Swapping out iron J 202 heads for aluminum

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Mopar204

Mopar204

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Looking to swap out my slightly ported J 202 heads with the promaxx 185 shockers cnc
Just asking the experts here on what they thought about my setup and these heads going together. I’ll list my specs and my cams specs for you guys
Also willing to swap out my cam if needed

408 scat stoker kit with 20cc dished forged pistons
-mopar m1 single plane intake
-lunati hydraulic roller cam and lifters(Advertised Duration 270/278, Lift .515/.530)
-j 202 heads ported (64 cc)
-holley 750 carb
-9.7:1 CR

here is the link to the promaxx heads I’m looking at getting.
Shocker 185 Mopar CNC (Sold in Pairs) - PROMAXX Performance Products
Ive heard good things about them.
 
Without flow sheets on your iron heads, it's hard to tell. If somebody really knew what they were doin, you may not gain much.
 
Gearing, weight, transmission? Do you know your present assembled deck height?
 
I’m no expert but I will say that you would see more gains with just a cam change to: “something more aggressive” while keeping your existing heads than you will see from doing a head swap and retaining that cam. If you’re getting those heads you’d definitely want to upgrade the cam to compliment the heads and intake, gearing, converter etc
 
Yes, very small cam in a 408
Retro-Fit Hydraulic Roller. Great mid range torque and power. Likes 2000 RPM stall converter and works great in towing applications with lower gearing. Largest for inboard/outboard performance marine use. ;Advertised Duration (Int/Exh): 270/279 ;Duration @ .050 (Int/Exh): 219/227 ;Gross Valve Lift (Int/Exh): .515/.530 ;LSA/ICL: 112/106 ;Valve Lash (Int/Exh): Hyd/Hyd ;RPM Range: 1800-5800
 
Mopar204 said:
Looking to swap out my slightly ported J 202 heads with the promaxx 185 shockers cnc
Just asking the experts here on what they thought about my setup and these heads going together. I’ll list my specs and my cams specs for you guys
Also willing to swap out my cam if needed

408 scat stoker kit with 20cc dished forged pistons
-mopar m1 single plane intake
-lunati hydraulic roller cam and lifters(Advertised Duration 270/278, Lift .515/.530)
-j 202 heads ported (64 cc)
-holley 750 carb
-9.7:1 CR

here is the link to the promaxx heads I’m looking at getting.
Shocker 185 Mopar CNC (Sold in Pairs) - PROMAXX Performance Products
Ive heard good things about them.
Click to expand...
I like mine. There pretty good. The racked shaft stands should be addressed. There machined a bit shallow, the rocker shaft should sit in them more.

As said, a lot depends on what your heads flow now, at least up to the lift of the valve. If both heads flow the same or very similar up to your valve lift, there will be no gain really.

Looking at your combo, the cam is very small, but if it performs in the rpm range of your use, then leave it. A nice upgrade would be 1.6 rockers for added lift to take advantage of the cylinder heads increased air flow.

He single plane is hurting performance. You will pick up a good bit of very noticeable torque by switching to a RPM intake. That M1 single plane is really designed for use in the 3,000 - 7,000 rpm range. This is a cam duration approximately in the 250*@.050 range as a minimum.

You did not list the cars weight, gear ratio, tire size and transmission being used. If it is an automatic, going to a larger cam size will necessitate a higher stall converter.
 
Cam is small, would like an airgap better than that single plane.
Lots of variables, but i bet you see roughly a 3 tenths gain.
 
Trans is a auto 727 with a 2800 stall
Gearing is 411’s
zero deck
Weight is 3100lbs
Tire size is 275 60 15 et streets
Never really take it to the track but do have fun on the streets with it. Never really light on the throttle

Sorry I do not have any flow numbers on current heads

If you guys think that the cam is small and the intake is hurting my performance, that might just have to be my route I have to go. I’m really up to doing anything you guys think would be best.
Thanks for the input
 
Mopar204 said:
Trans is a auto 727 with a 2800 stall
Gearing is 411’s
zero deck
Weight is 3100lbs
Tire size is 275 60 15 et streets
Never really take it to the track but do have fun on the streets with it. Never really light on the throttle

Sorry I do not have any flow numbers on current heads

If you guys think that the cam is small and the intake is hurting my performance, that might just have to be my route I have to go. I’m really up to doing anything you guys think would be best.
Thanks for the input
Click to expand...
Get an Air Gap. Without opening a can of worms about fast rate cams, Chevy lobes etc decide on hydraulic or solid but look for something around the low 230°s +/- @.050” hyd (245° Or less @ .050” if solid) but no more on at least a 108° LSA, maybe a 106° and at least .550” lift or more. You got the gear for a bigger cam, but the converter will limit how much bigger. I like conservative when it comes to cams, and since your not much for the strip I’d be very careful on going too big. My take
 
12many said:
Get an Air Gap. Without opening a can of worms about fast rate cams, Chevy lobes etc decide on hydraulic or solid but look for something around the low 230°s +/- @.050” hyd (245° Or less @ .050” if solid) but no more on at least a 108° LSA, maybe a 106° and at least .550” lift or more. You got the gear for a bigger cam, but the converter will limit how much bigger. I like conservative when it comes to cams, and since your not much for the strip I’d be very careful on going too big. My take
Click to expand...

if I went with the rpm intake and a cam like you suggested, hydraulic, probably need that custom ground right? I’m still running the stock adjustable rockers. And what do you think I should get for a converter stall?

I appreciate all the help btw
 
You'll definitely feel/see some kinda improvement. As the cam grows..the more itll show. Atm it's in the range of a j head..that if well worked will make great power and run with the .100-.500 lift flow of the shocker.
Even if the heads flowed the same 'which they dont' they're lighter weight and the exh port is a lot more efficient moving more out begining at far lower lifts than the j heads.
J head exh port isnt doing much past 190-200 cfm...mostly 190's, Ported.
Could be part throttle just gets better... the kind where you just barely tip it and it accelerates and revs up faster on it's own.
We dont really know though... being I ported my own j heads and they are 186cc and flow in the usable 270 cfm range. I'm saying "ported " can mean 230-290 cfm and any volume in between and up to 190cc.
I have never seen one bigger than 190. They would have very thin bowls at that level.
I guess one thing to consider is that recently somebody got a set of these Shockers and put them on their own flow bench and they claimed that they did not hold to the numbers advertised. The numbers could easily be met by a j head or exceeded...from what I saw.
So everyone is pretty much on the money, hard to say.
 
Mopar204 said:
Looking to swap out my slightly ported J 202 heads with the promaxx 185 shockers cnc
Just asking the experts here on what they thought about my setup and these heads going together. I’ll list my specs and my cams specs for you guys
Also willing to swap out my cam if needed

408 scat stoker kit with 20cc dished forged pistons
-mopar m1 single plane intake
-lunati hydraulic roller cam and lifters(Advertised Duration 270/278, Lift .515/.530)
-j 202 heads ported (64 cc)
-holley 750 carb
-9.7:1 CR

here is the link to the promaxx heads I’m looking at getting.
Shocker 185 Mopar CNC (Sold in Pairs) - PROMAXX Performance Products
Ive heard good things about them.
Click to expand...
If those are the same J heads I CCed for you a few years ago there is not much porting going on…
 
Mopar204 said:
if I went with the rpm intake and a cam like you suggested, hydraulic, probably need that custom ground right? I’m still running the stock adjustable rockers. And what do you think I should get for a converter stall?

I appreciate all the help btw
Click to expand...
Anything you source will pretty much have to be ground after you order it due to the supply nonsense, you could maybe find specs of a so called “shelf cam” or as I refer to them “catalog cam” that might be a match for what you need, or call around with your specs and see what they come up with. For an excellent well regarded converter? Me? I’ll take a Turbo Action 10” 3500 rpm “tight” for the cam you have now, up to quite a few steps bigger. I have one, ran it on my street/strip 410 with an Isky 280 Mega, 232°@.050” on a 106° LSA w/4.10 gears. Outstanding street manners and flashed to 3500 at the strip. But there are others to consider just as well.
 
67autocross said:
If those are the same J heads I CCed for you a few years ago there is not much porting going on…
Click to expand...

they are the same heads. Ya maybe I should’ve been more clear. Maybe slightly ported would’ve been better wording to use.
 
I like 12many’s suggestion. 230*@.050 (Hyd.) is as big as I would go and you’ll not have to change the converter.

The stock rockers are costing you lift. They are inaccurate. If you have the coin, I myself would use a 1.6. A 1.5 is fine. The 1.6 is just icing on the cake.

Id finish it off with a RPM.

That’s all I would do. It’ll be a nice street machine with chops.
 
Mopar204 said:
Yes
Click to expand...
I have some flow numbers posted on the site for Shockers if you want to check them out…they are a good head but the advertised flow is a bit on the happy side…if you buy them at the local dealer they go through them so you can be 100% sure they are good to run …
 
rumblefish360 said:
I like 12many’s suggestion. 230*@.050 (Hyd.) is as big as I would go and you’ll not have to change the converter.

The stock rockers are costing you lift. They are inaccurate. If you have the coin, I myself would use a 1.6. A 1.5 is fine. The 1.6 is just icing on the cake.

Id finish it off with a RPM.

That’s all I would do. It’ll be a nice street machine with chops.
Click to expand...

Ideally if I were to have it in the budget should I do cam, rockers, intake and converter?
 
Mopar204 said:
Ideally if I were to have it in the budget should I do cam, rockers, intake and converter?
Click to expand...

do you have the stock stamped steel rockers or the 273 style adjustable rockers? If the latter, run em!
What are your actual goals for the car? If its just to be a cruiser, leave it alone and save your money.
Ifs its about significantly improving performance, installing a “ real” convertor in the car along with a performance cam will make a world of difference. Huge difference!
If your just wanting a street brawler, i would install a mid 240’s @50 solid cam and a tight 8 inch convertor.
It would wake up in a hurry, and in that case, the intake would become way less of a liability. And drive just fine on the street.

You really need to post specifically what you want the car to do
 
273 adjustable. Wanting to stick with hydraulic roller lifters. Wanting to improve performance, the car has decent power right now but this is one of my only hobbies and am always chasing more power. So leaning towards a performance cam and a converter. If rockers and an intake will also help I don’t mind swapping some parts.
as for my goals, a good street machine with the option of the track would be idle.
 
Mopar204 said:
273 adjustable. Wanting to stick with hydraulic roller lifters. Wanting to improve performance, the car has decent power right now but this is one of my only hobbies and am always chasing more power. So leaning towards a performance cam and a converter. If rockers and an intake will also help I don’t mind swapping some parts.
as for my goals, a good street machine with the option of the track would be idle.
Click to expand...

not a fan of hyd roller deals at all, but lots of guys run them.
With a bigger cam, however you do it, moving to an 8 inch vert is by far gonna show up the most on an ET slip. Any smallblock loves convertor, lots.
 
B3422w5 said:
not a fan of hyd roller deals at all, but lots of guys run them.
With a bigger cam, however you do it, moving to an 8 inch vert is by far gonna show up the most on an ET slip. Any smallblock loves convertor, lots.
Click to expand...
Good to know. Thanks
 
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