Intake valves hit pistons

[CobraV8]

I took the engine out and removed the heads for a camshaft swap. What I found was this:



all intake valves hit the pistons. Looks like the valve reliefs were too small in diameter. I only checked exhaust valve clearance when assembling the engine, I guess I'll clay both intake and exhaust valves from now on.

I expect all intake valves to need replacement for sure. Also the valve seals (intake and exhaust) are leaking badly.

I guess that the rods could also be bent. What is the best way to check them for straightness?

I was hoping to get the cam installed and have the engine back in the car within the next two weekends. This just turned into a complete engine rebuild

Simon

[Rick Parker]

Generally the standard valve reliefs that are made in the pistons (forged pistons) are sufficient for most off the shelf Hipo cams. The piston will be chasing the exhaust valve more agressively than the intake and will need more attention. It's always a good idea to check clearances, during mock up assembly; especially if you alter the cam timing by advancing or retarding the cam at time of installation.
Good luck

[CobraV8]

[quote=Rick Parker;1073123]Generally the standard valve reliefs that are made in the pistons (forged pistons) are sufficient for most off the shelf Hipo cams. The piston will be chasing the exhaust valve more agressively than the intake and will need more attention. [/QUOTE

Rick, that's exactly what I've heard. I was really surprised to see the impressions in the pistons were on the intake side.

The old cam was a Performer RPM, I did not expect any problems with the valve reliefs.

Any advice on the connecting rods? I assume they could be bent, but how to check this? A slight bend in the rod might be hard to see...

[olddog]

Picture didn't work for me.

The extra time to clay the intake valve would have been fairly small.

If you mock it up with a light spring on the valves, you can measure clearance with a dial indicator by pushing the valve in until it touches the piston. You repeat at many different crank positions. Then you know when the valve is at its closest point.

I would think that the push rods would bend before a piston rod. If the push rods are all straight, the valve may have been kissing the piston fairly light. Hopefully the connecting rods will be fine. Does the top half of the rod bearings look normal?

I would think a good shop could check the rods for you. I would think at reasonable price.

[Rick Parker]

The picture did not open for me either but I can imagine small 1/3 circular bright marks in the valve reliefs. Its doubtful the rods are hurt as it would rock the piston if it was a very minor interferance or it would have been quite audible (ie: loud) and never driven after initial startup. I have seen too where on occasion if the engine is over reved the rods will momentarily strech and allow the valves to hit the piston. This is why a specific minimum clearance is set depending on application, valve springs, anticipated RPM etc.
Example: I had a Datsun 510 AutoX car several years ago with a real well built OHC 1800 13:1 domed Venolia pistons, (2) 45 DCOE carbs big cam, crank fired ignition 8000+ RPM engine. Fun car to drive. I missed a shift once and buzzed it to about 8500-8700. It immediatly began to run poorly on only 3 cylinders. I thought I had bent a valve but realized it didn't have any bad mechanical noises. After investigation what had happened was the rod had stretched momentarily and hit the ground electrode on the plug and closed it up. After replacing the plug it ran fine.

[RICK LAKE]

CobraV8 Simon, to start with, I couldn't open the picture.
Here comes the questions, What is the piston clearance to the deck of the block? Was the deck of the block cut to straighten? Where the heads machined down? What is the crush of the head gaskets? That camshaft should not have hit the pistons unless some of these machine operations where done to the block or heads. Was the camshaft setup correctly? Some camshaft come with a 4 degree advance built into them.
If you drove the motor 5k miles before fining this problem, it sound like a over rev issue with the motor. When the block and heads are cold it is alot more possible to have an interference issue than when hot. This also depends on the material the block and heads are made from. Aluminum expands faster and larger than iron.
As far as repair of the motor, rods and pistons to start should be replaced. A hit is a hit. If you put the rod through the block the party is completely over. Have the crank checked for balance and cracks. You could have the rods checked for length, cracks, and have new bolts installed. Pistons will need to be checked for pin play, damage to the bottom of the skirts hitting the cylinder walls. Clearance and trueness of the bores in the block.
Where the edelbrock heads in stock form? There should be no valve contact with a cam under .575" total lift unless machine work. The other issue could be the valve springs are not the correct ones for the camshaft. It is real easy to not have the correct spring pressures, open and closed. High rpm could have the valves floating and hitting the pistons. If you have the stock springs from edelbrock, and a high rpm range of 6,500 a smacking is very possible. Like others have said, rebuild, repair, and make sure the valve train is up to the rpm range you want to run. You will need new valve springs if you are changing the camshaft any way. Much camshaft companies will give you a listing of what pressures to use for the valve springs in the closed and open postions. Check coil bind too. You can run as small as .060" but this IMO is too tight. I run .090" min. Good luck. Rick L.

[CobraV8]

Here's the picture again, I hope it works this time:



The heads were new when I purchased them and are not milled, as well as the block.

Pistons are flat top TRW , head gaskets Fel-Pro #8548-pt 1 (0,047" compressed)

The camshaft is an Edelbrock Performer RPM, valve springs are the correct ones for this cam. I isntalled the cam straight up and checked it with a degree wheel.

I did not expect any problems as all the components are sold as a matched kit by Edelbrock. They even had an engine build sheet on their homepage using exactly the same head gaskets and pistons. CR is 9.5:1, so this is a fairly mild street engine.

The RPM range of this camshaft goes up to 6500 according to Edelbrock, so the springs should take this RPM. Pushrods were hardened Trick Flow. However in case of over revving the engine I'd also expect the exhaust valves to hit the pistons first?

The engine was still running strong, I did not notice anything that sounded not normal.

I will disassemble the bottom end next and take pics of the bearings. Pushrods looked straight, I will check them again on a glass plate.

[RICK LAKE]

CobraV8 Simon it looks like you hydro locked the lifters and got contact on the intake valves. All the marks are new??? As far as the exhaust valves, they are smaller and where clearing inside the piston cuts. Unless you have anti pump up lifters you will have this problem again with a 6,300 rpm range. Fly cut the piston tops is the only way to fix this. I don't know what method you use to adjust lifters. I run hydro roller lifters with a .015"-.017" plunger setup. I also have a 65-80 psi oil pressure system. My lifters pump up at about 5,700 rpms. I do goto 6,200 rpm max. There is no damage from the lifter because of the clearance differents. If you turn down adjusters to spec, 1 -1.5 turns after contact, This is what cause the damage. At lower rpms, the oil is bleeding out of the lifters to stop valve to piston contact. You said you degreed the camshaft. Some timing chain setups have advance or retard built into them. Edelbrock likes their own parts used as a whole from heads,intake,camshaft,lifters, timingchain kit, and distributor gear. BECAREFUL with running a polygear. It needs good lube between the camshaft gear and itself for cooling as well and lubing gear contact area. Setup of the distributor end play also needed. Check camshaft end play too. I think you will find that the damage depth on the pistons is about .020-.030". This would be about the correct distance the plunger in the lifter would be between normal running and pump up. Rick L. They sell a piston cutter for doing this with a drill. Google it or check Jeg's or Summit. I think they both can get of carry this tool. Rick L.

[vector1]

recut the eyebrows bigger, put the valves in a bench press and check for runout, assembly and enjoy.

[Barry_R]

Isky sells a tool for valve pocket work in engine. Or wrap the whole thing in saran wrap and open up only the spot you're working on - like a surgeon does. They forged to pocket walls vertically and the valve is coming down at an angle - poor piston design that dates back to the 70's. Did not matter back then with smaller valves, matters a lot now.

Valves are probably bent - thats why they leak. Might be turnable - or replace. A valve job and trimming the piston brows and your done. Rods and pistons themselves are gonna be fine. Pushrods need to be checked too - might've got bent.

[bobcowan]

Repalce all the intake valves. Don't even bother trying to check them. If they hit the piston they're damaged. Between the crank shaft and the cam shaft, the valves are the weakest parts. Eventually one of them will fail, and then you're really hosed.

[madmaxx]

There is no such thing as an "anti- pump" up lifter. The way you prevent a lifter from pumping up is set the lash on the lifter to about 1/8 turn after zero lash. Bottom line is if the valves do float and the lifter does it job and takes up the slack it can only "pump up" 1/8 turn. Keith Craft sells some high rev lifters, they have a cir clip for the retaining ring instead of the wire clip which can pop out if. KC also makes some other modifications to the lifters which I am not familiar with but they work.

Anything above 5600 rpm with a hydraulic lifter and you are in valve float territory. You go above 6000 rpm with anything but a mild street cam and they are going to float.

[madmaxx]

I looked at your new cam specs. It is aggressive for a street cam. If you are going to turn above 5500 rpm you better have about 400lb open and 150 seat or the valves will float.

Even if you set your lifters close to zero lash, remeber it is possilble for the lifter to launch off the peak and hammer on the back side, over time it will destory the camshaft.

By the way a quick way to check a cam is to pull the distributor, in 5 minutes you can see the #1 intake lobe backside and if you turn over the engine the whole lobe. You do need a mechanics mirror though.

[Jerry Clayton]

In addition to your valve notches not being at the proper location for your Edelbrock heads with the size valves you have----the absence of any carbon build up on the remainder of the piston top indicates that you probably don't have enough clearance in the squish area--either the pistons are above the deck or your gaskets are thinner than .047 compressed. Or possibly some pretty severe reversion/scavaging

[CobraV8]

Thanks for all the advice guys!

Some of the intake pushrods are slightly bent, however most can not be distinguished from the ones on the exhaust side. I would have replaced them anyway when installing the cam, as shorter ones are required with the retrofit roller lifters.

I will order new intake valves, check everything carefully and cut the valve reliefs bigger if all parts are ok.

One thing I noticed is the timing chain seems to have a lot of slack for a double roller with less than 5000 miles. Looks like too much to me:



Of course this is far from ideal when piston to valve clearance issues exist.

I was thinking about a gear drive, but a quick google search revealed that most people seem to favor timing chains.


Also the leaky valve seals are on the exhaust side too:



Consequently it might have nothing to do with the bent valves. How is it possible the seals leak like this after only 5000miles? Valvetrain geometry is ok, the shiny spots where the rollers contact the valve tips are exactly in the middle of the stem.

I'll have to take the credit for the mistake with the intake valves, but besides this I'm not too happy with the quality of the parts...

[CobraV8]

Originally Posted by Jerry Clayton

In addition to your valve notches not being at the proper location for your Edelbrock heads with the size valves you have----the absence of any carbon build up on the remainder of the piston top indicates that you probably don't have enough clearance in the squish area--either the pistons are above the deck or your gaskets are thinner than .047 compressed. Or possibly some pretty severe reversion/scavaging

I think this very strange looking carbon buildup might be the consequence of the oil dripping in the combustion chambers. It seems to be worse in the cylinders where the spark plugs were fouled the most.



I'm 99,99% sure the pistons don't stick out of the block, but I'll check again. Gaskets are Fel Pro 8548-pt 1.

[madmaxx]

One thing that you might want to do and I highly recommend is contact Keith Craft and have him sell you the cam, lifters, distributor gear, push rods and tell him what you are looking for as far as torque and RELIABILITY. In other words an engine targeted to run 5K miles is built more radical than 100K miles. The idiots techs you are talking too at comp, lunatti, crane, are just that idiots. You need someone who installs these things and has a track records. Surprisingly his prices are the same as what you get them from summit or jegs. what spring pressures are they recommending? I had a comp cam that floated the valves with their recommended springs at 5600 rpm, there response "valve float is an issue over 5500 rpms would you like us to sell you some heavier springs" wtf, all my expense and labor. Make sure you get a billet cam not sadi cast bullsheet. Once again KC knows this stuff.

[madmaxx]

Another good contact is Blykins. He has built a number of engines and is an engineer to boot. Do a search and you will find his contact info. The more you talk to the better once you get 3 saying the same thing you might be on to something. If you rely on the "tech support", we will be hearing about your next rebuild also, LOL!!

[CobraV8]

I know that mentioned gentlemen have an excellent reputation, but I already gathered all the parts over the last months.
I bought only brand name parts from well known companies however (Comp Cams and Lunati), so I hope to be on the safe side.

The springs recommended by Comp are 132lbs seated. I know these are a bit on the soft side for the camshaft, but heavier springs also tend to cause problems like collapsing the lifters and raised stress levels for all valve train parts. If the solution was that simple, the stiffest spring available would just be used for every application.

One thing I don't understand is why so called "rev kits" aren't used more widely on these engines. These very simple and cheap devices place springs on the lifters, effectively eliminating the inertia caused by the lifter's weight.

People spend lots of money for titanium retainers, beehive springs and ultra-light rockers in order to lighten the valve train. The use of a rev kit to cancel out the lifters weight seems uncommon however. Some are available for Chevys, however I only found one for Fords made by Price Motorsports, and this one is available only for 9.5" deck height blocks.

For hydraulic roller cams with link bar retrofit lifters such a kit would be very beneficial, as these lifters are really heavy.

Maybe I'll fab up my own rev kit, I'll do some calculations for the springs required for my lifter's weights.

[RICK LAKE]

madmaxx. Hey Max give your voice a rest. You have no idea about some things. There are anti pump up lifters. If you took the time to read and talk to tech people you would know this. Poor info again. Yes some of the tech people are not the shapest in some companies, but when you are paided 10-12.00 per hour, don't expect an engineer every time. Talking to KCR, Bylins, Barry R. for info is a plus, BUT they don't make a living off FREE info. It doesn't pay the bills. Rhodes used to make bleed down lifters for high lift camshafts to raise the vacuum in a motor and Cranes sell anti pump lifters with a different bleed orfice inside. It has damn little to do with the clip that holds the lifter togeather. A machined "C" clip is better than the wire chip that are on most lifters. There is a different between normal driving and racing. Rick L.