Block Types?

[2nd.gunman]

Ok guys i know there are two types of blocks.

the early block used from 76 to 84? with a rope seal

the late block used from 84? to 93 with a one piece rear main seal.

aside fron the rear mains and engine number location is there any other differences in these blocks?

i have a 78 250 with the original points dizzy and want to swap in a elec dizzy i got out of an 83 XE. I've heard the shaft size is different and i'll have to sleeve the block to take the dizzy.

any thoughts

 

[SONNY]

i changed the points dissy on my eairly x-flow to an xe one with no changes or mods,so i guess they fit.maybe mine is gonna blow but she runs realy good now

 

[Anonymous]

The distributor boss (hole in teh block for the dizzy shaft) in teh electronic ignition cars is smaller by about 20thou. If you put the electro dizy in the points block the dizzy shaft is not supported properly. Remember it drives the oil pump. Addo and others have written about mods to the electro dizzy shaft before, do a search.

You can fit a 302 Windsor 2 peice neoprene seal to the older rope type blocks. Its what my engine builder uses and recommends. It's ACL part number HN064. Much less drag than a rope seal. Personally i have had trouble installing rope seals. Takes preparation and skill to install reliably, the neoprene is perfect for non experts like me.

The water passage holes are differen for cast iron x-flow heads than for alloy. The holes are in the same spot but a different shape. also cast iron head blocks have no dowels for the head.

These engines are so cheap now that you should just decide if you want iron or alloy x-flow. If you go for Iron make sure you get a electronic ignition one.

Dom

 

[alloydave]

Theres 2 different sizes of 1 peice neoprene rear main seals in the later blocks .

 

[SONNY]

if the block hole is smaller in the alloy head engines why did mine have a points dissy in it when i bought it?if the hole is smaller then the points dissy shouldn't fit?is this right?

 

[Fingers]

There are at least 3 types of Alloy head type block, rope rear seal, neoprene seal with 84DA casting No. (on the L/H/R) and late neoprene seal type with 87DA casting No. The late block will take the later type crankshaft from EB-EL type engines.

 

[2nd.gunman]

so when did they change the distributor boss
early alloy, 84DA or 87DA?

did XD's have electronic ignition? and if so will it fit an XC block?

i'm trying to decide wether to just get a better coil and new set of leads and plugs for the points dizzy or fit the XE elec dizzy i have with new leads/coil/plugs? it's a 78DA block with HF-4 alloy head extractors, small cam and modified ADM Weber, but will be fitting a 2-brl holley on a redline mainfold soon.

 

[Fingers]

The distributor boss diameter changed when they went to alloy head. XD with iron head had points, XD with alloy head had electronic. I have had an electronic distributor modified to use in an early block, a machinist put a steel sleeve on the shaft from memory, it was a long time ago and I dont know how much it would cost as it was a freebie done by a mate.