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High compression?

Holey76 - Square Nut

Holey76 - Square Nut

1/2 ton status
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May 31, 2023
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Hey all, i put together a 5.7 and just put it on the road. Under wot conditions, i get oil burning. Oddly, i keep seeing the oil dipstick push up. Tested compression and got 215-220 psi on all 8. I tried running a pcv, but brake booster failed, so i added a valve cover vented cap. Do ya suppose theres enough blow-by at 3800 rpm to push oil dipstick? In addition, I've tried 3 seperate brands of vc & gaskets, but cannot stop oil from running out like a seive
 
that is a lot of static compression I have 2 sbc engines that run @175, and I think that is high. one of them has Chinese dip stick and tube, it is always pushed out 1/4", I am also running stock style PCV system. It sounds to me like the rings didn't seat. Did you do a ring break in cycle ? put a mechanical fuel pressure gauge in you valve cover and see how much pressure is in the crank case.
 
I put a break in additive in and ran it around at 3800-4500 rpm for 50 miles, then drained.
I sould say that i put a fine hone finish on it because i used 1/16" c-m rings. Before i put it on the road, compression was 190. The dipstick is chineseand does come out 1/4 to 3/8".
So if there is excess pressure, what do i do ?
And did you use a tandem pvc? Or single?
 
Wes, i only got about 10 min in, on a break-in cycle, as there was air in the coolant, and temp started to go too high. I topped it off and took it for a fairly hard push.
Prob not the ideal break-in, but...
 
yeah not the ring break in I am used to. I take mine out to a long very lightly traffic street and gently accel to 40-50 mph cost down to @ 10mph do this over and over again 10 to 15 times.
Holey76 said:
I put a break in additive in and ran it around at 3800-4500 rpm for 50 miles, then drained.
Click to expand...
I hope that is a typo 50 minutes and not 50 miles. Cam break in should be 1800-2200 rpm for 20-30 minutes, varying rpm's gently during this time period.
 
I'd be curious to see what the rubber glove test showed.

Seal up the engine, except for maybe the dipstick tube and put a rubber glove over it. L, or balloon. See if and how quickly it fills up
 
Wes Harden said:
yeah not the ring break in I am used to. I take mine out to a long very lightly traffic street and gently accel to 40-50 mph cost down to @ 10mph do this over and over again 10 to 15 times.

I hope that is a typo 50 minutes and not 50 miles. Cam break in should be 1800-2200 rpm for 20-30 minutes, varying rpm's gently during this time period.
Click to expand...

Wes Harden said:
i was in town driving and though i pushed it a bit, some was also stop n go.
Click to expand...
I guess my concern here is 2 things: excessive blow-by would mean a tear down, or wait to see if rings seat ?
I've NEVER had a sbc that dumped oul out the valve covers like this. I used cntr bolt with those blue rubber gaskets, alum parameter style, and stamped steel parameter and got the same results. Have any of you had oil blown out the vc like that ?
 
That pressure implies you have a compression ratio nearly 15:1. What kind of parts did you put in this engine? Have you used that gauge on any other engines lately?
 
Blue85 said:
That pressure implies you have a compression ratio nearly 15:1. What kind of parts did you put in this engine? Have you used that gauge on any other engines lately?
Click to expand...
Ya, way higher than i calculated. Kb pistons .150 dome, mls 23? thou head gasket (cant recall for sure) and 64cc chamber'd heads. But it doesn't ping n rattle, so
 
Ya, I've used the guage on the engine at initial test b4 start up (190 psi) and the engine before i tore it down (95 psi) and had it for about 20 years.
 
assuming a couple of other measurements compression calc come out to almost 11 to 1
 
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