Too tall of a piston in a 351-W

junkyardjeff · December 10, 2011, 11:58:53 PM

I got this early 80s rebuilt 351-W long block that I have in my 55 sunliner that seems to be a miss match of parts that has a noise I cant identify,before heading to Daytona Beach I installed a rebuilt trans and rear end that got rid of the loud howl and now noticed the noise in the motor since I did not have to turn the radio up so loud on this trip. It sounds like something hitting something and did not change while pulling each plug wire off and since I had 3 or 4 plugs close the gaps when breaking in the motor something is not right and thinking the pistons are slightly tapping the heads,if thats the case I was wondering if the block or heads could be milled too much or a too tall piston installed. I think I read somewhere that there was a deck height change and is there a different pin height difference between 302 and 351 pistons,since it has a cam with a 302 firing order who knows what other wrong parts it has and plan on finding a scope to look in the cylinders to see if there is some interference issues.

wayne petty · December 11, 2011, 12:20:25 AM

jeff...

depending on the heads...

you could have heads that have 18MM threads. same size as an oxygen sensor..

and .. there are heads with 14mm threads.... but there are heads that use an 7/16 reach spark plug.. and ones that use a 3/4 inch reach spark plug..

its kinda hard to mix up spark plugs.. as the short 14MM plugs won't even catch one thread in the 3/4 inch reach spark plug heads..

got casting numbers off the bottom of the block.. and off the head... so some of us could identify the block and heads for collision issues..

there are multiple crank strokes that could be in a modified 351W

4.000 in.
3.850 in.
3.750 in.
3.500 in.
4.100 in.
4.250 in.

these are some of the possible rod lengths

6.200 in.
6.000 in.
6.125 in.
6.300 in.
5.955 in.
5.956 in.

so you might want to use a wire.. and measure the stroke as close as you can through the spark plug hole..

junkyardjeff · December 11, 2011, 12:40:50 AM

I will see if I can get some casting numbers but if I remember correctly the block had a E4 casting number and where are the head casting numbers located. The heads are later versions with the smaller plugs

wayne petty · December 11, 2011, 12:49:13 AM

Quote from: "junkyardjeff"I will see if I can get some casting numbers but if I remember correctly the block had a E4 casting number and where are the head casting numbers located. The heads are later versions with the smaller plugs

block is above the starter

http://351winsor.com/joel/Engine_Diagrams_Pics/302fordblockcasting.gif

the head casting numbers are hidden under the intake ports..

http://farm4.static.flickr.com/3045/3050235935_1ee5db1341_b.jpg

i don't expect you to pull the intake...

how about a picture of the spark plug damage.. and or the spark plug numbers...

i have found 3/4 reach spark plugs threaded into 7/16 reach heads..

if you have 3/4 reach spark plugs.. are the first 6 or 7 threads removed so it would be impossible to start a short reach spark plug..

there are ford small block heads that use this spark plug...

3/4 reach

http://contentinfo.autozone.com/znetcs/product-info/en/US/aut/XP104/image/4/

7/16 reach

http://contentinfo.autozone.com/znetcs/product-info/en/US/aut/XP24/image/4/

then there are the old style 18MM spark plugs.. that come in extended electrode and also hidden short side electrode..

http://contentinfo.autozone.com/znetcs/product-info/en/US/mtc/SP-420/image/4/

tomslik · December 11, 2011, 04:38:45 AM

Quote from: "junkyardjeff"I got this early 80s rebuilt 351-W long block that I have in my 55 sunliner that seems to be a miss match of parts that has a noise I cant identify,before heading to Daytona Beach I installed a rebuilt trans and rear end that got rid of the loud howl and now noticed the noise in the motor since I did not have to turn the radio up so loud on this trip. It sounds like something hitting something and did not change while pulling each plug wire off and since I had 3 or 4 plugs close the gaps when breaking in the motor something is not right and thinking the pistons are slightly tapping the heads,if thats the case I was wondering if the block or heads could be milled too much or a too tall piston installed. I think I read somewhere that there was a deck height change and is there a different pin height difference between 302 and 351 pistons,since it has a cam with a 302 firing order who knows what other wrong parts it has and plan on finding a scope to look in the cylinders to see if there is some interference issues.

The firing order change ain't no big deal..ford did it on the leter 302's (went to the 351 firing order)

the "howling" part doesn't jive with the direction that you're going with the diagnoisis though....

junkyardjeff · December 11, 2011, 09:51:55 AM

The howl from the trans and rear end were so loud it probably drowned out the noise in the motor some,I went from 2.79 gears to 3.00 so the motor is spinning a little faster on the highway which also might have something to do with it too. Now about the plugs closing the gaps,after the break in I think a couple done it again but never done it again and never could figure out why it did it in the first place and I think it has the shortest reach plugs in it.

enjenjo · December 11, 2011, 12:42:20 PM

If the skirt clearance is too much, the piston can rock enough to hit the head.

junkyardjeff · December 11, 2011, 03:56:53 PM

I think I am going to put a used motor in to get me by until the Y block is built,there are too many things that could be the problem and will most likely need to be completely torn apart to fix correctly so I am not going to spend too time and money to fix it when I am planning on another motor.

kb426 · December 11, 2011, 06:09:25 PM

You're comment about breaking the plugs makes me think it might have some pop up pistons in it. If that is the case, removing some of the dome will fix that. If the deck clearance is too close, how about thicker head gaskets?

junkyardjeff · December 11, 2011, 07:06:49 PM

I plan on using the motor for another car after I get the Y block done so when it gets pulled I will tear it apart and check it over,I am going to see if I can borrow a scope and look into each cylinder to see if the noise is coming from wrong or pop up pistons. Since its been years since I had sbf apart is it possible the pistons are in backwards.

junkyardjeff · December 21, 2011, 10:46:48 PM

I changed the oil and can not get the noise to reappear so it looks like it did not like the department store house brand oil,I went to 15w40 diesel oil this time.

wayne petty · December 21, 2011, 11:25:18 PM

jeff..

i don't recall if you ever posted which spark plug you were having problems with...

if you are using conventional short spark plugs.. but for the 90 motor.. with the extended tip...

you might want to swap to a shorter side electrode version like this bosch HR9AC+ box number 7972

here is a picture..

http://contentinfo.autozone.com/znetcs/product-info/en/US/bos/7972/image/4/

perhaps these would NOT get hit by your rampaging pistons..

they stock this number at my local AZ.. 1.99 each..

junkyardjeff · December 22, 2011, 08:58:17 AM

The gaps have not closed since it was first broken in but is probably due for a tune up and will look into those plugs,if the weather holds out I will take some more highway trips and see how it does but I am thinking the noises were related to it not liking the oil. It had a constant one or two lifter tick plus the other noise and both are gone for now and the oil pressure is fine.