[david500o8]

Morning everyone, Haven't posted in the forums in quite some time because you've all helped fix my problems I've had with my car. However, a couple months ago my engine went out, causing us to rebuild the engine. I posted pretty much the full story (and the general pain this engine rebuild became), in the Talk forums so this is the short version.




My engine went because the #3 exhaust spring snapped in two, and since we already had the engine torn down we decided to do a full rebuild. Once the engine was back in the car and driving, I noticed oil pressure dropped from 40 down to 0 once the engine is warm. You can hear the lifters knocking when you hold it at a certain rpm (does it in park and neutral, not just limited to driving under load)The oil pressure issue has been happening since we first started the engine after the rebuild. I'm using 10w-40 like I always used. The engine reaches temps of 200+degrees in this heat right now, and just swapped to a 165degree thermostat. It helped, but not enough to really justify itself.


Aside from it being bearing clearances (which we're hoping it isn't, we measured everything and gave those numbers to the company we bought our rebuild kit from) what else could it be? And how should we fix it?


(My engine is a 1970 302 with 78 heads)

 

[rex1965]

Okay, since the lifters are causing the knocking in the valve train, it pretty much confirms you have low oil pressure, since you have some oil pressure when cold, the most likely cause is excess bearing clearances. I am assuming you cleaned everything in the rebuild, and you should have checked the rod and main bearing clearances with some plastigage, that you can get from your local supply house, there is nothing wrong with checking with a micrometer, but there is room for error, if you don't know how to use them right, and the bearings may need to be undersized because someone could have had the journals turned down to true them up, previously, unless you know the full history of the engine. Also I assume you replaced the cam, rod, and main bearings when you did the rebuild, and it is paramount that the oil holes are lined up on the cam and rod bearings, and the correct bearing half is installed on the block side to oil the main bearings, and if you removed the oil galley plugs in the front of the block that you replaced them. 10w-40 is like water when hot, it is okay to use when bearing clearances are tight enough to maintain enough oil pressure. You could drain the oil and use a straight 30W oil, since you don't have enough oil pressure after the rebuild, just to see what your oil pressure does, I'm guessing something was missed. And did you prime the engine, by using a drill running ccw and a adapter on the oil pump drive rod to circulate oil throughout the engine before you started it? Please post your results. And the last thought was the oil pressure relief valve in the oil pump could be stuck open. Good Luck.

 

[sp66stang]

did you use break in oil? zddp with your 10w-40?

 

[david500o8]

Thanks for the responses guys, I've been busy trying to figure out what I can do to fix it without pulling the engine apart again, and it looks like I'm going to try running straight 30 (or 40) oil, to see if it helps keep pressure up in this heat, and then I'm throwing on a High pressure/High volume pump. Anything special I should be looking for?

 

[silver69]

Save yourself the hand wringing and wondering... pull it back down and take it all to a reputable machine shop and get everythig sized. Unless you find you put the main or rod bearings in upside down or a journal or two wiped down to copper/bronze and its obvious what happened. Before re assembly clean all oil and water passages in block and crank with a set of engine brushes and wash thoroughly and blow air through. Dont know what else to tell you man but it is what I would do if it were mine. Not what you may want to hear but..... Guess what I just did....destroyed a rear main seal by spraying brake cleaner on the oil pan to clean up oil spilled from valve cover. That stuff turned the new rear seal to rock and pieces broke out of it ...leaked like a 1/4 inch hole in the pan. Been wrenching for 30 years and still did something that seemed harmless but was backbreaking to fix. By the way dont use brake cleaner on anything but brakes....can says so too lol.

 

[kenash]

Morning everyone, Haven't posted in the forums in quite some time because you've all helped fix my problems I've had with my car. However, a couple months ago my engine went out, causing us to rebuild the engine. I posted pretty much the full story (and the general pain this engine rebuild became), in the Talk forums so this is the short version.




My engine went because the #3 exhaust spring snapped in two, and since we already had the engine torn down we decided to do a full rebuild. Once the engine was back in the car and driving, I noticed oil pressure dropped from 40 down to 0 once the engine is warm. You can hear the lifters knocking when you hold it at a certain rpm (does it in park and neutral, not just limited to driving under load)The oil pressure issue has been happening since we first started the engine after the rebuild. I'm using 10w-40 like I always used. The engine reaches temps of 200+degrees in this heat right now, and just swapped to a 165degree thermostat. It helped, but not enough to really justify itself.


Aside from it being bearing clearances (which we're hoping it isn't, we measured everything and gave those numbers to the company we bought our rebuild kit from) what else could it be? And how should we fix it?


(My engine is a 1970 302 with 78 heads)

I would pull the pan and then a main and a couple rod caps to see how they look. Before you broke a spring(?), was the cam successfully broke in?

 

[david500o8]

Afternoon everyone, it's been awhile since I've updated and I finally figured out the issue. The bearings the shop gave us were right or the cam, but weren't correct for the crank. Plasti gauged the clearances and it didn't even touch the plasti gauge.

Another issue (which is the reason we just pulled the block again) was the knocking sound I've been hearing. It's not from the top end or the pistons, it was the crankshaft literally moving backward and forward a good quarter if an inch. It was enough to move the rods and timing chain (more amazed it didn't slip timing). Turns out we had out main thrust bearing in the wrong place. Even though it was numbered as the last bearing, it was supposed to go in the middle, which is what caused the play in the crank. Waiting for the machine shop to order new bearings (different shop, mind you), will update tomorrow when everything gets here.

Hopefully when everything is back together, I'll have good oil pressure with NO knocking sound anymore.

 

[kenash]

OK, will you be doing the assembly? I suggest you create a logbook of all of your assembly specs. Good luck!

 

[rex1965]

You should have borrowed a set of micrometers from your local auto supply house if they have them to loan or rent, and mic your crankshaft, to see the amount of wear, egg-shape, and taper on all the bearing surfaces, also is there the possibility the crankshaft was ever turned undersized, all of these would make a difference also. There is also a procedure to align the thrust bearing to put the front surface on a flat plane. My 2 cts. Good Luck. Glad you are finally getting it figured out.

 

[david500o8]

Right guys, got the new bearings installed, Clevite 10 under bearings (I think that's right) and after the install the preppy little 302 sits happily all day long at a healthy 40-60 oil pressure (depending on idle or driving conditions). Now the only thing I have to set is the timing; I've been driving the car everywhere and it loves burn outs (non posi at the moment, so it's more depressing spinning only one tire haha). While the bottem end is great, it could be better, and there's obviously something off because when you punch the gas, where it used to throw you in the back seat, it now "gently" revs itself higher. Slower than molasses in winter, ain't going to win any races anytime soon hah.

Now my question is the timing; The engine has an Rv cam, 275 lift, biggest cam I can install in the '78 heads without major modification. I'm used to setting timing on the stock cam, so I don't know if I'm supposed to advance timing or retard it (and how far in either direction?) I'll post a video of it running when I get the chance. Thanks guys!

 

[kenash]

When one starts changing things, any adjustments whether fuel related or timing will be a test 'n tune thing. All engines respond differently , even with the same mods. What I usually do, is start with bumping the initial a couple degrees and see how it runs. Running a distributor vac? It may like full vac vs. ported?
Keep detailed records of each change. Don't make a bunch of changes to different systems at once.
Happy Trails......

 

[david500o8]

Just drove the car Kenash, hah that's what I've been doing; Advance dizzy, drive, repeat :grin: And I'm not sure about Full vac Vs Ported; I'm running a 600cfm Holley with vac secondaries, but from what we can tell its never opened the secondaries (and I've had this carb on for a long time, before the engine blew, and when I first had it installed it caused the engine to bog down when you pressed the pedal down all the way till it eventually caught up). With the build done, and everything matching the carburetor, the engine still only has good performance at idle and 1st gear, anything above that and it's like a sail boat without wind, there's just nothing. (A side note; When you really get on it, there's a puff of oil smoke poppin up, can't tell if its from the valve cover but could that be a sign of something that's off killing power?) Not sure if its the carburetor or the engine timing at this point; Feels like a little of both

 

[kenash]

Just drove the car Kenash, hah that's what I've been doing; Advance dizzy, drive, repeat :grin: And I'm not sure about Full vac Vs Ported; I'm running a 600cfm Holley with vac secondaries, but from what we can tell its never opened the secondaries (and I've had this carb on for a long time, before the engine blew, and when I first had it installed it caused the engine to bog down when you pressed the pedal down all the way till it eventually caught up). With the build done, and everything matching the carburetor, the engine still only has good performance at idle and 1st gear, anything above that and it's like a sail boat without wind, there's just nothing. (A side note; When you really get on it, there's a puff of oil smoke poppin up, can't tell if its from the valve cover but could that be a sign of something that's off killing power?) Not sure if its the carburetor or the engine timing at this point; Feels like a little of both

OK. Have you checked the distributor timing is advancing?

 

[david500o8]

The distributor is advancing yes, and I just got my secondaries to finally open. There was a main vacuum tree we put on the back of the engine during the build to connect some vac lines going to my transmission that were never hooked up, so I disconnected the main vac line going to the splitter and plugged it and ran the engine again. I put a screw in the part for the vac secondaries to make it a make-shift mech. Secondarie carb (a tip from my drag raceing uncle) and sure enough, when I give it gas they open. About to test drive it now, at least I know the secondaries work; Now to work out timing and Carb tuning

 

[kenash]

Mate, it seems you're making strides.
Happy Trails....

 

[david500o8]

Happy trails indeed, all this thing needed was that extra fuel, that sucker sat me in my seat like never before! :grin: Once I rid these performance killing 2.70 highway gears and swap in some 3.50s I should really feel this engine. Can't wait to see how she performs when I actually get 'er completely tuned hah, I'll keep you guys updated!