After putting in a Rebuilt 350 TPI in my car how long should i wait to let her loose? Some says a good breakin is 700 miles. Is that right? I want to burn of some of the rubber on my tires before i replace them!

 

I usually say 1000 to 1500 miles to break it in b 4 u romp on it too much some say dont go above 3000 rpms till u hit 1000miles.

 

hour or two, go through 3 or 4 heating and cooling cycles, varying rpm all with 30w dino oil

 

Yep, let it heat up. Tighten down the headers after it cools, make sure it's not leaking anywhere, give the exhaust a once over. Things will have moved a bit after the first heat cycle. Check the timing, because the chain will have settled a little. Do that a couple of times and you should be good to go. Might want to give the valves one last check before laying into it.

 

Really thats all?? I thought thats was the genneral break in for the cam but u should still baby it for a while. The 67 E-Type jag I have just had baleced bluprinted my guy said the 1000 to 1500 mile break in b4 I romp on it? just wondered. thnks

 

Well, I'm not going to tell you what to do with a car that has that much money in it. If it was me and he told me I had to take a leak in the front yard before I could drive it I would. Car manufacturers make engines and drivetrains all the time. Do you think they employ people to drive them 1000 miles before they can sell them? Break in is basically a catch all so that the builder can't be blamed for something breaking when you run it too hard. The cam and lifter will develop a wear pattern that is specific to each lifter and lobe, but that has nothing to do with it's reliability. BMW says that the M3 they sell can't go over 60 mph or over 3000 RPM before so many miles, then you take it back and BMW changes all the fluids in the critter. They probably look for metal flake and what not. All the engines that we make are run on a lug curve immediately after assembly to make sure that they're good. We don't make as many engines as Ford or GM so they design and build them and develop quality control so that as soon as Joe Schmo buys it he can hammer it out of the dealership w/o it breaking.

 

Yes very true and yes I have 10 grand in the motor alone on the jag. I'm not gonna take a chance with that. Plus Ive been with out the car for 2yrs while its being restored frame up show winner. Thats why I dont want to dump too much into my camaro as of yet. Im into the jag for about 30 grand total and shold have it next month. thnks for the answer. Im just a hobbiest mechanic not a profesional (even though I did go to school for it) Ilove playing with cars.

 

Lots of mine have been drop it in, crank it up, qualify... a few others have been crank it up, let it warm up for a couple of minutes, then a dyno pull...

Think about it this way. What do you do to a new car to break it in? Do the same thing. Or, if you had somebody build you the motor of your dreams and you paid for a dyno printout, what would they do? I guarantee it wouldn't get 1500 miles worth of babying before it went to the dyno.

Make sure the engine runs right from the get-go: not too rich, not too lean, timing right, etc. Too rich especially will waste new rings.

The main thing is to follow the cam mfrs recommendations, which are usually something like 20 min at 2000 RPM minimum (note that's minimum, not maximum) for 15-20 minutes, then do whatever with it. No synthetic in a motor with a flat tappet cam for the 1st 20 minutes. If your springs give open pressure above 350 lbs or so, take the inner springs out for the 1st 20 min. If it's a roller cam motor, you can start with synthetic, the factories all do; and no particular break-in is neccessary. It doesn't have any effect one the rings. When you make your first oil change depends on how it was built. If moly lube was used, change it after the 20 min cam break-in and again at 500 miles; if you build the short block with oil and use cam lube or white lithium in the valve train, and keep it clean (no shop towel lint for example), the 1st oil change should be at the 1st normal change interval (3k miles or so) again following factory recommendations.

To seat the rings quickly and give them the right pattern to last a long time, for the first few miles, give it about ½-¾ throttle in some gear that will let you take it from about 2500 RPM to about 4500 RPM, leave it in that gear and let the engine brake the car back down to 2500 RPM, run it up to 4500 RPM again, etc. for maybe 5 or 10 times. But that's not necessary, just a little finesse. As long as you don't take a street build and immediately do 7000 RPM passes, it's kind of hard to screw it up.

 

cool thnks so many knowledgeble people here. so much info.

 

what about just getting up to the speed limit a little faster then normal? I don't know if i will be able to resist the temtation!!

 

If it's a roller cam motor, let it heat up/cool down for a few hours of driving, and then let 'er rip.

 

Its just a mild cam.