I was wondering if I could get pics or write up on how far to raise the intake runner roof on a LT4 intake? Can anybody give my an idea of the performance gain from such a mod? Would it be worth it with my setup? (see sig)

 

It would only help if your intake ports were also raised, unless I am misundetanding you. As far as how much, you just need to leave enough surface for a gasket seal. Maybe an 1/8" or so. Of course, you would need to trim the gasket.

Rich Krause

 

Do a "search" for posts by "Arnie". He has researched the LT4 intake very thoroughly, and has some definite opinions on the benefits or lack thereof. He has specifically addressed the "raised runner" aspect, which may be more chimera than fact, at least in the "stock" manifold.

 

Allen, are you refering to raising the ports to the point of having welding required? I assume so since basic porting doesnt take much technical info.

You can gain some hp by rasing the roof (straightening), but not a ton. Mabye 5-10hp on your setup....10 would be probaby be pushing it tho.

I dont have any pictures, but a few guys here have done it...hopefully they will be able to chime in. It only really involves laying some weld right above the injector bosses on the outside of the intake and grinding some inside to improve the flow path.

Jason

 

When I did my intakes I always just raised the section above the injecter opening. I went .085 on all ports and just made them semetrical(sp).

As far as raising the port to match the head there are benifits in flow but some have stated GM left it for anti revertion. we did get 16HP out of porting an LT4 intake to match the heads(308cfm@.600).

I was going to raise the intake ports on my LT4 heads 1/4 inch to get closer to a 215RR type runner but decided it would be just as easy to convert a High port head.

It can be done but it will cost for all the welding and port work.

 

The wording of your ? would suggest an extreme raising was intended. This intake has SOME advantage over the LT1 intake when raising the roof in the more traditional manner. I say some, with additional material (behind the injectors) still needed to do an effective job. As noted, this method still nets an increase for one's efforts. However, I consider a more effective (I state 'more effective' by maintaining a superior port roof approach angle in relation to head) method of raising the roof, would be to raise the entire intake, similar to what Mindgame did in HIS.....chimera ? when a gm intake was mated to a performance RR head via intake spacers. Certainly more involved than just adding a little extra material, and removing alot elsewhere. However, in it's own rite, this method becomes easier, because you raise the intake to suit whatever heads you chose to mate with, still maintaining a suitable port roof angle.

As for being more...chimera than fact, well, my reasoning is at the root of the chimera, in a way, cuz to improve on any oem intake, I go 'against the grain' by rationalizing, if any material were to be removed from anywhere, it should be from the root/base (in plenum area itself behind injectors) of the port, in lieu of port roof at the flange.

Anyway, to give you an answer, my way (or Mindgame's), the sky is the limit. The more traditional way, without additional material, a little gain will result, raising port roof at flange, enuf to mate to a gm type of LT4 heads (unraised). WITH additional material added behind injectors, which btw, is limited to the physical space needed to install/seat the injectors, actually, about the same, it will just be more worth the effort.

 

i came in a bit late on this one...
but i was just wondering if i could get you guys' thoughts on the single plane intake as opposed to the traditional lt1/lt4?
how much (if any) benefit is there by going to the single plane with 1,000 cfm tb?
accel and holley both sell setups like this and look as though they could be run on the lt1 by plugging the distributor hole..
jeremy