340 top end rebuild

[Rdchallenger]

Well boys and girls, this 340 and I are not the best of friends. Haven't truly liked each other since the first start up.

Knew something was wrong as it had no top or bottom end power. Opened it up, cam was retarded horribly, a pushrod went through a lifter on cyl 7, and camshaft flattened on same cyl.

Putting in new valve springs comp 901-16
Hughes lifters
Voodoo cam shaft
And adjustable 273 rockers.

Keeping fingers crossed.

[blown motor]

We always hate when that happens but now you can build it right. Have you given thought to throwing a little more money at it and building a stroker?

[Rdchallenger]

We always hate when that happens but now you can build it right. Have you given thought to throwing a little more money at it and building a stroker?

Nah, not for a weekend cruise car with the occasional Carlisle trip. As long as I can pull a burnout now and then and keep up on the interstate, I'm happy.

I just got a Pontiac Solstice GXP on the cheap that I can do fast stuff in to keep me content 

[Jocigar]

I've called three shops just to get rough estimates on rebuilding a 340 and all refused to use hydraulic lifters due to premature wearing issues.     

Why can't they harden cam and lifters properly anymore? or is it today's oil.     25 years ago it was plug and play with no thought of cam or lifters failing.   I wonder if purple shaft and lifters are any better quality directly from Mopar if available.

[Mrbill426]

 

[MoparLeo]

Why the 273 ( not the same strength as the T/A rockers) rockers ? Problem with hydraulic lifters ?
Factory rockers are good for any RPM you are going to see on a street car and no adjustments.
Engine is going to need to be completely torn down and cleaned out, so a rebuild is going to happen again.
The stroker option is not much more money and will give lots of benefits.

[Rdchallenger]

I've called three shops just to get rough estimates on rebuilding a 340 and all refused to use hydraulic lifters due to premature wearing issues.     

Why can't they harden cam and lifters properly anymore? or is it today's oil.     25 years ago it was plug and play with no thought of cam or lifters failing.   I wonder if purple shaft and lifters are any better quality directly from Mopar if available.

I'm thinking a lot of failures has to do with the oil now not having enough zinc in it. My problem was a compound thought of an oil pump problem during breaking in that led to a series of unfortunate events.

I'm using Lucas break in oil for this then either will use Valvoline VR1 or Lucas hot rod and classic car oil.

[Rdchallenger]

Why the 273 ( not the same strength as the T/A rockers) rockers ? Problem with hydraulic lifters ?
Factory rockers are good for any RPM you are going to see on a street car and no adjustments.
Engine is going to need to be completely torn down and cleaned out, so a rebuild is going to happen again.
The stroker option is not much more money and will give lots of benefits.

273s because 340 adjustable rockers are an astronomical price usually, and the A body boys are always swearing by the 273s as being just as good. Even though stamped rockers may be just as good, I like having that adjustment aspect and figured I'd give them a try.

Gonna let it ride as far as the engine goes without a complete tear down as it has been flushed as well as no scoring what so ever on the rod bearings, which is usually a tell tale sign of bigger problems when taking the oil pan off. 

[MoparLeo]

Running it when a lot of metal has gone through it is a recipe for heartache. Go the extra step now. Like pouring metal in with the oil and hoping the filter will get it all.
I would run a matched cam/lifter/spring setup from the same manufacturer. The tolerances and heat treating of the components will be more compatible.
Properly degree the cam. Very important.
Run the break-in lubes that they recommend. Call their tech dept before you buy.
Have your questions ready about the engine build and expectations you have with it.
The more info you give them, the better recommendation you will get.
When you mismatch parts they can just say you should have run ours.
Old saying " The quality is remembered long after the price is forgotten."
There is no economy in cheap. It is less costly to do it right once, than to have to do it twice.

[MOPAR MITCH]

Primary reason for lobes and hyd lifters (flat, not roller) going bad... is low/no zinc, plus requires high zinc break-in oil.. at least for the first 1-2 hours of running the new cam/lifters.  Then... use only high zinc oil for the rest of the life of that assembly.

[73chalngr]

Motor trend has a good article on how to build a 400 hp 340. I just googled it and it came up  .400 hp should smoke the tires.

[Dakota]

Primary reason for lobes and hyd lifters (flat, not roller) going bad... is low/no zinc, plus requires high zinc break-in oil.. at least for the first 1-2 hours of running the new cam/lifters.  Then... use only high zinc oil for the rest of the life of that assembly.

More on this topic on this YouTube video.   

https://youtu.be/cPpFOAd2mGw

[chargerdon]

For what its worth.   I built a 360 stocker (408 with .030 over pistons) with the block built by a machine shop using Scat Stocker kit and i did the top end myself.   

I used Lunati vodoo 703 cam and Lunati dual springs and Hydraulic lifters all Lunati.   Did break in using break in oil and zinc additive.   It promptly wiped a cam lope in about 200 miles.   Called Lunati tech and they said it was my fault for not using break in oil with high zinc instead of an additive and that i also did NOT follow their instructions of only putting in the outer springs during break in and then after break in installing the inner springs.   I countered with OH YEAH then why did only one l lope and the other 15 still look perfect.   They said .."it happens" but honored their warranty anyways and had Summit ship me a new camshaft and gasket kit.   

I changed the oil filter then Flushed the block by pouring thru it about a gallon of kerosene to make sure there was no metal from the cam lobe then changed the filter.   Put in the new cam and a new hydraulic lifter, took out the inner springs, and used Joe Gibbs break in oil with high zinc for the first 200 miles.   No problems.    Changed the Oil and Filter and cut open the old and no metal sparkle at all.   Put in the inner springs...(a job i hated...i had bought a spring compressor to assist and still you have to compress remove the keepers without dropping them, put in the inner spring...compress and put in the keepers...   Process is tedious as you have to keep rotating the engine for TDC on the cylinder and then using an adapter hook up the air compressor hose and fill so that when you do remove the keepers the valve doesn't drop down into the engine and do it 8 times.   Yuk...  )   I used Joe Gibbs high zinc 10-30 oil. 

Then drove the car about 500 miles until a push rod went thru the stamped steel rockers.   My guess was that the dual springs was just to much for the original stamped rockers.   Was going to replace all of the rockers with Mopar Performance rockers that supposedly are stronger but Mopar no longer makes them and the place i was going to buy from was out of stock.    So, instead bought a set of 273 Rockers and of course a new set of push rods that are necessary and installed them...love the adjustability.   

All of that was about 2,000 miles ago...I then changed the oil using Valvoline VR1 that has high zinc 10w-30.    No problems other than my oil pressure using a mechanical pressure gauge when cold is around 65-70 PSI but when fully hot drops to as low as 15PSI at idle.   That bothers me but, been told that all that is required is 10 PSI per thousand RPM and im above that.   Still, kinda wish i had used a High Volume oil pump.   Researched the bearings the machine shop used and they are a "racing" bearing that has slighly higher tolerance...   Hmmm. 

As far as power is concerned, it will burn the 235x60x14 tires with 3.23 suregrip from a dead stop so easy it is ridiculous the low end torque and that is with only an Edlebrock 600 CFM carb and air gap intake manifold and headers.   Last summer i needed new rear tires, so before getting them, on the street in front of my house, i did a little brake on burnout, then dropped the hammer and released the brake and did a dual streak burn out of over 70 ft !!!   From a dead stop,  to do the fastest take off,  i cant give it more than half throttle until it gets to at least 15 MPH before flooring it in first or it will break the tires loose.   I used track addict app on my cell phone and on a no traffic road ran an 1/8 mile in 8.6 seconds and 86 MPH.   It hit 0-60 in 4.9 seconds.   Pretty darn good on smallish street tires and only a 3.23 rear end.   Gas mileage is another story...  i get around 10-13 MPG if i keep my foot out of it, but, its o damn much fun to jump on it.    Its an automatic and in High gear doing 40MPH and jumping on it will still pin my shoulders to the seat...what a blast.

So, yes, when with matched lifters, springs and cam and use HIGH ZINC oil like Joe Gibbs or Valvoline VR1.    It can be done !!!