BajaIceBreaker

I'm rebuilding a blown motor and need advice on which intake to use.
First, here's some specs...
454 cid .030 over
9.25 : 1 compression
Forged dome TRW pistons
Crane Roller cam
full roller rockers
** IMPORTANT STUFF **
Canfield aluminum heads
2.25 intake 1.88 exhaust
Intake runners 310 cc 2.45 X 1.75 rectangular
Require Fel-Pro #20-1275 intake gasket
What else do need to know?

Griff

Performer Air Gap most likely would be a good choice for dual plane. If you want every bit of top end possible, then probably a Merlin single plane.

BajaIceBreaker

The Air Gap won't work. It's not designed for the large square port heads. See illustration below.

picklenjim

If you want a intake with out those holes you can get a Dart,Brodex,or Merlin in a single plane design or a Merlin Sportsman II in dual plane.Those are some pretty stout heads for a 461" motor.If you run a mechanical fuel pump be sure it's the best,highest output you can find.Otherwise you will be dropping exhaust valves on the top end.Should be running Manley Inconel exhaust.Their very expensive but the only thing that will hold up to extreme high temperatures of a hi perf marine engines.

Ghostrider

I run an Edelbrock Victor Jnr single plane and it doesn't have those holes anyway. Slightly less agressive than the merlin or dart manifolds but will let you run great up in the RPM. That's my suggestion anyway.

What is that manifold you have on it in the pic?
What are those exhaust? They look like EMI.

BajaIceBreaker

Ghostrider,

The manifolds that are on there are the original 454 Mag Intakes from Merc. They've been sand blasted and the extra holes were filled. They were supposed to be temporary, but they've been on there for 2 years.

Picklenjim,

That interresting that you said that. I'm curious... I am still running the original mechanical fuel pumps, and Holy 4150 600 cmf carbs. The heads are fitted with inconel valves, but not Manley, they are a different brand... (got a brain fart right now). Anyway, I blew an engine, snapped off an exhaust valve. I would swear it was defective, but the engine shop said that I was probably running my carbs a little lean. You think my fuel pump wasn't keeping up with the cfm?


I mean when it gave loose, everything seemed fine... 5200 RPM, Temp 150, oil press. 65 water pressure pegged over 20 lbs. waves were 2 - 4 but the drives never came out of the water, for a little over 40 minutes at WOT. All of a sudden... the valve didn't want to be there any more.

But it's not like I was beating on it.

BajaIceBreaker

I like this. But didn't know if it's right for me.


I especially like the extra bosses in the water jackets. I like the idea of running water hoses to the rear. These Mark IV's are known for running a little hotter in 7 and 8.

Griff

600cfm carbs??????

You need at least 800cfm carbs.

picklenjim

Ya,you would probably be better to go with something like the victor jr.Ghostrider was talking about or the Merlin dual plane.The dual plane would give you more low and mid range and their good to 6000 rpm which you aren't going to see anyway.I think them Merlin and Brodex single planes are for big inch motors.When I was talking about high temperatures of marine engines what I meant to say was high exhaust temperatures.MY BAD!! I did the same thing on my engine,melted the head off an exhaust valve.Looked like someone cut it off at the stem with a torch .The sad part is I did it twice before I realized it was too small of a pump.And I was only running at wot for a couple minutes.I now have a holley marine 130 gph and Inconel valves and have not had a problem.Jegs has several holley marine pumps.

BajaIceBreaker

BTW... yes.. those are EMI Revolution Marine exhaust. Amazingly light weight... WOW!!!