00paul

My intentions are to share from my mistakes and pain, and maybe give you all something interesting to read.

I'll start with the backstory if anyone is interested. If not interested, the noise seems to be excessive piston rock in the bore. Thanks to Mamo for the advice on how to check that. Wouldn't have started a thread without him pushing me to share.

Got an awd trailblazer for my kid hauler a couple years ago. It's got a Magnuson supercharger, unknown model, and supposedly a 402 stroker. Price seemed ok enough for what I was getting, even if was a stock long block. Cam sounds pretty gnarly, exhaust is so loud it makes babies cry (not a fan but not a deal breaker), and gets a whopping 8 mpgs. Supposedly built trans with 3k stall (seems like 3k stall driving).

At least it's quicker than my beater minivan. Runs consistent 8.0s at 87 mph in my local 1/8 (2500 ish da). Belt slips down to 3 psi on back half of the 1/8, so got some left in it if it can fix the slip. Pulls pretty hard up to 40 mph, fun daily. Had some slight motor noise at cold start, went way hot. Sounded a lot like my stock ls1 Camaro, I figured piston slap, and figured not a problem. Me and my assumptions.

Couple years in and now motor noise doesn't go away when warm. Pulled serp belt, noise still there. Unplugged each injector, noise doesn't change. I'm thinking lifter or valve spring at this point. Stethoscope didn't narrow it to one side or other, so I'm thinking lifters going in. I didn't know much about the engine internals it came with, so I could at least figure out what I bought.

Supercharger looks like it's a mp122, hits 6 psi max when driving. Block says 6.0 and is aluminum, bore is 4 inch with a tape measure, stroke is 4 inch with a tape measure. I measured the runners on the 243 heads and compared to a set of stock 243 heads I had laying around, doesn't seem ported. Weighed valves, valves weigh the same, so I'm guessing stock heads. Found some guide wear, sad day.

I don't see any damage to any parts causing my noise. Some slack in timing chain, so I figure I'll do lifters, chain, and valve springs. Didn't know about guide wear at this point yet. Pulled the cam numbers and ran thru Google. Comp cam roots lsr blower cam 239/243 .624/.624. Called a few shops and asked if the cam was any good for my build. I was told a few times to buy their cam and wasn't told why it would benefit me.

I desperately wanted this motor to be fixed cheap and fast, but realized I have no idea what parts work well together.

I have dealt with Tony Mamo for my Camaro clutch and throttle body on the tbss. He was cool enough to talk about the motor I eventually wanted to build for my Camaro. The guy spent 20 minutes talking to me about tires too. Super decent dude to deal with. I like people willing to share why I should do something, so I emailed him and asked if he was interested in help me with a basic valvetrain rebuild.

He said he was happy to help. Told me my cam was killing my mpgs and bleeding boost off. He convinced me to change cam and lifters. He seemed to really want to push aftermarket rockers. His reasoning is triple the heads service life. I'm a car mechanic (OEM stuff), really don't want to come home and wrench, so I like the added reliability, even if they are expensive.

With his advice and tips, I cc'd my heads and weighed the valves. Then I found the guide wear. Bummer. So we talked about repairing my heads vs aftermarket. When he told me I would see another 75hp and 5 mpgs, I was sold pretty quick. Who doesn't want to go faster when you were originally anticipating just a repair? So ordered mamo 227 heads and custom cam/lifters, stuff showed up in a few days, quick turn around.

Tony sends me a dial indicator bridge to measure my piston to deck height. He sent me a cool YouTube video on how to do it. Watched several times, then didn't touch it for a few days. I measured wrong when I got to it and felt pretty embarrassed when Tony told me what I did wrong. Important to pay attention. I got the measurements right. Also, I did pull numbers off the pistons, wiseco dished.

Tony suggested I measure how much piston rocks in the bore to check piston to bore health. The lowest I measured (total piston rock at Tdc) was 0.024". Most were between 0.024" and 0.031". Then I found what I'm assuming is my noise, one reads 0.071". Pretty noticeable amount of rock there.

I emailed Tony and he called me back pretty quick. He told me that the 0.024 isn't great, but 0.071 is really bad. He suggested getting block to a machine shop and have the bores measured. That was last night. I'm borrowing a dial bore gauge and gonna measure bore tonight. I hope this thing has enough left in it for just new pistons and a hone.

I'm gonna be pretty sad if I have to sleeve this block. I've wanted a sleeved 427 with ls7 heads for years for my catfish. I wanted that big na power with a stick. Now it looks like my tbss will get a 427 first. This also sucks because I now have bad a$$ cathedral heads and cam meant for a supercharged 402. Only money right?

I've been toying with snatching out my 60k mile ls1, camming it for the mp122, and throwing that in the tbss. Then I can rebuild the sleeved ls2 for the car I rarely drive now (no back seat and drive kids everyday) and take my time with it. This minivan sucks to drive everyday, barely peels out.

I'll let you all know what happens and will eventually run both at the track again.

Shout out to Tony for dealing with me while Ive got no clue what I'm doing, patient man for sure. I can't speak on how good his parts are, but I can tell you his customer service is among the best. Everytime I talk to him he is patient and makes sure I understand what we are talking about about.

Hopefully this helps someone diagnose their own motor noise or steers them to a good dude.

Sucks to order parts and later find out you need more. So what I learned from this, don't cross your fingers and hope shortblock is good, take the extra time to check it. Saves money and sanity. I'm glad I didn't just reassemble this thing just to hear that tapping again.

I suppose I ought to look at all the bearings too huh?

​

SlowTBSS

Tony is great to deal with, I have his entire top end, Mamo 235s, on my 402 in my TBSS. Hope you get everything sorted out. Look forward to some updates.

DualQuadDave

iTrader: (6)

Welcome to the club, I am an orig owner 2008 TBSS myself. I also build my own motors and have lots of experience, as well. Sounds like a fun project, the 227 heads make good power. I would not sweat the piston slap, just get another block and throw your rotating assembly in. Your pistons may be old design, some of the early strokers had poorly designed piston skirts and basically wore themselves out immediately. The newer stuff is def better. Me personally, I would ditch the blower you have and go NA. The blower will make torque, but heat sinks like crazy and is limited in ultimate power. If you want big power, do a bigger motor or go real big and do a Procharger or big Whipple. Just a thought.

A TBSS specific side note. These trucks have absolutely horrible oil pans. Basically every TBSS will spin a rod bearing at some point. Mind you, there are different fixes for the problem, but I would pull your motor and have a look at the bottom end. I bet it has a bone stock pan on it, not even a PCM pickup tube/tray. That knocking may be a rod bearing, acts like it the way you described it. Either way, I would def look.

00paul

Measured bore last night, bores are 4.031" to 4.037". Looks like I'll want another block or have this one sleeved.

I was told when I bought the car it had custom baffles welded in the oil pan, time will tell.

Tony and I talked about sleeving it to 4.125". He thinks the heads will be fine with a different cam. I do worry the supercharger is going to be a restriction on the bigger motor.

I haven't considered going na, I did think about a newer design supercharger, but that idea goes on hold with the extra money I'll be putting in the motor now.

Not sure what's going to end up being the best decision.

Sleeve it, order a different cam and run the 227 heads.

Try to find a used block and run it the way we originally planned.

I've got a 60k mile ls1 in my Camaro. I don't know if my 4 inch ls2 crank and the 227 heads will work with the ls1 or not. maybe with the crank, it's close enough in cubes to reuse my new cam and heads, and still be quicker than the old setup. The 227 heads are 64cc. Not sure if I would need pistons for the ls1 too.

I could later sleeve the ls2 for a big na motor for the Camaro, which has been a long term plan of mine for the car.

I'm going to spend some time thinking it through. Gonna be a couple weeks before I can get enough time to pull the engine out.

SlowTBSS

I would have to agree with Dave on a few points, I'd pull the motor and check the rod bearings. Also the baffles could be the Kevin Hanson baffles, they do work, however you'll want to plug the bypass on the pan, that's what cost me my engine.

Definitely think about going NA. At 400+ cubes with the 227s and a Mamo cam, I'm willing to bet you can make 600+ hp at the flywheel on motor alone. Based on my engine, anything smaller than a 2650 or a 3.0L Whipple would be too small and inefficient.