351w Head and Cam question

[Lazerbeans]

First of all, I have been lurking for a while now, and this is an awesome site for panther owners. I do have a few specific questions, that I cannot seem to get answered sufficiently, and I trust your guy's information. I have a 1990 ex-cop car vic with the 351. My questions actually come down to; what kind of pistons are in the engine. I would like to cam and put heads on the engine, but without knowing if there are valve reliefs in the pistons, I have no way of knowing what I can and cannot use. Also are the pistons basically the same as mustang 85+ pistons, such as foraged aluminum and piston reliefs? I know the piston pin height would be different, but other than that. Would it be safe to assume that if a particular head or cam or combination worked on a 5.0HO, it would work on my engine? Just to be clear its stone stock below the intake, 1990 351w.

[Nathan in MI]

Here's a picture of the 351W in my '89 Vic, which would be the same as yours. You can see the valve reliefs there. I can't tell you exactly how big they are since I never measured them, but if my memory serves me correctly I think they were around 1/8" or 3/16" deep.

[Lazerbeans]

Actually that is some help. Just the fact it has valve reliefs is a good thing to know. Sounds like I may be able to get by with what a 5.0HO getts by with in a very rough way. Getting a look at the those valve reliefs lets me know that if I use the "drop valve" method of seeing how much P/V clearnece there is that I wouldn't within reason run the edge of a valve into the notch. Thanks man

[Mercracer]

I don't see any valve reliefs in that picture. What I see is the huge compression killing crater (dish) in the piston which is so large that it covers the area where you would normally see the valve reliefs in a 302/351W piston. An Explorer motor has relatively small eyebrows and I run an almost .550 lift ex valve cam. Anything (lift and duration) which works on a HO 5.0 should work on there. You can not use a HO roler cam as your block is not cast for the lifters. You would have to use the retrofit link bar style rollers.
Those craterous slugs in your motor are made of weak plain old cast aluminum, not forged like a Mustang or of a hypereutectic composition like an Explorer or later Mustang.

[Lazerbeans]

"Those craterous slugs in your motor are made of weak plain old cast aluminum" LOL Sounds like you have had a bad personal experience with a 351W. And I was using the term "valve reliefs" loosely. Next time I refer to them I will use "" I am also aware that the block was not a roller block. As far as the "dish" in the pistons, they may be big, but they allow the engine to have virtually the same compression ratio as 302's; 8.8to1. If you're not carful you will drop a 302HO compression that low if you use the wrong head gaskets. The dish is not a bad thing, the dish allows a more even mixture of A/F; nothing to get in the way of the flame kernel, and allow less time for something to happen, leading to less timing. I am not the only one to think along these lines, for example Speed-o-Motives web site; "A combustion shaped dished piston can improve the flame travel in the combustion chamber. A dish allows the flame to travel further and expand more before it is stopped by a metal surface. This rapid flame travel makes it unnecessary to run big spark advance numbers." or read the article yourself at http://www.speedomotive.com/t-showbymodel.aspx. The pistons might not be plain aluminum. The engine in that configuration was taken from the truck line; in fact the intake has a "truck" part number. As serious as Ford takes their trucks, I would tend to think that the pistons would be something a little more. But in the end that's just speculation.

[Outlaw440]

The pistons might not be plain aluminum. The engine in that configuration was taken from the truck line; in fact the intake has a "truck" part number. As serious as Ford takes their trucks, I would tend to think that the pistons would be something a little more. But in the end that's just speculation.

No, lol. Ford didn't give a rats ass about truck powerplants in the 80's. Using more expensive pistons in a sub-200hp application would have been a waste of money on their part.

But on the other matter you brought up, dish vs. flat top. Given two engines (can be any engine) with the same compression ratio, a dish piston will make more power than a flattop. The explanation is rather complex, but what you mentioned already has to do with it. Jay Allen gave me (and others) a very detailed explanation on this subject, i have some notes on it as well, if someone is really interested.

[Mercracer]

The pistons might not be plain aluminum. The engine in that configuration was taken from the truck line; in fact the intake has a "truck" part number. As serious as Ford takes their trucks, I would tend to think that the pistons would be something a little more. But in the end that's just speculation.

Low compression ratio, mild cam, mild timing.. Plain old aluminum. There was no motivation to use anything else. Even the 4V HO 5.8 motors used standard cast aluminum pistons. The change to hypereutectic pistons in the mid 90s had zero to do with "performance" and all to do with efficiency for emissions and fuel usage. The positive byproduct is that the same engine will make more power.

[gadget73]

Yeah, truck motors didn't get anything special. The only "good" parts they got were E7 heads, and those are not all that impressive.

[Lazerbeans]

No, lol. Ford didn't give a rats ass about truck powerplants in the 80's. Using more expensive pistons in a sub-200hp application would have been a waste of money on their part.

But on the other matter you brought up, dish vs. flat top. Given two engines (can be any engine) with the same compression ratio, a dish piston will make more power than a flattop. The explanation is rather complex, but what you mentioned already has to do with it. Jay Allen gave me (and others) a very detailed explanation on this subject, i have some notes on it as well, if someone is really interested.

Yea, I would love the notes on the subject. If its not too much trouble, PM or something. You can never know too much about engines, and in the end for me, thats why I like cars; the engineneering.