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Yipee....

For some of you who have been following my BHG incident that happened around the end of June on the Redpra, I finally got my Redpra back last Thursday.... Am now curious as to what my new compression is on the motor. Can anybody give me a estimate???

85 5MGE that was formerly a 9.2:1 compression motor.

0.015 was taken off the head surface. Was told that this was more or less around "average". 0.010 would be minimal, and 0.020 would have been quite a bit...

Replacement HG is a new stock OE Toyota HG, which is either a 1.5mm or a 2.0mm thickness (anyone know the correct thickness on this, before it's crushed/torqued down??).

Anyone know if compression changed much at all??? Am still on 89 octane gas & no pinging under a load, or going up hills.

If anyone wants to know what else was done to the head, LMK & I'll post the info later.

And yes, I did take pic's of the motor before & after, and the head after I got it back (forgot to take before pics, after it was pulled off the motor).
 

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do a compression check if you want to know about how much its changed. Stock PSI with the 9.2 compression is 180psi. Hows she feel now?
 

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SupraFiend said:
do a compression check if you want to know about how much its changed. Stock PSI with the 9.2 compression is 180psi. Hows she feel now?
whats the compression on the lower compression (8.XX I think) 5MGE and the 6MGE?

CJSREDPRA- sorry for hijacking your thread :wink:
 

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I'd kinda doubt it went up to 9.5:1, probably 9.3:1 or so would be my guess. If I ran my #'s right its only about a 2cc change which is pretty small. I highly doubt you'll run into any problem. I have domed pistons and .035" of material removed and it still runs fine on 91 octane.
 

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Thats the numbers my CR calculator threw out (I didn't feel like doing the math). You're right, thats about 2cc. I double checked and 2cc will cause that much difference.

Original: (460cc+56cc)/56cc = 9.2

New: (460cc+54cc)/54cc = 9.51

Christian
 

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Stock cambers are 56cc? If thats true I should have 10.46:1 compression in my engine :shock:
 

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Discussion Starter #8
Coolness Aaron & Christian!! :D

So the consensus is that my new CR should be 9.5 huh???? Sounds good to me... Am glad that it's not too big of a leap, so it sounds like I should be fine for the majority of the time, when I'm on 89 octane. Thanks guys.

Zank. the 6M is a 9.2 compression motor.
 

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zankone said:
SupraFiend said:
do a compression check if you want to know about how much its changed. Stock PSI with the 9.2 compression is 180psi. Hows she feel now?
whats the compression on the lower compression (8.XX I think) 5MGE and the 6MGE?
I think Zank is asking what the PSI should be. The 6m would be 180, I'm not sure about the 8.8 engines, check a haynes manual, it will be there. Probably 160.

Its weird, I just did a compression check on my 85. It went from 155 at the front to 145 at the rear, going down a little each cylinder for the most part. Average numbers for an engine that old (180 k kms) but I was still a little suprised as it feels so strong. I actually got into a little race with a first gen fwd turbo talon the other day and easily pulled on him. He was embarresed. :D I don't think I should be able to beat one of those, I thought they were around 200hp, maybe the fwd ones are less.
 

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Stock cambers are 56cc? If thats true I should have 10.46:1 compression in my engine
Thats not the size of the actual chamber in the head, but the size of everything (ie piston dish/dome, head gasket volume, and cylinder head chamber)

Christian
 
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