When to notch the bore on a 383

[road chicken]

I have searched here and didn't see a good definitive answer to this, if i missed it please post is so we don't go around again.

I have a 30 over 383 (4.280) that I'm putting Eddy RPM 84cc heads on, and my question is specifically when do I need to notch the bore for the 2.14/1.81 valves. I'm not concerned about valve to piston clearance, that I understand.


On the one hand Eddy instructions call for 0.035 clearance to any part of the engine, and the old Mopar Bible calls out that the bigger valves in BB heads are no problem with the 440's 4.32 bore. That would lead me to believe I need to notch the bore about .020 on each side, ( roughly, I know I won't "KNOW" until I measure it).


Yet I have seen articles where they just bolt them on ( with .040 head gaskets) and run them with no problem, the cam used in one write up is a Comp 285X hydraulic with 1.5 rockers. I haven't seen anyone here mention bore notching either when using these heads.

The cam I'm using is the old 284/484 108 CL , 1.5:1 rockers, Cometic 0.027 thick MLS with a 4.350 bore.


I will measure the clearances when do the assembly but what is the rule for valve to bore clearance? This will bring up another question of how to properly notch the bores for this clearance, if needed.

Thanks RC.

 

[69Bee]

My 64 426W 0.030" over (4.280") had 2.14"/1.81" valves, and I had no issues.

The 0.035" rule usually only refers to the minimum distance between the piston and head. The only Mopar engines I believe had bore notches was the 426 Max Wedge because of the 1.88" exhaust valves.

As far as the proper way to put notches in the block, I will list them in order from easiest (cheapest) to hardest (best):

1) With a hand grinder and carbide bit (not precise or accurate)

2) On a Bridgeport mill (more precise, but not totally accurate)

3) On a Bridgeport mill with DRO (real precise and accurate)

4) On a CNC Bridgeport mill (best method, but probably most expensive)

Personally, I think that you would be just fine, and have nothing to worry about. If you use the Cometic MLS gasket, make sure you have the block decked, preferably with CBN mill or grinder. The surface finish Ra needs to be low, as specified by Cometic. MLS gaskets are designed to seal against very smooth surfaces, and will leak when they are too rough.

Good luck, and Merry Christmas
Dave
Precision Machine Service

 

[road chicken]

Thanks Dave. It's no small concern because this is a top end swap not a fresh build. So hangin over the fender with a die grinder... not what i wanted to find out i HAD to do. :/ I will measure it all up with clay and see. Is there a rule of thumb of the bore to valve clearance at all?

I know your point with the mls gaskets, although this time around I'll check for flatness and some copper spray to fill in the rough spots. I know , not ideal, but it seals fine with the .020 SS factory gasket dry and the block was decked 30,000 miles ago and the eddys are new. I will have those smoothed to the proper finish if they aren't already ootb ....so ... You can laugh at me if it leaks DUMBASS TOLD YA SO! lol This would just optimize the combo if it works.


And Merry Christmas to you as well

 

[lewtot184]

if the valves and chamber overlap the bore i'd notch. i used to notch my 383's.

 

[road chicken]

If that is the case, which i hope not, but the clay will tell the story. Even if it did, how much clearance do you notch it for.

BTW going back to the gaskets... HYLOMAR on the Cometic gaskets, not Copper.

 

[69Bee]

If you are using Cometic MLS (multi-layer rubber steel), they need to be installed DRY. Any sealer will ruin the sealing capability of the gasket. As far as the heads, the new Edelbrock heads will be fine to use with the MLS gaskets as is. They would have been either ground or cut with Diamond on a mill, so are smooth enough. How was the block decked 30K miles ago? Did the shop use a grinder, or CBN, or was it an old carbide cutter setup like the Storm Vulcan pie shaped mill?

 

[road chicken]

If you are using Cometic MLS (multi-layer rubber steel), they need to be installed DRY. Any sealer will ruin the sealing capability of the gasket. As far as the heads, the new Edelbrock heads will be fine to use with the MLS gaskets as is. They would have been either ground or cut with Diamond on a mill, so are smooth enough. How was the block decked 30K miles ago? Did the shop use a grinder, or CBN, or was it an old carbide cutter setup like the Storm Vulcan pie shaped mill?

The racing hylomar is what Cometic suggests, IF sealer needs to be used.

I don't remember what they used to deck the block, it's been 13 years since the work was done/ engine built. I'll know more when I pull the heads. From what I remember is was pretty smooth like it had been ground. I just don't know if it was Ra 50 smooth.

 

[Meep-Meep]

The 4.25" MW blocks got a bore notch but the EX valve on those was 1.88" and cam lift up to .520". Do check with clay as suggested, but if you don't go crazy on the lift you might be OK without a notch.

 

[road chicken]

It will be fine. I transposed a number. The valves have .150" clearance, not .015. My fault. I'll see when i do the piston valve check. it's only an 484/284 with a .040 quench height.