rebore 2.8 or 3.1 to supercharge ??

[bjornmk1]

I need to bore my(2.8-'87 or 3.1-'89) engine to 3.57"(90.8mm)
for the fitment of my ford cosworth forged pistons.

I'm not sure if there is any differance in wall thickness for these engines,
the 2.8 seems a bit more stout on the top of the cylinder...



BTW i'm gonna use my 2.8 crank because the pistons have almost the same compr.height as the stock 2.8 ones with iron heads.(budget forged pistons that only cost me about 200$ )

I will probably use my aluminium heads from my 3.1 block.
this should all fit...RIGHT???

engine will be blown by a m90 supercharger from a ford,so I think it
would be wise to install fell pro sd(severe duty) headgaskets,along with clevite (77 ??)bearings for the bottom end.

ANY COMMENT IS WELCOME

[Ortie666]

are these pistons dished? because if there not you may not be able to supercharge it, thus if they were flat tops you would have some 12.5:1 compression with aluminum heads..

[bjornmk1]

well they are dished..20ccm actually,butt
they will likely grow to 22ccm.

together with some headwork on the 3.1 alloy heads
the compression should be fine.

I'll post some pic's of the pistons tomorrow

[fivepointhustla]

It would be smart to run the severe duty gaskets. You shouldn't really bore out the 2.8/3.1/3.4 unless it is a minimum, .030-.040 is about the maxi would go. Why not have the block resleeved to 3.5? Doubt they'll fit but if so that would be good.

[bjornmk1]

the new bores would have to be 3.57",since my forged pistons are this size.

I already had a 4inline block done(sleeved) once,but for that example there was enough meat for a sleeve.

I really don't know how a 3.5L can be achieved in that way ..since the wall thickness is only about .177" ??

clear me up please..

[bjornmk1]

is boring the 2.8 to a diameter of 3.57 gonna work ?
(will this hold in long term?)

heard of some people on the pennock fiero forum
that those engines sometimes got bored to .60 and more

sure hope my pistons will be usefull

[bjornmk1]

boring to 3.57

is it ok to bore a 2.8 to 3.57" ?
i know normally .60 is the max. butt
did anyone go larger than this without problems???

[Doubt_Incarnate]

ARI i belive is a company that has gotten away with boring and stroking 2.8 fiero motors to 3.4L. The thin walls and boost is probably a death sentance.

[bjornmk1]

boring

but I am boring to 3.57@
not to 92mm or more.

and if you take care of the cooling of the block..than I
think there wouldn't be to much of a problem.

B

[Doubt_Incarnate]

all you can do is try at this point.

I read in a summit catalog than you can partialy fill the water jackets with block filler and it supposedly improves cooling, as well as reinforces the bottom end, another plus for boosted apps.

[bjornmk1]

block filler

gonna look at that one right away..
sounds like an extra safety measure

thanx bud.

[bjornmk1]

has anyone ever done this hardblok fillet thing?

seems risky to me for a "virgin filler"

I think it's worth the invesment though

B

[geoffinbc]

Will all this trouble youa re having you should just go get a 3.4L

[Doubt_Incarnate]

his goal is to have a large bore but maintain the short stroke to work with a set of pistons he already has. Looking for around .070" over, and an eaton M90 supercharger. i'm just worried about cylinder walls, i know franz cracked a block and he's just N/A and was within bore limits on a 3.1. Keeping the shorter stroke might save it tho. maybe if stuff isn't being compressed as fst it will live longer.

[bjornmk1]

engine back from the shop

hi guys,got my 2.8 engine block back from the shop.

it was dye checked and magnetic tested before it was bored
to 90.82 .millimeters and decked.

I had them put new cam bearings in it and check the crankshaft
for wear and size...and after aproval they polished it.

here are some pics