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#72182 10/25/12 12:36 AM
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efi-diy Offline OP
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Ok I'm curious - most of the time I hear folks are running Holley carbs or edelbrock - why not a QJet much better for mileage..


51 GMC 4.2 turbo
Can't solved today's problems using the same technology/thinking that created them
efi-diy #72184 10/25/12 12:54 AM
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1. no good manifolds
2. no known baseline jetting - the closest engine is much hotter

panic #72210 10/27/12 10:43 AM
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without going to a pontiac ohc website, suffice to say practically all pre-smog Q-jets used ,071 primary jets and varied the metering rod size. when used on '66 chev 327s the metering rod was a .045 (.046s would have a slight stumble-factory tech bulletin--back when the factories were concerned with drivability and smoothness), 396s would use.044 rods. If you can find these rods/jets these days, the above would be a fair starting point.

If I remember correctly, the pontiac ohc sizes were not too far away-but you need to check for the pre '68 stuff . In the smog era they generally went to stranger rod/jet combos that I would'nt trust to recommend for our type of rods as they were generally quite a bit leaner due to the emissions"dangers" (kinda like Gore's "global warming"-yeah, yeah- I've seen the brown air-but are you gonna believe me, or your lying eyes?)and you dont want to have to use all the ugly heated air cleaner plumbing to make them not stumble.

I had a four bbl pontiac manifold setup once, all cast iron and was heaaavy. I found no easy way to "adapt" it to the chevy bolt pattern.

BINGO!!

- Tom Lowe, or Marc, this is the intake manifold we need cast up in aluminum for the 194/292 motors-this would end the offy/clifford squabbling forever (might be good for a carb version of the 4200 with a little plumbing work-totally diff casting).

It would have superior bottom end performance due to the Q-Jet and match any clifford at the top end-you could use cast it like clifford and use a system of carb adapters like clifford so the holley diehards could use it too, as well as an adapter for a two bbl. Maybe an adapter to add hot water carb heat plumbing to bottom of manifold (stock they followed standard inline practice of bolting the intake to the exhaust for carb heat).

There is nothing to be ashamed of, or scared of, using a Q-jet - you cant be over carbed due to the adjustable secondary air valve (well maybe on a Crosley four banger-but Doug Roe used one on a turbo'd chevette 1400 motor), and this is a 750 to 800 cfm carb.

To answer why there aint no Q-Jet manifolds-I think its too small of an interest thing, folks are too scared of Q-Jets to fork over dough for one, and cliffords were designed before Q-Jets were around so no adapters worth a ____ were possible to adapt to them.

And some folks think of 3.08s as the only way to milage.

preacher-no choir #72215 10/27/12 03:59 PM
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I agree, that's a potentially successful commercial project.
It offers small primaries for good response and mileage with a large plenum.
Of course, the big question still remains: is there enough sales volume to make money? I can't see 1,000 pieces, which is what you need to offset the staggering start-up cost. 100 pieces may run $500 each.
It's probably cheaper to use a Clifford with a 1/2" adapter plate to mod the bolt pattern, but it gives up whatever Pontiac learned that made them use that weird shape on the Sprint 4 × 1 manifold - the front and rear intake runners are very different.

panic #72218 10/27/12 09:03 PM
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The Q-jet to any clifford Or Offey intake is easy. I may even still have a few carb plates around.


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Twisted6 #72219 10/27/12 09:24 PM
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efi-diy Offline OP
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To do a full up manifold ... the design is just time so not hard to do, getting the patterns made different story.. this is at least a $2500 hit. Pulling it out of my pocket well if I had paid up orders for 40 manifolds OK then the orders would cover off the NRE/patterns/tooling.

But the manifold would still be $500 - 600 a pop (cutters/coolant, and power to run the mill is not free never mind making $3/hour) - don't think anyone would dig that deep. Now if we had a pattern maker that wanted to partake - different story.

I tried a group buy previously and it was a mess. Some folks made partial payments, some backed out and want $$ back etc..
If this was to happen another person would need to do the leg work on the GB and send in payment. It could be done with progress payments..

- design done funds paid to get the patterns made
- patterns done ready to send to the foundry - payment made to get the castings done
- castings in house ready for machining - payment to do the machining
- manifolds ready to ship - final payment.

All said and done this is >$20K hit for 40pc.

The other approach is to license the process that steedspeed uses - its patented (requires a royalty payment)and make then from billet - still need the fixtures.

How about a taller adapter that would bolt onto the existing intakes (clifford/offy)?




Last edited by efi-diy; 10/27/12 09:53 PM.

51 GMC 4.2 turbo
Can't solved today's problems using the same technology/thinking that created them
efi-diy #72220 10/27/12 09:51 PM
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I would like to try building my own intake. Lots of people do it for bent engines, inline would be easier. Make cardboard and tape pattern using the same shapes you wish to cut from sheet aluminum. cut taped corners to separate patterns, trace and cutout. Bend as needed, weld together. Finish with flanges cut from 3/8 wrought aluminum plate and some machining. Material cost less than $100, maybe free depending on what materials I have on hand.

I know easier said than done but does not seem too difficult.

strokersix #72222 10/28/12 12:19 AM
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To get some idea of the cost, sheet aluminum V8 manifolds (where all the R&D is already done) are about $2500.


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