DOHC sensor help tbird guy here

J

jamesD

Registered
Sup fellas?

just received a low mileage DOHC shortblock in good order

some questions

2 sensors, top of block in middle of valley.. what are these?

also.. looks like a notch in side of one piston, haven't looked at others.. this normal or a whoopsy on part of machinist?

let me know

couldn't find general tech forum so hope its in the right spot!

Jim
aircav_cmdr@yahoo.com
flchapter@tccoa.com
 
RE: DOHC sensor help tbird guy here

Off the top of my head I am going to guess and say they are knock sensors.
 
RE: DOHC sensor help tbird guy here

Yes, two knock sensors beneath the intake, on top, center of block. A branch of the main wiring harness resides here also, traveling to the altenator, coils, sensors.

A notch on the "side" of the piston doesn't sound good. There may be a notch on "top" of the piston to either clear the plug, or to alter the compression ratio. The only thing on the side should be three grooves for the piston ring set.
 
RE: DOHC sensor help tbird guy here

[div class="dcquote"][strong]Quote[/strong]
Yes, two knock sensors beneath the intake, on top, center of block. A branch of the main wiring harness resides here also, traveling to the altenator, coils, sensors.A notch on the "side" of the piston doesn't sound good. There may be a notch on "top" of the piston to either clear the plug, or to alter the compression ratio. The only thing on the side should be three grooves for the piston ring set.
[/div]

side is bad word eh? hehehe thought about it.. checked them all out.. they all have it

the notch is on the "edge" and can be seen when looking from the top.. does not go to the first ring groove

the notches are on the "front" side of the engine on all the pistons

look like probably to clear plug or something.. this going to matter much w/ NPI SOHC heads bolted on?

JD
 
RE: DOHC sensor help tbird guy here

Maybe. Have you already looked into what the valve clearance and compression will be with those heads?

Why wouldn't you just get some DOHC heads to put on it? I don't understand why you'd take a DOHC shortblock and put the worst possible 4.6 heads on it. For the price of the head gaskets and bolts, i'd at least look into some DOHC heads.
 
RE: DOHC sensor help tbird guy here

to be honest.. i dont' want to deal with the electronics plus extra moving parts in a DOHC swap

i did not come over here to start a pissing contest about which SOHC heads are better than the other.. you want to read about that.. go to www.modulardepot.com

i am sticking NPI because i am saving as much $$ as possible, and PI heads bump the CR up way too much (pi motors have a -17cc dished piston and a smaller CC in the head).

We have done some crunching and compared with others who have done it & determined that the NPI SOHC head and the mark8/cobra shortblock will yield an approx 10.5:1 CR.. which is fine w/ the custom ground cams i have...

what bolts are you talking about? if it is head bolts.. i already have head studs.. don't need bolts.. head gaskets aren't a problem.. i have a friend on the inside.
 
RE: DOHC sensor help tbird guy here

Head bolts is what i was talking about.

You'll see a noticeable performance gain there, with that compression ratio. Should run good. I've done plenty of reading over on modular depot as well, i was going to refer you there to look into the compression ratios and such if you had not already.

With cams and a little port work those heads should flow well enough. I'm interested in seeing how it comes out when you're finished.
 
RE: DOHC sensor help tbird guy here

[div class="dcquote"][strong]Quote[/strong]
[div class="dcquote"][strong]Quote[/strong] There may be a notch on "top" of the piston to either clear the plug, or to alter the compression ratio. The only thing on the side should be three grooves for the piston ring set. [/div]side is bad word eh? hehehe thought about it.. checked them all out.. they all have itthe notch is on the "edge" and can be seen when looking from the top.. [/div]




this is to give a focal point as to what way the piston needs to be in the bore, at least thats what it's been for in every other engine iv'e torn apart.
 
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