Cam swap without pulling motor

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I see the rationale. Thanks for that perspective. I sure wish it was possible to try these multiple scenarios without two sets of heads, hours of work and a dyno.

If a wide top cut is the objective I could (and probably should) stay with the 1.88 valve.
 
I doubt the bigger valve will do all that much for the seat for the pants feel in the vehicle.
 
Earlie A said:
Since the heads were off and the compression is low, I had the heads milled 0.070" as seen in the picture below. I realize that changing pistons is the best way to go about upping the compression. You guys told me that and you are correct. This is just something I wanted to try. A previous refresh already had milled the heads 0.008" so the total off the deck face is 0.078". The intake face of the head was also milled 95% of the 0.078".

The factory 1.88/1.60 valves are shown on the right. I have a set of 2.02/1.60 nail head valves that I would like to install (as seen on the left), but I'll probably have to sink the intake valve a little to get some top angle. If I install the 2.02 valve the valve job would be 38/45/60/75.

What is the minimum top cut width I should try to get by with? Milling the heads removed the ridge in the chamber on the short side of the intake valve. I bet removing this ridge has increased high lift reversion flow.

View attachment 1716296682
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With that much shaved off of the heads, wouldn't you also need to shave the intake side of the head for the angles to match? Maybe that was already done.
 
Ricks70Duster340 said:
With that much shaved off of the heads, wouldn't you also need to shave the intake side of the head for the angles to match? Maybe that was already done.
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You are correct. The intake face of the head was shaved around 0.070" as well. We targeted 95% of the 0.078" removed from the head.
 
PRH said:
I doubt the bigger valve will do all that much for the seat for the pants feel in the vehicle.
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You might be correct. Here's my thinking. The nail head valves are much flatter on the chamber side. I hope to measure tomorrow but it looks like 3-4 cc will be removed from the chamber with the new valves. I'm hoping to get around 9:1 or slightly higher. This is turning into a mild performance build as well. RPM Air Gap manifold and headers going back on. Now shooting for 230-240 with additional porting.

Check out the flow curve below. Test 646 is before surfacing. Test 655 is after surfacing. No other changes. I am beyond shocked. I keep looking for some testing error that I have made like leaving the spark plug out. Can't find anything. Short side shrouding is gone and I suppose some shrouding on the cyl wall side. But 30 cfm?

IMG_3039.jpg


IMG_3040.jpg
 
Wow, that’s a first!!

I’d probably flow another hole and see what you get.

I can see putting the new valves in, in your situation.
You have the valves and the means to do the job. It’s just some time.
If the new valves are single groove, that’s all the more reason to swap them.

I’m actually working on some 915 heads myself right now.
My least favorite part of porting factory SB iron heads is whittling down the intake guide bosses.
 
PRH said:
Wow, that’s a first!!

I’d probably flow another hole and see what you get.

I can see putting the new valves in, in your situation.
You have the valves and the means to do the job. It’s just some time.
If the new valves are single groove, that’s all the more reason to swap them.

I’m actually working on some 915 heads myself right now.
My least favorite part of porting factory SB iron heads is whittling down the intake guide bosses.
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I wouldn't mind grinding the cast iron if it weren't for the guide boss. They do take some time.
 
Getting down to choosing a head gasket and measuring for pushrods. Here's some specs: cast iron heads milled down 0.078" with nail head valves measure out to 53cc chamber. With piston 0.106" in the hole, a 9.1cc dish and 256/265 cam with an intake closing of 56 ABDC I get the following static and dynamic compression ratios:

Felpro 0.051" gasket: Static-8.88, Dynamic-7.54
Felpro 0.039" gasket: Static-9.1, Dynamic-7.72
Cometic 0.027" gasket: Static-9.32, Dynamic-7.9

3600lb truck with 727 transmission, factory 2500 stall, 3.55 gears to be a street driver.

I'm inclined to go with the Cometic gasket. Is that pushing the limit on CR with these non quench heads and pump gas?
 
If I were building it for a customer, and it absolutely positively had to run on pump gas, it would get the thick gaskets.
 
PRH said:
If I were building it for a customer, and it absolutely positively had to run on pump gas, it would get the thick gaskets.
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57 years old and I still hate it when a grown up tells me what I need to hear.

Thanks.
 
Fwiw, I hope you use the thin Cometics.
Then we’d both know if that was over the edge or not.
 
It looks like the Cometic MLS gasket is out. The oil hole for the rocker shaft passes through the deck surface on the head at a fairly steep angle. Milling 0.078" from the head has changed the location of the oil hole enough that I'm not comfortable with the MLS gasket's ability to seal since this gasket relies on a raised ring around the perimeter of the hole. The 1008 Felpro looks like it would still work since it is fiber. Might have to enlarge the gasket hole slightly.

I would still like to use the Cometics if anyone knows of a workaround. I would also consider the Mr Gasket 0.028" gasket. I don't have one of those but the pictures look like it is fiber as well (the description on Jegs is graphite/steel). Anyone have experience with the Mr Gasket?
 
Earlie A said:
It looks like the Cometic MLS gasket is out. The oil hole for the rocker shaft passes through the deck surface on the head at a fairly steep angle. Milling 0.078" from the head has changed the location of the oil hole enough that I'm not comfortable with the MLS gasket's ability to seal since this gasket relies on a raised ring around the perimeter of the hole. The 1008 Felpro looks like it would still work since it is fiber. Might have to enlarge the gasket hole slightly.

I would still like to use the Cometics if anyone knows of a workaround. I would also consider the Mr Gasket 0.028" gasket. I don't have one of those but the pictures look like it is fiber as well (the description on Jegs is graphite/steel). Anyone have experience with the Mr Gasket?
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Used those on my old 360 that went 11.30 to raise compression a bit. Zero issues with them at all. Would use again.
Bare in mind they are thin enough to where you should take a good look at the mating surfaces before slapping things together to make sure things are clean and level
 
Heads have been surfaced recently. Block has not. Block was just scraped to remove the old Felpro gasket residue. If there is any question at all about the Mr Gasket I would just use the Felpro 1008 and lose a small amount of compression.
 
Earlie A said:
Heads have been surfaced recently. Block has not. Block was just scraped to remove the old Felpro gasket residue. If there is any question at all about the Mr Gasket I would just use the Felpro 1008 and lose a small amount of compression.
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I would use the 028 then. And I have used( and currently use my new motor the 1008)
Nothing wrong at all with that Mr Gasket. It’s a steel shim gasket, pretty darn robust.
 
B3422w5 said:
I would use the 028 then. And I have used( and currently use my new motor the 1008)
Nothing wrong at all with that Mr Gasket. It’s a steel shim gasket, pretty darn robust.
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Made different than an MLS? If I enlarge the oil hole will it still seal?

Thanks
 
Earlie A said:
As much as I would like to pull the motor and put in better pistons, that’s just not an option right now. Too many other life priorities. I am going to use the Lunati Voodoo 258/265, 213/220, 0.454/0.475 112 LSA cam that I have sitting around.

Here’s my question. Does it make sense to use 1.6 rockers? I have a set of the Speedmasters from Black Friday. I know I want to keep the duration down because of the sub-8 compression ratio, but would the additional lift be beneficial? I think the Voodoo cams are fairly fast opening anyway.

Truck is 1979 D150 with 360, 727 trans and 3.55 gears, factory exhaust manifolds and iron heads. Heads are currently getting 1.88 valve job and some mild porting. Might do a Performer or an RPM intake.
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Aluminum heads and roller rockers on that 7 to 1 short block are like putting silk stockings on a pig. I would either buy a set of pistons, or start over with a 5.9 magnum to build.
 
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