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J

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Discussion Starter #1
Okay, so the specs on the Edelbrock TBI intake manifold say that it won't fit the Caprice. What intake manifolds have folks gotten to work? Can the stock unit be improved?
 
T

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Discussion Starter #2
No after market manifolds fit the caprice. You can however make them fit. Heres the deal... since the distributor is tucked under the cowl in the back of the engine bay they made our intake manifolds with larger distributor holes so that you can angle them more to get them out of the engine bay. You have to bore out any new manifold that you get in order to make them fit. You can also use any manifold that ever went on a gen1 sbc for these, the ones for the older style heads will however need additional modification on top of just the distributor hole they used a different bolt angle for the manifold and you have to drill the holes at a different angle. If you choose a 4bbl manifold you will have to have an adapter plate, holley and turbocity sell them along with a few other places. Hope this helps
 
J

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Discussion Starter #3
So is there a way to mod the Edelbrock unit, or am I better getting a 4bbl manifold and making the mods?
 
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Discussion Starter #4
I'd personally go with the 4-bbl unit but I haven't ever heard anything bad about using the edelbrock tbi manifold, the only thing you'd have to do to is have the distributor hole bored out to match your stock manifold.
 
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Discussion Starter #5
Originally posted by TierAngst:
I'd personally go with the 4-bbl unit but I haven't ever heard anything bad about using the edelbrock tbi manifold, the only thing you'd have to do to is have the distributor hole bored out to match your stock manifold.
And any competent machine shop can do this? I wonder how much the charge is likely to be. Have to do some research to see what the price diff is between 4bbl intake + adapter + hogging out the hole is vs. TBI intake + hogging out the hole...
 
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Discussion Starter #6
With a bit of no how and the right tools you or a friend may be able to do this... if you don't feel comfortable with it sure any machine shop should be able to do it for you for pretty cheap.
 
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Discussion Starter #7
I put the Edelbrock TBI on my 93. Machine shop wanted $65 and a week to work the dist. opening. Car needed to get put together and since I was one of the first to use it, didn't know about the problem. To rectify it, I bought a truck dist. of the same vintage and then with the help of a friend, placed dist. in hole, then placed intake on. Dist. was about $100.00 but we got it running. Also, brake vac line needs to be fabbed because stock set up won't work. Fuel lines need to be tweaked slightly. Original brake vac port needs to be plugged which then interferes with upper rad hose. Made it work by grinding down head of brass fitting. And finally...unable to notice gains, if any. Others have theories on that. After I did mine, many recommended getting a 4bbl intake with Turbocity adapter. FWIW. Do a search on Edelbrock TBI, I did many replies about this and several very detailed ones about 6 years ago when I first did this.

Sean
 
J

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Discussion Starter #8
Is there anything reasonable that can be done with the stock TBI manifold to improve it, or is it more cost effective to mod a 4 bbl intake?
 
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Discussion Starter #9
If you decide to move to a bigger TB than you can port the stock manifold to match the size, thats the only thing I can think of that you can do to it. You actually have to do this if you go with a big enough TB, otherwise the butterflys will hit the manifold.
 
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Discussion Starter #10
Okay, but performance-wise, it's as good as it's ever going to get?
 
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Discussion Starter #11
I've never heard of spending hours of their time modifying the stock intake manifold to find out if it was worth the time or not, honestly though I'd just buy a new manifold if you want a performance manifold... if you're not that worried about it people have put some respectable numbers down with the stock manifold.
 
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Discussion Starter #12
I think that's the way I'll be going - just clean any scunge off the manifold and go with the improved fuel delivery and exhaust removal. Stock has been working, it probably won't hamstring me.

Get the improved TBI, probably use the cop injectors and improve fuel flow and let that do for the delivery side.

The exhaust and EGR will come first, though, and this'll be my project for probably some time to come.
 
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K

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Discussion Starter #14
A few comments.

I doubt the stock intake offers that much of a flow restriction for a stock LO3 or LO5. For the slightly modified LO3 and LO5 cars that I've known about, ridden in, or driven myself, it's probably still not a large restriction.

The stock factory exhaust is always the biggest restriction, followed probably by the stock mild GM cams. People that modify both also probably fail to properly retune the EPROM (chip) to cope optimally with the new mods so again the stock intake probably isn't the problem for them either.

To drive that claim home, Chris (aka Fast355 on Thirdgen.org and Fast305 on FSC.com) has used the stock TBI intake on several of his Gvan truck TBI engines that he's dyno'ed, and he's had well over 250 rwhp on each of them, and run them under 16 sec on the track in the quarter mile (5300 lb van). So using his example(s), I'd still say the stock GM TBI intake is fine. IMO money is better spent elsewhere than on a replacement TBI intake.

I know of at least one example of a ported factory GM TBI intake manifold that was used on a 91 LTZ Caprice. It was done by a neighbor on his old "winter beater".

The major mod to it was cutting out the upper part of the center divided between the L and R bores, so it had the effect of a spacer to allow both plenums drawing more fully from both bores. Two small water jacket holes had to be welded closed in this process, and the water jacket is there IMO to stabilize the intake temperature from fuel evaporative cooling and from EGR heating.

I don't know how much improvement the manifold gave by itself because the car was also treated to full N10 duals from a 96 Impala SS, a Caddy cold air sewerpipe + cone, and 1.6 stamped steel rocker arms, so the intake gains were combined with the other mods. The car did feel both quicker and faster than a stock 9C1 LO5, and the GTech reported mid 7's sec to 60 mph.

I did the exact same porting, as above, on my "spare" 91 TBI intake. I also did some mild porting on the runners especially on the lower-plane runners because they always flow less than the upper plane (based on reading in one of Vizard's book). I still have to get the water jacket holes welded closed and then the intake installed so I can't report on gains. HTH.
 
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Discussion Starter #15
Unlike the old days when factory intakes were small and restricting, the late factory aluminum carb and TBI intakes were very well designed intakes. Until you get in to serious performance, an intake swap will gain you very little, if anything.
 
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Discussion Starter #16
I gasket matched my junkyard intake. Can't say I noticed anything.
 
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