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Corvette
C4 Forum
1988 Convertible for sunny day drives
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<blockquote data-quote="Tourmax" data-source="post: 175997" data-attributes="member: 5304"><p>Alrighty. since the LT1 intake is mainly just cutting and welding, I'm going to start on that first. A couple side by side pics:</p><p></p><p>[ATTACH=full]31277[/ATTACH]</p><p></p><p>[ATTACH=full]31278[/ATTACH]</p><p></p><p>So, things that need to be done:</p><p></p><p>1. Modify the rear of the LT1 for ;</p><p>a. Distributor hole</p><p>b. Shave off/alter the EGR bosses for space to fit the HEI distributor</p><p>2. Coolant crossover and thermostat housing needed</p><p>3. bolt holes to be moved/altered</p><p>4. TB mounting to be altered</p><p>5. Throttle and TV cables to be sorted and mounted</p><p>6. Fuel lines</p><p>7. Adjustable Fuel pressure regulator.</p><p>8. LT1 TB linkage to be sorted/altered</p><p>9. TPS to be sorted (LT1 is different than the L98)</p><p></p><p>First of all, let me say I'm not reinventing the wheel here. LT1 swaps on to an L98 has been done for more than a decade now and been accomplished many different ways. Essentially, you're making your own mini-ram" manifold. The TPiS mini-ram is rumored to have been made as a copy of the LT1 intake and released a few months before the LT1 came out.</p><p></p><p>1. a. Distributor hole:</p><p></p><p>Couple options here. You can cut the distributor hole and install an angled spacer with hold down bolt, or you can cut the whole back of the manifold off and weld on the L98 rear, or you can cut out just the dist hole from an old TPI manifold and weld that in:</p><p></p><p>[ATTACH=full]31279[/ATTACH]</p><p></p><p>[ATTACH=full]31280[/ATTACH]</p><p></p><p>[ATTACH=full]31287[/ATTACH]</p><p></p><p></p><p></p><p>I'm leaning towards doing either the whole rear of the manifold or cutting out the dist hole and welding it into the LT1 intake. Using the whole back of hte TPI manifold keeps the Distributor in the correct location, it moves the proper holes for mounting to the LT1 intake and ensures enough "meat" to cover over the 113 head cooling passage. Whichever way I go, the manifold will have to be bolted into a steel jig to keep the warping to a minimum. Aluminum will move like crazy when you weld it if not bolted firmly into a jig. Even then, I'll probably still have to have the sealing surfaces trued up after welding. Still thinking about if I want to do that myself or send it out.</p><p></p><p>1b. Shave EGR.</p><p></p><p>Well, no emissions testing here so I can "file 13" the EGR if I want. But, I'd like to keep it. The Maritimes experiences "smog" from the US (we're been called the US east cost's tialpipe) and I'd like to emit as few NOx particles as I can. EGR also helps with preventing knock and improving MPG. It's off at idle and WOT, so it has no effect ofn HP, like a lot of people thinks. The problem is the large cap HEI distributor won't clear the LT1 EGR bosses. Typically, most just shave the EGR right off:</p><p></p><p>[ATTACH=full]31288[/ATTACH]</p><p></p><p>[ATTACH=full]31289[/ATTACH]</p><p></p><p>[ATTACH=full]31290[/ATTACH]</p><p></p><p>That leaves plenty of room for the large cap HEI:</p><p></p><p>[ATTACH=full]31293[/ATTACH]</p><p></p><p>Unfortunately, EGR is essentially deleted. You can get away with teh smaller GM cap distributor and the remote col, but you still can't use the EGR valve due to clearance issues.</p><p></p><p>But, once upon a time, GM actually made a few design prototypes that used the LT1 intake on distributor engines:</p><p></p><p>[ATTACH=full]31291[/ATTACH]</p><p></p><p>[ATTACH=full]31292[/ATTACH]</p><p></p><p>Now, these are ultra rare and finding one is......well, impossible. I'm betting it was for the marine division to use the LT1 in a boat application, but the LSx (marine) probably put a stop to that design line. But the design is what interests me. The egr Bosses are well out of the way of a distributor and it's nearly the same EG "in" port as the L98 with 113 heads. When I chop off the bosses, I'm going to look at welding the manifold back up with the EGR bosses like the GM prototype and try to retain EGR. If I can't, I'll go to a cam like the LT4 specs, where EGR is a function of the cam's overlap and reversion of EG into the combustion chamber. The LT4 has no EGR valve because it manages it through the cam design.</p><p></p><p>2. Coolant passage crossover/Thermostat housing.</p><p></p><p>the LT1 intake is "dry". Meaning, no coolant passages and therefor, not thermostat housing. The LT1 has the housing built into the water pump. The usual fix for this is swap in a couple fittings in the head passages (front or rear), a couple hoses and a remote thermostat housing:</p><p></p><p>[ATTACH=full]31294[/ATTACH]</p><p></p><p>It may work, but man that just looks sooooo janky! I don't like stuff that looks tacked on or rigged up and that just won't work for me. It may be functional, but it would drive me crazy knowing that was under the hood like that. High probability of it coing loose and contacting the serptine belt system as well. So I'm going to look at chopping up the front of the LT1 intake and adding the coolant passages with the thermostat housing. Here's an image where someone took one of those prototype LT1 intakes and added a passage and thermostat housing:</p><p></p><p>[ATTACH=full]31295[/ATTACH]</p><p></p><p>As you can tell, it's been pretty extensively reworked but it looks a lot better than that remote housing "zap strapped" to the engine.</p><p></p><p>3. Intake bolt holes.</p><p></p><p>The LT1 has the "new" bolt hole angles. Meaning, they enter the head at a 72 degree angle as opposed to the SBC/113 heads which enter the heads at a 90 degree angle to the gasket surface. In welding on the front and rear of the TPI lower manifold, that means those 8 holes will already be changed to the proper 113 intake bolt angles. The center 4 bolts (two per side) are easily re-drilled. The center holes are also in the wrong place for the SBC/113 heads. That's an easy fix; weld 'em up and re-drill them in the correct spot.</p><p></p><p>4. TB relocation.</p><p></p><p>As you can see in the comparison pics at the top, the LT1 TB flange is more forward and lower than the L98 TPI plenum mount. That's a problem for adding the thermostat housing, it moves the throttle body into conflict with some of the accessory bracket and being too low causes another problem:</p><p></p><p>[ATTACH=full]31298[/ATTACH]</p><p></p><p>[ATTACH=full]31299[/ATTACH]</p><p>'</p><p>You can see the Vette MAF ducting has to be pretty "cranked" to mate the stock LT1 TB location to the MAF ducting. And, while the slightly forward location of the LT1 TB compared to the TPI might not seem like an issue (because the ribbed duct can be compressed slightly), it also means the throttle cable is too short. but more importantly, the 700r4 V cable is no longer going to fit properly. So the TB has to move up and back on the LT1 intake.</p><p></p><p>Luckily, the guy with the prototype LT1 intake has also shown that it can be moved:</p><p></p><p>[ATTACH=full]31297[/ATTACH]</p><p></p><p>Cut, reposition and weld. Easy peasy. You loose a little plenum volume, but it still dwarf's the L98 plenum volume. I've got a possible plan in mind to add plenum volume as well, so it should come out bigger (or about even) than the stock LT1.</p><p></p><p>5. Throttle and TV cables to be sorted and mounted</p><p></p><p>Most of that will be fixed with moving the TB mount on the plenum, but I will still have to measure and mount the TPI cable bracket to maintain the proper alignment. Critically important for the TV valve to not burn up the 700r4. The LT1 throttle body also has the wrong bracket on it to take the L98 cables. That will be a simple swap from an old TPI TB to the LT1 TB from AS&M.</p><p></p><p>6. Fuel lines</p><p></p><p>Obviously, the LT1 lines are not compatible with the L98 lines. The LT1 is on the drivers side rear and the L98 is the passenger side front. You can buy kits that fix this, but I may just build my own and change it to a parallel fuel rail at the same time.</p><p></p><p>7. Adjustable Fuel pressure regulator.</p><p></p><p>Yep, need one. If I plumb my own lines, adding one is easy and I can mount it wherever I want.</p><p></p><p>8. LT1 TB linkage to be sorted/altered</p><p></p><p>Talked about it in #7. Bascially, swap the brackets from the L98 TB to the LT1 TB.</p><p></p><p>9. TPS to be sorted (LT1 is different than the L98)</p><p></p><p>So, the LT1 TPS is different thant the TPI. Different mounting on the TB, different electrical connector. Luckily, the LT1 TPS puts out the same signal as the TPI TPS, so it's just a matter of swapping out the TPI connector for the LT1 connector.</p><p></p><p>There's a bunch oif little things to be addressed like vaccum ports, PCV setups and that sort of stuff, but it's small little bits that is usually easily handled by welding up some ohomes and drilling/tapping new ones.</p><p></p><p>Well, that's enough talking about it. Time to start cutting stuff up!</p><p></p><p><img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink ;)" loading="lazy" data-shortname=";)" /></p></blockquote><p></p>
[QUOTE="Tourmax, post: 175997, member: 5304"] Alrighty. since the LT1 intake is mainly just cutting and welding, I'm going to start on that first. A couple side by side pics: [ATTACH type="full" alt="fr_4146_size880.jpg"]31277[/ATTACH] [ATTACH type="full" alt="fr_4145_size880.jpg"]31278[/ATTACH] So, things that need to be done: 1. Modify the rear of the LT1 for ; a. Distributor hole b. Shave off/alter the EGR bosses for space to fit the HEI distributor 2. Coolant crossover and thermostat housing needed 3. bolt holes to be moved/altered 4. TB mounting to be altered 5. Throttle and TV cables to be sorted and mounted 6. Fuel lines 7. Adjustable Fuel pressure regulator. 8. LT1 TB linkage to be sorted/altered 9. TPS to be sorted (LT1 is different than the L98) First of all, let me say I'm not reinventing the wheel here. LT1 swaps on to an L98 has been done for more than a decade now and been accomplished many different ways. Essentially, you're making your own mini-ram" manifold. The TPiS mini-ram is rumored to have been made as a copy of the LT1 intake and released a few months before the LT1 came out. 1. a. Distributor hole: Couple options here. You can cut the distributor hole and install an angled spacer with hold down bolt, or you can cut the whole back of the manifold off and weld on the L98 rear, or you can cut out just the dist hole from an old TPI manifold and weld that in: [ATTACH type="full" alt="100_0298.jpg"]31279[/ATTACH] [ATTACH type="full" alt="LT1 intake distributor conversion pics 11-29-2012 001 large.jpg"]31280[/ATTACH] [ATTACH type="full" alt="CIMG2940.jpg"]31287[/ATTACH] I'm leaning towards doing either the whole rear of the manifold or cutting out the dist hole and welding it into the LT1 intake. Using the whole back of hte TPI manifold keeps the Distributor in the correct location, it moves the proper holes for mounting to the LT1 intake and ensures enough "meat" to cover over the 113 head cooling passage. Whichever way I go, the manifold will have to be bolted into a steel jig to keep the warping to a minimum. Aluminum will move like crazy when you weld it if not bolted firmly into a jig. Even then, I'll probably still have to have the sealing surfaces trued up after welding. Still thinking about if I want to do that myself or send it out. 1b. Shave EGR. Well, no emissions testing here so I can "file 13" the EGR if I want. But, I'd like to keep it. The Maritimes experiences "smog" from the US (we're been called the US east cost's tialpipe) and I'd like to emit as few NOx particles as I can. EGR also helps with preventing knock and improving MPG. It's off at idle and WOT, so it has no effect ofn HP, like a lot of people thinks. The problem is the large cap HEI distributor won't clear the LT1 EGR bosses. Typically, most just shave the EGR right off: [ATTACH type="full" alt="IMG_0155.jpg"]31288[/ATTACH] [ATTACH type="full" alt="mvc-250s.jpg"]31289[/ATTACH] [ATTACH type="full" alt="mvc-252s.jpg"]31290[/ATTACH] That leaves plenty of room for the large cap HEI: [ATTACH type="full" alt="126_2678.JPG"]31293[/ATTACH] Unfortunately, EGR is essentially deleted. You can get away with teh smaller GM cap distributor and the remote col, but you still can't use the EGR valve due to clearance issues. But, once upon a time, GM actually made a few design prototypes that used the LT1 intake on distributor engines: [ATTACH type="full" alt="mvc-00a1s.jpg"]31291[/ATTACH] [ATTACH type="full" alt="mini2.jpg"]31292[/ATTACH] Now, these are ultra rare and finding one is......well, impossible. I'm betting it was for the marine division to use the LT1 in a boat application, but the LSx (marine) probably put a stop to that design line. But the design is what interests me. The egr Bosses are well out of the way of a distributor and it's nearly the same EG "in" port as the L98 with 113 heads. When I chop off the bosses, I'm going to look at welding the manifold back up with the EGR bosses like the GM prototype and try to retain EGR. If I can't, I'll go to a cam like the LT4 specs, where EGR is a function of the cam's overlap and reversion of EG into the combustion chamber. The LT4 has no EGR valve because it manages it through the cam design. 2. Coolant passage crossover/Thermostat housing. the LT1 intake is "dry". Meaning, no coolant passages and therefor, not thermostat housing. The LT1 has the housing built into the water pump. The usual fix for this is swap in a couple fittings in the head passages (front or rear), a couple hoses and a remote thermostat housing: [ATTACH type="full" alt="126_2674.JPG"]31294[/ATTACH] It may work, but man that just looks sooooo janky! I don't like stuff that looks tacked on or rigged up and that just won't work for me. It may be functional, but it would drive me crazy knowing that was under the hood like that. High probability of it coing loose and contacting the serptine belt system as well. So I'm going to look at chopping up the front of the LT1 intake and adding the coolant passages with the thermostat housing. Here's an image where someone took one of those prototype LT1 intakes and added a passage and thermostat housing: [ATTACH type="full" alt="mvc-001s.jpg"]31295[/ATTACH] As you can tell, it's been pretty extensively reworked but it looks a lot better than that remote housing "zap strapped" to the engine. 3. Intake bolt holes. The LT1 has the "new" bolt hole angles. Meaning, they enter the head at a 72 degree angle as opposed to the SBC/113 heads which enter the heads at a 90 degree angle to the gasket surface. In welding on the front and rear of the TPI lower manifold, that means those 8 holes will already be changed to the proper 113 intake bolt angles. The center 4 bolts (two per side) are easily re-drilled. The center holes are also in the wrong place for the SBC/113 heads. That's an easy fix; weld 'em up and re-drill them in the correct spot. 4. TB relocation. As you can see in the comparison pics at the top, the LT1 TB flange is more forward and lower than the L98 TPI plenum mount. That's a problem for adding the thermostat housing, it moves the throttle body into conflict with some of the accessory bracket and being too low causes another problem: [ATTACH type="full" alt="photo (1).JPG"]31298[/ATTACH] [ATTACH type="full" alt="photo.JPG"]31299[/ATTACH] ' You can see the Vette MAF ducting has to be pretty "cranked" to mate the stock LT1 TB location to the MAF ducting. And, while the slightly forward location of the LT1 TB compared to the TPI might not seem like an issue (because the ribbed duct can be compressed slightly), it also means the throttle cable is too short. but more importantly, the 700r4 V cable is no longer going to fit properly. So the TB has to move up and back on the LT1 intake. Luckily, the guy with the prototype LT1 intake has also shown that it can be moved: [ATTACH type="full" alt="mvc-001f.jpg"]31297[/ATTACH] Cut, reposition and weld. Easy peasy. You loose a little plenum volume, but it still dwarf's the L98 plenum volume. I've got a possible plan in mind to add plenum volume as well, so it should come out bigger (or about even) than the stock LT1. 5. Throttle and TV cables to be sorted and mounted Most of that will be fixed with moving the TB mount on the plenum, but I will still have to measure and mount the TPI cable bracket to maintain the proper alignment. Critically important for the TV valve to not burn up the 700r4. The LT1 throttle body also has the wrong bracket on it to take the L98 cables. That will be a simple swap from an old TPI TB to the LT1 TB from AS&M. 6. Fuel lines Obviously, the LT1 lines are not compatible with the L98 lines. The LT1 is on the drivers side rear and the L98 is the passenger side front. You can buy kits that fix this, but I may just build my own and change it to a parallel fuel rail at the same time. 7. Adjustable Fuel pressure regulator. Yep, need one. If I plumb my own lines, adding one is easy and I can mount it wherever I want. 8. LT1 TB linkage to be sorted/altered Talked about it in #7. Bascially, swap the brackets from the L98 TB to the LT1 TB. 9. TPS to be sorted (LT1 is different than the L98) So, the LT1 TPS is different thant the TPI. Different mounting on the TB, different electrical connector. Luckily, the LT1 TPS puts out the same signal as the TPI TPS, so it's just a matter of swapping out the TPI connector for the LT1 connector. There's a bunch oif little things to be addressed like vaccum ports, PCV setups and that sort of stuff, but it's small little bits that is usually easily handled by welding up some ohomes and drilling/tapping new ones. Well, that's enough talking about it. Time to start cutting stuff up! ;) [/QUOTE]
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