3100 bored over compression?

[kill_them_all]

Had my 97 3100 bored over .020. I believe the stock compression was 9:6.1. I did not have the heads decked. Anyone have any ideas? Will I see any type of increase power wise? My first rebuild. Thanks.

[TheProfessor]

you might notice a slight increase
like maybe 5 hp or so i would guess

[blackbombshell95]

whats teh most a 3100 can be bored over? without going to paper thin?

[TheProfessor]

.60 over is the max but i wouldnt go more that .40

[smilinguy99]

If your motor was pretty worn and stale, you should be pleased. And if it was stale, I trust you are getting a nice valve job too.

Basically you will be back to square one with performance. Compression may only go up a tenth of a point or so. Good luck.

sg99

[kill_them_all]

I got my block and parts back today, bored over .020 with new sealed power pistons, hasting rings, durabond cam bearings, clevite main and rods, galley plugs, melling oil pump, and new pbm roller lifters. If anyone wants my old roller lifters let me know, they are fine I was just not going to take the chance.

As far as the valve job, I bead blasted the heads, polished the valves, ground the valve margin, ground the valve seats, ground stems to match amount removed from margin, replaced pushrod guides, tested springs, shimmed .030". Pressure and vac tested them. They seem to be good.

Any other suggestions? Thanks.

[v6h.o.]

Re: 3100 bored over compression?

Had my 97 3100 bored over .020. I believe the stock compression was 9:6.1. I did not have the heads decked. Anyone have any ideas? Will I see any type of increase power wise? My first rebuild. Thanks.

Rule of thumb for Compression Increase to Power increase:

for every full point of Compression change = 4% power Increase/Decrease *depending on which way you go about it.

example:
9.5:1 CR. on an engine with lets say 160 HP

change compression to 10.5:1
4%(1.04) x160 = 166.4


With only .020 off the heads i'd say your likely sitting just around 9.8-10:1 range.

You would have to CC the chambers to know for sure.

[TheProfessor]

how much do you want for those roller lifters
and how many miles on them

[kill_them_all]

V6HO - I did not have the heads decked, I just had the block bored out to .020.

Professor - make an offer, they have 182k on them and where working perfect.

[v6h.o.]

? somehow i saw .020 and was thinking compression change... sorry.
i need to get more sleep. fuck i hate working saturdays.. one more hour to go.

[kill_them_all]

V6HO - you work at a dealer correct?, how is that, I am going to school to become a mechanic and was going to try and go into independant shops, what do you think?

[geoffinbc]

Dealers pay better and they pay flat rate. So if you learn to be quick you can make mega bucks.

A guy Eric at my dads work it a master. He can re and re a getrag 282 in about 3 hours where book time is 6+. He can overhaul an automatic in about 3 hours that includes removal and reinstall into the vehicle. He is just amazing I just ask him any question and he can answer it. If I give him a symptom he can diagnose it. Its really amazing what he can tell you about a vehicle.

Back in his young days my dad said he would pull in double time and a half consistently. Working long hours he was making 6 figures a year.

[TheProfessor]

ill give you 20 bucks for the roller lifters
gotta wait till i get paid though