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I just built my first engine, a pretty radical chevy 350 and bought a cam that specifically said that it was the biggest cam you could run with a stock converter. Its 274/274 duration and .450/.450 lift. https://www.summitracing.com/parts/sum-k00172/overview/ link to the cam. I finished the truck up had it running just fine and everything. Perfect oil pressure, didn’t run very hot or anything. Revs really quick and responds well. However, the first time i took it down the road, it felt like it just didn’t want to do anything at all. pedal to the floor and it just barely accelerates. Once i got up to a certain speed it felt like it really picked up, but I didn’t push it too far because i thought something was wrong. Turned around and tried driving up a slightly steep driveway and it eventually just sat there. pedal to the floor and running but wouldnt move at all. The engine just wouldn’t rev at all beyond a certain point with that uphill load on it. I towed it to the top of the hill and checked tranny fluid etc… seemed fine. Keep in mind this is an engine that should have more than enough power, 9.5:1 compression, flat top pistons, aluminum 202 heads etc… I’m thinking maybe the rear end in it combined with the beefy cam is probably throwing off my torque converter and I need a higher stall and a rear end more along the lines of a 3.73 or so. The truck is a 79 chevy c10 was originally a diesel so i believe the rear end is a 2.73 and i know this is extremely high for a hot rod. My question is should i start with a different rear end or buy a new higher stall converter? or is there something I’m missing. Attached are files of it sitting still and one of me taking off in it with the pedal to the floor.
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Did you remember to upgrade your fuel system to be able to support the increase in fuel consumption?
It has an edelbrock 650 mechanical choke. And an aftermarket performance fuel pump. Can’t remember the exact specs but i remember making sure it had a decent fuel flow. The only thing fuel wise I can think of is if maybe I have a vacuum leak somewhere or if the secondary metering rod springs need to be changed since it’s such a lopey cam.
Just making sure it wasn’t overlooked.
Id lean more towards the converter.
The way you make it sound is the engine is performing well but while driving it can’t put out the power.
To me if it is putting out the power but isn’t making it to the wheels you have slippage somewhere so I wouldn’t blame the diff, it could rob power, it not be able to handle it but your explanation sounds like a lot more power than that is being lost.
I was thinking as such. I just wanted some more experienced opinions. Get some ideas. I’m really having a tough time figuring out where i should go next. This project was a build my dad and I have been slowly buying parts for over 4 years. His health has been much worse over these years and I have to keep a budget in mind. I wqnt to get as much information as i can before i spend money on it. And as i said his health is so bad he can’t really get out to help me figure it out himself. I appreciate qny knowledge or advice you guys give. I’m open to all ideas.
Its as if something is bogging the engine down and not letting rpms go up. It’s not like a slipping problem where you give it more rpm and nothing happens. Its you hold it to the floor and its almost as if the truck is trying to pull out in 3rd gear.
To be honest most Ive seen from differentials is whining from dirty gear oil or just plain torn up.
I think it’d be better to check the basics
You may have upgraded the fuel system and everything works well on neutral but tape the fuel pressure gauge to your windshield and see what it does under load.You could also try shifting the transmission manually into each gear and see if you get any specific problems out of certain gears.
For the torque converter same thing a lot of the time they make sounds when going out.Other than that vacuum leaks could cause this because pressure and best changes openings under load so it might not be noticeable at idle.
Other than that I’d be looking at diagnosing the clutches in the automatic transmission, but I’m no transmission expert so take it with a grain of salt.
I’ll check the fuel pressure as soon as i can. And the transmission was behind a chevy 350 beforehand, a different block that was mildly built. The transmission did awesome beforehand the fluid never smelled burnt or looked bad, the guy i bought the truck from said it was recently rebuilt. You could feel the 2.73 rear end being a problem but for the most part the transmission was strong. However, the truck sat with no engine in it for quite some time and i feel like theres a chance the torque converter couldve been slightly out enough to leak tranny fluid or something. My gut tells me that the vacuum might be an issue. Beforehand with the previous engine, the vacuum modulator line was hooked up to the front of the carb rather than in the intake manifold. I hooked it up to the manifold this time and plugged the one on the carb.
Follow your gut, I’m willing to bet it’s either vacuum or fuel.
Seems you’ve already reasonably rules out transmission problems.Make sure the fuel pump rod isn’t completely wasted and short stroking your fuel pump, if you have a mechanical pump on it still.
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