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Hi all, My car currently has 91k miles. It is a 96 LT4. Recently the car was taken to the shop for a misfire I could not link to any of the electronics in the car. A compression and leakdown test was done on the car. Basically, the car would HIGHLY benefit from a rebuild, needs valve and piston ring job. I am 3 owner and I haven't taken it to the drag strip like the previous owner did and Im thinking maybe (like in most cases) he didnt tell me EVERYTHING he did or didnt know. Im trying to keep this short. Anyways the mechanic and his machine shop buddy gave me a quote of " expect no less than 9K from start to finish on this job". Im gullible sometimes and Ive done pretty much everything to this car except headers and tie rods and Ive never done engine work but even I knew that is an INSANE amount of money. This seems like a fun but painful job for me (a first timer) but my older brother has experience building an engine or 2 for his 1983 or 85' (correct me if wrong) Z28 Camaro. He had a rebuilt engine and car but they burned during the California fires last year, Tubbs fire. He was able to find a new one at a good price and he done work to it because he loves those cars but they still have their bugs. This would be a team effort. Im asking for any tips, tricks parts to make the most of out my rebuilding experience. The rain season is coming up and at the latest I would like this car ready before the summer. I want to add the GM LT4 Hotcam (or the kit) and maybe bigger valves. I want to get whatever horsepower I can without spending a fortune. I ruled out porting and polishing of the heads because I figured I will not be driving at high RPMs daily to get the benefit. I know I am a newbie and I want to make this as fun and educational for me as possible and as easy as I can. I know some of you seasoned vets can help me out. I want to save money and live better (like Walmart says). What are some performance parts I can add while Im there upon reassembly? Pros and Cons of each part? Where and which parts are best for me to get? Anything? I love this car and I like C5s but I love this 96 C4 and I know I can lay some hurt in the way it is right now but its time I get serious. Keep in ind I live in Commie California and everything I do, I try to do according to the books. Every mod I add, I make sure I CAN pass emissions. Plans after this hopefully, Xpipe, wheels, tune, gears (3,73). Any and all help or tips appreciated. Please feel free to include links if possible. Im 21 (I loved Corvettes since I was younger) and this is my first Corvette and I love and want it to last me a long time before I even consider selling. I got this car at a very good price and I want to enjoy this car. Cams? Valves? Valve springs? rockers? heads? general rebuild parts and tips? Im open to recommendations just keep in mind emissions for performance parts. Current mods: Borla Catback, Pace setter armor coated shorty headers, dual core radiator, MSD Coil, SLP CAI (Cutlid for emissions), TB bypass, Airfoil, drilled and slotted rotors and semi metallic pads. Otherwise stock LT4 with replaced parts and well taken care of by me. Im not trying to brag but I have taken excellent care of this car and will continue to.
Last edited by BatmobileLT4; Oct 31, 2018 at 03:19 AM.
9k is more than a basic rebuild. 9k will buy a high horsepower stroker crate engine. GS registry has information on the LT4 and its features. The LT1/LT4 max hp book would be a good reference. If this project is a not going to DIY, I would not allow engine to be disassembled to where it's not drivable. Then price shop it. Presently high horsepower 383 lt in C4 parts for sale asking 5k a considerable savings of 9k
...9k will buy a high horsepower stroker crate engine...
Can you be more specific? The only crate motor I know of that's a drop in replacement for LT1/4 is from Golen engines. They range from $6300 - $7500 and will still need Injectors, throttle body, flex plate, crank hub, ECU tune, headers, and probably an upgraded fuel pump. And it really only makes sense if doing all of this to also port the LT1 intake. My research into this was an additional $2500 in parts and diy install
It's expected some old parts would be reused. What I'm saying IMO 9k is too much for a stock rebuild of a LT4 ,even with the added expense of the hot cam kit and overbore and pistons.
Well this is a project I will be doing myself along with my brother. I know w=quite a few people who also have experience working with small block chevys and this is s still a 350 just with some variations here and there. 9K is a lot and I would not consider paying that when I could just use that money for a crate motor with trans or even towards a C5! My guess is the mechanic wants to get it back to me in the highest form he could get it to perform but even then thats just crazy. My brother has a contact for a local machine shop thats does great work at an affordable price. For me it shouldn't be too bad and I could get some other recommendations from the machinist who runs the shop. I know for damn sure that if I do this project its going to come out less than 2K and a hell of a alot less than "9K at the least". I understand its a lot of work but 9K was just an off the wall estimate for something like a rebuild with a cam and overbore. anyways Im excited for this project and I am handy and I learn quickly but for something like this I need to take my time and do it slowly. So any bit of information regarding installation of certain parts and things to watch out for and so forth are very helpful. Opti and Waterpump are new so thats out of the way. Any reason for me to upgrade to the LT4 Extreme Duty timing chain since I will be down there?
Be aware that special tools (or build your own versions of the special tools) are required to work on the LT1/LT4 engines. There is a toolset to pull the balancer. There is a toolset to service and work with the waterpump and to be able to get into the timing chain.
If you are truly serious about working on these engines, you need to take the time to read a lot on this forum. I found out about these tools from other folks here, as I get ready to tear into my engine and rebuild it.
You should also get a copy of the factory service manuals, either electronic or paper.
If you are contacted to buy an electronic version, I recommend you do so. I did and was satisfied with it. It is an exact electronic copy. I also found a paper set for a good price on Craigslist. I find I use both the electronic version and the paper versions.
First of all EVERYONE wants to spend someone else's money, ESPECIALLY MECHANICS. And in your particular case, your mechanic is telling you total bullshit. Sure you can spend $9,000, and if you can afford such a luxury, well I envy you. But with that said, lets get some real world experience from someone who's been there.
I bought a 96 six speed, LT4 car with similar mileage. I'll limit my commentary to the engine. Seemed a bit down on power, but what did I know ? never drove an LT4 before; otherwise seemed to run fine.
So how did this start?
Pulled valve covers; just for a little "lookey see" and what did I see? One rocker arm completely off the valve stem and two rocker arms partially off their respective valve stems.
OF COURSE an LT4 has a "one year only" valve train to fix a problem that never existed. Unless you want to pull (unscrew) each rocker arm mounting stud, and use conventional rocker arms and guide plates, which in retrospect would be the best way, you are stuck with the oem LT4 valve train which LOOKS like any other (Scorpion) full roller rocker arm, but believe me it A'INT and nothing interchanges. WHY? because the LT4 uses NON adjustable rocker arms mounted on a pedestal mount with 10mm mounting studs to attach the rocker arms too (not 3/8" or 7/16" studs like any other Chevy). The good news is that the base of the stud that screws into the head in the same as any other Chevy with screw in studs.
The LT4 rocker arms are "self aligning" which means there are two little discs on each side of the roller tip; and by two little, I mean TOO little, if the were slightly larger they probably would be more effective, but they aren't.
So now I'm stuck with finding three genuine LT4 rocker arms, since the locating discs on the originals had gotten beat up. I did find them at a Chevy dealer (eight years ago). Good luck finding those today, and if you do, be prepared to pay WAY more than you would for another rocker arm, that at least superficially looks just like it.
The source of all this misery was the last three lobes on the camshaft that were completely rounded off (did I mention that the engine seemed a bit down on power?) with other's starting to go, with corresponding lifter damage.
Sooo...time to swap in an LT4 Hot Cam, along with a set of LT4 matching "Hot Cam" springs and LT4 specific valve seals, the valve stem diameter is smaller and the LT4 exhaust valve seals (red) and more heat resistant than other valve seals. Yeah, I did it myself without pulling the engine.
Of course you have to remove the timing chain. One real upgrade on the LT4 engine was the use of a true roller timing chain ( not an LT1 "link and pin") chain; an oem LT4 timing chain is good, but if you can afford it, I highly recommend the LT4 "extreme Duty" timing chain; check the price difference, and you'll understand the reason I say "if you can afford it".
Removing the timing chain cover requires removing the water pump, the Opti , the balancer, and the balancer hub. And installing new water pump, opti, and crankshaft seals into the timing chain cover.
Oh, and removing the timing chain cover disturbs the pan gasket so you have to drop the pan; and who's not gonna install a new oil pump? and in my case I also rolled in new rod and main bearings.
Last but not least, and LT "improvement" that, again, fixed a problem that wasn't a problem, was the use of a oil pump stub drive to drive the oil pump off of the camshaft gear (formerly done by the rear mounted distributor), which is buried in the lifter valley. This MIGHT have been alright, except the body isn't metal, its some 25 cent word for plastic / nylon. They harden and crack with age and heat...so inspect / replace that little disaster waiting to happen, and for gods sake replace the gear on the stub drive with the one Chevy recommends for use with its camshafts...I reused the old one..."hey it looks okay" mainly because new gears weren't then available (they are now) and AGAIN that stub drive looks like it could use any Chevy distributor gear, but it can't; the shaft diameter (i.d. on the gear) is smaller than all other distributor gears.
Last but not least, at the forward end of the lifter galley is the bearing that supports the after end of the water pump drive; not many people replace these, but if the bearing wears and gets sloppy, there is no way that the oil seal in the timing chain can accommodate the extra play and will inevitably leak.
So at the end of all this, it was a lot of labor, but if you take it a step at a time, it's not overwhelming and the cost of parts, LT1 parts are expensive and LT4 parts even more so, still nothing close to $9,000. I'm old but I did everything with the car up on ramps; nothing more.
Ah, but the bottom line, my fellow Californian, with one original cat and one new cat (the matrix was completely missing from the cat on the drivers side) the car sailed through California smog without any problem. I posted my results under "LT4 Hot Cam versus California Smog, the results are in"; I don't know if its still accessible.
Good luck; but don't get suckered (brow beat) into an full engine rebuild at this point.
Last edited by mtwoolford; Nov 1, 2018 at 02:00 AM.
Oh, one other thing, if the engine isn't burning oil, and the plugs show no indication of oil contamination, your lower end is probably tight and in good shape; these engines have a pretty bullet proof piston / ring pack/ oil control system. Mine never used oil.
And if you look at the LT4 heads, especially cut aways comparing them to LT1 heads, you'll see what little gems they are, especially with sodium cooled exhaust valves.
On your mods, those headers need a CARB exemption number, otherwise you'll fail the "visual" part of the smog inspection.
And DO get the two volume Factory Service manual (this is non negotiable) along with a CD "1984 - 1996 Chevy Corvette Parts" disc; it'll give you pictures and oem part numbers for each nut, bolt, whatever in a C4...you'll need the info when you start chasing "one year only" LT4 parts.
Forget buying a special tool for the balancer hub removal; its way easier with a handful of 7/16th fine thread cap screws, if you get that far, there are plenty of threads on this subject. Just be aware that done correctly the hub slides right off; if it seems "stuck", it ain't, and trying to force it off will only ruin the hub and maybe the nose of the crank in the process. You have been warned.
Last edited by mtwoolford; Nov 1, 2018 at 01:57 AM.
First, expect ~$3-4k for a rebuild if you do it yourself and what you do.
Get yourself good measuring equipment that can go down to the tenths (0.XXXX). You need a good dial bore indicator, a good set of mic’s, and a CLEAN AREA to work in.
Machining should be ~$2500 depending on what you opt to get done. Personally with your goals, I would pick up a AL FW and new clutch. I would then have my crank balanced w/ the flywheel (balance is the key to longevity on these motors). ARP the bottom end. No need to ARP the heads. Have the heads freshened; LT4 heads flow pretty well so really just a standard cleanup on the heads to get them flat is all that’s needed. Have the shop put the cam bearings in.
Other things to jump on:
Get the steel oil pump shaft (it’s like $20)
Get the non-universal piston ring compressor (pending on what size piston you have)
Biggest thing about rebuilding the motor is take your time, measure 40 times and be thorough.
Pulled valve covers; just for a little "lookey see" and what did I see? One rocker arm completely off the valve stem and two rocker arms partially off their respective valve stems.
OF COURSE an LT4 has a "one year only" valve train to fix a problem that never existed. Unless you want to pull (unscrew) each rocker arm mounting stud, and use conventional rocker arms and guide plates, which in retrospect would be the best way, you are stuck with the oem LT4 valve train which LOOKS like any other (Scorpion) full roller rocker arm, but believe me it A'INT and nothing interchanges. WHY? because the LT4 uses NON adjustable rocker arms mounted on a pedestal mount with 10mm mounting studs to attach the rocker arms too (not 3/8" or 7/16" studs like any other Chevy). The good news is that the base of the stud that screws into the head in the same as any other Chevy with screw in studs.
The LT4 rocker arms are "self aligning" which means there are two little discs on each side of the roller tip; and by two little, I mean TOO little, if the were slightly larger they probably would be more effective, but they aren't.
So now I'm stuck with finding three genuine LT4 rocker arms, since the locating discs on the originals had gotten beat up. I did find them at a Chevy dealer (eight years ago). Good luck finding those today, and if you do, be prepared to pay WAY more than you would for another rocker arm, that at least superficially looks just like it.
.
The stock rockers are the same as Crane Cams Gold Race limited self aligning rockers. Whole set is about 350 bucks.
In regards to this rebuild... personally I'd send it to a builder who knows the engine and have them do the work. This guy charges 1500 bucks plus parts and machining. http://www.ellweinengines.com/
OEM rockers were made by Crane for Chevrolet. Designed for a unique 10mm stud using a non adjustable or torqued nut. All have been discontinued for several years. Someone disassembled both a new 3/8" and his original OEM 10mm rockers to repair a hard to locate new OEM rocker. I had and sold off a set of rockers and nuts, because I couldn't locate more than 6 studs.
Also of note, there was a recall on the stock rockers (coming apart and spewing needle bearings into your motor). You can search as to which VINs were affected. Might be a good time to consider something aftermarket.
Thank you very much all of you this information is gold!! I will be buying the service manuals. Currently I have the Chiltons and the owners manual for the car. The high horsepower lt1/lt4 engine book will be ordered as well. A couple questions, first for the balancer..I cant just go to OReilly and rent a balancer removal tool? Or are they just crappy and non compatible? Second when you guys say "ARP" you mean the brand that sells the bolts and such right? Thats what I immediately think of. Also I think some of the plugs when I last did them had some signs of oil so valve seals need to be replaced at some point. Benefits of the Extreme Timing Chain? Did Hotcam need a tune when installed? (will get a tune but I need the car drive-able so I can drive it to a tuner). Lastly, any one know where I can get an engine rebuild gasket set SPECIFICALLY for LT4? Even if the bottom end is fine, Its going to be worked on for the cam, I want that cam badly. Also if I get the Hotcam kit I believe Ive read threads where the springs are the weak point of the set. Whats are some good replacements for longevity?
Any links for parts used or that can be used on LT4s are very much appreciated if you would like to do so. My brother did recommend chagning the clutch out since we are down there but Clutch kits are expensive and the stock one is fine (at least to me) for now. Not sure if thats good thinking by me haha.
OEM rockers were made by Crane for Chevrolet. Designed for a unique 10mm stud using a non adjustable or torqued nut. All have been discontinued for several years. Someone disassembled both a new 3/8" and his original OEM 10mm rockers to repair a hard to locate new OEM rocker. I had and sold off a set of rockers and nuts, because I couldn't locate more than 6 studs.
"modified" crane rockers were used, oem part number 12557779, modified to use on the (larger) 10mm (upper part) of the rocker arms stud. 10 mm = 0.393 inch ; 3/8th inch = 0.333 inch; so stock or aftermarket rocker arms designed to fit a 3/8 inch stud won't fit on a stock LT4 head without first changing out the oem stud. sorry.
"modified" crane rockers were used, oem part number 12557779, modified to use on the (larger) 10mm (upper part) of the rocker arms stud. 10 mm = 0.393 inch ; 3/8th inch = 0.333 inch; so stock or aftermarket rocker arms designed to fit a 3/8 inch stud won't fit on a stock LT4 head without first changing out the oem stud. sorry.
Your math is bad. . . 3/8 = 0.375". You get about 0.020" more meat on the 10mm units. If you're really concerned about breaking a stud/your rocker walking around (high spring rates), just make a jump to 7/16" rockers. . . Might be tough to find some that clear the valve covers though. . .
With the rocker I believe the new arm was swapped on to the old trunion. Since I didn't do it I don't know the details. I will try to find link but it was several years ago.
Used parts...The LT4 had the best of the GEN2 parts. LT4 parts are more commonly searched for to upgrade LT1s. The GM extreme chain is price is rediculous. Cloyes manufactured it for GM I just theirs. With cam ... I believe if minimal resurfacing of heads is done. The OEM rockers and studs will still work with "Hot Cam". Other cams may require different rockers ( narrow body) studs and lock nuts. Self aligning can re-use guide plates and push rods. Non aligning will require hardened guide plates and push rods.
1996 LT4 Corvette Engine Rebuild!! TIPS/HELP!
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