TransAmTBI

bolt up to stock 305 87 and up motor with center bolt valve covers??? i thought it was bolt on but it isnt till 87 and up... I think i have to get the regular oerformer.. not the stock replacement but its still good i guess...

anyone know the difference. the one that isnt right part number from jegs is...305-7101

the one that fits is 305-2104

from summit its "edl" instead of 305


is the rpm that much better than the one i want>?

BronYrAur

iTrader: (1)

The RPM will bolt up but you have to slightly modify the bolt holes on the intake to match your heads. Do a search on it and you'll see some good thorough descriptions of what has to be done.

TransAmTBI

my search realy isnt helping to find what to do exactly.. anyone help? find me a post that has what to do to make it fit? or know off hand?

does anyone think te regular performer intake for carbs is a bad idea? is it alot worse than the RPM?

Knyghtmare

I was going to get the RPM Intake as well... I was considering the heads tho too... would that all work for my 91?

r90camarors

I was pretty sure edelbrock made a performer rpm for '87-up (center bolt) heads. Maybe you got the wrong one? Try doing a search covering every board, I know it has been described a few times. Basically, it should be just the four inner bolts that aren't lining up-you have to drill the intake holes at a different angle.
If you have the stock cam and/or heads or anything close to it, you would actually be better off going with a performer intake. You have to keep in mind that matching the power bands of the heads, cam, and intake is probably the most important part to an engine buildup performance wise. With the stock cam, an rpm would not be as benificial as a perfomer because you will lose too much low-end torque, and not gain enough in the upper rpms because the cam would be holding you back.

TransAmTBI

i would never change the intake without getting a cam first!! i got a lt1 cam ripe for installing... some people would think i was crazy for not changing the heads also but I've changed the head gackets and swore unless I was doing a engine swap I would NEVER take the heads off again! lol

I dont know if i'm cable of drilling stuff yet but i'm def not getting the stock replacement! its carb manifold or nothing! lol

I'll deal with the throttle bracket when i get to it!

thanx for the info

AJ_92RS

The manifold you have now doesn't have the correct angle on the 4 center bolts for your heads? Is that what's wrong?

So take or send it back and get the one that does.

Here's a list of the CORRECT ones.

PERFORMER

SB-Chevy 262-400 w/1987-Up Heads, non-EGR
350-2104 Manifold only --- $156.99
350-2104PK Power Package --- $538.99

SB-Chevy 262-400 w/1987-Up Heads, with EGR
350-3706 Manifold only --- $195.99

Oh wait...... I think I understand now.

You're worried that if you take the RPM back and get the Performer that you'll loose some power? You will loose anything above 5500 RPM, but don't worry about it. It's not going to be a SOTP feel.

Or..... as mentioned, you can elongate the holes on the manifold you have. It's not hard to do. You just put a drill in the hole and make this shape o
into this shape 0

Then you get some tubing (aluminum will work) that's just big enough to go over bolt, cut it at an angle on one end so it sits flat on the intake. Then put a washer in there so the tubing doesn't cut into the intake

Like this...

AJ_92RS

TransAmTBI

yeah my major concern was with part number 2104! non egr... i would lose power compared to rpm...

thats a good diagram... so the only thing I really have to do is make holes bigger then use tubing to angle bolt? I hope I can do this!

TransAmTBI

one more question.. how thick of tubing? wont it bend if I tighten it too tight? or do I not use that long of tubing?

AJ_92RS

Right. I made that pretty long just to show you what to do. It doesn't have to be that long. About 1/8" to 1/4" on the "high" side will be plenty. It's just there to help distribute the load.

And intakes are only torqued to 35 ft/lbs. You can use steel tubing if you want but it's harder to find that small.

And you don't want the holes bigger, you just want them elongated.

Find a drill bit that fits snug inside the whole. You'll have to take off more material toward the top of the hole on the intake. If there's some way for you to grind it flat (like a Dremel), you can eliminate using the tubing.

Be careful though. There isn't a lot of material toward the top of the intake mounting flange. Lay the intake on the heads and you'll see what I mean.

TransAmTBI

ok then if thats all i got to do then i'm going for it!

kdrolt

The other option is to use either beveled washers or spherical washers. The beveled washers are a pair of wedge shaped metal that allow you to bolt at a non-90 degree angle. The bevel angles are fixed though, and you need an 18 degree angle because the later manifolds take a bolt that mates with a 72-degree angle, versus the 90-degree angles from the earlier models. IOW the center-most bolts for 1987- don't go in at a 90-degree angle.

The spherical washers allow a much wider range of angles, because the mating surfaces of each pair are both spherical (one is part of a ball, the other is part of a socket).

Both of the above require less vertical space than the solution provided by AJ92RS, but both are probably more expensive than his approach. And his diagram suggests that the center bolts are vertical, and I don't think they are. My guess is that he intentionally exaggerated the angles in the diagram to get the point across. YMMV.

Both the beveled and spherical washers can be found if you go here and then search for them:

http://www.mcmaster.com

Note that the beveled washers (and not belleville which is something else) aren't listed by the angle -- so you'll have to work out the trig yourself. Or just buy the spherical ones, because they should handle 18 degrees of alignment correction with not problem. HTH.

EDIT: Apparently the vertical center bolts are needed on the Vortec (L31) heads. I hadn't realized that before. FYI.