Hello, I recently did a 2000 lm7 swap mated to a th350 in my 1979 camaro.
The engine has a "sloppy stage 2" (228/230/585 trickflow) cam with pac 1218 springs, 7.5inch pushrods, 862 heads, 3.08 gears and stock converter in the th350 (for now). The rest of the engine is pretty much stock. Truck intake with a custom cold air intake using the stock MAF . I'm using the stock PCM with a reworked harness using only the sensor 1 O2's and emissions deleted. The PCM has VATS deleted and has a "tune" by a semi-local shop that the tech put in it when I brought him the PCM for programming. He said the tune should make it run enough to move it around a garage and beyond that he didn't know how it perform. I took the car for a test drive last night for the first time and found it is an absolute dog. It feels what is comparable to "limp" mode. When driving it vaguely sounds like the engine is choking itself and you can hear it through the exhaust. It doesn't sound like backfiring if that's what you're wondering. When also slowing down the RPM drops considerably to the point where it will almost stall....until I actually stop to make a turn. Then it does stall. I have to pedal it in neutral and drop the transmission into gear to get it to move because it would just stall again. I used my scan tool to check values of various sensors and readings. KOEO the throttle angle will read 0-100% fine. KOER the throttle angle will only read up to maybe 40-50% even though Im opening it WOT via the butterfly valve. I checked fuel pressure today and it sits around 50psi and when I bring the RPMs up it drops to 40-45psi. The engine runs pretty well when started and just sits there idling. If you blip the throttle it sometimes will take a second to rebalance the RPMs and catch its breath. Doesn't seem to change cold or at operating temp. But when attempting to accelerate it will just dog it out until you reach whatever speed you want. The th350 also will only let the engine shift as high as 4500 RPM. I've got a vacuum line running from the auxiliary 1/4 port on the passenger side of the intake down to the modulator. Checked vacuum at the port, and its there. Have not checked if it makes it down the line at the modulator. I used this same transmission with the old SBC and didn't have this issue. There's a lot of drivability issues as of right now so its hard to diagnose stuff. As well as there are no engine codes for me to go off of to even point me in the right direction of solving the stalling and no power issue. Someone with some wisdom on the cam swap after math on these engines would be greatly appreciated.

 

The first thing that comes to mind is fuel pressure. Unless your tuner knew it was less than stock pressure (which should be 58psi), it will not be getting enough fuel. If you are running a deadhead system it should stay at that pressure. A return system will obviously be different. I am also curious about the 7.5" pushrod length. It could very well be correct, but just based on stock 7.4" and the size of your cam I would have expected something closer to 7.45". I am not sure what you are scanning with, but could the low tps% reading during koer simply be a delay in the scanned value, since I am guessing you are not holding the throttle pegged wide open for long with it running.

 

Im using an inline fuel pump with a return setup controlled by the stock fuel rail with the built-in vacuum regulator. I went out and used a vacuum gauge on the car and it seemed to be at 10inHg at a shitty idle. I did not test the fuel pressure vacuum line, I had it on the auxiliary port and brake booster port so not sure if that's being a factor in the fuel pressure. The 7.5inch pushrod length was a bit of a tricky situation. So I first tried the stock pushrod which was from the start a no go. Way too small. I had the cam on the base circle with the rocker torqued down and was probably a quarter inch of "lash". I used a pushrod length checker from my local engine shop guy. I took it to where I was building the engine and had the tool sat at whatever length (I dont remember) and kept adjusting it until "0 lash" was found with the rocker bolt finger tight. I tightened the rocker arm down until it was lightly snug. Then it took a full turn and say maybe 5/8 of an inch for that bolt to be torqued and tight. I then took the pushrod tool back to him and he suggested the 7.5inch. It very well could be wrong tbh. I have kinda had that doubt in the back of my head for a while, but at the same time it is believable to be the right size since there was such a difference trying to use stock pushrod with the cam I chose. As for the scan tool, I thought that too so I have the option to use a waveform and I pulled that up and even it showed it was only getting to 40-50% even when I had the throttle almost wide open. You are correct though I hadn't held it open for too long since it was also not at operating temperature yet.

 

I would do a compression test on at least 1 cylinder to make sure the numbers are within a reasonable range. There is always the tiny possibility of installing a cam a tooth off, which will usually start, but not run worth a ****.

 

Okay so did a compression test and theres definitely an issue
2: 125psi
4: 125psi
6: 125psi
8: 125psi
1:125psi
3:125psi
5: 90psi
7: 10psi
So I pulled the rocker cover off, checked that all the valves on the passenger side were moving which they were. Then I pulled 5 and 7's rocker arms off and 5 went down to 60psi and 7 went up to 100psi. I don't have the stock pushrods to sub back in to see if it makes a difference, but I can get a set from a buddy mid week this week. No push rods seemed to have been bent in this process. As I did the compression test with the rockers off 5 and 7 I could hear a slow hissing sound. Not sure where it was coming from. Hopefully I did not do any internal damage because of all this

 

Compression is an issue for sure but you also have 3.08 gears and stock stall and a "Just to get it running tune" None of that is helping you either.

 

**Update**
Stock pushrod length bumped compression back up to normal. Still misfired afterwards. Diagnosed injectors #7, and 8 went bad at some point during the engine build. Put new injectors on those two cylinders and it no longer misses and runs nicely. It drives a whole lot better, but is slow imo. I'm fairly confident that the stock stall and the 3.08 gears are a huge factor right now. I have to change the stall before I take it to a shop to tuned/dynoed. I think I will leave the gears alone for now as they would still be nice for cruising, just not as quick accel.

 

FIRST, thank you for the update; everyone who has read this thread, or does so in the future, greatly appreciates it.
Since I am mostly active on the Automatic Transmission section of this forum and have read threads/questions about converters for 10+ years, let me say that buying a quality ($700+) converter gives you the best ROI of any performance upgrade.
Before I knew better, I bought a $375 TCI converter and the car was a slug in normal traffic. Switched to a $750 converter (like CircleD or other sponsors here) and it really woke the car up.

 

What makes the difference on the higher quality ones compared to lesser quality? Tighter tolerance in the "stall" rating? Where does Hughes converters stand in those quality rankings as well

 

I too always appreciate it when someone comes back with a conclusion to a problem. (Lots of dead end threads on here with no answers...)

 

Like I wrote, before I knew better, I bought a cheap TCI 3600 converter for my 4L60E. For street driving, before the engine revved to 3000+ RPM, there was little acceleration and just a lot of noise. Above the 3600 stall speed, it felt fine.
On advice here, I switched to a Yank 3600. The difference was immediate. With this converter I could accelerate briskly keeping the RPMs under 2500! Of course if I quickly went WOT, the engine would immediately rev to the 3600 stall speed.
In other words, it was much much tighter at low RPMs.
The TCI might have a higher max "torque multiplication", but it only occurs over a narrow RPM band; I prefer it over a wider RPM band.
One tell-tale on the cheap converters is their steel "ring" around the converter body. This is because they started as a low performance GM converter for 4/6 cylinder cars, were then rebuilt by TCI for a higher stall (same cheap internals) and a ring welded on so that they fit a 4L60E flexplate. One issue is they have a tiny lockup clutch which is easily burnt up by a V8 engine; the tune has to release the lockup over 30% throttle to save the clutch.
In contrast the Yank Converter is much beefier, has better and stronger internals.
I then switched to a CircleD "triple disk" (about $1500). This has a triple-disk lockup clutch which can handle WOT (or at least my 600 ft/lbs) while locked up. I believe these are made by their CNC machines and are called "billet" converters.

Here is a recent thread in the Automatic Transmission section: (There are many more)
https://ls1tech.com/forums/automatic...er-brands.html