To LT1 or Not To?

[OutlawDrifter]

Also, that RamJet cam will produce gobs of torque, great for a daily driver. That's why they use it in the RamJet 350 and "High Torque" 383.

Don't be afraid of aluminum heads, I've put 300k+ miles on aluminum headed pickups that pull trailers.

Find a good L98, swap the cam, clean it up, and call it a day. If it were me I would update the ECU at the same time to something better.

 

[ccreddell]

LT1s are fantastic motors and they fit our trucks quite well-and, its been done a few times. Heres the info;

http://www.gmtruckcentral.com/articles/lt1swap.html

 

[slowburb]

Don't be scared of a "395" cam in a daily driver that hauls or tows. I'm not, and mine is on 33's, 6" of lift, and well...4.56 gears.

 

[Brother Al]

]it seems your already convinced of what your under the impression of so nothing i say would be pertinent.

I have a foot on both sides, but YES, I am leaning towards the LT1... otherwise I wouldnt have posted this thread, and YES, I do listen to good information, when its backed up with details. Im also reasonably wary, being that all posted on the WWW is not gospel.

slp cars still had a modified TPI cross ram, or similar,

No, far from a "crossram"...The '91-'92 SLP Firehawk utilized a very unique and still coveted "SLP T-Ram". Its essentially an EFI tunnel ram w/ 11" runners, (hence T-ram name), and it was designed by Ryan Falconer... it wasnt a gimmick, made the '92/'91 Firehawk a beast that gives the 4th Gen LS1 & LS6 cars a spanking, and it even passed Federal 50-State Emissions no less.

we run aluminum heads on our gas tow rig as well, no issues.

as far as the base design sure the iron heads were "modeled" towards vortecs, in no way are they though. stock for stock sure maybe kinda similar, LT1 aluminums ported, valved and polished, no contest better. i wouldnt evne bring up the poor excuse 4.3 lt engine, i had my hand in a few of those, after snapping cranks i wont touch them again with the lack of moderate hp/tq they produced.

Sure, a lot of folks run aluminum, as do most of the automakers now, but there is a distinct reason GM and other automakers used cast iron heads on "traditional" truck engine designs... (Gen 1 and 2 SBC)... it wasnt to save money. Cast iron heads on a cast iron block equals less variables in the thermal expansion between the heads and block, which is a very good thing when hauling heavy loads up and down hills as the engine ages. The intake is much less of an issue in vehicles... until electrolysis starts eating up the water passages. Which also happens to heads in very salty areas. Which is why ships use cast iron engines... same reason... electrolysis. This is also why everyone uses EDP primers on new sheetmetal (non-aqueous electrophoretic deposition)... GM and others also used zinc-plating on nuts, bolts, and other misc bits... this is also the reason for galvanization. At sea, most ships use sacrificial Zinc plates, so electrolysis eats the zinc first, and prevents the iron/steel from disintegrating...

That said, I live in New England... Winter Salt, + Heat, + Dissimilar Metals = Big Headaches Down the Road... as seen on many newer trucks, the combo of iron and aluminum is great for seized manifold bolts, spark plugs, and other accessory woes... again, electrolysis at play... weaker metal corrodes first and the areas between dissimilar metals become a place where electrolysis is hyper-active.
Aluminum is Crap?, no, certainly not, but lets not confuse my needs with your needs.
Also, with concern for warpage, it happens on both aluminum and iron heads, but more commonly on new aluminum heads... hence the need to have them resurfaced. Being my likely desire to play with a Caprice LT1 in my K1500, Im looking at "seasoned" cast iron heads. When you build engines for play, you are not running it for 100,000 miles without tearing it apart, so again, its my needs vs yours.

That said, LT1 iron heads were NOT modeled after L31 Vortecs". Quite contrary... the initial LT1 heads were designed in the late 80's, alongside the cast iron Vortec 4.3L V6 heads. Which is also why GM used a TPI for the Gen I Vortec 4.3L...
As for the B-Body, GM needed more flow to support towing, police, and fleet/taxi duty in a car than the LO3 and LO5 could give. The L99/LT1 reverse flow system allowed for much better cooling of the heads, so the LTs can run higher compression on regular pump gas than their older SBC siblings, (including the Vortec 350). The main reason the LT1 engine development stopped was that the SBC was already up against its basic design limits vs the more stringent emissions/CAFE regulations. GM readily admitted this in the early 90's, which blew my mind because the LT engines were pretty bad ass... GM bean-counters were probably the main reason some form of the LT engines never made it into the trucks... point of cost & emissions car vs truck... this is why the LO3 and LO5 truck engines didnt even get roller valvetrains, despite the car lines switching in 1987. LO3/LO5 were about as cheap as GM could reasonably make them.

The L99 4.3 V8 (265ci chevy) is not a monster, but its better than the LO3 305 and LB4 4.3 V6 it was designed to replace in many ways, and it made more torque and horsies than the larger Three-Oh-Why.... Not sure what you mean about their cranks being junk?!!??? From what I recall, GM used the same core blank for the larger LT1... but machined it for a 3" throw, used longer rods, reused LO3 pistons. Basically they did what they shouldve done back in the early 80's, ditch the 305 and bring back the 265 SBC. Now, if you are mistaking the Pontiac 4.3L 265 V8 SBC from 1981, not sure how thats even possible... Yeah, those cranks gave in faster than Bernie Sanders at the DNC Convention... They took a Pontiac 301, cheapened it as much as possible, added an ultra-weeble-wobble crank, and cast it so hollow that you could crack the block with a good sneeze... That, however, is so very not true of the L99 "baby LT1"... It survived just fine in the majority of '94-'96 Caprices, including Taxi and Police fleets.

You keep saying that the Iron LT1's are not like the Vortec. Pre-LT1 "Swirl Ports" have mundane/traditional smogger style valve chambers and the Aluminum LT1 had a semi-similar chamber design as the L98. The iron LT1 has a very distinct, large "heart-shaped" combustion chamber w/ an unshrouded intake valve & deep runners, almost identical to the Vortec's. It is also much more meaty, so its not prone to cracking like the stock save a penny thin-cast L31 Vortec.

Sure, aluminum LT1 heads can be ported and polished to flow better than a stock cast iron set, but if one does the same to cast iron heads, they will again outflow the aluminum. The main reason people want aluminum is because A.) Aluminum is much lighter, B.) Car Magazines praised it as a "Must", C.) its far easier to massage aluminum than cast iron. D.) aluminum transfers heat readily, so you can push higher compression on pump gas without detonation...

More, since Vortec heads never existed in GM aluminum stock, it only leaves me with aftermarket Vortec aluminum, GM stock Vortecs, Bowtie Vortecs, or aftermarket Vortec cast iron.
Aftermarket aluminum; I dont have $1600 to dump into "fixing" new heads or the luxury of making a number of dyno runs to properly heat cycle these heads, yeah, no thanks... Stock Vortecs, only option is New because my experience has proven that "good" boneyard cores are always cracked between the valves... so, Im left with Bowties or aftermarket iron, which also means $$$$ and having a shop address the typical problems found on most of today's out of the box heads... rather put the money into other things.

really depends on your capability.

you say you want torque, well thats where TBI accels if you choose to undrestand how to modify it. your comparing alot of apples to oranges here, tpi is ok on these trucks, did the swap a few times, did lt1 swaps, carb swaps , ls, 8.1 etc adn tpi vs tbi in a gmt400 is a worthless debate build for build.

My capability... hmm, well, since Im building a fresh chassis from the ground up... yeah, not really out of my realm.
Understanding a TBI? Its a hunk of aluminum controlling a fuel leak, Id prefer a Qjet any day... it was GMs cheapest solution for claiming to have EFI and meeting emissions/CAFE requirements. Ive done the "Ultimate TBI Mods", several times for others, and I used a couple mods on my truck. Again, Im a 3rd Gen Guy, and have had a few TBI trucks, so there's no mysteries here. As for the "Race Car" about Carbs and EFI... No idea what you are talking about here... EFI DOMINATES all forms of racing and TBI doesnt outshine direct injection in any way, othwise everyone would be using it and Chevy would have put TBI on Vette's... oh yeah, forgot they did... the crossram-esque Crossfire 305 and 350.

i wouldnt even go through the extra wiring to put an lt1 in a truck.

once again comparing a car to a truck is apples to oranges, if you want to do it then do it but having done multiple of what your saying cannot be done, or isnt comparitive etc it is. TBI will do fine, leave it or vortec swap it or put in your lt1, put lt4 heads on it or whatever. as fara s vortec goes the spider injection was a crappy design based more so on the poppets and fuel distribution. its very reliable, not as torquey but not as bad a system as everyone thinks. the mpfi upgrade is nice, mpfi swapping is the same thing just requires a bit more aftermarket help. with your comment about how is 8 injectirs better than 2? its all about how you build it, we can go as fara s saying why isnt every racecar FI? its a stupid suggestion to think about but once again, apples to oranges, they can do the same but have different manners.

I'll start with the wiring... going from an OBD1 Caprice, Fleetwood, or Roadmaster to this truck, wiring is pretty much the same. Just a matter of sorting the differing pinouts and moving them to match in the stock GMT400.

OK, sure you can get a TBI w/ Vortec to do the same or better than a L98 or LT1. Its all relative, IF YOU put the same amount of time, money, and parts into the Vortec, L98, LT1, or a Briggs 'n Stratton.... but you see, Im not looking to spend $1600+ on Vortec heads, incl. machining down the spring guides, adding screw-in studs, porting and polishing it to perfection, and then praying they don't crack before I move on. TBI vs TPI apples to oranges is certainly true here, but Im not on a quest to make TBI be far more than it was designed to be vs what an LT1 actually was. Again, Im looking to find out what the pitfalls of the LT1 swap are, and decide if its worth my time vs building something with a TPI or maybe even say screw it and do the LS 5.3 swap...

 

[slowburb]

Build a new old school Chevy 302 with baby LT1 parts and L31 parts. Put an LT1 EFI setup on it with a ramjet cam. Done.

 

[TylerZ281500]

Build a new old school Chevy 302 with baby LT1 parts and L31 parts. Put an LT1 EFI setup on it with a ramjet cam. Done.

that was one of my favorite ideas in my head, until i did it. cranks are stupid weak on those, to allow for the RPMS that motor needed to be any what efficient or build power the crank let go. and no one makes an aftermarket crank for it. so all my machine cost was throw in the trash as well as parts cost. i wouldnt imagine the money someone would want for a nice aftermarket crank for one of those.