Decking a 250

I bought a 6 = 8 kit from Clifford Preformance and he says to zero deck the block. However with the new pistons the machine shop says to zero deck the block would mean to take off 140 thousands i know that is to much. How much can I mill the block.
Thank Don

Don, welcome aboard. I'm going to also post your question in the small six performance section of the forum.
Next time when you purchase parts you might consider Vintage Inlines. Bill

Dons66":6v2shj6v said:

I bought a 6 = 8 kit from Clifford Preformance and he says to zero deck the block. However with the new pistons the machine shop says to zero deck the block would mean to take off 140 thousands i know that is to much. How much can I mill the block.
Thank Don

Click to expand...

I had 80 thousands taken off mine. You need to CC your head first to figure out what to take off. The 255 pistons are another choice.

If I remember typical deck clearance is @ .120" on 250's so .140 may not be out of range - depending on your projected CR goals.

You need to CC your head first to figure out what to take off. The 255 pistons are another choice. ( 65-coupe )

What head and what Pistons are being used, were any included in the 'kit'?.

250 in my '61 Comet has AMC / IHC 258 pistons which needs no block decking . 258 pistons need original rod small end bore enlarged @.020" and a cylinder overbore @ .070". 3.68 to 3.75" bore & - 258 STD pistons raises comp. height @ .133" . ( TRW/SealedPower # 470NP')

have fun

See ''My Budget 250 build '' Lavron fixed it with the longer 2.5 hsc rod that also gives you a better rod stroke ratio

Ok thanks for the info. i will find out what the machine shop has done i know they bored the block .030 and i believe the head was shaved 0.80according to what the 250 kit says on Clifford engine blueprint section. I will follow up on Monday afternoon after i talk to the machine shop.
Thanks for the help.

Pls let us know what you find out. What are the cam specs?

any deeper interest - many of us peruse "the Handbook", while awaiting delivery from Matt (25$? @ vintage inlines dot com) one could ck out the above tech archive. It has just as good info as the Handbook for this specific need..
(both contain the suggestions mentioned above plus so much more).
HTH,
stick around.
Ask more after reading.


@ 5 posts I hope its not to late to say:
W E L C O M E !!!

I have the falcon 6 book already, however it does not tell you how much you can take off the block, Also the Cam is 264 hydraulic.
Once again thanks. Don

"...could ck out the above tech archive..."
at the top line on this page - the big blue box w/the
crossed screwdriver/wrench. I defer to these experts as I have this lill niggelin @ back of my
mind that wishpers against decking a 250. It's so quiet back there that I guess it because quench
v tq trade offs. U begin to geta 200 motor (not stroked):

https://www.jalopyjournal.com/forum/thr ... ck.590241/

https://grassrootsmotorsports.com/forum ... 733/page1/

Not sayin those 2 will help but most go another route for + effect.

There used to be a guy on here name Faron(FalconSedanDelivery) that recurved distributors. If memory serves me I recall him arguing that you should take no more than .040" off the deck of a 250. .060" max. and it wasn't advised. Some say you shouldn't take anything more than a clean up. Others have taken plenty more off. A search should bring it up. I took .032" off mine(.108" virgin) and used 2.5 HSC pistons but still ended up with .064" deck height with the gasket.

Faron took 120 thou off the block, 100 thou off the large log 170 small chamber head, and Gene has his engine. The best recomendation I gave was to keep block machining to a minimum and use longer conrods to make up the 120 thou shorfall. The more you deck the block, the less metal to keep the block true, and the more risk of circumfrential around stud cracking.

I like Cliffords approach to looking after its customers. Running a family business is never easy, and caparitive prejudice against a brother who has kept at it is sad.Trust the advice of the people who have put together the package for you Dons66.

There are several ways to make 250 sixes rocket like scalded cats.

As FalconSedan Delivery said...opinions are like a holes.Everyone had them, but the Fact is, his 250 log head did almost flat 14 second 1320s at almost 100 mph with just production carb parts tripled up and an auto C4. Anyone who follows thr advice of the late Ak Miller or Jack Clifford is gonna.be streets ahead.

OK i think i will go with 55 thousand and hope for the best. once again Thanks Don

some one (give rotating assemby to machinest) should coordinate the machining & prts.

Who will do the assembly?

Thanks for all your help. i went with 50 thousands off the block. I am assembling the engine the machine is making sure everything is balanced.