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Probably water..Looks like rust pits..time for sleeves as I don't think this will clear with a hone. Darton makes good ones. So check them out. Machine shop time for sure.
To avoid confusion, lets call the last engine (the one with the erosion in the cyl), lets call it "Block#1". It was from the 87 944S where the valves got whacked by the piston. I measured the area of the pitting to be 100.17mm.
I am not in a rush for, not do I "need" another engine. But I was really hoping to have a spare block in excellent condition. Preferably an 87+. But obviously that didn't happen
The other block I acquired recently is "Block#2". It arrived in incomplete condition. It is an early block and came with some nice looking 9.5:1 pistons. But no crank. I suspect the crank said "goodbye cruel world" because of a turned rod bearing.
Now here is a comparison of Block #1 on left & Block #2 on the right. I just measured the bores on Block #2 to be around 99.9mm.
So that's good right?
The part that I don't know about is the finish of the bore. It has light cross hatching, almost like someone went over it with a scotchbright pad or steel wool.
What can I do to finish the bore, or is it good to go?
To avoid confusion, lets call the last engine (the one with the erosion in the cyl), lets call it "Block#1". It was from the 87 944S where the valves got whacked by the piston. I measured the area of the pitting to be 100.17mm.
I am not in a rush for, not do I "need" another engine. But I was really hoping to have a spare block in excellent condition. Preferably an 87+. But obviously that didn't happen
The other block I acquired recently is "Block#2". It arrived in incomplete condition. It is an early block and came with some nice looking 9.5:1 pistons. But no crank. I suspect the crank said "goodbye cruel world" because of a turned rod bearing.
Now here is a comparison of Block #1 on left & Block #2 on the right. I just measured the bores on Block #2 to be around 99.9mm.
So that's good right?
The part that I don't know about is the finish of the bore. It has light cross hatching, almost like someone went over it with a scotchbright pad or steel wool.
What can I do to finish the bore, or is it good to go?
Should not have cross hatch. Should be smooth. You might be able to do the felt pads/sunnen paste hone on the NA block. The s block should be taken over size. Wossner makes replacement pistons for a good price.
Ok painted it last night quickly with a spray bomb of cheap rust paint. Now the old paint is lifting because I didn't use a sealer primer. No biggy... will paint the whole car again once mechanically & aerodynamic wise everything is 100%.
When you bore a 2.5 to 102mm dia or 104mm, how many ltrs displacement is it? How much more more hp/torque would it deliver over 100mm in a 8 or 16 valve engine?
Dear Noah: Boring an engine just a few mm isn't going to give you much more power. What will give you displacement, is STROKE, and the is highly relevant to torque and power. Unless you really bore an engine out big, you won't get much more out of it. Just go to the max size that you can get away with without having to sleeve the block is usually the easiest, so you can easily source pistons, rings, etc.
When you bore a 2.5 to 102mm dia or 104mm, how many ltrs displacement is it? How much more more hp/torque would it deliver over 100mm in a 8 or 16 valve engine?
102 = 2.6, 104 = 2.7 (rounded up)
1987 944NA was 2.7L, about 162hp/165 lbft...compared to your 88 which was something like 152/150 IIRC. that 2.7 also had 10.9:1 compression versus your 10.2 which does help torque a bit.
there's a guy in OHIO selling a complete 64k mile 2.7 engine for $1250 or so+ship...be cheaper than boring and rebuilding.
but trust me...again, i have to say...get the MAF/MAP before thinking of displacement. my 2.5L, 9.5cr engine makes the same power/torque as that 2.7/10.9 engine with my MAF and cam advance.
although if you're crazy and have access to good fuel...i have a recipe in mind for a 3.0L 8-valve with 12:1 compression on the cheap. id say it would easily get over 200hp/tq. and i can sell you some parts to make it happen
ok the '88 8v is 158hp in North America.
What is say 11.5:1, 12.5:1, 13.5:1 compression ratio 2.5litre? Anyone know?
I don't think there's a simple answer to this question. You'll know when you try it.
I'm also not sure what is the max CR in an 8V head that will not knock like crazy.
This is why I stayed conservative and went with ~11:1 or something.
-Revisiting the concept of removing liners from wheel wells and venting the front fenders. Need to build aluminum panels to protect stuff & if I pull the trigger, I'll also relocate the charcoal canister to under the hood.
-Removed the front bumper & noticed my spin out at the autocross ripper *****'s front valence pretty good.
-Figured a way to quasi-ram air the car. Going to start that on friday.
-Engine stuff: Super pumped that the engine repair facility that rebuilt 2 of my heads answered like this:
"Alusil? Oh yeah we work on them... we have the lapping compound & the pads"
"Boring out the holes? Sure. It's about $60 for 2mm & $80 for 4mm. Including lapping"
10-04-2015, 06:00 PM
