shaving the block/heads to up compression

[bjornmk1]

I need to have 0.023" shaved of the block
so how much would need to be adjusted/shaved of the LIM for
proper fitment.

does anybody have experience with this procedure ?
I guess it's almost the same if you would have the heads shaved 0.023".

this will give me a CR of 7.6:1 for boosted aplication.

anyone ??

[bszopi]

The CR sucks. People on here are running 9.5 on relatively stock 3400s with no problems.

Which head gaskets are you using to come up with that CR? Just asking, because if using the AL head gaskets (comp thickness of 0.060"), you could gain that clearance by going to the iron head gaskets instead (0.040").

[john_V63400]

yeah trust me dont go 7.6:1... I was at 9.1 with 8psi of boost on my 01 GA GT and let me tell you it sucked.
I could feel the difference from the stock CR. SLOW. Felt like a Turbo LAG
Then when my S/C broke I couldnt even burn tire, all it did was just bark.
Im at 9.5 with 12psi of boost, and Ive had it close to 15psi.
I have forged pistons too, but 9.5 on 8psi stock internals is fine.
Unless your going to be running sum rediculous amounts of boost like over 20. i would still imagine thier be some turbo lag.

[bjornmk1]

I am shooting for 13-15psi.
I wanna have a 2.8L crank in the 3400 block
together with (stock bore and CH) forged pistons .

so my pistons are about .110 in the block bore.
I'm thinking of having a total of .07 shaved of the heads and block.

I am aware that doing so would need machining the LIM.
the question is how much needs to be removed from each side/bottom ??

[bjornmk1]

BTW I am building the block for supercharging NOT turbo.
with that amount machined off...it should be at about 7.9-1
which seems a reasonable CR for a max. 15-16psi of boost.

[bszopi]

I still think its a little on the low side, but...

If I get a chance (I'm not guaranteeing anything!!), I can draw all the stock dimensions up in CAD, and then make the different adjustments and see what would be needed for the LIM.

[john_V63400]

too low, i've had 15psi on my 9.5 no problem.
trust me dont do it that low
Only reason Im tuned down to 12 psi is I afraid the tranny wont last long

[MY91GT(Z)]

i think gtp r in between 8:1/9:1 and theyre run fine i have 3.4 pulley on mine w/ supporting mods w/ no problems and im bout 10psi for now and can go higher

[ForcedFirebird]

Mine was running 7psig and had 8.9:1, even with severe detonation (last time sounded like a cannon), I didn't hurt the pistons, only the rod bearings.

.110 is way to far down in the block, you are killing quench.

So this also answers my question to you earlier about using 6" rods because of the difference in 2.8 and 3400 wrist-pin heights. I forgot that the 3400 piston stand .020" proud of the block. This means if you were to use 6" rods, your pistons would be too high. I'm not getting where this number came from, though, (.110") because if the 3400 pistons are .020" proud, and the crank is .3" shorter, you should be further down the bore than that.

So you have bolted the crank in and measured your TDC?

[DEI37]

You make power from compression first. Then timing, then boost. Get back up to 9:1 or better. Work from there. I run 8.6:1 on 11psi or so. It still feels a little weak sometimes...mainly thanks to the 2.93FDR.

[sharkey]

the difference in stroke is actualy .317", so the difference would be .158". take the .020" that the 3400 piston sits above the deck, and you would need the piston to come up .138" to be at 0 deck. so im also not getting were this .110" is comming from.

if your going to run a 2.8l crank in a 3400 block with ironheads, you are going to need custom pistons or another length rod. being your boosting it, id go with forged pistons anyways so the price of going custom wouldnt be that much more anyways.

[ForcedFirebird]

if your going to run a 2.8l crank in a 3400 block with ironheads, you are going to need custom pistons or another length rod. being your boosting it, id go with forged pistons anyways so the price of going custom wouldnt be that much more anyways.

He has a 3400 block, 3400 heads and 3400 forged pistons with a 2.8 crank.

[bjornmk1]

yep thats right.
I plan on using the 3.4 ironhead gasket(.040)
It looks I would also need custom pushrods.

I owned a vw g60 once and it has a 8:1 CR and it ran fine with 15psi boost.
so around 8:1 for the destroked engine would be reasonable.

maybe I can go with 8.5:1 that's about .100 off the deckheight.
I am not sure yet if the intake can be shaved that much in order to
get it to fit again.

anyone ???

[ForcedFirebird]

yep thats right.
I plan on using the 3.4 ironhead gasket(.040)
It looks I would also need custom pushrods.

I owned a vw g60 once and it has a 8:1 CR and it ran fine with 15psi boost.
so around 8:1 for the destroked engine would be reasonable.

maybe I can go with 8.5:1 that's about .100 off the deckheight.
I am not sure yet if the intake can be shaved that much in order to
get it to fit again.

anyone ???

You still haven't told us how you came up with that measuerement. I think there is something wrong for you to be .110" down in the block.

[bjornmk1]

it is about .150 now