Author Topic: compression test (Read 375 times)

Namvet · « **on:** October, 16, 2010, 03:12:25 AM »

Ran a compression test on a 302 and the numbers were 145, 146, 149, and the rest were 155. I actually think the three lower numbers were higher than that but I believe the gauge wasn't sealed up the way it should have been.
I am going to put in a 20W-50 oil today and see if the grey smoke disappears.
I think those numbers were pretty good. If anybody thinks otherwise please let me know.
I also put on a new PCV valve and the idle speed dropped right down to almost stalling. Could someone explain that to me. Thanks

AzPete · « **Reply #1 on:** October, 16, 2010, 03:56:34 AM »

Old PCV valve was not functioning and now the new one is. It does pull vacuum thru it so that could make a difference. Might want to re-adjust the mixture too.

monkeystash · « **Reply #2 on:** October, 16, 2010, 05:10:47 AM »

Oil smoke should have a blue color to it. It could be your valve seals too.

Namvet · « **Reply #3 on:** October, 16, 2010, 12:19:10 PM »

Just took it out for a ride. Cleaned the plugs, regapped them to .060, and put the 20W 50 oil in. Ran great, no more smoke. What should I expect from a 302 running about 185-190 degrees at about 900- 1000 rpm idle and 2000 rpm on the road. I am getting 25 idle and not quite 30 running. Runs just over 50 on cold start.
Thanks
God watchover the soldiers

camachinist · « **Reply #4 on:** October, 17, 2010, 01:28:59 PM »

Oil pressure sounds normal. Compression numbers are, IMO, indicative of a decent ring/valve seal, moderate compression and a mild/OEM camshaft. If you want further information, a leakdown test and oil content analysis can assist. Everything sounds nominal to me. Drive it.

Namvet · « **Reply #5 on:** October, 17, 2010, 05:56:49 PM »

Thanks for the replies. One more question. I have a 650 Holley in this thing. A little big but like I said it runs fine. Adjusted the idle speed but the idle mixture screws seem to do very little unless I open them up very wide. Could the Holley be too big? If it ain't broke don't fix it but I have wondered what having too big a carburetor would affect.

AzPete · « **Reply #6 on:** October, 17, 2010, 06:05:04 PM »

If the throttle plates are opened up to far to get the idle speed correct, you could be past the range for the idle circuit to be effective. I would set the mixture screws at the 2 turns out and see if you can bring the idle speed down. Then fine tune a bit on the mixture screws a bit more.

Other than that, you might check to see if the carb is leaking fuel anywhere internally.

Just some ideas.....

camachinist · « **Reply #7 on:** October, 17, 2010, 06:20:23 PM »

I've run as big as 800's on 289's with no adverse effects on idle. Properly adjusted, even with racing cams, you can get a steady idle only a couple hundred rpm above OEM. Try screwing the screws all the way in (gently touching the seat), then backing off 2 turns, then starting the engine and turning each one in 1/4 turn at a time until the idle deteriorates, then back out to the smoothest idle; then reset idle speed and adjust one more time for quality. I usually do a final adjustment for an automatic in drive (wheels chocked, parking brake set) just for fine-tuning.

How is the idle quality right now? What does your vacuum gauge read in gear (presuming automatic)? Out of gear?

Namvet · « **Reply #8 on:** October, 18, 2010, 10:47:39 AM »

It idles great, I do not have a vacuum meter but I think I will get one to check. I will do as you suggest and post what is going on.
My son is coming back from Afghanistan tomorrow. I think he has been there five times and to Iraq 4 times. Army Ranger. He does shorter tours than regular Army but it is usually four or five months here and then four or five months there.
Thanks