What is considered excissive "Blow-by"? - Team Camaro Tech
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post #1 of 16 (permalink) Old May 14th, 14, 03:34 PM Thread Starter
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Chad
 
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What is considered excissive "Blow-by"?

Running a 406 sbc, roughly 9.5 to 1 and hardly any miles. What is considered "excessive" blow-by for an engine? I'm getting a constant vapor of air and oil while engine is running. I cant run just a breather filter on my valve covers due to oil eventually dripping out. And when i have tried a oil cap and breather filter it blew the cap out when trying to seat the rings (throught they may have not been seated). Got back to the house after cycling the engine, getting in it hard and off coasting down and the oil cap was gone, oil on the underside of the hood. I currently have new performance head gaskets (felpro 1014 for better cooling) and a new set of apr studs, but dont want to put them on if i need to do a .010 bore and run new pistons/rings.

I really would like to just keep it all together but if it needs to come apart for new parts I'll just have to head that direction. Gearheads chime in
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post #2 of 16 (permalink) Old May 14th, 14, 05:08 PM
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Re: What is considered excissive "Blow-by"?

Do a leak down test yet ?

Run time has been how long ?

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1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #3 of 16 (permalink) Old May 14th, 14, 06:58 PM Thread Starter
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Re: What is considered excissive "Blow-by"?

No leak down test yet. Motor burns a quart about every other time i drive it, fouls spark plugs fast, has a smoke at idle that i can not get rid of and only has about 500 miles on it.
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post #4 of 16 (permalink) Old May 14th, 14, 07:23 PM
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Re: What is considered excissive "Blow-by"?

Who built it ?
Rings gapped wrong or maybe upside down ?

Put air to each cylinder and listen to where you hear the air blowing by....there's your problem.
Valve covers....guides
Intake....valves
Oil pan....rings
ETC....

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post #5 of 16 (permalink) Old May 15th, 14, 06:14 AM Thread Starter
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Re: What is considered excissive "Blow-by"?

Bought the bottom end complete. machine shope was supposed to check and replace what was needed rings, bearings, etc. Or at least they charged me for new rings bore hone and all that good stuff. I put the top end together and was very meticulous about it.
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post #6 of 16 (permalink) Old May 15th, 14, 06:34 AM
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Re: What is considered excissive "Blow-by"?

I would start by going back to who built the bottom end and question them about your issues, they should perform the test for you as it seems like a ring issue and if they are a reputable shop they should be willing to help you locate the issue and if they are at fault fix it for you. 1000 to 1500 miles rings should be set, but seems like a heck of a lot of oil usage and blow by even during the seating process your experiencing now. For example we just rebuilt a 69 Mach 1 351 last weekend, just honed bores and new rings, very lil blow by, using about quarter of a quart every 200 miles or so and each time we drive it, less and less smoke out the exhaust.
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post #7 of 16 (permalink) Old May 15th, 14, 07:37 AM
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Re: What is considered excissive "Blow-by"?

Sounds like an incorrect cylinder hone grit was used for the current rings. Probably done too fine. I.E. 500 rather than 300.

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post #8 of 16 (permalink) Old May 15th, 14, 01:32 PM
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Re: What is considered excissive "Blow-by"?

Chad, the oil cap blowing off is a bad omen.
Your plugs foul. Are they fouling equally?
If one or two adjacent plugs are fouling look for an intake gasket leak.
If blue smoke is pouring out of the pipes when coasting from high RPM then maybe someone left the seals off of the intake valves.
Were the pistons new when you got the lower end (assembled)? Do you know who put the short block together?
Leak down test time, like Doug asked.
But none of your symptoms are a good omen.

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post #9 of 16 (permalink) Old May 15th, 14, 03:03 PM
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Re: What is considered excissive "Blow-by"?

Also, if it is indeed a 406 then the original 400 block has already been bored out .030" over the stock 4.125" diameter...

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post #10 of 16 (permalink) Old May 15th, 14, 04:16 PM
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Re: What is considered excissive "Blow-by"?

Quote:
Originally Posted by powerwindows View Post
also, if it is indeed a 406 then the original 400 block has already been bored out .030" over the stock 4.125" diameter...
4.155"
Still miss mine once in a great while

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post #11 of 16 (permalink) Old May 15th, 14, 08:02 PM
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Re: What is considered excissive "Blow-by"?

Thats excessive. Something is wrong, do a leak down before anything else, then take the motor and leakdown results back to the builder.
That sucks, good luck with it.

Sean

1968 rs with an old school 354" SB2.2 pump gas motor.

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post #12 of 16 (permalink) Old May 15th, 14, 08:04 PM
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Re: What is considered excissive "Blow-by"?

Quote:
Originally Posted by DOUG G View Post
4.155"
Still miss mine once in a great while
That fancy new LS still hasn't beat the best the old dinosaur 406 ran yet, has it?

Sean

1968 rs with an old school 354" SB2.2 pump gas motor.

Repetition does not transform a lie into a truth.

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post #13 of 16 (permalink) Old May 16th, 14, 01:25 AM
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Re: What is considered excissive "Blow-by"?

I agree with all of the above Fred , Doug but like Fred said its all bad omens more than likely the bottom end was done wrong. When you do a 400 on the bore you need to use toque plates and then plateau finnish Sunnen method. Don't waste time pull it out tear it down . Go back to who built the lower end and ask lots of questions . Good Luck keep us posted . Alex
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post #14 of 16 (permalink) Old May 16th, 14, 01:49 PM
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Re: What is considered excissive "Blow-by"?

Quote:
Originally Posted by 68rs406 View Post
That fancy new LS still hasn't beat the best the old dinosaur 406 ran yet, has it?
LOL, no. But only by .2 in the 1320 and a lot of tuning yet.
60's are .1 better and wheels up.
Can't wait to dial her in and then add a little giggle gas.....9's and the driver will need the diaper.

Did find an issue....maybe ? and I hope to see 10's next time out (anything in the 10's and I'll be happy......for now )

42ci less....way smaller cam at .050....much more "street" friendly.

Not knocking a 400 combo, but this is all factory parts too, minus cam

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #15 of 16 (permalink) Old May 16th, 14, 06:25 PM
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Re: What is considered excissive "Blow-by"?

Quote:
Originally Posted by DOUG G View Post
LOL, no. But only by .2 in the 1320 and a lot of tuning yet.
60's are .1 better and wheels up.
Can't wait to dial her in and then add a little giggle gas.....9's and the driver will need the diaper.

Did find an issue....maybe ? and I hope to see 10's next time out (anything in the 10's and I'll be happy......for now )

42ci less....way smaller cam at .050....much more "street" friendly.

Not knocking a 400 combo, but this is all factory parts too, minus cam
Lol, just a guy with an old dinosaur poking a guy with an LS... I like 'em all, anything that makes power.

That thing will go, there is no doubt in my mind. what did you find?

Sean

1968 rs with an old school 354" SB2.2 pump gas motor.

Repetition does not transform a lie into a truth.

Franklin D. Roosevelt
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