tackle the failed smog part 1

[8177]

posted once before but its not on the forum. If you see it and I don't delete the one with the least answers.

If you have been following along with the struggles to get the wife's jeep smogged I'll let you know that everyone has been a great help. So lets get this party started. Going out to a compression test in a bit but before I even waste any more time and money I need an answer concerning the Cam and timing. The CARB requires that the 258 be timed to 6 deg BTDC. I have an after market cam in it Crower 44243. The Cam card is speaking Swahili and I don't even know if I can run it at the right timing. Intake duration 256 lift .437. Exhaust duration 264 lift .445 Intake opens -11.0ATDC closes 25.0ABDC exhaust 38.0BBDC closes -14.0BTDC lobe separation 112 duration in 194 exh 204 lobe lift intake .273 exhaust .278 at .50 lobe lift.
If I cant get the timing to 6 deg all is lost.
Jim

Once again if a mod sees the other post delete one.

 

[8177]

Doesn't really matter. The compression test is 75 dry 100 wet and nothing will hold.
But I guess I need to know if I can time it to 6 BTDC

 

[69jeepcj]

Yes you can time it to 6*, but the engine will not run at peak performance. It should run fine but probably run better around 8-10* with that cam. Im not the greatest with cams but know that most aftermarket cams will benefit with the timing advanced over stock timing. Where ever you set the time, you should adjust the carb for highest vac with a vac gauge afterwards. My engine (chevy engine)should be timed to 8* and comp cams and others on corvette forums told me to time it to at least 12*, I've had it timed from 6* to 20* btdc but it ran best at 18*. It is timed now at 12* because I haven't mapped out the total timing and don't want to get into detonation. It ran fine with all of those time settings but like I said it was best at 18*. Once you install a aftermarket cam other than stock, you can throw away the stock timing specs, because the engine was timed from the factory with the original cam and that has now been changed along with the timing requirements.

 

[69jeepcj]

Really the best thing to do would be call crower and tell them the cam you have and see where they suggest setting it at. I did that with mine and comp confirmed what others had told me about setting it around 12*. Hope some of this helped... Yours will not need as much timing as mine does but I would advance somewhere around 8-10*

 

[8177]

Well the PO and I had a meeting today. he gave me back 1000 bucks and we called it even. The fuel injection kit would have been put on later anyway. so now I have to deal with the engine. The engine was rebuilt a while back and bored .30 over. What is the max the258 block will hold on a bore? And assuming that .30 over pistons were installed and the cylinder walls are not all scored can I just put in oversized rings instead of boring it out again. Or maybe just new.30 over. I'll hone the cylinders of course. I know this all depends on the condition of the cylinder walls.
Jim

 

[69jeepcj]

That was good that he gave you some money back. I believe .60 over is about the standard max bore on most engine blocks, having been bored to .30 already I think you can go .10 more to make it a .40 over bore. Then if anything ever gos wrong again you could bore .20 more for the max of .60. I think after .60 the cylinder walls are too thin. As far as putting in oversized rings now, I don't know. I have not dove into a engine rebuild yet but, it's coming in the next year or two I hope. So I really couldn't tell you a whole lot about the actual rebuild, the farthest I have gone into an engine so far is a cam, lifter, push rods, and timing set. still have a lot to learn before I do a complete rebuild I think, but its coming.

 

[8177]

I'll have to find out what a .30 over bored cylinder is supposed to measure and see what mine are. Then measure the pistons and go from there.