78' 440 Choosing Pistons 87 Octain Gasoline Spark Knock Flat Top Notched?

[Auggie56]

I'm slowly approaching the point in getting my short block together, and quite frankly I not sure what type and brand of piston in need. This is for a street driven toy that may find itself on the track a time or two. I'm seeing notched and flat tops plus almost no standard bore ones available. What about the factory flat tops in mine? This engine has 25K on it and no pistion ring ridge in the cylinders. And yes price is a factor with me.

Thanks

 

[Mike67]

Why is your block apart in the first place? May get away with a ball hone and some new rings...probably invest in a bore gauge and check that cylinders are concentric up and down the cylinder.

 

[Auggie56]

Why is your block apart in the first place? May get away with a ball hone and some new rings...probably invest in a bore gauge and check that cylinders are concentric up and down the cylinder.

It came from a motorhome and the pan was thick with sludge, so it really needed to come apart just to clean it. Glad I did as one-rod bearing was showing a bit of the bronz shell plus there was a bent valve.

 

[dvw]

Have you measured the bores? Adding new pistons to a oval or tapered bore is senseless. Either just use the original pistons with a ball hone or get a proper bore job and correct compression height piston for your desired compression. Have you measured the deck heights at all 4 corners? I'll bet they vary as well. Design a package that you want first. What is your budget, fuel type and intended usage? 87 octane will require low compression. The factory pistons are low enough in the bore they won't need notches for a cam needed for a 87 octane build. Deck height variance won't change compression ratio much at this level either. I'd budget aftermarket heads before a piston and bore job.
Doug

 

[wyrmrider]

Running stock heads get the KB with the quench dome- only way to make a stock head work
flat tops still leave that big area a long way from the spark plug which is prone to detonation
The kb's are much less sensitive to fuel and timing
lowering the compression down the hole is a vicious circle
the lower the compression the more throttle to get the same power which equals more heat- there is no other fix than either a closed chamber head and matching piston or the KB piston with the stock head
buying the Edelbrock head with the open chamber is a big mistake- it does not fix the combustion chamber problem
only after getting above solved and compression where you want it can you think about a cam

 

[PRHeads]

My.02......
9:1 compression MAX...... with proper quench........ for something that’s going to get a mild cam and has to be happy on 87.

For a std bore 440, that means a total volume above the piston at TDC of about 113cc’s.

My preference would be 84cc closed chamber aluminum heads, .040 gasket, and pistons at zero deck with an 18cc inverted dome/valve pocket.

 

[PRHeads]

.

 

[wyrmrider]

good advice
If closed chamber heads are not in the picture

Step-Head features an elevated quench & is mainly used on heads that have a recessed quench such as some Chrysler applications.It allows builders to maximize what quench they have.
KB 184 new catalog page 30
I helped design this piston
lots of dyno and fleet tests
your best shot $$$wise
there is also a piston that will give you another point of compression but you will have to get the tune dead nuts on in other words a PITA for U
want to go deeper CC your heads

 

[Auggie56]

Running stock heads get the KB with the quench dome- only way to make a stock head work
flat tops still leave that big area a long way from the spark plug which is prone to detonation
The kb's are much less sensitive to fuel and timing
lowering the compression down the hole is a vicious circle
the lower the compression the more throttle to get the same power which equals more heat- there is no other fix than either a closed chamber head and matching piston or the KB piston with the stock head
buying the Edelbrock head with the open chamber is a big mistake- it does not fix the combustion chamber problem
only after getting above solved and compression where you want it can you think about a cam

Any issues using pump gas (87 octane) with theses quench dome pistons? They look like they would increase compression substantially. I had the stock heads done last spring and had them surface grind twenty thousand off, one to make sure they where square and two increase compression, however so slight.

 

[BSB67]

With the closed chamber aftermarkets heads available today, it's silly to build a reverse dome motor for an open chamber head, IMO. Then once you're done screwing around with working on the dome/gasket/head to get the clearance right, you're somewhat stuck with it. But if you are bent on using your open chamber iron heads, it is an option. Personally, I wouldn't do it with someone else's money.

 

[Auggie56]

With the closed chamber aftermarkets heads available today, it's silly to build a reverse dome motor for an open chamber head, IMO. Then once your done screwing around with working on the dome/gasket/head to get the clearance right, you're somewhat stuck with it. But if you are bent on using your open chamber iron heads, it is an option. Personally, I wouldn't do it with someone else's money.

One thing I don't want to do is to sink a bundle into this project. I'd rather stick with these heads and get what I can get with pistons as It's just a toy that I'd like it to run better than what I have with low compression ones now.

 

[Auggie56]

https://www.summitracing.com/parts/uem-kb400ktm-020 ????

 

[BSB67]

Is that mine? I don't have what you're showing. I have been having some puter problems this evening.

 

[BSB67]

One thing I don't want to do is to sink a bundle into this project. I'd rather stick with these heads and get what I can get with pistons as It's just a toy that I'd like it to run better than what I have with low compression ones now.

Okay, a few more questions to help me understand;

1) What is a bundle?
2) What is you budget?
3) Are you, or are you not boring and honing?
4) Is this motor going to the machine shop for anything?

 

[Auggie56]

Is that mine? I don't have what you're showing. I have been having some puter problems this evening.

Mine froze up towards the end. See below.

 

[Auggie56]

Is that mine? I don't have what you're showing. I have been having some puter problems this evening.

Mine froze up towards the end. See below.

 

[Auggie56]

Is that mine? I don't have what you're showing. I have been having some puter problems this evening.

Mine froze up towards the end. S

Okay, a few more questions to help me understand;

1) What is a bundle?
2) What is you budget?
3) Are you, or are you not boring and honing?
4) Is this motor going to the machine shop for anything?

Test test.

 

[Auggie56]

What is a bundle? Educate me, please.

What is your budget? 2k max.

Honing, yes. Boring maybe yes as a standard size pistion appears to be rair??? This low compression 1978 engine alleged to have twenty five K on it. I think this maybe true as there is no sign of ring ridge. and it did come from a motorhome.

Machine shop? Yes cam bearing installation. Measure cylinder size to see if machining is needed.

I'm pretty sure this is the piston needed. https://www.summitracing.com/parts/uem-kb184-040/warnings/

However, it looks like they may be required to be machined for clearance.
"Due to the multiple variables possible with any engine combination, all compression ratios listed are approximate. To accurately calculate the static compression ratio of any engine, the following values must be known: Bore diameter, stroke length, rod length, deck height, combustion chamber volume, cylinder head gasket compressed thickness, and cylinder head gasket bore diameter."


Starting appear to be a can of worms. Pipe dream at this point. Just might go rings and bearings and call it a learing experience.

Many thanks.

 

[BSB67]

What is a bundle? Educate me, please.

What is your budget? 2k max.

Honing, yes. Boring maybe yes as a standard size pistion appears to be rair??? This low compression 1978 engine alleged to have twenty five K on it. I think this maybe true as there is no sign of ring ridge. and it did come from a motorhome.

Machine shop? Yes cam bearing installation. Measure cylinder size to see if machining is needed.

I'm pretty sure this is the piston needed. https://www.summitracing.com/parts/uem-kb184-040/warnings/

However, it looks like they may be required to be machined for clearance.
"Due to the multiple variables possible with any engine combination, all compression ratios listed are approximate. To accurately calculate the static compression ratio of any engine, the following values must be known: Bore diameter, stroke length, rod length, deck height, combustion chamber volume, cylinder head gasket compressed thickness, and cylinder head gasket bore diameter."


Starting appear to be a can of worms. Pipe dream at this point. Just might go rings and bearings and call it a learing experience.

Many thanks.

Maybe check back when you get back from the machine shop.

 

[dvw]

Your approach is backward. At 25k you want to get cam bearings replaced but haven't measured the bore yet? Chances are the cam bearings are in better shape than the bore has no wear. That doesnt mean that it won't run. Just not to its full potential You could run it as is with aluminum heads and back the timing off if needed. This us providing the bearings and rings are ok. Or a Summit quicky rering and bearing kit, new timing chain, cam lifters, used Eddy heads, Performer RPM , headers, and run it. Even then your budget will require shopping for used parts. New pistons without boring and stock heads is the wrong path in my opinion. The last motor I built like mentioned above went 12.80s in a 65 Belvedere with pistons over .100" down in the hole. I'm sure it would run on 87 with the timing backed just a touch.
Doug