Redrilling Magnum heads for LA intake question

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ProStreetDuster

ProStreetDuster

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I just dropped off my Magnum heads to have them magged and then if there good have them redrilled so I can use my collection of LA intakes for my 340.
My Question is for those that have done this, did you drill the heads to except the standard LA bolts? I believe they're 3/8ths intake bolts or did you go with the smaller stock Magnum intake bolts? I'd rather use the 3/8ths bolts I just want to make sure it doesn't cause a weakness problem.
Also is there anything else I need to be aware of when having this done?
Bolt length, intake gaskets etc?
 
I didnt drill mine but bought the EQ heads for the la intake. They are drilled for the 3/8" bolts. Things to be careful of is making sure they align perfectly with the intake locations or you will get binding. you may want to put a small chamfer on the holes to make it easier to start the bolts.
 
How much did those EQ heads run ya? Were they complete or just bare heads? If these magnum heads end up being cracked that's what I'm going to get.
 
I paid 750 for the complete heads and shipping. I when through clearwater, they changed the springs to match my cam and everything for me.
 
I just got a set of dual drilled heads from Hughes. (wanted the EQ with the LA pattern, but they were out of stock). Hughes drills them with the 5/16 Magnum bolt size rather than the factory LA 3/8. Don't know whether it sucks or not. One thing though is the smaller bolt head is probably easier to turn on the bolts between the runners.

Steve
 
I have never heard of this before, but it interests me. Do the ports in the old-style intakes line up well, or are there alignment issues like when you re-drill the chevy vortecs?
 
I got some time to play with my stuff over the weekend.

The port alignment with my heads is pretty well perfect, using an Edelbrock Air Gap intake.

I will say after installing the intake with this arrangement that it does require some finagling. I had to get some shorter bolts to get bolts into the four innermost holes because of interference with the runners. In fact, I had to put the passenger side rearmost of these in first because you have to tip the intake up to do it. I don't know how anyone makes it work with 3/8" bolts.

The smaller head size on the 5/16" bolts is helpful for getting these bolts down, I had no way to get a torque wrench on them. Different intakes may be easier.

I tried to be a little more delicate than usual as it takes some finesse to get the bolts started, and I don't think there's margin to repair the threads if they get damaged.

I'm trying to figure out what to use for sealant on the bolts as most of these are not blind holes and I don't want oil climbing through there and seeping out onto the intake.

Its too bad the selection of intakes for the Magnum bolt pattern isn't better as I think the Magnum arrangement is a much lower hassle, better solution.

Steve
 
LXguy said:
I got some time to play with my stuff over the weekend.

The port alignment with my heads is pretty well perfect, using an Edelbrock Air Gap intake.

I will say after installing the intake with this arrangement that it does require some finagling. I had to get some shorter bolts to get bolts into the four innermost holes because of interference with the runners. In fact, I had to put the passenger side rearmost of these in first because you have to tip the intake up to do it. I don't know how anyone makes it work with 3/8" bolts.

The smaller head size on the 5/16" bolts is helpful for getting these bolts down, I had no way to get a torque wrench on them. Different intakes may be easier.

I tried to be a little more delicate than usual as it takes some finesse to get the bolts started, and I don't think there's margin to repair the threads if they get damaged.

I'm trying to figure out what to use for sealant on the bolts as most of these are not blind holes and I don't want oil climbing through there and seeping out onto the intake.

Its too bad the selection of intakes for the Magnum bolt pattern isn't better as I think the Magnum arrangement is a much lower hassle, better solution.

Steve
Click to expand...
Thanks. Some good info on this thread. I am old school, havent played with the magnum heads, one reason being the intake situation. Very helpful.
 
As far as alignment goes, I placed the gasket on the head so it lined up with the head perfectly (Edelbrock gasket # 7276).

I bolted the intake in place and torqued it down. I scored the protruding portions of the gasket so that I could line the gasket back up once the intake was off to view the alignment: Single planes are lots easier. LOL!

Here's the worst aligned ports.

IMG_0698.jpg


The ports on the head appear to be slightly larger than the ports on this intake, which is good. Obviously it could be port matched and made better, but its pretty darn close out of the box.
 
"I will say after installing the intake with this arrangement that it does require some finagling. I had to get some shorter bolts to get bolts into the four innermost holes because of interference with the runners. In fact, I had to put the passenger side rearmost of these in first because you have to tip the intake up to do it. I don't know how anyone makes it work with 3/8" bolts.

The smaller head size on the 5/16" bolts is helpful for getting these bolts down, I had no way to get a torque wrench on them. Different intakes may be easier"

ARP bolts use a 3/8" head so you can get a small wrench around them. I had to use a crows foot on my torque wrench to tighten one or two bolts but its not that bad. Plus they have a little lead on their screws to help you find the holes easier.
 
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