Thread: LT intake manifold modification for distributor

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Doesn't hardly seem like this has been over a year---winters are too short--most be global warming

That is a neat mod! Can you show us the finished manifold and maybe the dist mounting piece you weld in?

I'd like to see the finished deal too. There are a lot of LT guys that would probably love to have this mod.

Just curious. Did the LT1 manifold survive the surgery???? Street rod engineering at it's best!

WoW-going on 2 years---------


Did 3 manifolds back when these pics were done-


Just last week end a guy brought in another one for me to do so after I finish up re paneling my garage door it'll be cleaning core and making chips and welding-I'll try to get pics of the finished job and some of the different dist that have been used---not a lot of room for the big cap hei like thingies

The multiple chamber openings you cut into made me wonder if this was doable. Not sure what each was other than the egr, but thought this might take multiple patch pieces to make it work. If you were able to get a clean finished look, this would be quite an impressive mod to say the least.

Or, for about $300 - http://www.summitracing.com/parts/NAL-24502592/ Seems to me that the machine shop costs would be equal to or more, but I may be wrong. Of course when you're doing the machining it's a different story, as your rates for your own work can be zilch.

Duece4------I usually get a clean, finished look to any mods I do on my stuff


Roger-------the manifold is a way to go if a person wants to just put a carb on an LT1 for some other era car, but the costs are a lot higher than the $300 ------you will need a carb, air cleaner, fuel pump and lines, regulator,etc plus of course the complete ignition system-a person going that route will be spending maybe as much as $2500?----


Now , not to say that he won't be spending $$ on this conversion, but it does allow the keeping of an excellent EFI system and basicly just getting rid of the opti. I myself never had any issues with an Opti but I want to move it out to get rid off the wires down there so I can mount the alt and a/c close to crank area-- However, on my wifes 33 I did move the engine back toward cowl for more room behind radiator and its tight where the dist goes----but the driveshaft is shorter!!!!!!!!!!!!!!!!

I have mounted both the a/c compressor and alternator down low on my engine. I can see where the opti spark dist would interfere with this. I don't think I could have found enough room for the LT1's extra length over the short water pump setup, but for some builds that require the low mounting, the reverse flow and TPI might have been worth all the manifold fab work. Going from a manifold shown in Jerry's post to a functional manifold is quite a leap to make.

Originally Posted by jerry clayton

....Now , not to say that he won't be spending $$ on this conversion, but it does allow the keeping of an excellent EFI system and basicly just getting rid of the opti. I myself never had any issues with an Opti but I want to move it out to get rid off the wires down there so I can mount the alt and a/c close to crank area-- However, on my wifes 33 I did move the engine back toward cowl for more room behind radiator and its tight where the dist goes----but the driveshaft is shorter!!!!!!!!!!!!!!!!

I'm not familiar with the opti-spark distributor system, but as I understand it inputs to the PCM for crank position (laser through disc w/360 tiny slots), and the PCM then triggers the output to the coil based on the spark map that's in the PCM, and also triggers the injector pulses based on this crank position input, right? When you make this change you'll use an electronic distributor, but what do you do for the crank position sensor? Sounds like a neat modification, and I expect I can find out about it on the hot chevy sites with a little Google mining but it's lots easier to ask the guy who's done it before.

Roger-basicly this just moves the rotor/cap part to the rear of manifold--with the later years LT there is a more modern sensor in the timing cover so that and the fact that the 1996 and up ( on all vehicles OB2) are much more advanced than the early ones-----I think that most of the problems people had with opti was self induced-washing engine with high pressure washer, etc-also there was a vent system tied into the intake manifold and air cleaner so clean dry air would circulate but when pepes put fresh cold air intakes, etc , etc they lost the oem system of the vent-then the heat/cool cycles probably created a vapor/condensation issue-------My distributor will just be a rotor/cap with the coil, timing functions still done by the PCM.
However I am doing one for a guy that is taking off a coil/plug like the new LS engines as it didn't meet expectations and he will be doing his with a FAST XT? instead of the oem-(oem is limited to 6 or 7000 rpm)


Duece, if you haven't changed the intake or exhaust its not a hot rod??????????
I believe that the LT water pump being driven from the cam is more compact than the older engines by eliminating another pulley. the issue with my install into my wifes 33 is that now that we want to add a/c, we need something on each side of the crank and to lower them (alt, a/c) enough to clear the wire terminals of the opti gets down low and close to steering stuff. I have thought abought driving alt off tail shaft but if we run air will need more amps/mile and in slow moving traffic probably wouldn't keep up. If you have looked at front of LT1 engines, keep in mind that there are different length lower pulley/dampners from various installs-vet, Camaro/firebird/buick/impala/etc

Looks like there are several LT1 intake mods going out there. Opti Spark to dist with several paths taken from plugging holes to major milling of material and adding plate along with dist mount shim being welded in. Others are modifying LT1 intake to fit SBC first gen. Wow. There are a few photos of modded intakes out there. Some are very well done; others not so much for looks but probably work fine. Neat stuff for sure!

So if I understand what you're saying, you're leaving the low voltage part of the optispark (PCM inputs) in place on the front, eliminating the cap & rotor, and installing a stand alone dizzy in the back for the HV function? I agree, most of the opti problems seemed to be self induced by power washing....

Roger-----there are several ways of triggering the ignition , it might be just with a regular dist and coil with the advance curve set from weights /springs or up to being triggered by a system like the Fast stuff where actually the spark trigger is set at quite an advance setting( 50-60*) and the system retards the spark event to the setting programmed -------The minimum required is a crank position sensor which can be a simple pick up at the dampner or flywheel. Some of ( probably all) of the latest systems have reluctor wheels on one end of the crank ( most rear counterweight) of around 50-60 notches with one unique pattern to differentiate # 1 tdc-------
On Robins car I intend to use the trigger up front and use the OB2 PCM with just CAT deletes and maybe speed density-probably what ever Corey wants to tune it to----Did I tell you that he is now working at Victor/Dana research center?


Duece-------putting one of these manifolds on the earlier engines allows a well designed EFI to be adapted to early engine however there is no thermostat housing at the front and you have to either weld some fitting bosses in place or use a fabricated piece on the front of the head as these are designed for a reverse flow coolant routing on the LTs.


And as far the appearance of the fab work-------there is a thin line to walk-------one goal is so its not ugly , another well fitted and nice professional looking work, and another---invisible to modification but maybe a slight trace of something a little different from anything the viewer has seen stock leading him to believe somethings been done----
For me-------it gets more difficult to live up to the bar that I have historily been compared to every year as I get older------but it will be good enough that I won't get docked any points at any show I might enter and may or not be pointed out in any Magazine article----

Originally Posted by jerry clayton

Roger-----there are several ways of triggering the ignition , it might be just with a regular dist and coil with the advance curve set from weights /springs or up to being triggered by a system like the Fast stuff where actually the spark trigger is set at quite an advance setting( 50-60*) and the system retards the spark event to the setting programmed -------The minimum required is a crank position sensor which can be a simple pick up at the dampner or flywheel. Some of ( probably all) of the latest systems have reluctor wheels on one end of the crank ( most rear counterweight) of around 50-60 notches with one unique pattern to differentiate # 1 tdc-------
On Robins car I intend to use the trigger up front and use the OB2 PCM with just CAT deletes and maybe speed density-probably what ever Corey wants to tune it to----Did I tell you that he is now working at Victor/Dana research center?

Thanks Jerry, I'm aware that there are lots of options for triggering the ignition, and my question was more to what's your plan, since you seemed to be glossing over that key point, but were saying that you're retaining the OEM EFI. As they say, the devil's in the details, and it sounds like the answer is that you're taking care of the distributor move and then looking to Corey for the details on what he'll need to make it work. If only we all had that Corey resource available!