Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (http://www.hotrodders.com/forum/)
-   Engine (http://www.hotrodders.com/forum/engine/)
-   -   Ford 400 Dished to Flat Top Pistons = Rebalance Crank? (http://www.hotrodders.com/forum/ford-400-dished-flat-top-pistons-rebalance-crank-174930.html)

My79Ford400ciF1504x4 03-21-2010 09:11 PM

Ford 400 Dished to Flat Top Pistons = Rebalance Crank?
 
Hey, so if i bought a set of flat top pistons to replace my dished ones for my 400m, would there have to be any other changes made? I wouldn't have to change anything like rods I believe, but would i have to have the crank rebalanced to accommodate the new pistons?

stroker_SS 03-21-2010 10:09 PM

You may be able to find pistons of the same weight as those that are in your engine in which case no rebalancing would be necessary, although many will recommend it.

Are you going to be doing any other modifications to this engine while it is out of your vehicle being machined the new pistons?

Although not necessary having the rods resized and new rod bolts installed(I like arp's) is really worth it.

What kind of budget are you working with?

cobalt327 03-22-2010 08:27 AM

Quote:

Originally Posted by My79Ford400ciF1504x4
Hey, so if i bought a set of flat top pistons to replace my dished ones for my 400m, would there have to be any other changes made? I wouldn't have to change anything like rods I believe, but would i have to have the crank rebalanced to accommodate the new pistons?

First off- often the weight of an aftermarket piston will be similar to the OEM piston it replaces. Not always, and not exactly- but should be close. It's easy enough to weigh them both to see how they compare.

If the piston set is weight matched- or you do this op yourself- a rebalance isn't absolutely necessary, IMO. What will change is the balance factor (percentage of reciprocating weight to rotating weight), but only by a small amount. Since this factor is a compromise in the first place, if the OEM balance was good (which it often isn't), changing to a weight-matched set of pistons can be considered w/o rebalancing.

If you were swapping rods and pistons or swapping cranks, I'd have to advise you to rebalance it. But like Stroker_SS hinted at- if you can afford it- do it!

My79Ford400ciF1504x4 03-22-2010 01:01 PM

OK, so for the most part when i buy a set i should look for some that are balanced with my other ones, but if not then its not a big deal as i understand, correct?
Anyway as for the improvements that i am going with is: New cam, timing gears and spring set, 351c 2v open chamber heads (already have these), a set of head studs, guide plates, and rockers. And then a rebuilt kit with bushings and gaskets and stuff. So i just figured if i was in that far then i would raise my compression some more. Any other tips? Im trying to keep the budget low so im not planning on having anything special or custom made or anything.

stroker_SS 03-22-2010 01:11 PM

Some things you left out, are you going to have a shop build this for you or are you going to be assembling it your self?

If your going to be putting it together yourself you should give the shop your whole rotating assembly (pistons,rods,crank) and have them mic the crank, rod big/small end, check the rods to ensure straightness, won't hurt to have the crank/rods/block inspected for cracks.

The pistons you get may have a lowered compression height so the deck should be milled to compensate for that.

I understand the need to stay on a budget, but if you can't afford to do it right the first time can you afford to do it again?

cobalt327 03-22-2010 01:19 PM

Quote:

Originally Posted by My79Ford400ciF1504x4
OK, so for the most part when i buy a set i should look for some that are balanced with my other ones, but if not then its not a big deal as i understand, correct?

You got me over a barrel on this one, Hoss! lol

When I think of the Ford 335 series, I usually don't think 'high performance'- and that's no fault of the engine's potential, more my own shortsightedness.

Given the work you're doing- and how you're likely going to run this engine- I'm going to recant and say that you'd be wise (all things considered) to go ahead and bite the bullet and balance it, if the revs are going to be in excess of 5K RPM w/any regularity- UNLESS- you find that the replacement pistons closely mirror the weight of the OEM pistons.

ericnova72 03-22-2010 01:27 PM

If you are going to keep it under 6000 rpm I wouldn't worry about the balancing one bit. No reason to use the 351C 2v heads either, they are no different than the M heads you have now, exactly the same open chamber casting.

cobalt327 03-22-2010 04:37 PM

That engine has a 4" stroke... and 2-bolt caps.

My79Ford400ciF1504x4 03-22-2010 08:03 PM

Yeah I do plan to do it my self, with the help of my friend and his grandpa who is a mechanic. Anny suggestions as to where i should buy them from? I know that there are only a few places. The cam set that I have picked out is one that is 800 to 4800 rpm, its going into a truck. I have looked up a lot on this engine and i basically understand that it is a tall decked Cleveland with a bigger stroke 4 and 4, I know the valve timing is crap and im replacing all that and I have read alot on the heads stamped M, which i have read are prone to crack, and with no surprise mine were cracked multiple places on each head. So i decided to get a Cleveland 2v open set which already had a valve job done on them. I also have read that the M head has a 78.4 cc chamber and the 2v open Cleveland's have a 76.2 cc chamber, anyway mine were cracked so i needed a new pair. So, any other tips you guys have? And by the way I really value you guys responses, they help me a lot.

cobalt327 03-22-2010 08:28 PM

Quote:

Originally Posted by My79Ford400ciF1504x4
Any suggestions as to where i should buy them from? I know that there are only a few places. The cam set that I have picked out is one that is 800 to 4800 rpm, its going into a truck.

AFA where to get the pistons, etc. from- I'd probably at least look at Competition Products, Northern Auto, Summit and Jegs to see who had a better deal.

You might get lucky and get them to tell you what the pistons weigh so you can do a comparison.

Try to see if you can use the head gasket thickness to get the quench around 0.040". If you get it around that figure, it will tolerate CR and/or less octane better.

It sounds like you got it pretty well sorted out. :thumbup:

Good luck!


All times are GMT -6. The time now is 01:36 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.