Oil pump hits new ARP main bolts

[RDJ]

I went to bolt on the oil pump in my new long block. I used new ARP main bolts. I guess the heads on the ARPs are thicker than the stock bolts. As you can see from the pic (upper right), the oil pump won't bolt down because the ARP bolt hits the oil pump housing. The oil pump is an OEM type MellingM-72. I guess I have one of two choices.

1) Use one of the old (or get a new one) stock bolts.

2) Get an oil pump that can clear the ARP bolt. Is there one that will clear this problem?

Or, am I just being lame and putting this thing on wrong?

 

[70aarcuda]

there is no oil pump that will clear....

either grind arp bolt/oil pump for clearance...or use stock bolt..

 

[Longgone]

That`s a common problem with those bolts. How about using a new factory style bolt?

 

[raymond]

Take the cap back off and spot face the area around where the bolt head or stud nut seats. I thing you have to machine it about .120" from memory, then if it still tight you may have to cut a little off the stud as well. Take some measurements before you pull it apart, they will all be a little different.

 

[FASTBACK340]

Take the cap back off and spot face the area around where the bolt head or stud nut seats. I thing you have to machine it about .120" from memory, then if it still tight you may have to cut a little off the stud as well. Take some measurements before you pull it apart, they will all be a little different.

Here's what I did, which is exactly what Raymond suggested:


I had my machinist spot-face the rear main cap and use a shorter stud with a 12 pt. ARP nut, which is smaller in diameter.

Now it clears....

 

[RDJ]

Thanks. You would think that since this is a common problem, ARP would either make a proper kit for the 340/360, or at least let us know that we will have to scramble to make it work.

 

[340sFastback]

People have been calling ARP for quite some time now and apparently they aren't going to correct the issue.

 

[1wild&crazyguy]

I couldn't fit a washer under the 12point on mine but did the same and ground the stud down along with .020 of the nut, also ground the pump like mentioned.
I was just gonna use a stock bolt but the torq diff bothered me for some reason.

 

[djwhog]

I milled the pump some, then there was another bolt ARP has with a smaller head, had to mill it some and all fir but bareley. I think there are a lot of threads on this issue you can search too.

 

[RDJ]

Thanks. I ended up removing the washer, grinding the top of the bolt, and grinding the oil pump.

 

[moper]

yup. Just make sure the pump sits flush on the block. I trim the stud/bolts and use the 12pt kits on mine.

 

[340sFastback]

Thanks. I ended up removing the washer, grinding the top of the bolt, and grinding the oil pump.

That is how my machine shop dealt with it along with using the 12 point nut.