'84 258 Intake Manifold Question - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 02-08-2010, 08:10 AM Thread Starter
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'84 258 Intake Manifold Question

Beginning the process of swapping my brothers '84 258 over to TBI (despite having the parts for over a year ).

Anyway, he had an adapter for dropping a MC2100 on it (stopped that silliness upon seeing what a HUGE difference the TBI had on mine ). Because of the adapters slotting (held the bolt heads captive) where it mated with the intake, we both assumed the intake was flanged to allow the use of bolt/nut to secure it to the manifold (was gonna use studs in the bottom of the new TB adapter dropping down thru the intake). However, looking at it clearly shows the intake actually uses blind studs to secure the carb.

Since I'll be machining the adapter from stock manifold to Rochester TB (should be MUCH better than stacking adapters... OEM to 2bbl & then to TB), I need to figure out how to mount it. While the intake bolt pattern appears to interfere with the TB's bore, that still looks like the best method (will use socket heads & hand blend the TB bores into the smaller/closer intake pattern).

So, can anyone tell me what the OEM studs (holding the carb to the intake) are size/pitch wise? Maybe the depth of these holes into the intake?

This info will negate tearing his down to pull the studs prior to machining the adapter...

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post #2 of (permalink) Old 02-08-2010, 03:16 PM
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If you are thinking of building your own check out these posts. TiminMB did a GM/Megasquirt and made his own adaptor and posted great instructions, well worth reading even if you plan to use the GM computer.

4.0HO manifold for GM TBI swap-wet flow problem - Off-Road Forums & Discussion Groups

258 Homemade Fuel Injection using Megasquirt DONE! - Off-Road Forums & Discussion Groups

Aluminum 2bbl intake modification question - Off-Road Forums & Discussion Groups

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post #3 of (permalink) Old 02-09-2010, 07:19 AM Thread Starter
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We are gonna "build our own"... well, basically just install the GM TBI with some ECM mods (ZIF socket & tuned). Did this on my 304 and it's been great!

Just need to know the stud size/pitch at the manifold

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post #4 of (permalink) Old 02-09-2010, 07:50 AM
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Quote:
Just need to know the stud size/pitch at the manifold
IIRC, Jeep Part # 070-200-2401

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post #5 of (permalink) Old 02-10-2010, 07:31 AM Thread Starter
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Quote:
Originally Posted by LEVE View Post
IIRC, Jeep Part # 070-200-2401
Thanks Larry! Are those the carb>manifold studs or manifold>head? Not a I-6 guy, but seems there would be 4 equal length studs for the carb-manifold? (unless the pic is generic?)

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post #6 of (permalink) Old 02-10-2010, 08:49 AM
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Jegs defines it as a carb stud kit... so I suspect it's a generic pict... as there's only three nuts there too...
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post #7 of (permalink) Old 02-10-2010, 12:29 PM
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When I replaced my BBD with a MC 2100 I used shorter studs. I just got standard studs from the hardware store and cut the fine thread end to the length needed. I am about 90% sure they were 3/8" diameter (if that is wrong they were 5/16"), fine thread on top and coarse on the bottom. They were definately common thread size though.

For what you are doing I would not use studs but instead use alan head bolts. Just drill a counter bore in the top of the adapter for the head and you should be good to go.

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post #8 of (permalink) Old 02-10-2010, 03:20 PM
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For what you are doing I would not use studs but instead use alan head bolts. Just drill a counter bore in the top of the adapter for the head and you should be good to go.
...Humm... About 15 years ago I tried an MC2150 on my I6. I would have had a hard time getting an allen head wrench on the bolt to tighten it. It was pretty tight as it was using an open-end wrench or a socket with a swivel.
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post #9 of (permalink) Old 02-10-2010, 03:29 PM Thread Starter
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I used socketed flatheads to secure the adapter to my V8 2bbl manifold, just not an option in this case...

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