340 clearence issue

[aussiemark]

I bought a couple of 340 engines one has been modified and I can't figure what is causing the problem basically the valve spring retainer is contacting the valve guide at full lift. It has cracked a retainer and the multi groove valve locks are breaking of at the grooves (the engine has pieces of broken valve locks through out). It has std push rods, rockers and hyd lifters I don't know the cam specs or history of the engine. The block has been o'ringed but has std pistons and was assembled with normal Felpro head gaskets which I thought was strange (should have high comp pistons and copper gaskets to warrant being o'ringed) any ideas?

 

[sfort]

The block and heads may have been decked or milled. Can you tell? Could the valve guides have been replaced and not installed properly?

 

[aussiemark]

Original valve guides, heads and block have been machined I don't know how much but the hyd lifters seem to have the correct preload. The only thing I can think of is maybe the cam has too much lift perhaps it is a custom grind that is just wrong. Perhaps machining the guide tops down 60 thou will fix it but I am trying to find out what caused this problem.

 

[moparleo]

The first thing to do since you have to do it anyway, is to determine total lift of the cam. So remove the pushrods and set up your dial indicator to read at the lifter. Or remove the cam and check for specs on the cam ends. No guessing. You just break parts that way.

 

[IQ52]

You have more valve lift than retainer to seal clearance. You will need to remove the cylinder heads and cut the guides down to get proper clearance. Determine the valve lift by measuring the the lobe lift and multiplying by the rocker arm ratio. Remove a valve spring and reinstall the retainer and locks and measure the retainer to seal clearance. Then cut the valve guides down so that you have .060" clearance between the retainer and seal at maximum lift. If you are breaking guides, retainers and locks, you may also have some bent pushrods.

 

[moper]

You also might want to replace the cam. Chances are if the valvetrain is all beat up, the cam lobes and lifter faces are also damaged.

 

[aussiemark]

I will just put this one aside for now and rebuild the tired original untouched 340, I wasn't that keen on the o'ringed block anyway both of them have close date codes that will be good for the Challenger anyway and I have a feeling the modified one has had a lot harder life then the standard one.

 

[krazykuda]

You have more valve lift than retainer to seal clearance. You will need to remove the cylinder heads and cut the guides down to get proper clearance. Determine the valve lift by measuring the the lobe lift and multiplying by the rocker arm ratio. Remove a valve spring and reinstall the retainer and locks and measure the retainer to seal clearance. Then cut the valve guides down so that you have .060" clearance between the retainer and seal at maximum lift. If you are breaking guides, retainers and locks, you may also have some bent pushrods.

x2

 

[aussiemark]

Yes, that is what I thought just wanted to confirm. It was put together by someone who didn't understand luckily I checked it out and got to it in time there are no bent pushrods and the cam and lifters look fine. It was well on it's way to dropping a valve with that cracked retainer which could have destroyed the engine. The o'ringed block is a bit hard core for me I just want a standard type engine for a street car so I will use the standard 340 and sell this one and someone can build a more serious engine.

 

[jimynick]

Why get rid of it? The O-rings won't hurt anything and as long as the deck height is reasonable, just run it with regular head gaskets or pick the wire out of the grooves and be done with it. I WOULD give it a careful measuring though. 340 blocks aren't growing on trees anymore. Just my 2 cents worth

 

[AUSTA]

Valve Clearance

I bought a couple of 340 engines one has been modified and I can't figure what is causing the problem basically the valve spring retainer is contacting the valve guide at full lift. It has cracked a retainer and the multi groove valve locks are breaking of at the grooves (the engine has pieces of broken valve locks through out). It has std push rods, rockers and hyd lifters I don't know the cam specs or history of the engine. The block has been o'ringed but has std pistons and was assembled with normal Felpro head gaskets which I thought was strange (should have high comp pistons and copper gaskets to warrant being o'ringed) any ideas?

Mark have you tried Neil at Southside he just machined up 2 x 340 blocks had to go +60 due to a Mopar madness stuff up running E/Q heads on one 44 C day with aircond on lucky if it gets to half temp shaved the tops off the KB243 pistons .39 gaskets can send build sheet engine dyno 376 HP in Perth A66 Challenger rebuilding TA Go Mango with Burnt Orange interior cloth inserts..

 

[aussiemark]

Mark have you tried Neil at Southside he just machined up 2 x 340 blocks had to go +60 due to a Mopar madness stuff up running E/Q heads on one 44 C day with aircond on lucky if it gets to half temp shaved the tops off the KB243 pistons .39 gaskets can send build sheet engine dyno 376 HP in Perth A66 Challenger rebuilding TA Go Mango with Burnt Orange interior cloth inserts..

I have two 340 engines both are standard bore 4.040" one has been freshened up with new cam and timing kit and for some reason the block has been o'ringed it is a late 1969 date code. The other one is untouched, tired and dirty it is an early 1970 date code the freshened engine is the one with the valve clearance problem perhaps the cam is too big? I just want to build a very standard 340 to put in my 1970 Challenger sunroof car it will never be raced just want a bit more muscle then the matching #'s 318 which I will preserve so the car can be put back to original latter. I will use the untouched engine and sell the other one maybe someone who wants a serious engine will benefit from the o'ringed block I just don't need it.