340 break in question

Small Block Mopar Engine

  1. I8NEMO

    I8NEMO FABO Gold Member FABO Gold Member

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    Hi all,
    Sunday I decided to hook up fuel and start the 1969 340X for the first time, what a glorious sound, and a milestone for this build. A substantial inlet bowl fitting leak shut things down and kicked my butt for the next hour so the run time was all of 15 seconds. This is only the 3rd new motor ive started in my life so I have limited experience but am aware of cam flattening dangers. My touted and experienced buddy who ( has built countless sprint car and hot rod engines)built the motor has cautioned me in that the assembly lube is probably gone now and no more dry runs, the next time it fires, it's gotta go 15 minutes at 2k rpm which I plan on doing. Needless to say im feeling some stress.

    What has been your experiences breaking in new engines and having to pause? I can add, the build sheet is still awol so I don't have compression or cam specs. If your wondering here's the complete engine story which explains my apparent casualness and ignorance of the internals - in 2014 I had a truck fire in my warehouse, sprinklers killed the fire, enter fire restoration, so the whole building was gutted. I asked my buddy Bob if I could store my 340 parts at his place for awhile during fire restoration. Unbeknownst to me he went ahead and built this motor as a surprise and at no cost. This thing sounds like a high strung beast, lots of cam lope, just sounds incredible. Im back to only 4 or 5 hours of sleep like a kid waiting for Santa.

    Thanks

    32796.jpeg
     
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    • aaronk785

      aaronk785 Well-Known Member

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      I’ve done this a couple times and never had a problem. I would pre oil and make sure it starts right away.
       
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      • RustyRatRod

        RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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        I don't know WHY people are so SCARED of RPM on initial fire. 2K is barely off idle for break in purposes. I use 2500 as an ABSOLUTE minimum and vary between that and 4K all through the initial break in process. You're after splash lubrication and you don't get a lot at 2K. As long as you have a good zinc additive in the oil or are running oil with a good amount of zinc in it, you should be fine on the next fire, if you can keep it going this time and above 2K. That's just high idle on the choke.
         
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        • abdywgn

          abdywgn dismantler

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          just my opinion...to save yourself the stress and did I do the right thing, take the intake off and put lube on the lobes and lifters. Little extra work but you won't being second guessing yourself if something goes wrong.
           
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          • oldkimmer

            oldkimmer FABO Gold Member FABO Gold Member

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            Get a known good carb. Kim
             
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            • flyfish

              flyfish C8H18+N2O = :-D

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              I've had it happen a few times before, trying to get it to run and get initial timing set whilst keeping it running....long story short, you're fine, just get it up to 2k and do your cam break in for 20 min, varying from 2k-3k slowly for the time. Then shut it down an check things over (valves, leaks, etc). If all is well, drive it up to 3500 in 2nd gear and let off a few times letting it pull against the motor to slow you (making sure the rings are seated), then dive it like you are going to drive it ....aka, hammer down.
               
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              • ir3333

                ir3333 Well-Known Member

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                buddy broke in his duster....2500 rpm for 15 minutes, set the timing at 34 total and changed the oil.
                took it to the strip and ran mid tens all weekend!
                 
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                • lemondana

                  lemondana BlackDart

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                  I know a guy that just restored a 69 Barracuda with a 318. He didn't have the coolant in or any of the belts on, not ready to run. He said yea-I started it up the other day and just let it idle for a little bit, I'll break in the cam when I get everything hooked up. I'm waiting to hear that he has a flat cam
                   
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                  • dartfreak75

                    dartfreak75 Restore it, Dont part it! FABO Gold Member

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                    Keep us posted on that im curious to see what happens.
                     
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                    • dartfreak75

                      dartfreak75 Restore it, Dont part it! FABO Gold Member

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                      First off sounds like you have a good buddy there! Lol I am in a similar boat with my engine except this is my first ever solo build and break in. I'm extremely nervous about it. I'm trying my best to get everything sorted out before the first fire! If I was in your situation i would probably pull the intake off and relube the cam. That maybe over kill but it's better than ruining a engine.
                       
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                      • krazykuda

                        krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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                        I've had leaks when breaking in an engine... If it's a critical leak (oil or coolant), I shut it down immediately before doing damage, fix the leak, top off all fluids, then resume the break in....

                        It's worked ok for me so far....
                         
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                        • dano

                          dano Evil Handy Man

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                          Rusty is correct. Its OK to rev it up and down during the process, 2k being the minimum RPM. We've had to stop during break in for many reasons, distributor failed, leaks, etc and finished the break in and never had a flat cam. There has only been 3 flat cam in all the engines my dad and I built, one was my 340 with the guides to tall for the cam lift, (one of our first builds, lesson learned the hard way and I'm proud to say the 3rd revamp of that engine fired up this fall with no issues or leaks). The second was a 350 for a friend and he said he would break it in, well one happy 600 Double Pumper with incorrect float height or too much fuel pressure later whipped the cam out with fuel dilution. The 3rd was in my dads 390 Ford, and no reason found for that one, Comp Cams replaced the cam and lifters for free, this was when they had a bunch of junk lifters in the mid 90's.

                          New oil with Zinc, pre-oil and fire it up. 2-5K for 15- 20 min. Fan in front of engine.
                           
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                          • Tinmannz

                            Tinmannz Well-Known Member

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                            ^^^^^^^^ A great stress reducer. Works better than a bottle of ‘Tums’.
                             
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                            • I8NEMO

                              I8NEMO FABO Gold Member FABO Gold Member

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                              Thanks guys, as always much good info and support here. Im running a new factory mechanical pump with a new Holley 3310. Ive inspected bowl and nut threads, reinstalled the bowl inlets that came on the carb and ditched the 5/16 inlets I got to accommodate the SS tubes factory style dual feed with smaller tube nuts. nice to actually get some bite with a3/4" wrench vs 1". Adapted from there to barb's and finishing out with fuel hose for now. Will leak test with a 6 psi electric pump. Also had the time, so pulled the oil sender and verified gauge needle movement via compressed air. In the excitement on Sunday I remember verifying tach before engine quit. I'll keep you all posted and thanks again.

                              Tim
                               
                            • dano

                              dano Evil Handy Man

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                              Just take your time, don't rush anything. Double check and have some help that knows what your doing.
                               
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                              • yellow rose

                                yellow rose Overnight Sensation FABO Gold Member

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                                Make DAMN sure you have at LEAST 35 degrees of timing on that engine AT 2000. That’s a MINIMUM. I’d rather see 40 or even 45 total.

                                Retarded timing builds heat, can stick exhaust valves, kill the top ring and such. Do NOT retard the timing.
                                 
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                                • RustyRatRod

                                  RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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                                  True story. I built an engine for a member here several years ago. Unfortunately, his wife got very sick plus they went through a hurricane....just hard times in general. He ended up selling it. A friend of a friend bought it locally. Went in a 67 notchback Barracuda. REAL nice little 360. Zero deck height. 10.5:1 measured compression. Nice lumpy old school Erson grind. Just a really nice little street motor. I dumped its first oil in (Lucas 10/30 hot rod oil) plus extra zinc additive and even primed it. Even got oil to the top just slobberin all over the place before he took it. I stressed over and over and over and OVER how important it was to get RPM UP immediately on initial startup. Saw him about a week after initial fire and asked him how it went. "Oh it cranked right up and we let it idle till it got warm and it's all broke in now". I don't know WHY people cannot get this stuff THROUGH their heads. This has been a couple years ago now, but the car is still running great, so I guess all that extra zinc saved his ass. Sometimes people just refuse to listen.......not referring to the OP here, just tellin the story.
                                   
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                                  • 413

                                    413 Well-Known Member

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                                    Use brake in oil From Joe Gibbs, Lucas, Penn Grade, etc. why 2K for 15 minutes?? That not enough time or RPM. 2500-3000 RPM Varying RPM for 25-30 minutes.
                                     
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                                    • I8NEMO

                                      I8NEMO FABO Gold Member FABO Gold Member

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                                      Thank you!
                                       
                                    • I8NEMO

                                      I8NEMO FABO Gold Member FABO Gold Member

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                                      I hear you Rusty, I'm bringing the carb to Bob tomorrow for a once over then he's coming to the shop for break in. That,combined with everyone's experience here has me much more at ease. I'll keep you posted
                                       
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                                      • abodyjoe

                                        abodyjoe Well-Known Member

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                                        only thing the assembly lube is for is to lube the first few seconds until it builds oil pressure.. i'm sure since it ran you have oil up there so as long as the motor fires fast (not a ton of cranking) this time around you should be fine.
                                         
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                                        • moper

                                          moper FABO Gold Member FABO Gold Member

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                                          Last thing I do before the intake goes on is brush on some Joe Gibbs Driven assembly paste on the lobes. I used to use the Crane cam paste but now when you order it the package is JG...
                                          After that between final assembly and starting on the stand it’s not rotated more than 3-4 rotations to check for top end oiling and pre-oil. Then it’s fired and goes 2-4K. Time depends on a lot but usually 15-20 minutes at 2500+ does it. I have yet to have one of my engines wipe a camshaft.

                                          image.jpg
                                           
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                                          • mopardude318

                                            mopardude318 Well-Known Member

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                                            Where do you get that? Out of stock or not available anywhere. Lol
                                             
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                                            • RustyRatRod

                                              RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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                                              • 70aarcuda

                                                70aarcuda Master Hoader of SBM FABO Gold Member

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