robertfrank

iTrader: (27)

So if you're wanting to put a carb intake on your tbi engine, here's how I did it. Tell me what you guys think. I have all the links for everything you can use in the description.

DynoDave43

iTrader: (11)

Thanks Robert.

I have a spread bore carb GMPP (12496820) intake for Vortec heads that I want to use on my 305 when I add the Vortec 059 heads to it. I was hoping there was a spread bore intake adapter that would A) position the throttle plates of the TBI unit in a way that they did not hit the carb opening of the intake, and B) did not move the TBI unit fore/aft compared to it's factory location, making throttle linkage connections more of a plug and play. I see several designs for sale on ebay, but you never know how they will fit/work. I like how thin that one is. Firebird hood clearance is very tight. I'll have to watch that trans cable adjustment.

Also good into on the EGR relocation. I had seen those adapters, but wasn't quite sure if one was needed. Looks like I better get one on order.

Schurkey

I can't watch with audio turned on. Perhaps this is answered:

Where is the brake booster vacuum supply connected?
How does the coil mount? (Does the manifold have bosses in the right place?)
Is that a negative-backpressure EGR valve?

With all the stuff in the right rear corner, there's no space for the heater-hose quick coupler as used on the pickups.

I put a GMPP manifold on my '88 K1500 after installing older-style aluminum heads. (6 bolts on each side, all at the same angle) This is the "ZZ4" intake.

Managed to use stock EGR after making an adapter plate to go on top of the adapter you have.
Coil needed a fabricated bracket because the coil mounting posts on the manifold aren't positioned right for the stock TBI coil.
Put the MAP, EGR solenoid, and the EST module in approximately the stock location, by hanging them off of one of the choke-stove mounting bolts.
Heater hose quick-coupler got crammed into the Right Rear corner just like stock, using a brass tee, a short nipple, and some creative (internal) threading. Still have decent access to the distributor hold-down bolt.
Brake booster plumbed into manifold behind throttle body, had to bend and cut the formed-steel tube then splice it back together with a short piece of vacuum hose.
The "ZZ4" manifold positions the TBI about 1/8 inches up, and about 1/8--1/4 inch forward using a thin steel adapter plate like you have (but suitable for the spread-bore carb flange on the manifold.) Throttle and cruise cables worked fine. Had to readjust the trans TV cable.
Your manifold and mine both have the correct threaded boss beside the TBI throttle lever, to attach the alternator-to-manifold brace.
Your manifold (I think) and mine have the thermostat housing in the correct location to attach the belt-tensioner-to-manifold brace.
Neither your manifold nor mine have a suitable boss to attach the A/C compressor brace to the manifold. I still need to weld something up.

Those 3 braces are used on the C/K pickups and maybe Suburbans/Tahoes/Blazers; the accessory mounting may be different on the cars.

Schurkey

The throttle/cruise/TV cable bracket for TBI is hung off the rear two intake manifold bolts on the 6-bolt intake manifold flange. The Vortec intake flange is completely different. The bolts are spaced differently, and they go in at a different angle. You'll have to adapt/fabricate something to hold those cables at the LR of the engine.

Won't help. EGR is handled entirely differently on the Vortec manifold because there's no exhaust gas crossover in the heads.
You'll have to pull exhaust gas for EGR from the L exhaust manifold using an external, metal tube and fittings just like GM did. After you get exhaust gas to the manifold, you may/may not need additional adapters to fit the EGR valve. I don't know.

The fast, simple, easy way around all that fabricating is to NOT use Vortec or Vortec-style heads. Use the aluminum TBI heads sold by Summit. Then the stock TBI intake with all the TBI-correct parts drops right on and fits like it was made to. If you use the stock TBI manifold, you need to use stock TBI intake gaskets, that have the restricted water passage at the back.

If I didn't already have the aluminum heads and ZZ4 intake, that's what I'd have done. It's probably what I should have done, despite already having heads and manifold sitting on the shelf.

https://www.summitracing.com/parts/sum-162108

dmccain

iTrader: (2)

I played the easier route and went with F-body L98 heads, bored stock intake and bored TBI. Works really well, pulls pretty strong. I wanted Vortec heads at first but in the end I just wanted to keep it simple.

robertfrank

iTrader: (27)

There's a vacuum port right behind the throttle body for the brake booster.

The coIl bolts into the same place as stock but i do need to modify the coil bracket itself on the rear for it to fully bolt on..

There's two coolant ports on the front of the intake that can be used for the heater core. I just got a 5/8×3/4 elbow and modified the stock heater hose to work. I should've mentioned that in the video in hindsight

DynoDave43

iTrader: (11)

Well this thread is sure going to come in handy, no doubt. Sort of makes me want to trade for a Chevy II with a straight 6, but we'll get there.

With all of the variations and permutations in SBC intake design, I was sure there would be some issues. I was particularly concerned about accessory bolt holes. I don't mind having to fabricate a bracket or two. I plan to take some very detailed measurement and photos to try and get things back to a position as close to original as possible.

There is a TBI adapter that I saw that had slotted holes for the manifold bolts. I'm not sure if that would be of value or not. I wasn't in love with it.

As for the height, I'm anxious to measure this GMPP intake against the factory TBI intake. Maybe I'll post a plan view if that intake and see if you guys can help me account for what on that intake. EDIT: Done. New there is HERE.

Yes, I'm aware of the Vortec tube that feeds exhaust gases to the intake. I have two of these engines in trucks. I'm not entirely sure if I'm keeping EGR and AIR. I'd like to, but it adds a number of messy complications. In both cases, headers aggravate the situation. But there are always workarounds. none will be painless I'm afraid.

As for the adapter, the EGR still mounts in the same bit of real-estate I believe, so have this adapter to relocate it a bit may prove to be handy. With all of the supply delays, and parts being discontinued, my inclination was to acquire one of these adapters now, while I have the option to do so. If I don't use it, it can always be sold later.

Those are interesting. Probably not the right answer for me, but it would certainly be nice to lose a little weight off the front of the car. Tempting in that respect. But if I'm spending $1100 for heads, I'll make the jump to a 350. Everything for my engine has been acquired with very minimal funds (for better or worse). Along with that, many of the Summit speed parts are made in China, which is a non-starter for me. They are also 62cc instead of 58cc for the L30 Vortecs, which is a compression drop I don't need. And they have 2.02 intakes, which can be sketchy on clearance for a 305 without block work, and they still remain more shrouded than the Vortec valves will be.

I'm admittedly not an expert in this area. There are quite a few details in those photos that are quite interesting. Still learning. I appreciate all the feedback.

Schurkey

Drop a level across the throttle body flange, measure each end down to the China Rail. The front measurement is likely to be less than the rear measurement. Compare to the stock TBI manifold.

I was surprised how close the ZZ manifold was to the TBI. If it wasn't for the thin steel adapter plate, the height of the throttle body would be almost identical.


Better be sure the bolt pattern/gasket shape is compatible.

The Summit heads I listed are made by Trick Flow (Summit owns TF) in the USA. I won't promise where the valves or other hardware included with the heads, are made.

DynoDave43

iTrader: (11)

Thanks again for the detailed reply Schurkey! And the photo. While we don't have the same casting number, I hope mine proves to be as low as your (but it's not).

Yes, I did that per the Edelbrock description.






I bought this intake based on everything I had read about it. Not the best way to do things, but I tried to do my homework.

PACE posted this GMPP drawing...



...but they took the somewhat unusual approach of measuring from the intake bolt hole center-line to the carb pad. Can't really compare that with Edelbrock, and not an easy measurement to take accurately at home on the bench.

Doing my best to keep the level balanced, a paint stick across the bottom of the intake to give me a flat "shelf", and using a stainless ruler off that shelf up to the level, I came up with 3.875" front, and 5.313" rear. Using Edelbrock's "add those two numbers and divide by two for carb pad height" I come up with 4.594".

Members have posted that an Edelbrock Performer will fit under the hood of a T/A. The Vortec Performer 2116 has a front number of 3.87", a rear of 5.28" for a calculated pad height of 4.57".

So if I'm right, this GMPP manifold will come very close to working. My plan is to create an insurance policy for clearance to the hood by A) using a Corvette drop-base air cleaner lower (based on a recommendation here on TGO), modified to accept a Rochester TBI, and B) have a friend with a Bridgeport mill off the top of the carb pad down to be flush with the runners at the front. If it's not the right tool for the job, I'll find a machine shop that can do that for me. It's not much material, and there's plenty of material thickness and bolt hole depth to take that thin amount off. I'm hoping that helps give me the space to run a thin adapter. Unfortunately it's not quite as much material as the shadow in this image makes it look like, but I'll take whatever I can get.



That's my concern with that design...that in sliding it back and forth, that part of those slots would leave an opening that would be a vacuum leak. It "should" be sealed all around to the interior of where those bolts are, but it's just another variable to think about.

I think I had heard that the Trick Flow were Summit owned, and USA made. Didn't know these were Trick Flow made. They certainly look good. Now that I go back and look at the Summit ad, there is a modestly sized little Made in the USA logo in the upper right corner. I know it's just about impossible to avoid the CCP entirely, but I sure try to when I can.