piston choice 4" merc crank blown motor

M

my4dv8

Well-known member
Flathead pistons, What are your preferences for a street motor. 4" merc crank , SCOTT supercharger, mild cam. with visual HP . We had EGGE 4" pistons @100 over (Yup with the top machined off the "too high EGGE pistons to clear the offy heads.) We are now doing a (maybe) crack free block in its present STD bore ,so are looking for new pistons of a smaller size .
Someone on ebay is selling 4 ring merc pistons but we know nothing about them .What are the Ross 3 ringers like for a basic blown street motor, or are there better 4 ring choices? We wont be racing or looking for ultimate boost, just a reliable street motor.
 
I would never put cast pistons in a high performance engine.
I have used Ross for many years.
You call them and tell them exactly what you are using them for and they will make them up. They will take standard available rings and pins.
They take the hassle out of getting pistons.
 
I'm useing a set of Ross forged 3 5/16" pistons with a Merc crank 4 1/8" under a GMC 671 blower. Motor has been together many years, no problems. They are three ring pistons, four rings are one too many.
 
Flathead said:
I'm useing a set of Ross forged 3 5/16" pistons with a Merc crank 4 1/8" under a GMC 671 blower. Motor has been together many years, no problems. They are three ring pistons, four rings are one too many.
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Flathead, what pistons are you using, special for the 4 1/8, or standard 4 inch Merc? Popups?
 
Piston choice for a blown engine would be a forged piston like Ross. However for a non boost street engine (Less than #5) I'd go with a quality cast piston that can be fir tighter. Unfortunately you'll have to remember not to keep your foot in it for very long.
 
I'm not useing Flathead rods, so I used 3 3/4" stroke pistons to help adjust for length differences. There are more choices in heavy duty aftermarket rods now than when I built this motor. On the Jahns type cast pistons I use the 4" stroke piston with the 4 1/8" stroke crank to get a tight fit to the head. I don't know if that works well with the Ross pistons. You could try it, and flycut the head to tailor the clearance. You want to watch the compression if you are planning on much boost.
 
Flathead said:
I'm not useing Flathead rods, so I used 3 3/4" stroke pistons to help adjust for length differences. There are more choices in heavy duty aftermarket rods now than when I built this motor. On the Jahns type cast pistons I use the 4" stroke piston with the 4 1/8" stroke crank to get a tight fit to the head. I don't know if that works well with the Ross pistons. You could try it, and flycut the head to tailor the clearance. You want to watch the compression if you are planning on much boost.
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What rod bearings are you using?
 
well this is the first ive heard about egge pistons needing the tops machined,i would contack egge b4 going and buying ross pistond it sounds to me maybe something else ie off heads chambers trev
 
I just put EGGE pistons in my 50'Merc motor and can't use the higher compression heads because the pistons sit a little higher than stock.
 
292 Chevy 6 cyl. rods. Offset bush the pin holes down to Ford size, narrow the big end, hone for floating bearings on a 2" journal. Unless you're a scrounger and have a friendly machine shop nearby, it may be cheaper to buy custom rods these days. I didn't have much choice when I did this. Ford rod caps will fit too, if you have some extras. Match caps and rods for balance considerations before machining. I have two motors with this setup.
 
Yup EGGE sem to have the recipe wrong, we had to mill some off our EGGE pistons also to clear the low compression OFFY heads in a 4" merc motor.. This is why we are asking for info on pistons with a better quality control.We are hopeful to find something suitable at around .040 O/S so some positive leads would be appreciated to good pistons..
 
my4dv8 said:
Yup EGGE sem to have the recipe wrong, we had to mill some off our EGGE pistons also to clear the low compression OFFY heads in a 4" merc motor.. This is why we are asking for info on pistons with a better quality control.We are hopeful to find something suitable at around .040 O/S so some positive leads would be appreciated to good pistons..
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Hi "my", stay with Ross on the pistons, they've got them down to a sort of science on the Flatheads!

If the budget dictates avoid any cast pieces, although with the power you will make they would probably survive, like Ron stated above!

The Ross pieces for your application will weigh about 316 grams and give excellent service! We use these at a 3.228" finished bore size!

Thanks, Gary in N.Y.

P.S. You have a "PM".
 
I've been using Egge pistons for years and never had a problem with them. Have a new set ready for the econo engine, will have to check them out. Yes the Ross pistons are probably the best Flathead pistons on the market today, as a forged piston they require a larger piston to bore clearance and they do cost more. I've used Ross pistons in the Hydro and Bivlle engines, plus they come in the stroker kits. Someting to think about.
 
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