Machine work needs for mild 351w
Thread Starter
|
Tuned
Joined: Feb 2007
Posts: 414
Likes: 0
From: Kingman, Ks
Machine work needs for mild 351w
I'm getting ready to build a mild 351w to go in my 1995 F150 and I'm in need of some insight on machine work requirements. First off the block is a 1995 roller 351w with 175,000 miles on it. The build is going to be in the neighborhood of 270-300 hp and about 400 ft/lbs of torque, with rpms under 4500 98% of the time.
I've talked with a very reputable machine shop that can do just about anything you want them to. The guy I talked with said that they first magnaflux everything, and then hot tank it. After that the check bores of the pistons, crankshaft journals, rod journals, and cam bearing journals.
Now he told me that a lot of Fords need the cam bearing journals trued up, has anybody ever heard of or done this?
Also what is necessary and what isn't? I planned on boring .030 over for pistons, .010 under for crank, align hone main if needed, and possibly deck the block a little just to make sure it is flat. Also was going to have them balance the rotating assembly too, is that necessary?
If I have left any important machine work out, please let me know and also tell me what you think I should have done to it. This is my first time at building an engine from scratch.
I've talked with a very reputable machine shop that can do just about anything you want them to. The guy I talked with said that they first magnaflux everything, and then hot tank it. After that the check bores of the pistons, crankshaft journals, rod journals, and cam bearing journals.
Now he told me that a lot of Fords need the cam bearing journals trued up, has anybody ever heard of or done this?
Also what is necessary and what isn't? I planned on boring .030 over for pistons, .010 under for crank, align hone main if needed, and possibly deck the block a little just to make sure it is flat. Also was going to have them balance the rotating assembly too, is that necessary?
If I have left any important machine work out, please let me know and also tell me what you think I should have done to it. This is my first time at building an engine from scratch.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
For what you're doing, you may not even need to bore it. Check the cylinders first before buying new pistons. Ford went to low tension piston rings back in the 80's, this change nearly eliminated bore wear, you may be able to get by with just a rehone to rough up the walls and new rings and bearings. No need to rebalance it, even with new pistons. But if it makes you feel better and you can afford it, then do it. The crank may not even need work either, if it shows no signs of wear, have it mic'd before having it turned. Never heard of Ford cam bearings having unsual wear or the journals being out of line. And lastly, if you do decide to bore it and buy new pistons, pay close attention to what pistons you go with, pin height and the dish volume was changed several times over the production run on 351W's. The 95 block I have in my 95 has got the older style dish pistons in it that bumped the comp ratio up a quarter point or so over the pistons they used in 95. This is not a bad thing, but something you need to do the homework on to avoid lowering the comp ratio.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Let your machinist tell you what the motor "needs" after everything is measured. Unless the engine suffered some type of oil related failure it may not need much of anything and I'm a firm believer in not fixing what ain't broke. The general concensus is these engines were rather well built and the factory machining was well done so it would be unusual to fine something right out of whack.
Thread Starter
|
Tuned
Joined: Feb 2007
Posts: 414
Likes: 0
From: Kingman, Ks
Thanks baddad and conanski for your insight. So you are saying that the motor may not need much machine work, just hot tank and magnaflux it and go from there? May not even have to bore it? I can still see crosshatch on the cylinders except for some places where is looks kind of washed. So I suppose maybe I won't have to bore it.
I was doing some more research and came across something saying that the crank end of the rods can turn oval shape after time? How likely is that?
I was looking at getting flat top pistons to bump compression which ones will work?
I was looking at these.
Speed-Pro Hypereutectic Pistons ZH336CP - SummitRacing.com
Would these and GT40 heads keep my compression at 87 octane gas range?
I was doing some more research and came across something saying that the crank end of the rods can turn oval shape after time? How likely is that?
I was looking at getting flat top pistons to bump compression which ones will work?
I was looking at these.
Speed-Pro Hypereutectic Pistons ZH336CP - SummitRacing.com
Would these and GT40 heads keep my compression at 87 octane gas range?
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
The rods would break from stress far before the big ends would need resizing. If you hot tank it, it'll need new cam bearings afterwards. As for magnafluxing, if it ain't leaking coolant now, it should not need to be mag'd. One more thing on boring: these later blocks can and do sometimes have enough core shift (the bore "jugs" moving while the block was cast) to negate any chance of doing an over bore, I've seen a couple 90's 5.0 blocks that I'd hesitate to bore .030 with the core shift they had. I just honed em and reringed em and left em std. A look at the bottom side of the block will give you a good idea if the cores have shifted, look at the wall thickness, shifted cores will have walls with one side thinner than the other. If yours has walls as such, it's better to just hone it and rering it in my opinion
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
I did the math and came up with a 9.15 to 1 comp ratio using those, so they should be "good to go". But look at everything, especially the core shift before ordering pistons.
Thread
Thread Starter
Forum
Replies
Last Post
302 F-150
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
18
Sep 3, 2008 01:11 PM
gyger1
Big Block V8 - 385 Series (6.1/370, 7.0/429, 7.5/460)
8
Apr 25, 2006 07:21 AM
jesse460
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
6
Oct 14, 2002 11:10 PM
