[grandville455]

You guys that run or have a IA2 with a 55 mm tunnel, How thin is that area back there on yours? I was at the Machine shop Monday, and my engine guy showed me mine, obvious core shift, Wasn't very happy when i seen it to say the least. I know it's probably no big deal to most.

[AG]

Mine is different.

[Tom Vaught]

AG, Is your block also machined for a 55mm Camshaft?

Tom V.

[AG]

No, but the material around the tunnel isn't skewed to one side like Grandville's which is what I wanted to show.

[johnta1]

Darby, have you had the cam centerline to block/crank centerline checked?
(and I guess the lifter holes)

[grandville455]

Originally Posted by AG

Mine is different.

Measure that same side as where i measured and then Take about .138 off that what would u have left roughly, as that's half of the 55 mm size.

[grandville455]

Originally Posted by johnta1

Darby, have you had the cam centerline to block/crank centerline checked?
(and I guess the lifter holes)

John
AP is the one that had the 55 mm tunnel bored, as my engine guy didn't have the BHJ fixture for a pontiac when i was ordering the block

[Scott Roberts]

Originally Posted by grandville455

John
AP is the one that had the 55 mm tunnel bored, as my engine guy didn't have the BHJ fixture for a pontiac when i was ordering the block

Your current machine shop can measure all of that for u..

[grandville455]

Originally Posted by Scott Roberts

Your current machine shop can measure all of that for u..

Thanks, I'm just worried how thin it is at the back, and yes i know i can have a custom plug made to fit that instead of stressing it with a frost plug there, which we're gonna do,More money out of my pocket that i shouldn't had to pay to have this plug made , let alone my engine guy check this to make sure everything is straight! It appears others aren't this bad? How much thinner are the journals on that side with that core shift? All stuff that makes me go WTF after spending this kind of money !

[Dragncar]

I know its too late but I understand some guys go 50mm on the rear bearing because of this.
Are you going babbit or needle bearing ? If the final O.D. is the same you would think the roller bearing outer shell would add a little rigidity at the thin spot.
It does add a fer HP too.

[grandville455]

Originally Posted by Dragncar

I know its too late but I understand some guys go 50mm on the rear bearing because of this.
Are you going babbit or needle bearing ? If the final O.D. is the same you would think the roller bearing outer shell would add a little rigidity at the thin spot.
It does add a fer HP too.

I’m using the babbit bearings. How would the 50 mm work, my cam is already 55?

[Mark G]

Originally Posted by grandville455

Thanks, I'm just worried how thin it is at the back, and yes i know i can have a custom plug made to fit that instead of stressing it with a frost plug there, which we're gonna do,More money out of my pocket that i shouldn't had to pay to have this plug made , let alone my engine guy check this to make sure everything is straight! It appears others aren't this bad? How much thinner are the journals on that side with that core shift? All stuff that makes me go WTF after spending this kind of money !

You bought the wrong block.....JMO

[Dragncar]

It wouldn't now that your block has been bored. I know some guys went with a 50mm on the rear journal only. You can get away with it because its the last one. Need custom cam and all that. Just leaves a little more material around that thin rear area.
I think you will be fine. Maybe others who are running a 55mm will post. I hear it gets thin but it still works OK.
AP has done plenty of 55mm. Since they bored it they would know if it is a issue. Sure they have seen it before.
But it might have been nice if they would have picked out one that was thicker there sinece it was going 55mm.
I doubt you bought the wrong block. Stand up guys.

[Mark G]

Originally Posted by Dragncar

It wouldn't now that your block has been bored. I know some guys went with a 50mm on the rear journal only. You can get away with it because its the last one. Need custom cam and all that. Just leaves a little more material around that thin rear area.
I think you will be fine. Maybe others who are running a 55mm will post. I hear it gets thin but it still works OK.
AP has done plenty of 55mm. Since they bored it they would know if it is a issue. Sure they have seen it before.
But it might have been nice if they would have picked out one that was thicker there sinece it was going 55mm.
I doubt you bought the wrong block. Stand up guys.

Maybe Mr Standup will take care of the extra cost.. my MR1 no problems.. just say'n

[grandville455]

Originally Posted by Dragncar

I know its too late but I understand some guys go 50mm on the rear bearing because of this.
Are you going babbit or needle bearing ? If the final O.D. is the same you would think the roller bearing outer shell would add a little rigidity at the thin spot.
It does add a fer HP too.

I’ve heard they were thin back there when going to a 55 mm , but it appears mine is worse then others I have spoken too, I bought this block cause I wanted the best and I was the of the future if I ever got crazy, well does my future now get limited cause of this? Idk? I know nothing bout the mechanics of the block, but these are supposed to handle 2500 all day, does my block still fit that parameter! Yes extra cost that I shouldn’t have to incur, my machinist sent me another pic today, the main feeds are way off compared to the bearing!! So more shop expense , n this too is cracked in a couple of places which well have to sand roll n debur. I’ve sent frank a message on Monday, still waiting to hear back, if I don’t hear by Friday I’ll call him.

[Scott Roberts]

Originally Posted by Mark G

Maybe Mr Standup will take care of the extra cost.. my MR1 no problems.. just say'n

My MR 1 was a disaster.... my IA2 was perfect.. Darby should call and see what they will do..

[Mark G]

Originally Posted by Scott Roberts

My MR 1 was a disaster.... my IA2 was perfect.. Darby should call and see what they will do..

Fair enough Scott no one is perfect what works for one might not work for someone else .Both are great blocks IMO..

[Big Bear]

Looks like small cracks around the oil gallery counter bore next to the cam tunnel. Should be machined/ground out so they don't travel. Barry

[Mark G]

Originally Posted by grandville455

I’ve heard they were thin back there when going to a 55 mm , but it appears mine is worse then others I have spoken too, I bought this block cause I wanted the best and I was the of the future if I ever got crazy, well does my future now get limited cause of this? Idk? I know nothing bout the mechanics of the block, but these are supposed to handle 2500 all day, does my block still fit that parameter! Yes extra cost that I shouldn’t have to incur, my machinist sent me another pic today, the main feeds are way off compared to the bearing!! So more shop expense , n this too is cracked in a couple of places which well have to sand roll n debur. I’ve sent frank a message on Monday, still waiting to hear back, if I don’t hear by Friday I’ll call him.

I hope someone steps up for you Darby....Best of Luck

[grandville455]

Originally Posted by Big Bear

Looks like small cracks around the oil gallery counter bore next to the cam tunnel. Should be machined/ground out so they don't travel. Barry

Thanks mark I do too! Exactly, this could become a issue down the road? I’m just gonna call frank tonight, he’s got the two pics I sent him of the tunnel , I didn’t start the thread to bash AP not my intent, I was curious if mine was worse then others, cause it’s damn thin and obviously it’s shifted during the casting process. I just want to be happy and get what I paid for and expected .