really scratching my head on this one.
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Sorry read gauge wrong, reads between 10 and 12 in hg
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I've got just about the exact same cam in my 454 and 12 is about all you're gonna get at idle. Doesn't seem to adversely affect my brakes though
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Will the brake booster hold vacuum? Check the brake booster vacuum check valve. If the check valve is leaking, the booster may not store sufficient vacuum to function properly.
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^^^This
After you shut the engine off and remove the check valve from the booster, do you hear a whoosh of air?
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I've isolated all sources of external vacuum components. The only two that need manifold vacuum are the vacuum modulator for trans, and the brake booster. Capped off all vacuum ports at manifold, and carburetor, besides the pcv valve. I know I can't rely on the vacuum gauge, but it is not running correctly either.Talked with tech support at Erson cams, and he advised that tohe cam should provide plenty of vacuum and have crisp throttle response. I know it is on an 110 degree centerline, but it really isn't that radical of a cam. I tried to post a video of engine running, just to give an idea of what I'm talking about, but it won't let me attach, says file is too big. Video is only five seconds long.
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If the valves were improperly adjusted, could it give me the symptoms I'm experiencing. I normally adust by moving pushrod up and down until all slack is out, and then go another half turn. I didn't adjust though, builder installed and adjusted everything other than the intake manifold.
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I finally found time after an 80 hour work week to investigate further into the issues with my engine. I took everyone's input into consideration and started by hunting through possible issues. Cam is where it should be, valves are lashed to 0, and another 1/2 turn lashing both valves in firing order sequence. Went through all vacuum connections no improvement, tightened carb to base a little more, no improvement. Lastly, just as an attempt to humor myself, I yanked the intake. Sure, enough there were visible signs intake was leaking coolant on driver's side head. Even though it was leaking internally, would that also cause a huge vacuum leak???
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An internal leak from the corner coolant passages will dump coolant into the oil through the valley, but shouldn't introduce coolant into the runners. While you have the manifold off, make sure the gaskets properly fit the intake and heads to provide an effective seal around the ports. Pay particular attention that the gasket seals along the lower edge of the flange where it meets the valley.
Did you ever verify that the vacuum check valve at the brake booster is holding vacuum inside the booster?
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Yes, brake booster is holding vacuum, did a simple test by using a bicycle pump with pressure gauge and manually pressurized it to about 5 pounds on gauge, and it held pressure until I removed gauge and undid my psycho-rigging of a valve stem and barbed fitting to seal hose to check valve. Oddly enough when I placed the intake gaskets on the heads they fit the ports very well, and also the ears rested on the top of both China rails. I placed a bead starting at the ears and across the rails on the front and rear. Also put a small bead around each water port, and a small dab in the center of each to help hold it in place. I let the permatex set up for a few minutes,then installed imanifold straight down. I think the reason it leaked was because of improperly torquing them down, as I just snuvgex them and gave them a good cinching down. Hopefully, the intake is not warped, but haven't checked it for flatness yet. Also, forgot to put permatex on threads of I take bolts which is why I think I leaked a small amount of coolant into the lifter valley. Waiting on weather to permit, and I will reinstall intake after checking mating surfaces to be true.
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Yes, brake booster is holding vacuum, did a simple test by using a bicycle pump with pressure gauge and manually pressurized it to about 5 pounds on gauge, and it held pressure until I removed gauge and undid my psycho-rigging of a valve stem and barbed fitting to seal hose to check valve. Oddly enough when I placed the intake gaskets on the heads they fit the ports very well, and also the ears rested on the top of both China rails. I placed a bead starting at the ears and across the rails on the front and rear. Also put a small bead around each water port, and a small dab in the center of each to help hold it in place. I let the permatex set up for a few minutes,then installed imanifold straight down. I think the reason it leaked was because of improperly torquing them down, as I just snuvgex them and gave them a good cinching down. Hopefully, the intake is not warped, but haven't checked it for flatness yet. Also, forgot to put permatex on threads of I take bolts which is why I think I leaked a small amount of coolant into the lifter valley. Waiting on weather to permit, and I will reinstall intake after checking mating surfaces to be true.
Finally got everything installed and fired up today. Still same problem. Just repainted heads and intake so leaks would be easier to find. After shutting engine down, I noticed rust spots around where the manifold meets the heads on drive side, and same rust spots on front of intake.What the heck is that from??? Intake still leaks, Why???
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Were the heads or intake manifold milled? Did you check the dry fit of the intake manifold gasket flanges against the cylinder head gasket rails to verify that the sealing surfaces are parallel and achieving full contact, before tightening the manifold bolts? How much gap is there between the top of the china walls and the underside of the intake? Did you install end gaskets between the intake and china walls or discard the gaskets in favor of silicone sealant? You really need to post pics with your responses to help clarify.
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If the block has been decked or the heads have Been cl shaved it can make the intake really hard to seal up
But of its dumping water into the cylinder it should show up on the spark plugs
Or on a cylinder leak down test
Also your pressurizing the brake booster won't show of its holding vacuum
It should have a check valve that will hold vacuum but won't hold pressure
Although the water leaking into the engine shouldn't affect the vacuum at the brake booster
Sounds like two separate problems
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A faulty seal between the water jacket and cylinder will result in pressuring up the coolant system and water being ejected out the overflow in a relatively cool engine. Compression blows by the head gasket into the water jacket. This happened on a 305 I had. I bought a "small block" head gasket set with said gasket's having a diameter of 4.10 inches. The 305 bore size is 3.76 inches. This difference in diameter resulted in very little sealing surface between the cylinders and lower water jacket openings. Pressure in the coolant system got so high the over flow couldn't handle it and it blew the upper radiator hose off. A set of 3.76 inch gaskets fixed the problem. You don't have to look at the plugs to see if they are wet. You'll know from the "explosion" Scared the crap out of me.....
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Thanks for all the responses, intake is not leaking, and brake booster I'm pretty sure is not the issue either. I was turning the engine over by hand to watch the valve operation. I found at least three rockers that I could push down quiet easily by hand. The engine has ran for a total of maybe 40-45 minutes, including the 25 minute initial break in. Do you think that the lifter are collapsed, or if they were just adjusted to tight to allow them to pump up??? Really trying to avoid engine damage. I know I can find out by starting engine and then allow it warm up, andreadjust with it running. Back off rocker nuts until it chatters, and then tighten it until noise goe away, and give additional 1/2 turn. Is this a good idea, or am I risking engine damage.
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...I was turning the engine over by hand to watch the valve operation. I found at least three rockers that I could push down quiet easily by hand....
Toward the pushrods or toward the valve springs? Unless you have the strength of a locomotive, you shouldn't be able to budge the rockers in either direction with your bare hand.
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Towards the pushrods, but I figured out the problem. The engine builder installed the lifters dry, and adjusted the valves too tight. It took about two hours of adjusting to get the lifters to pump up. Vacuum is at 14" and the needle is pretty steady. Thanks for all of your help, this site is great!!!
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