My 390 has around 2,500 miles on a rebuild
2291 pistons bored 30 over.
Rebuilt C8ae-h heads
Crane 901 cam
Performer intake
Headers and 2 1/2 inch duals

The guy that built my motor decked the block and the heads have been shaved a little for the rebuild.
The motor pings pretty well on anything other than 91 octane with the existing cam so I will be swapping out the cam for a 941 cam

Now finally the question!
When I swap out the cam I will be using a 428 Police Interceptor intake instead of the Performer.
The porting on the interceptor is a little larger than the C8 heads so I was wondering if I should just install the manifold and run it like it is?
Pull the heads(which I don't really want to do) and match port them to work with the intake?
Or Pull rocker assemblies, Tape everything "top of heads and valley" and match the ports with a die grinder using a vacuum and compressed air to clear the chambers?

I know the third option is risky but not sure if anyone here has ever reworked their heads while still attached to the block.
The motor is in my F-250 and the truck is used as a hauler and tow rig.
I may see a few full throttle moments at times but it won't be a race truck.
With all said does anyone think I will notice much of a difference running the heads as they are or having the intake side match ported?
Sorry about the long winded post.
Thanks, Ken

 

Do not do the third option!
Do not do the third option!
Do not do the third option!
Do not do the third option!
Do not do the third option!

There. You'll get best results by pulling the heads and matching the ports. By not having them matched, you'll get an air dam, causing all sorts of turbulence. It would be a significant restriction to airflow. If you dont feel like matching the ports, then you shouldn't even swap intakes, as there would be no benefit, and you may even be going backwards.

Edit: Oh and on the pinging problem, yeah, I'm not surprised it pings like that. I dont know what head gaskets you're currently running, but if you pull the heads, be sure to use Mr. Gasket .020" thick steel shim head gaskets when you put it back together. I know it seems counter-intuitive since they slightly increase the compression ratio, but they also reduce the quench distance a lot. This makes the motor less prone to pinging by causing combustion chamber turbulence and increasing the speed at which the mixture is burned. Be sure to check that the block and heads aren't warped though, as steel shim head gaskets are more sensitive to that.

 

That large-port intake is going to kill your low-end torque. If not kill it, it'll certainly hurt it.

The Performer RPM might be a much better choice for the 941.

But what do I know?

 

Thanks for the quick replies.

I didn't plan on number 3 unless there was a couple good responses concerning it.
There have been times that I have heard of things that didn't sound right but everyone was doing it that way so I thought I would throw the option out there.

Well, I guess I will be pulling the heads and matching up the runners.
I guess I will swap to the thinner the gaskets at the same time also.
Like you said, it doesn't sound right to run a thinner gasket but I will have to take that chance.
Anyone have a part number for the 020 gaskets?
I will do a couple searches for them
I think I will stay with the plan to run the 428 intake.
The biggest issue of pulling the heads to me is the header bolts.
I hate dealing with them but I guess I don't have much of a choice.
Will I need to pull the heads apart to do the work on them or could I just clean them with brakeclean or something befoer and after the rework?
I will do a search on that also.
Thanks for the help.
Ken

 

It would be best to pull the heads apart. I'd hate to see some grit getting stuck between the valve and the head, and get sucked in the first time you fire it up.

I wouldn't worry about the header bolts. After only 2500 miles, they should still come out easily. If you have any doubt, you can use some liquid wrench on the top ones, since the hole goes through.

Gasket number is Summit part number MRG-1132. On installation, it helps to coat them with a sealant. I like to use Permatex Copper Spray-a-Gasket. You're not taking a chance on the thinner head gaskets. It's a proven engine building principle. You increase compression while reducing pinging due to increased combustion chamber turbulence. You already have the correct pistons for it.

 

Thanks for the info.
I'm not too worried about the bolts not coming out but just reaching the lower ones with the wrenches.
I will use the spray gasket.
I think I have some in the cabinet.
I will do a search on porting to see what should be cleaned up on the heads
Thanks, Ken

 

i have found the best place to get to the bottom bolts is though the wheel well. get a long extension and you should be fine.

 

That thing should scream with that intake on it!

 

I would run the 428 over a performer or rpm anyday. Depends how much porting has been done to the intake, i wouldn't want high riser runners though.

Krewat, is this post of yours slighty ?

 

Thanks for all of the help.

I will be installing the tranny this weekend and then start on the engine in a couple weeks.
Thanks, Ken

 

No, not at all! If the guy's going to run it, more POWER to 'im! If you know what I mean

 

I would not get to excited to much about this.The police interceptor is a great manifold.As far as the port match,I ran a 61 tripower on a set of C8AE-H heads with no port match and if you look at the measurments on the heads and the ports on the intake they are really off.I had absolutly no problems with this combo,granted it may have ran better if it were port matched but I would not want to bring any more tears to those chevy guys eyes than really necessary.Right now I'm running that same intake with a set of D2 heads with no problems.I own a cast iron CJ intake and ran it for a while wjth the C8's and I thought it matched pretty good.