new short block problem

[o2baquirk]

I am working on a 1979 fiat spider 2000 decided it was easier to get new short block from a Fiat parts supply house. Problem is the piston relief area is smaller and shallower on the new blocks pistons and the pistons will hit the valves. I talked to the parts house they say Fiat only makes 1 engine things should fit. the only way I will be able to make this work that I see is to get new pistons. Engine numbers check out my old engine is stock, any ideas. thoughts? I just had my heads done.

[o2baquirk]

Just found out that the European Valves are larger than the USA ones. And you could change out to the European ones but you have to change the pistons too about to measure mine

[So Cal Mark]

it's common to put oversize valves in the US versions without any changes to the pistons.

[BEEK]

just guessing , without seeing, im figuring you have 1800 style pistons, which have smaller valve reliefs. this will be an interfearance fit, meaning if you break your timing belt you will bend valves. which is not realy a problem, as :

1. you should never break a timing belt
2.even with a 2.0 with deep valve reliefs, you still can do valve damage, as the valves can colide with each other
3. the aux shaft, can be hit by the connecting rod and driven thru the side of the bloch anyway.

please post pictures of the piston,and the block id # above the block serial # :ie 131a.040.6, as an example

[majicwrench]

You said the valves "will hit"......in other words, you have not actually checked??
Keith

[o2baquirk]

we put it on an engine stand and turned it by hand

[FiatMac]

we put it on an engine stand and turned it by hand

When you did this was the engine completely assembled with the timing belt on and the cams timed properly? If not, you will have valve interference with the piston.

I agree with Beek; the pistons are probably those originally used in the 1800 engine. These pistons have shallow valve reliefs and a shorter compression height than the later 2000 piston. With the 1800 pistons, as long as the engine is properly timed the valves do not hit the piston.

The 2000 piston has very deep pockets so that even with the valves full open and the piston at top dead center (as could be the case with a broken timing belt) the piston and valve will not contact.

The 2000 piston has a longer compression height to give it approximately the same compression as the 1800 piston. Therefore, the two pistons can be interchanged in either engine without affecting performance other than the above prospect of valve to piston collision in the event of timing belt breakage, slippage, or miss-timing of the engine. Vendors here in the States generally only sell the later 2000 style “non-interference” piston.

[124JOE]

when you turned it by hand
was the sparkplugs in or out?

[o2baquirk]

THE SPARK PLUGS WERE IN THE MOTOR AFTER PUTTING EVERYTHING BACK TOGETHER I ROTATED THE MOTOR BY HAND AND AS THE ENGINE ROTATED THE VALVES CAME IN CONTACT WITH THE TOP OF THE PISTONS THE VALVES ARE THE LARGER EUROPEAN VALVES AND THE PISTONS HAVE THE SMALLER RECESS ANY SUGGESTIONS

[pastaroni34]

Have a machine shop cut the valve reliefs to fit? Seems simple to me.. of course this means taking apart your new short block.

[BEEK]

there is a timing issue, i use 12.5 -1 pistons , 2mm larger stainless valves and they do not hit even with 1/2' of lift. your lift events are not happening at the correct time. just my opinion as i have not seen any pictures, but i have built 1000's of fiat motors, yes 1000's

[124JOE]

i remember somone talking about a degree wheel
and a 109 degree seating

getting close like you are it needs to be closing just berore tdc

someone else was talking about a thicker gasket

i hope this helps