4.1 Guys step in i have block questions..

[434nova]

Picked up a 4.1 block low miles. One thing I do notice is the valley seems to have a lot of casting flash. Is this a common thing on the 4.1 blocks. Here are some pics as to what I'm talking about. Just want to make sure it's normal and not something wrong with the block.
Where the lifters go it has like slot cut in the block. I think it's just a casting flaw. But here it is

 

[RmvBfrFlght]

It is normal to have a lot of casting flash. It should be ground out and the surfaces smoothed. Note that the picture didn't show up.

RemoveBeforeFlight

 

[434nova]

My pictures aren't uploading for some reason. Let me try again.

 

[geetee]

Here is a picture of my 291 block:

 

[434nova]

 

[earlbrown]

Yours actually looks pretty good compared to mine. I had to spend quite a bit of time removing casting flash.


While you've got the rotary tool fired up, go ahead and groove the front cam journal bore, and open up the water intakes. You'll have a pitted area that shows exactly where the timing cover lands.

It's also a good idea to countersink the hell out of the head bolt holes at the deck area.

 

[t-typinator]

It's also a good idea to countersink the hell out of the head bolt holes at the deck area.[/QUOTE]



Is this to help prevent the block from cracking at the deck surface.
I know 4.1's are prone to cracking around the head bolt holes at the deck surface.

 

[Tom87GNX]

84-85 3.8 blocks are cast the same, my 140 block looks just like it


Sent from my iPhone using Tapatalk

 

[earlbrown]

It's also a good idea to countersink the hell out of the head bolt holes at the deck area.

Is this to help prevent the block from cracking at the deck surface.
I remember reading and seeing pics in the past of 4.1's cracking around the head bolts at the deck surface.[/QUOTE]


No,it's to get a better clamp load on the head gasket. Bevelling that hole moves the max loaded area outward away from the threads. If you look closely at a 109 block Buick countersunk the holes to keep the top thread from rolling up and lowering clamp load (I bevel the shit out of those too). There's not enough meat on a 4.1 to be wiping out that many threads so I just knock out 1 or 2 then put a healthy 45 on there.


Bevelling that sharp area might help with cracking but there's so many stress risers on a tapped hole, I can't imagine getting rid of one of them will make that much difference.

 

[t-typinator]

Is this to help prevent the block from cracking at the deck surface.
I remember reading and seeing pics in the past of 4.1's cracking around the head bolts at the deck surface.

No,it's to get a better clamp load on the head gasket. Bevelling that hole moves the max loaded area outward away from the threads. If you look closely at a 109 block Buick countersunk the holes to keep the top thread from rolling up and lowering clamp load (I bevel the shit out of those too). There's not enough meat on a 4.1 to be wiping out that many threads so I just knock out 1 or 2 then put a healthy 45 on there.


Bevelling that sharp area might help with cracking but there's so many stress risers on a tapped hole, I can't imagine getting rid of one of them will make that much difference.[/QUOTE]


Makes sense .

 

[434nova]

Has anyone pushed a stock block 4.1 in the 8's as they have a 109 ?

What's the fastest stock block 4.1 et on record?

 

[hotairgnx548]

Has anyone pushed a stock block 4.1 in the 8's as they have a 109 ?

What's the fastest stock block 4.1 et on record?

whats with the crack in post 5? need to get it to a machine shop before you do anything to it. p.s. mike liche is very schooled about the 4.1 john

 

[434nova]

Where do you see a Crack at ?

It's going to the machine shop to get Magnefluxed, sonic checked , check the deck height and bore size.

 

[hotairgnx548]

Where do you see a Crack at ?

It's going to the machine shop to get Magnefluxed, sonic checked , check the deck height and bore size.

click

Where do you see a Crack at ?

It's going to the machine shop to get Magnefluxed, sonic checked , check the deck height and bore size.

click on the picture in #5 post at the top near the valve lifter bore john

 

[434nova]

I think that is just raw casting. If you look at geetee block it looks like he dremel that area to clean it up. I'm taking the block this weekend to get checked out.

 

[hotairgnx548]

I think that is just raw casting. If you look at geetee block it looks like he dremel that area to clean it up. I'm taking the block this weekend to get checked out.

 

[hotairgnx548]

do you still have the block? look at 161613 picture and explode the upper corner that crack is deep! john

 

[czimpel]

do you still have the block? look at 161613 picture and explode the upper corner that crack is deep! john

That's just the way the casting looks on the 4.1 blocks. The pic is quite deceiving.

 

[earlbrown]

Oh yeah, one other mod to do is to drill a couple of steam holes on the deck and heads. A head gasket can be uses as a template since your deck surface is cleaned off.


The 4.1 has siamese bores so there's no way for air to escape on the lower half of the decks. The holes don't have to be YUGE, I used 1/16" on my 4.1

 

[434nova]

Earl do you have a arp part # for head studs using champion gn1 heads.