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Are forged pistons worth the added expense?

MikeH

Diamond Level Sponsor
I found that Racer Walsh has forged pistons for the Ford 2.8. With my planned engine mods would they be worth the added expense. Mods include ported/polished heads, 2.9 valves, 2.9 crank, offy intake, 390 Holley, cam (undecided which one), headers, cylinder bore .030 over. The Racer Wales pistons also feature floating pins with a 1.578″ compression height.
Stock compression height is listed as 1.539”.
https://racerwalsh.com/product/2-8-9-1-pistons/
 
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MikeH

Diamond Level Sponsor
I have my figures somewhere. I think it was with the different compression height. I need to find the stock deck clearance. I think it worked out to something like 10.2:1.
 

DanR

Diamond Level Sponsor
Mike, Not suree of the expense difference but with the "other" improvements, I probably would go with the forged.

I'm sure you will just go one more step and have the complete assembly balanced.
 

MikeH

Diamond Level Sponsor
Mike, Not suree of the expense difference but with the "other" improvements, I probably would go with the forged.

I'm sure you will just go one more step and have the complete assembly balanced.

Plan to, if I can find a shop with the adapters to do it.
Still need to find figures for stock deck clearance to see if I could even consider the pistons.
 

junkman

Gold Level Sponsor
If you want to run it on "pump" gas Premium , my engine guy says keep it under 10.5 or suffer the detonation.
 

MikeH

Diamond Level Sponsor
Found a deck clearance calculator. It gives me stock deck clearance of -.0549.
With a 2.9 crank and stock pistons(comp dist = 1.539”): .01249
2.9 crank and RW pistons ((comp dist = 1.578”): .05149

So I don’t think I could use the Racer Walsh pistons with the 2.9 crank.
2.8 crank and RW pistons: .016”
 

sunalp

Diamond Level Sponsor
If you want to run it on "pump" gas Premium , my engine guy says keep it under 10.5 or suffer the detonation.

That's exactly what my machinist said as well and he's seen his share of engines! I had my rotating mass and flywheel
balanced. I also lightened the flywheel by 5 lbs. Any more and there would be running issues.
 

MikeH

Diamond Level Sponsor
If it looks like compression would be too high, I could look at having pistons made or running the 2.9 pistons which are dished.
Does anyone have the 2.8 combustion chamber volume?

I guess I can break out the heads and measure mine.
 
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Barry

Diamond Level Sponsor
Mike,

The generally accepted limits for compression ratio to avoid detonation with pump gas are about 9.5:1 for iron heads and about 10.5:1 for aluminum heads.

You might get away with 10.2:1 compression with iron heads on premium pump gas, but you would probably have to reduce the ignition advance to something less than optimum.

Using an "octane booster" could be a work around, but it is a nuisance and there is the problem of forgetting or running out.

No idea what head gasket thickness you used to calculate CR or what head gaskets are available for the 2.9, but if my calculations are correct, an extra 0.010" of head gasket thickness will reduce the CR by about one-third of a point.
 
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MikeH

Diamond Level Sponsor
Looks like I’d be safe with stock pistons and the 2.9 crank.
My rationale is that with the Racer Walsh 9:1 pistons and stock crank the deck clearance works out to be .016.
With the 2.9 crank and stock compression distance the deck clearance is .013. So, at least in my mind, the compression would be slightly less than 9:1.
 

Barry

Diamond Level Sponsor
I doubt that you will be able to use 87 octane with 9:1 CR, but you should be OK with 89 octane.

The worst case for detonation is WOT at max. torque, so limiting the total ignition advance under those conditions can provide some margin for error. Centrifugal advance distributors are typically "all-in" by 3,500 RPM which is probably OK with the stock 2.9 cam (max. torque at 2,600 RPM), but might be a problem with a "hotter cam" that makes peak torque at 3,500 - 4,500 RPM. Depending on your engine combination, a "slower" centrifugal advance curve might be the way to go.
 

MikeH

Diamond Level Sponsor
I’m using the 2.8 with a 2.9 crank that’s been modded to accept 2.8 timing gears.
 

husky drvr

Platinum Level Sponsor
Mike,

Have you thought about calling Wiseco to see about having them make a set of pistons of the same pattern, but with the comp height adjusted to match your 2.9 crank stroke requirements? It might be less costly than RW's pistons.
 

PROCRAFT

Donation Time
Mike,

Have you thought about calling Wiseco to see about having them make a set of pistons of the same pattern, but with the comp height adjusted to match your 2.9 crank stroke requirements? It might be less costly than RW's pistons.
CP Carrillo Irvine Ca
 

Barry

Diamond Level Sponsor
Mike,

There is certainly nothing wrong (other than $$$) with using forged pistons, but cast pistons should be fine for a naturally aspirated (no boost or nitrous) street engine as long as you avoid detonation.
 

DanR

Diamond Level Sponsor
Plan to, if I can find a shop with the adapters to do it.

Mike, Remember the "Bob" weights I looked for over a year? Finally bought a set to get my V6's balanced....

Lots of shipping cost from you to me but, Perhaps I could get my local shop to balance for you.........
 

husky drvr

Platinum Level Sponsor
What I should have said I've a friend in Utah who builds a lot of small Ford motors and they get their stuff from Carrillo

No problem, I only suggested Wiseco because RW's pistons were made by Wiseco. That means Wiseco already has the piston pattern only needing one dimension to be changed.
 
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