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Discussion Starter · #1 ·
I did a compression check last night and this is what I have:

#1 - 127psi
#2 - 125
#3 - 125
#4 - 115
#5 - 125
#6 - 120

I am using the N47 head on a standard L28 block with flattops.

Do these compression figures look ok?

Thanks

Steve Graber
 

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> #1 - 127psi
> #2 - 125
> #3 - 125
> #4 - 115
> #5 - 125
> #6 - 120
> I am using the N47 head on a standard L28
> block with flattops.

Steve,
No, those look low. At least they are consistent. One thing that often works is to move the cam sprocket to the next hole. This slightly advances the timing, and will most often, increase your compression. If you had the head shaved, even a small amount, that is really necessary anyway. If you are not sure how to advance the cam one hole, ask, and I will write it out.
-Bob Hanvey
 

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> #1 - 127psi
> #2 - 125
> #3 - 125
> #4 - 115
> #5 - 125
> #6 - 120
> I am using the N47 head on a standard L28
> block with flattops.

Steve,
No, those look low. At least they are consistent. One thing that often works is to move the cam sprocket to the next hole. This slightly advances the timing, and will most often, increase your compression. If you had the head shaved, even a small amount, that is really necessary anyway. If you are not sure how to advance the cam one hole, ask, and I will write it out.

-Bob Hanvey

ps- Also check to make sure you are getting the throttes all the way open, for that can cause probs sometimes.
 

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Steve,
your engine is brand new, how many miles are on it? You need to break it in first then check it, it should come to be higher then. Give it about 1000-1200 miles to break in. Until you are there, just drive the thing and have fun. Insure it also, just think, the ticket could be...? What exactly do you want next around $100?
Joshua L.
 

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> Steve,
> No, those look low. At least they are
> consistent. One thing that often works is to
> move the cam sprocket to the next hole. This
> slightly advances the timing, and will most
> often, increase your compression. If you had
> the head shaved, even a small amount, that
> is really necessary anyway. If you are not
> sure how to advance the cam one hole, ask,
> and I will write it out.

> -Bob Hanvey

> ps- Also check to make sure you are getting
> the throttes all the way open, for that can
> cause probs sometimes.

Bob, Can you write this procedure out and post it on the forum. 180,000 on my Z and the timing chain is bound to be streached. Thanks Jerry
 

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Discussion Starter · #6 ·
> ps- Also check to make sure you are getting
> the throttes all the way open, for that can
> cause probs sometimes.

DOH!!! That's gotta be it Bob! I didn't open the throttle at all. So it wasn't getting enough air right? Also, it's a spanking new rebuild, so the rings aren't seated yet. Could that make a diff? What PSI should I expect to get from this engine. It does accelerate like a scalded cat.
 

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> DOH!!! That's gotta be it Bob! I didn't open
> the throttle at all. So it wasn't getting
> enough air right? Also, it's a spanking new
> rebuild, so the rings aren't seated yet.
> Could that make a diff? What PSI should I
> expect to get from this engine. It does
> accelerate like a scalded cat.

The PSi for your engine depends on your c.r. If I remember right, you had a higher compression engine than stock. With the N47 & 86mm flattops, you'd be at 9.8:1. If stock is 135psi, then you should have more than that. I would say 150psi would be about right. Then, depending on the cam timing, that number can rise or fall a few psi.
 

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Steve,
Yes, make sure the throttle is fully open. Second, I concur with Josh, run the engine for a while, and see where the readings are after the rings have had time to set in.
-Bob Hanvey
 
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