flightforlife07

Hey guys has anyone on here ever taken the f54 block and put flat top pistons in it and tried to run the n47 on it cuz i'm have a pretty big issue on how this is going to work.... I bolted the head on the motor set at tdc than when i tied the cam to the motor the first and last intake and exhaust vavles hit the pistons left a valve shaped imprint and broke the #1 cylinder exhaust valve. i guess my first question is can u run the n47 with flat top pistons? second will the little indentions in the pistons hurt the motor?

http://i83.photobucket.com/albums/j3...7/100_1360.jpg
Thats where i found the exhaust valve when i pulled the head off the motor.
http://i83.photobucket.com/albums/j3...7/100_1359.jpg
this is the dent left in teh #1 cylinder.
http://i83.photobucket.com/albums/j3...7/100_1356.jpg
and the remains of a broken valve stuck in the head....

SHADY280

wow you musta really cranked on it, or started the engine to break it off. yeah you can run the n47 head, but youll have higher compression, and youll need to prolly change the piston with the mark in it, cause it could crack.

FubarI33t

2mm head gasket should help. i think shady use'es a 2mm head gasket.

SHADY280

its 200 bucks, he could just run 4 deg timing, and 92 or higher gas, just till he gets it fixed.

FubarI33t

I know this is jacking. but while were close to it. What is the Best Block/head combo for N/A and high compresion?

SHADY280

p79 head decked .080", f54 block, stock flat tops, 1mm gasket. also easy to find setup

hoov100

on my 81 with flat tops and an n47 with a stock HG, all that was done to it was to make a fly cut of .50 to clear the valves, since you have the head off, you should convert you oiling system to the spray bar, much better for a higher C/R IMO..

flightforlife07

hah te best part of this whole thing is i wasn't cranking on it very hard just enough to get the ca to turn over. and i was using an adjustable wrench.. a little one i had no leverage. so do i have to have the pistons cut to clear teh valves or jsut run the timing off?

duowing

In the first pic. What is with the cylinder to the left? Is that oil or something?

flightforlife07

no i put assembly lube on the cylinder walls to keep them clean and stuff it'll be wiped off before i start the motor..... even tho it won't hurt them if i leave it in there...

SHADY280

you prolly had the chain on wrong, that is the ONLY way that could ever make contact, my clearances are tight, and i got .5" lift on my valves, so i dunno how it was assembled, but double check, its easy to miss stuff.

flightforlife07

the chain wasn't even on yet.. i was trying to tdc the cam so i could put the chain on right. but you are saying that the flat tops will work with the n47 but it'll be tight?

FubarI33t

so that's what happend. you set head tdc first, then block when doing that. other wise the valves will hit the pistion cause it's fully up. Lession Learned.

SHADY280

heck always set everything at tdc before even putting the head on to the block. and yeah if your flatops come right up to deck height youll be o.k, but if your pistons come above deck height, then your gonna be screwed. you need at least .025" clearance from the head to the piston top. its in the datsun engine builder book.

FubarI33t

i need to get that book about Nissan OHC rebuild.