Well a few months ago i posted a thread on asking people what they think is going on with my motor. After i accidentally put kerosene through it,i was getting massive amounts of blow by,extreme losses of power, and more smoke than a locomotive could ever produce. So One day after biting the bullet and deciding it was time for ANOTHER motor pull, I got home from school and just started tearing into things.
So to sum it up, pulled the motor right into the first week of october. I drug the Trans Am to the backyard and put a cover over her and thats where she will sleep until after winter. The motor is know down to just the bare block in the garage. Surprisingly, the rings were completely fine. The rod bearings though were awful. The bearing on the #1 piston had a deep gouge, and the rest were just all ate away. The pistons had obvious signs of wear,you could see burn marks from the motor getting so hot. But we were measuring my piston walls and theres pretty good sized gaps. So until we take it to the machine shop,we think my pistons are aluminum and they essentially warped from the massive amounts of heat. Something got inside my motor as well which was why the bearings had some scratches. The crank is fine though,and my main bearings are surprisingly ok.
So heres the plan. The block will soon go to the machine shop for cleaning,inspection,and to have some work done. Im having it bored 30 over. Then we gotta discuss how to make our new set up we thought of work. I have the Lo5 From a roadmaster. We want to put the Iron vortec heads on it. We also just purchased a LT4 Hotcam from a member,brand new. Has 480 lift compared to the stock cam which is less than half of that. So new springs bearings etc. We going to do the whole 9 yards.Were going to get a vortec intake as well and just get a adapter plate for my throttle body. Heres the problem, my motors stock compression is 9:1. After this if we keep stock flattops ill be over 10:1. So were thinking were probably going to have to get some dished pistons. If we can get down to 10:1 id be fine with that. Also,i need a 2400 stall for the tranny so i dont blow it. Thats about all i can remember for now. Im on my phone and this is very hard to post haha. Anyone got an idea on Horsepower ratings after all of this? After some posts ive read,i might be in the 360-380 range? Im also telling santa i want a new rear end with disc brakes and 4:11 gears so we shall see!

 

Burned Piston:


Crack in a piston:


Rod Bearings badly scratched and scuffed

 

This is getting into territory i dont have much personal experience with, but I think that if the motor detonated (causes the heat you saw on the pistons) that the hammering effect it has on the rotating assembly may well have been what caused the damage on the bearings. Some of the forced induction guys may have a better idea of how realistic of an explanation that is.

Onto the L05...

1. Is it a roller motor?

2. If it is not, you need to take special steps to make the LT4 hotcam work.

3. Vortecs with flat tops is fine. I think the worst case scenario is around 10.2:1 which is cutting it close, but with the right camshaft and the right tune and keeping in mind vortecs are VERY effective at tolerating compression you're on the bubble of it actually working out. you need to calculate your dynamic compression ratio. You can at least go to a small dish. 8-10cc or so. The upper limit of DCR for 93 octane is probably around 8.25. You ideally want it right around 7.8-8.1 for a real peppy motor. Different people may tell you different and they may be more correct than me, but right around 7.5-8.25 is the range you want to shoot for, while getting it close to 8.

4. "We also just purchased a LT4 Hotcam from a member,brand new. Has 480 lift compared to the stock cam which is less than half of that. " .480 lift isnt an LT4 hotcam. With 1.5 rockers they're right around .500 lift, and with 1.6 rockers that theyre designed for they're good for .525 lift. No need for the 1.6's, especially with vortecs as they dont respond much to higher lifts than .500 or so. So is it an LT4 hotcam? Or is it something else? Stock cam is probably around .415/.430 lift at the valve, compared to .500 for the LT4 hotcam. It's not twice as big. But dont you DARE run factory valve springs with it!

5. .480+ lift is the danger zone for Vortecs. they need to have the guide machined down to provide clearance for the rocker arm at those lifts. You can get around this buy using comp 787-16 retainers and beehive springs. For an LT4 hotcam, just factory OEM LS2/LS3/LS6 yellow (or blue now) springs will be sufficient if shimmed properly for the best compromise in retainer/guide clearance and pressure. More retainer/guide clearance means taller spring installed height which means less spring pressure which can result in valve float. (Do a search on this to get the details). To prevent valve float you can shim it up for higher pressures but you risk the retainers banging on the valve guides. Both are bad situations, the latter is probably a little worse. The GM LS3 beehives should be sufficient for an LT4 hotcam, but it's on the threshold. Otherwise you can use comp 918 beehive springs. If you get the valve guides machined down, you can run MUCH cheaper conventional springs, like Comp 981's with the LT4 hotcam.

6. LT4 Hotcam + vortecs in a 350 will net you around 325-350 crank horsepower, which is good for a 12 second car with the right gearing. 360-380 is pretty optimistic for crank horsepower, but if you get everything just right the lower end of that isn't completely unreasonable, but you wont see that with a TPI or TBI setup. Remember the factory ratings are in crankshaft(flywheel) horsepower, so compare 325-350 to 215 and that's the real difference. 100-125hp improvement over stock. So dont feel like 350 is low, a lot of people chronically overestimate the power they're making. You'll smoke any guy with camelhumps, that's for sure.

7. I would also suggest you ignore the roadmaster TBI setup and get the TPI Vortec base and re-use the TPI. The LT4 hotcam is a little big for it, but you can always go to an HSR or something later. The trouble will be tuning it. Look into the moates and EBL flash setups.

8. When fine tuning the compression ratio, you want to use your piston dish to adjust it. The quench distance is very important and you want it around .040, which is very tight but increases fuel economy, performance, AND resistance to detonation. this is one of those things that if you do it "just right" gets you to those higher power ranges than you should rightfully be getting to. Make sure you get pistons with a 1.560 compression height or pin height. Avoid 1.540 pistons like the plague unless you zero decked your block, and even then 1.560 is probably better. You want to have the top of your pistons and the quench pad on the heads (See the flat part that would be above the pistons thats not in the "tub" the valves sit in? Thats teh quench pad) to be .040-.044 inches apart. This is a pretty snug distance so you want to check clearances with your valves carefully during the build. That means mock ups and play doh etc. It's a big deal, so check it, but it's worth it. The .040 quench range will get you a ton of benefits and make it less likely to blow itself up. Use the piston dish to adjust compression the direction you need.

I hope grumpyvette shows up and posts up his links. they're fantastic.

http://forum.grumpysperformance.com/...19dbf47e516b40
Look for stuff about quench distances in there

http://forum.grumpysperformance.com/...19dbf47e516b40
Look for stuff about how to set up valve springs and pushrods etc in there.

 

Thanks infernal for all the info. It is a roller block that's for sure. There's a couple of things I'm still not sure on so I'm hoping someone will be able to clear them up for me. 1. Should I buy the stock flat top pistons that it originally came with? Or should I go with the truck lo5 dished pistons? Since I'm gonna be switching to vortec heads I don't want to be over 10-1 compression thiis will be a daily driver. 2. I bought a lt4 cam with a special grind .480/.480 and it says to use only 1.5 rockers. So will I need new springs and push rods with that set up or will stock ones work? This will be my first non stock rebuild so a lot of this is new to me. Thanks for any help.

 

I dont know about this reground cam. You need to know exactly what all the measurements are on it to build a good engine. The cam is the most important part of the puzzle along with the heads. I dont know what pistons you need because I cant compute your DCR because I dont know what your cam measurements are.

 

Hey i didnt know exactly what you were looking for so i took a pic of the Sheet for ya hopefully you can find it

 

Looks like it's 204/211 duration at .050... just by eyeballing it thats too small to make 10.2:1 work. Im not smart enough to figure out form that chart what your total duration is (not duration at .050) so I cant really check it.

Are you staying TPI?

 

No i have TBI right now so we were just going to get a vortec intake with a TBI adaptor plate

 

Well.... good luck with that. TBI's seem to have a rael hard time making big power. I think it's worth trying, if a TBI system is gonna make power, doing it on Vortec heads with a lumpy roller cam is about the best shot you can give it. Just a matter of getting enough fuel and air into it.

If you're married to that cam... Its actually shorter in duration than an L98 cam, but much more lift. It's honestly a pretty good cam for someone that's trying to work around the TPI's limitations. It might even be good for working around the TBI's limitations, but it seems like everyone who gets to the limit of TBI just trashes it before even trying to make it work. Just watch your fuel pressures and make sure it doesnt go lean at high RPM's. Big injectors, etc. Gotta watch it!

That cam will be easy to tune, and make tons of vacuum, work with your stock stall converter and stock gears, all that. But what it wont do is make lots of power. It will make, at the lower limit, stock vortec L31 power, so at least 250hp, which is more than L98, provided you can fuel the thing properly. Add headers, exhaust, you may be pushing 260-270, and you'll get pretty good gas mileage while you're at it.

Like every other hot engine build decision, you have to choose between practicality and low end power( "torque" ), or trading that away for high RPM horsepower. It's not one or the other, it's a continuum. The farther towards the high RPM power you shift the engine, the more changes you will need to make throughout the car to make it work and the more stress it all goes through in operation.

If you stay with that cam, go with some dished pistons. I'd get the compression down to 9.5:1.

http://www.summitracing.com/parts/pb...make/chevrolet

These are some low budget forged pistons, the LS guys like them, they should be overkill for your situation, but will be fine when you later on decide to go to aluminum heads or something. If you get your quench distance correct (.040-.044) these will run you right around 9.55:1 compression. If you dont pay attention to quench distance and end up with pistons way in the hole with a normal head gasket (probably the most common) you'll end up with 9.0:1 compression and it will be MORE prone to pinging anyway and get worse gas mileage, make worse power, etc.

Quench is the most important part of the picture, so make it right.

When choosing a piston make sure to avoid 1.540 compression height pistons. Just dont. Get something that's 1.560, plus or minus .005 is fine and wont make much difference. Just this by itself will help your cause tremendously. Most cheap rebuilder pistons are 1.540. Performance pistons are usually around the 1.560 range.

 

So do you think I'll need the dished pistons and different push rods with this setup? I knew I'd have to install a fuel pressure regulator to up the pressure. Just still not sure about the pistons and push rods. Thanks for all your info.

 

Depends. The pushrod thing you wont know til you put it together and check it. The dished pistons... if you get the quench right and you run that cam, yes. 11-14cc of dish. 12.5 is about perfect.

Play around with the compression ratio calculators to see how things affect compression. Always double check before you buy stuff. Your piston to deck clearance will be, if the factory machined the deck perfectly (unlikely) and you arent decking the block, .025. Real world numbers vary for a million reasons, but .025 is stock piston-deck clearance with stock compression height pistons (1.560) and .045 is the clearance with cheap rebuilder pistons with a 1.540 compression height. You want .040 from the top of the pistons to the pad on the combustion chamber, so you can see if you put a typicaly .040 thick head gasket on rebuilder pistons that are .045 in the hole... you are in terrible territory as far as quench goes. If your deck is good and you dont deck it, AND you get good pistons, they're still .025 down. You wont find many .015 thick head gaskets, but you can try to get it close with a .025ish thick one. Not ideal, but better.

Remember, piston to deck clearance + head gasket thickness = quench - get it as close to .040 as you can.

 

Thanks so much for all the information it really helps out. I will post as this rebuild progresses.

 

well im to a point where im 99 percent sure im going to sell. The reason being that we took it to the machine shop and after it was checked over to see what was needed, the shop said 1200 dollars to do it. Im not going to list off what it needs because im not in the mood right now. I love my car to death, it means everything to me..But after thinking. The car has 8 grand into it and ive had it for 3 years. Ive only put 8000 miles on it and its only been functional for 6 months out of those years.Ive had this 500 dollar Marquis with 300,000 miles for 4 months,have put NO money into it,and have driven 6 thousand. So my assumption: thirdgens are all, And i mean this in the most thoughtful way, pieces of ****. I feel theres not much need to look for another motor.After thats in, then its the tranny, the rear end(Broken gear) all new tires, a new master cylinder, a new heater core, The list goes forever. SO im to a screw off point. Im 18 years old and make 120 on a paycheck. Screw this AWESOME FAST CAR SPORTS CAR YEAH thing. Sorry guys.

 

Oh screw that. After all the work you've done to it, you can't dump it now! Our cars don't suck, they're just old. And due to the nature of them being cheap sports cars, they are put through some serious hell over the years. Plus if you have another car to drive anyway, what's the rush?

 

Kind of harsh words for an older car that you put kerosene into. The engine didnt blow up because it was bad, it blew up because you put kerosene in it.

You cant blame the car for this. I dont know the details of the other stuff but any older car that you pay someone else to work on will drain you to death. if you work on it yourself you'll have a better idea of what's going on and you 'll save a ton of money.

 

AGREED.....Keep your eyes and ears open for deals as well.

I picked up a complete L31 for $275.00 recently with a small amount of coolant in the oil. Knowing these motors I took a gamble on it. Come to find out it had been rebuilt not long before, only bored .020" over, needed intake gaskets and a timing chain. It had even been run on Royal Purple and was spotless inside other than the purple staining. Put a new timing cover on it and resealed it. Its going to make a nice little engine for not much more than $350.00.