7a block

[kelys]

Is it possible to use the 7a block for high performance, or make the bigger bore the block to weak to use


kenneth

[caterpillar]

you may rebore it to 83,00 (0,5mm).. then it will be some isue with the next sylinder..too narrow... so if you need to rebore the 7a (82,5) so will i use another block... from 81,00 (3b or aan) to 82,5 (7a) its only ca 100ccm increase...i would gone for the stroker 2,4 or 2,5 block...petrol or dieselblock 5pot

[Rocco]

you may rebore it to 83,00 (0,5mm).. then it will be some isue with the next sylinder..too narrow... so if you need to rebore the 7a (82,5) so will i use another block... from 81,00 (3b or aan) to 82,5 (7a) its only ca 100ccm increase...i would gone for the stroker 2,4 or 2,5 block...petrol or dieselblock 5pot

would you use a short S2 block with AAT 95.5 crankshaft for a daily car? max rev limit 7000rpm true?

[caterpillar]

i would NOT used low block 220 with the 95,5 crank...even if you use the 7000 rpm max... the pressure on the pistonsjurts are too bad.. and the rod angel in the piston are too bad... the engine will feel ok, but will last shorter,, with bad oilconsutions will come...the old 5 pot dont use any oil even after 3-400 000 km.... .. !! ive tryed so old engines..
if you have the dieselcrank, why not use the block too?? the conrod, stroke ratio are the same as the 3b, and aan, adu, spec if you use the 158 or 159conrods, and the the conrods anger to the piston goes down to nearly 70, the the lower pistonskuirt pressure....

[PRY4SNO]

From my research, there's nothing wrong with a 2.6L... the 7a should be as robust as any i5, especially with the stock crank.

Not sure why you'd need to overbore a 7a in the first place... if its bores are worn out of spec, find another one! They're cheap!

[kelys]

I am going to use stock lenght crank with longer rods, and shorter piston, to change the angel So if the 7a is strong enough i will use it. Will a stock crank 7a fit in a diesel block



Kenneth

[JP]

If you use too long a rod angle piston speed very slow which makes for very slow revving engine. Long rods are only good if building engine that lives between 8-10,000rpm anything below is not as good as keeping stock rod ratio.

As an example two engines same power one with 92.8mm crank and 164mm rods and one with 95.5mm crank and 159mm rods. Engine with shorter rods more stroke has better piston speed and is faster round track because quicker out of corners as engine revs faster.

[kelys]

Hi JP.

The reason why i use longer rods, is to change the angel from center piston to crank.
It is not because i want to stroke it. The crank is the same the rods is just longer



kenneth

[JP]

I know. The point I was making was related to rod angles. Reduced angle = better high rpm stability but slower piston speed. Slower piston speed = slower cylinder filling at low rpm making sluggish unresponsive engine. However if you are building engine to live between 8-10k rpm then its ok otherwise keep stock angles for best all round engine

[caterpillar]

the std 86,4 crank will fit right in the dieselengine block..236,500 (there are som varies on the deckheight) no prob... then you may have drysump in too.. and mekanic lifters.. and high lift cams.. 12-14mm valvelift..

[PRY4SNO]

Pretty sure that 034 used the 7a in stroker form for their time attack coupe quattro and motor build for the Castrol Top Shop Challenge, and EuroTuner GP winning entries.

for example,

http://www.034motorsport.com/1991-coupe-quattro-a-127.html

[caterpillar]

they do used the 92,8 cranc...in a 7a block.. correkt... but then you need to buy the item...its pretty rare un commen engines...( may in t3 as a 2,3 or 2,6 5 pot, and may in some eurovans t4; not 100% sure)...
best engine combo; my opinion) the dieselblock 236, the 92,8 crank; or for more rpm 86,4) long conrods... at least 158 or 159.. or even longer 165... drysump.. deasent portjob in the headunit...really some beast of some camshafts... others nice combos????