ICON 9976 with Magnum Heads?

-
B

BsB Duster

Active Member
Joined
Jan 25, 2018
Messages
42
Reaction score
18
Location
Iowa Park TX
Hey guys,
Can I get away with running magnum heads on my 360 with ICON 9976 pistons, or will the compression be too high to run pump gas? I was going to have my stock 360 heads rebuilt but I realized they are two different heads. One is a 3769974 and the other is a 4027596.
 
Link to slug?
Where does it sit in the bore?
Actual current compression ratio now with what head (cc) and gasket?
Current Magnum head cc is?
Actual bore size?
Best available octane for you is?
Cam specs @ .050 please.
 
rumblefish360 said:
Link to slug?
Where does it sit in the bore?
Actual current compression ratio now with what head (cc) and gasket?
Current Magnum head cc is?
Actual bore size?
Best available octane for you is?
Cam specs @ .050 please.
Click to expand...
Link to slug
SB Chrysler 360 Icon FHR Forged Pistons Flat Top 7cc 4.030 Bore IC9976-030
I don’t know yet where piston sits in the bore, it is a fresh and disassembled.
The gaskets are felpro 8553 stock replacements. Not sure on the compressed thickness as I can’t find a solid answer around .045?
Also don’t know magnum head cc haven’t preserved them yet. Most say stock are around 62cc?
Actual bore size is 4.030
Cam specs: Summit 6901 218 228 @50 if a different cam will be better I don’t mind getting something different.
 
If the deck height is nominal and this is an LA block, then these will sit about .011.012" down in the bore. That is a .050" compressed gasket (typical, reportedly can vary some) and a 4.18" bore hole. Head cc's ought to be in the 62-63 cc range typically.

With those nominal and typical numbers, static CR will work out to around 10.0. With that cam, dynamic CR will work out right at 7.7 with that cam at an ICL of 110. Will run fine on the street and be very torquey down in the low RPM's. You will have to pay some attention to the tuning and ignition timing and not be lazy on that count, but it won't be very hard to get it to run well and avoid detonation on pump premium.

You ought to get the rotating assembly re-balanced with these pistons; with stock rods, you're dropping the bobweight 40-50 grams lower than stock; that's well outside what folks consider to be the sloppy factory range.

What is the planned use for the car/engine? Trannie type? There are better cams IMHO, but, IMHO, whether it is worth changing depends on what you want to do, the transmission type, and how hard core you are about torque/HP.
 
LOL @nm9stheham , ya, there always a better cam.
Also, are you sure that math works out right? 10-1? With a Magnum head or LA? Magnum right? Seems right to me on a off the cuff thought...

That would be Max for pump gas and that cam if the distributor timing is right. Personally I think it a bit stout. Around here (NY) it’s ether 89 or 93, IDK about 91.


I just noticed that link says that piston is for a 3.31 stroke, the 3.58 is a 360 stroke, the 3.31 is all the other engines. Double check!

What is the tire size, gear ratio and trans?
The cam is small enough to use the stock converter.
Heck of a spread, 10*’s.
 
Do you already have those pistons? If so, can you verify the compression height on them?
That link says they are 360 pistons with 1.675 compression height, which sounds right, but then it says it’s for a 3.310 stroke.
Looking theses up on UEM’s website it says to call them for specs and availability.

Edit
Oops; rumblefish360 already got these questions in while I was logging and typing. Sorry.
 
nm9stheham said:
If the deck height is nominal and this is an LA block, then these will sit about .011.012" down in the bore. That is a .050" compressed gasket (typical, reportedly can vary some) and a 4.18" bore hole. Head cc's ought to be in the 62-63 cc range typically.

With those nominal and typical numbers, static CR will work out to around 10.0. With that cam, dynamic CR will work out right at 7.7 with that cam at an ICL of 110. Will run fine on the street and be very torquey down in the low RPM's. You will have to pay some attention to the tuning and ignition timing and not be lazy on that count, but it won't be very hard to get it to run well and avoid detonation on pump premium.

You ought to get the rotating assembly re-balanced with these pistons; with stock rods, you're dropping the bobweight 40-50 grams lower than stock; that's well outside what folks consider to be the sloppy factory range.

What is the planned use for the car/engine? Trannie type? There are better cams IMHO, but, IMHO, whether it is worth changing depends on what you want to do, the transmission type, and how hard core you are about torque/HP.
Click to expand...
I had the assembly balanced while at the machine shop. Also had ARP rod bolts installed and rods resized. The car is going to be a cruiser that will occasionally see the local 1/8th mile track. It has a 67 model a904 and that’s the main reason for the smallish camshaft because it has 19 splines and I can’t get a stall convertor for it. The rear in the car is an 8 3/4 with 4:30 gears on a 28 inch tall drag radial. I was planning to do the IMM aluminum heads but have had to change plans to get something less expensive that will still perform well. I figured the magnum heads would fit the bill. I’m hoping this setup will get me in the 350ish HP will close to 400lbs of torque. I might be way off here I don’t know
 
Doing a google search, I just found the UEM Facebook page and it lists 3.58” stroke for this 9976 piston, so that should be fine and does match the intended compression height.
Looks like a nice piston. Formed head relief instead of machined, to lower cost, but otherwise very similar to the IC741 that has machined valve reliefs and top.
 
rumblefish360 said:
LOL @nm9stheham , ya, there always a better cam.
Also, are you sure that math works out right? 10-1? With a Magnum head or LA? Magnum right? Seems right to me on a off the cuff thought...

That would be Max for pump gas and that cam if the distributor timing is right. Personally I think it a bit stout. Around here (NY) it’s ether 89 or 93, IDK about 91.


I just noticed that link says that piston is for a 3.31 stroke, the 3.58 is a 360 stroke, the 3.31 is all the other engines. Double check!

What is the tire size, gear ratio and trans?
The cam is small enough to use the stock converter.
Heck of a spread, 10*’s.
Click to expand...
I called and verified that they are for a 3.58 stroke 360 it was a misprint. We have 93 pump here. Tire size is 28 drag radial a904 and 4:30 8 3/4. I actually was trying to buy your j heads but was slower to respond and missed out.
 
I ran the numbers from the Icon catalog so no worries there. I never work off of a distributor data page, unless it is for something exclusively from that distributor, like this cam.

I have run 10.0 and 10.3 on the street, with DCR's of 8.0 and 8.3 respectively, at the same elevation as the OP. The 8.3 needed more care with the timing. The OP is well under that, so I'd not worry at all.

OK, on the trans, and the stock stall TC. My 8.3 DCR 351C was with a stock TC, 3.08 rear, similar but a bit smaller cam with 14LSA, and would not burn a lot of tire, but beat factory 440 GTX's every time. They would get me a half car lenght on launch, but by the time the 1-2 shift came at 55 mph, I was pulling past them, and once in 2nd they kept falling back. They would give up before getting to the 2-3 shift at 85 mph LOL. The 8.0 is my son's 340 in a '65 Cuda with a 3.55 and it takes considerable care on the launch to not fry street tires. With your 4.30 rear, this DCR, and a stock TC, it is going to have more torque at launch than you can connect to the ground.

The 114 LSA on the cam will help with mileage, and will make the transition from low RPM operation up onto the main torque plateau at mid RPM's smoother than a narrow LSA cam. It will build torque up smoothly with RPM, and will be nice on the street.
 
Bobzilla said:
Doing a google search, I just found the UEM Facebook page and it lists 3.58” stroke for this 9976 piston, so that should be fine and does match the intended compression height.
Looks like a nice piston. Formed head relief instead of machined, to lower cost, but otherwise very similar to the IC741 that has machined valve reliefs and top.
Click to expand...
Yes, there are from their lower priced FHR line of forged pistons.
 
BsB Duster said:
The car is going to be a cruiser that will occasionally see the local 1/8th mile track. It has a 67 model a904 and that’s the main reason for the smallish camshaft because it has 19 splines and I can’t get a stall convertor for it. The rear in the car is an 8 3/4 with 4:30 gears on a 28 .....
I figured the magnum heads would fit the bill. I’m hoping this setup will get me in the 350ish HP will close to 400lbs of torque. I might be way off here.
Click to expand...
I think your on target close enough.
I also have the old 904 / 19 splined converter. I had it re stalled @ Pro Torque, good for 650HP and laughing gas.
BsB Duster said:
We have 93 pump here. Tire size is 28 drag radial a904 and 4:30 8 3/4. I actually was trying to buy your j heads but was slower to respond and missed out.
Click to expand...
There not paid for yet. (Should be soon though....)
But I have bare builder 308 or 596 heads, I forget. In fact, I’ll have to dig them out later.

The Magnum heads are a good choice. A bit more involved that a straight LA head swap.
 
nm9stheham said:
I ran the numbers from the Icon catalog so no worries there. I never work off of a distributor data page, unless it is for something exclusively from that distributor, like this cam.

I have run 10.0 and 10.3 on the street, with DCR's of 8.0 and 8.3 respectively, at the same elevation as the OP. The 8.3 needed more care with the timing. The OP is well under that, so I'd not worry at all.

OK, on the trans, and the stock stall TC. My 8.3 DCR 351C was with a stock TC, 3.08 rear, similar but a bit smaller cam with 14LSA, and would not burn a lot of tire, but beat factory 440 GTX's every time. They would get me a half car lenght on launch, but by the time the 1-2 shift came at 55 mph, I was pulling past them, and once in 2nd they kept falling back. They would give up before getting to the 2-3 shift at 85 mph LOL. The 8.0 is my son's 340 in a '65 Cuda with a 3.55 and it takes considerable care on the launch to not fry street tires. With your 4.30 rear, this DCR, and a stock TC, it is going to have more torque at launch than you can connect to the ground.

The 114 LSA on the cam will help with mileage, and will make the transition from low RPM operation up onto the main torque plateau at mid RPM's smoother than a narrow LSA cam. It will build torque up smoothly with RPM, and will be nice on the street.
Click to expand...
Thanks for the information it sounds like I’m gonna have a nice fun combination for the street. I actually bought those pistons for $340 which wasn’t much more than the hyper pistons I was looking at. I should be able to spray a small shot at the track with them and be good to go.
 
rumblefish360 said:
I think your on target close enough.
I also have the old 904 / 19 splined converter. I had it re stalled @ Pro Torque, good for 650HP and laughing gas.

There not paid for yet. (Should be soon though....)
But I have bare builder 308 or 596 heads, I forget. In fact, I’ll have to dig them out later.

The Magnum heads are a good choice. A bit more involved that a straight LA head swap.
Click to expand...
I will give the guys at protorque a call when I’m a little closer.
 
if your deck height turns out to be - .020 use the .028 mr gasket
0 deck use a .040 one

easier to change the front drum and shaft?
Id run it with what you have it and see how you like it
do a stall test b 4 calling converter shop
every motor puts out different torque so stall is different
 
Wyrmrider said:
if your deck height turns out to be - .020 use the .028 mr gasket
0 deck use a .040 one

easier to change the front drum and shaft?
Id run it with what you have it and see how you like it
do a stall test b 4 calling converter shop
every motor puts out different torque so stall is different
Click to expand...
So your saying don’t use the gaskets that came with my gasket set since they are around .050 compressed? I don’t mind buying different gaskets just want to make sure I understand. Thanks
 
I only use ,050 gaskets when the piston are out of the block a bunch
.015 once
closed chamber heads
open chamber not so much takes a piston change then
 
A few “hand grenade and horse shoes” compression calculations. None of these numbers are going to be exact to the degree calculated but this will give you some idea. With the advertised compression height of 1.675 it should be about .012 down the hole. Those PermaTorque gaskets usually come in between .045-.053 compressed thickness and all points in between so 10.2-12cc’s, or .1 point of compression for the bore and stroke volume. Going by those parameters in a stock deck height block and a 62 cc head you’d have between 9.9-10:1 compression. An SCE .060 pro seal gasket SCE Pro Seal Composite Head Gaskets 569096 would give you somewhere close to 9.8:1. In the far corners of the inter web I have read that the severe duty PermaTorque 521SD come Fel-Pro Head Gaskets 521SD come in on a consistent.054 compressed thickness, and with the 4.18 inch bore have a volume of 12.2 ccs, or 9.93:1. A Fel-Pro 1008 HP gasket https://www.summitracing.com/parts/fel-1008/make/chrysler would come out with 10.2:1. With the pistons at zero deck and the 1008 head gasket you’d have 10.6:1.
 
I'd go the .040 fell pros at 0 deck and the ,028 mr gasket if .010 down
the mgnum heads have two quench pads
use them
open up around the valves if you need a few cc.s
easy to do when dong the valve job
 
Wyrmrider said:
I'd go the .040 fell pros at 0 deck and the ,028 mr gasket if .010 down
the mgnum heads have two quench pads
use them
open up around the valves if you need a few cc.s
easy to do when dong the valve job
Click to expand...
Oh hell yea!
 
As mentioned before, with a re-stalled converter combined with 4.30:1 gears, you could go with a better (not necessarily more) cam. At 10:1 or better, I would be inclined to go with a modern fast rate cam, specifically the Lunati Voodoo 262 hydraulic with accompanying mods that may be required with the Magnum 1.6 rocker arms.
Voodoo Hydraulic Flat Tappet Cam - Chrysler 273-360 262/268. If you’re wanting to exceed your hp goal and are running a performer rpm or the like, you could go bigger. The 268 Voodoo is a stout option, but probably more viable with that 4.30 gear, being your speed at 60 mph with a 28 inch tire (accounting for one inch of growth at speed) is going to be 3000 rpm.
Voodoo Hydraulic Flat Tappet Cam & Lifter Kit - Chrysler 273-360 268/276
 
You must log in or register to reply here.
-

Back
Top