im getting a le2 package. also lloyd is doing some work to my lt4 intake manifold. i was wondering what is required in making the lt4 manifold fit on lt1 heads. i know you have to port match but is it the heads or the intake manifold? thanks

 

It won't. The LT4 intake runners are too large for LT1 heads, you'd have to use an LT1 intake manifold...

 

With you having a '95, chances are your LT1 intake manifold has a port shape (at the flange) that has a 'crisp' rectangular shape to it. If it does, that means that intake actually has port openings LARGER than those of the LT4 intake manifold. Of note, the later ('96 & '97) LT1 intakes had ports that more closely matched the shape of the LT1 heads thenselves (not a true rectangle), and also were virtually identical to the LT4 intake's port openings. In either case, beyoond the flange shape itself, the port orientation itself was virtually identical to that of the LT4. Unfortunately though, the LT4 intake manifold intake will NOT bolt up to LT1 heads due to interference just below the valve cover surface. This is due to the LT4 intake having additional material cast at the top (externally) of the port. This allowed the port roof to be raised without breaking through.

To maintain this extra thickness, on the LT4 manifold, and still allow it to bolt up to the LT1 heads, requires the manifold contact surface, on the heads, to be milled an additional 1/4" higher, or closer to the valve cover mounting surface, thus duplicating the machining on a LT4 head. You could also, in lieu of the head machining, remove the extra 'as cast' material, from the LT4 intake manifold itself, to get the two components to mate. This however, would render the LT4 intake manifold virtually identical, not only internally, but externall, as well. This however, would negate any justification for purchasing that manifold, in the first place.

This post stating that the ports internally, are virtually identical, obviously flies in the face of the previous post, doesn't it?

 

so what you are saying is that it cant be done?

 

hes saying it can but its a waste of time. just get a lt1 manifold and port it out

 

No, didn't state that. Certainly can be done.... and one of two ways.

As noted above, again, the following:

Machine/mill the manifold mounting surface, of the heads an additional 1/4" further up, or IOW, closer to the cover mounting surface. This is necessary to accomodate the extra external height of the LT4 manifold. If you indeed desire to assemble such a combo, this would be the preferred way of accomplishing the goal.

The other approach would be to mill off, from the LT4 manifold, the 1/4" of extra as cast material, that is on the manifold, above the port roof. This is the lone diff of this manifold, from the oem LT1 intake manifold. However, if this approach is used, realize this one lone diff will then be wiped out, and consequently the loss of the extra cast material, that would allow raising of the roof of the port, to match that of the LT4 heads. This would then render the manifold no different from the LT1.

Note: The intake ports, of the LT4 heads are raised, in comparison to LT1 heads. The ports in the LT4 manifold, as cast/purchased from GM, are NOT raised to match that of the heads. The extra material cast on the LT4 intake manifold ALLOWS anyone so inclined, to do so, on their own. This has been posted, on this forum times, too numerous to mention. Archived posts are plentiful. Knock, and it shall be opened onto you.

EDIT: When I 'dropped the ball' mostly due to frustration (in regards to continually setting the facts straight on this subject), Fred (Injuneer) at times, picked up the slack. What a guy. In my book, doesn't deserve the 'abuse' he occasionally receives. Anyway, posts by him, as well as myself can be found.