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RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 12903-K
For some reason this .pdf was very difficult to find. Couldn't find it on RHS or FAST websites. It will help you find part #'s like fuel rails & injectors, size/thread of coolant passages needed for plugs or elbows, etc.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Greetings! Currently, I have an Edelbrock low profile elbow, part #3848, mounted to this RHS intake, part #12903. I just received a 90mm LS style throttle body which has 4 mounting bolt holes. The problem is the top 2 TB holes line up with the elbow, but the bottom 2 holes are millimeters apart. Any suggestions? I sorta just want to see if a local machine shop can 'slot' the bottom 2 hole on the TB. But why do I have this situation in the first place? Here's a general layout:
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
2 pics of the mismatch of the bottom 2 TB holes to the elbow. Which one is out of spec??? Elbow or TB? I want to order the Edelbrock gasket and find out, but I know I'm not the only one that's seen this.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Originally Posted by UltRoadWarrior9
Greetings! Currently, I have an Edelbrock low profile elbow, part #3848, mounted to this RHS intake, part #12903. I just received a 90mm LS style throttle body which has 4 mounting bolt holes. The problem is the top 2 TB holes line up with the elbow, but the bottom 2 holes are millimeters apart. Any suggestions? I sorta just want to see if a local machine shop can 'slot' the bottom 2 hole on the TB. But why do I have this situation in the first place? Here's a general layout:
I had to slot the holes on the TB. I also ran a 3848 and 95mm LS2 throttle body (cable driven)
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
So I machined the TB to fit the elbow with some careful grinding...
Today I got in (8) 42lb EV1 injectors. I suspected there was going to be an issue as the 12903 injector holes are machined to 15mm and the o-rings on the top and bottom of the injectors I got are spec'd @ 14.5mm. Is there a quick fix like oversize viton seals?
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
I ordered some larger viton o-rings from McMaster Carr. They are 1/8" thick, 3/8"ID 5/8"OD or .139", .359"ID .637"OD. I measured the injector diameter where the lower o-ring goes @ .321"....
However I got impatient this morning and came up with a possible better solution: tin foil o-ring shims. I previously was tinkering with electrical tape and magnetic wire. I was unsuccessful with the wire and the tape will not hold up over time with the engine heat. I think the heavy duty tin foil will be a great option to the over size o-ring.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Originally Posted by anesthes
So I meaured the injector holes on my Miniram and my HSR and I got 13.6mm on both..
-- Joe
Thanks for measuring your intakes Joe. That at least gives us an idea for about .9mm wider o-ring than the injector hole for proper fitment...
In my experimentation today I was working with .03mm thick tin foil and folded it about 16x for a measured .45-.46mm thickness. So total almost 1mm, since it's wrapped around the base of the injector. Long story short, I measured all my o-rings after mounting the shims on the injectors @15.3mm and it seemed a 'snug' fit into the RHS EFI intake. I'm confident that heat from a running engine will expand the injector and tin foil shims to make a tighter seal. I'll add just abit of RTV around the foil during final install in order to be leak-proof.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
This is getting interesting now...
Just got in the FAST Fuel Rails and brackets. Brackets too high as seen in the last pic. Would be a perfect fit if the hole/thread for the FR brackets were level with the injector bosses. Will take to a machine shop tomorrow to see how much it costs to shave off the metal and drill/tap some holes for these brackets.
The good news is the fuel rails do fit nice under the elbow, plenty of clearance. I was sorta worried about that.
Last edited by UltRoadWarrior9; 02-16-2016 at 06:23 PM.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
2 updates:
1) Found a local machine shop that would machine down the Fuel Rail stud mounts equal to the top of the injector bosses. Also, they'll drill and tap the holes necessary for proper stud mounting.
2) Received the over sized viton o-rings from McMaster-Carr. I tried 1 of them on an injector without one of my tin foil shims. Although the o-ring was a tight fit in the injector hole, the injector could be freely spun meaning a potential air leak. I put back the foil shim and oversized o-ring and it was a much tighter fit so I'm going with that setup.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Last update for awhile. Need to pay off the bills and start saving for the $2K AFR heads...
Here's some pics after getting back the intake from the machine shop. Cost me $125 to have the 4 fuel rail mounting posts milled down, drilled and tapped.
So far total I have invested in quite a bit of hardware on this RHS EFI intake:
$162 RHS single plane EFI intake manifold (preproduction bargain on ebay?)
$172 FAST billet fuel rail kit w/mounting hardware
$100 EV1 style 42lb/hr fuel injectors
$125 machine shop service to correctly mount above
$130 for low profile Edelbrock elbow
$85 90mm LS style TB
$70 for TB and IAC sensor/solenoid + connectors (98 5.7L Camaro parts)
$16 for 2x SAE-8 to AN-8 fittings (will need 2 more + crossover fuel rail + miscellaneous stuff to adapt to stock)
$12 TB gasket
$30 miscellaneous hardware: TB studs/nuts, elbow bolts/washers, coolant elbow, coolant plugs.
One side of my brain is trying to ignore the cost and justify the spending. The other side is lifting another beer to my mouth right now... Cheers!
Here's some pics for anyone wanting to go down my path.
Last edited by UltRoadWarrior9; 02-25-2016 at 07:51 PM.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Here's another .pdf I searched out regarding the Edelbrock low profile elbow I'm using, part #3848. I didn't receive the installation sheet when I got the 3848 from JC Whitney.
Originally Posted by anesthes
I had to slot the holes on the TB. I also ran a 3848 and 95mm LS2 throttle body (cable driven)
-- Joe
What accelerator/trans kickdown cable(s) did you use and did you use the bracket that came with the 3848?
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Originally Posted by UltRoadWarrior9
Here's another .pdf I searched out regarding the Edelbrock low profile elbow I'm using, part #3848. I didn't receive the installation sheet when I got the 3848 from JC Whitney.
What accelerator/trans kickdown cable(s) did you use and did you use the bracket that came with the 3848?
I used a throttle cable for a '98 Camaro. The bracket I used came with the 3848. I had to bend my pedal arm a hair to take up a little slack in the cable.
At the time, I had a manual transmission and didn't use a kickdown cable.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Originally Posted by articwhiteZ
fast make the spacers to use the short injectors....
Ah, very nice setup you have there. Thanks for posting! I wish I would've known about those short spacers, would've saved me $90. The FAST website is difficult to navigate. I can't navigate to those spacers, but I do see them when I search for the part #...
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Originally Posted by UltRoadWarrior9
Ah, very nice setup you have there. Thanks for posting! I wish I would've known about those short spacers, would've saved me $90. The FAST website is difficult to navigate. I can't navigate to those spacers, but I do see them when I search for the part #...
I'm curious what your injector holes measure?
I would have to take a look..but the info link you have posted list it. page 6. 15mm
this intake came from RHS as a wana try it price $150 polished..
and all the fast parts came to $150also a deal from fast to work with the intake.
this was almost a year ago..
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Originally Posted by articwhiteZ
I would have to take a look..but the info link you have posted list it. page 6. 15mm...
Yeah I guess I'm just wondering what they were thinking with a 15mm injector hole? Weld-in FI bungs? Why?
Anyway, regarding your guys' engine builds: What are you planning as far as compression, cylinder head manufacturer/part and cam spec's? Looks like you got a nitrous plate sandwiched in there? heh
I'm thinking 11:1, AFR 195 or 210, and XFI292 for my build. On the edge of streetable...
Last edited by UltRoadWarrior9; 02-26-2016 at 06:52 PM.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
this one right now with 72cc heads is at 11.2 to 1. with mls gaskets. NOS. yes 2 plates Dual stage.. heads AFR 220 with 1.6 cc rollers cam mech roller. 252@50. 620 lift.
in a Dart Block. 427cid. just a nice street eng. with a 4000 stall and trans brake. 28x13.5 tires with 4.11 locker...nothing over the top
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
You should ride with the V-8 twin turbo guys here, save $$. 1200WHP....
But I always liked sleepers. I'd sacrifice some HP for a quiet NOS spiked ride. I've started in the right direction with forged Scat bottom end. But I'm not starting there as I need to learn tuning with the original ecm first.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Having a problem locating a throttle/accelerator cable for a 4th gen camaro (98-2002), LS style.
Also, the elbow has to point forward. I did some preliminary measurements with my 2" cowl hood. It might barely fit with the 3848 pointing forward, not sideways like I was originally thinking in the earlier pics I posted.
The throttle and trans kickdown cable issue may become a issue. I can fab my own brackets, but I'm not even sure if the original 1986 cables can reach the elbow.
I've time to work this issue out, but any input is much appreciated!
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Did you ever get the single-plane EFI setup working? I'm trying to convert to single plane and the TV cable setup for 700r4 is proving to be a bit of an issue. Looks like the LS cable throttle body on that elbow would work?
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
Originally Posted by ChevelleFan
Did you ever get the single-plane EFI setup working? I'm trying to convert to single plane and the TV cable setup for 700r4 is proving to be a bit of an issue. Looks like the LS cable throttle body on that elbow would work?
-Dave
Anesthes (Joe) said a throttle cable from a 98 Camaro would work on a post above. Sorta hard to find, but last I looked Classic Industries had them in stock for around $35.
The TV cable for our TH700R4's is gonna be an issue, unless someone else can make a suggestion...
Although I'm closer to the finish of the 383 engine build, I'm still ways off from swapping it into the IROC.
Last edited by UltRoadWarrior9; 09-17-2016 at 05:02 PM.
Re: RHS® 23° Small Block Chevy Single Plane Intake Manifold 12902, 12902P, 12903, 129
I used the factory TPI throttle cable/TV kickdown bracket on my singleplane conversion and it ended up working perfect. If I remember correctly.....I put the bracket in a vice to get the 90* bend on the bottom and drilled a hole in it and bolted a short piece of flat steel with a hole in the end to bolt onto the throttle body stud. When I got rid of the Extreme Velocity elbow and put a regular carb style air filter on it I had the bracket trimmed to fit under the air cleaner base along with a spacer under the base. I also have a 4 inch cowl hood on the car.
Last edited by crackitoff; 11-03-2016 at 05:13 PM.
02-10-2016, 05:08 PM
