camshaft question...

[ambulancechser]

greetings...just started a mild engine build.it's a combo of parts from a 95 12 valve into a late model (2002) 24 valve block.sticking with a 12v head.

my question concerns the cam...i'm using a regrind,and just got to the point of a trial fit...the cam seems to be a bit snug in it's bores.i realise that it's a bit of a subjective opinion,but on a cam install in a fresh block,how hard should the cam be to turn by hand?

i used a bore guage and went through the bores 3 times (except #4,which i couldn't reach),and took a micrometer to the journals.i'm getting consistant readings of .003 clearance for # 1 and #7...and .004 for the others.the cam turns smoothly until i try to get the # 1 and #7 journals in...then it gets a bit hard to turn by hand (just by grabbing the cam snout...the gears not on yet).

any thoughts?iv'e torn down several diesels of various types,but this is my first build from scratch...any advice appreciated.

 

[f6jbob]

You can always pull the soft plug on the block at #7 journal to make sure its ok.

 

[Tate]

Bent cam? Get some v-blocks and a dial and do a runout on it.

 

[ambulancechser]

problem resolved... the soft plug was already out,so i had access to the rear journals.
i suspected a bent cam,so i pulled the cam out far enough to expose the two front journals,and set up a dial indicator on the front of the block.that end was straight,so i did the same to the two rear journals on the other end...same result.the cam is straight.

also,the drag was consistant when i turned the cam by hand.i took multiple measurements on the the 5,6 and 7 bores and noted that number 5 was a tad inconsistant.it had a high spot.i have no clue why,though i'm taking all these measurements with the mains tourqued.all the bores at the rear of the block are on the tight side of spec'.just a hair over 3 thou' clearance.


to boil it down...i fixed it with a brake hone on number 5 bore.20 minutes later the cam turns smoothly. thanks for the tips.