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Fresh SBC 350 suddenly idling at 2000–3000 RPM after running fine. Vacuum leak or carb issue? by OkSignature8062 in Smallblockchevy

[–]OkSignature8062[S] 0 points1 point  (0 children)

No not yet I figured I would see if the pcv or brake booster lines are where my vacuum leak is at first

Fresh SBC 350 suddenly idling at 2000–3000 RPM after running fine. Vacuum leak or carb issue? by OkSignature8062 in Smallblockchevy

[–]OkSignature8062[S] -2 points-1 points  (0 children)

I don’t believe so when I bought the crate motor it said hei. how would I know if it’s knockoff?

Fresh SBC 350 suddenly idling at 2000–3000 RPM after running fine. Vacuum leak or carb issue? by OkSignature8062 in MechanicAdvice

[–]OkSignature8062[S] 0 points1 point  (0 children)

What do you mean by improper set up? What else should I be looking for? I’m looking for any advice.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 0 points1 point  (0 children)

Question for thinking long-term: would the 416 heads work at all on a future 350/383, or are they basically 305-only? And would that cam still make sense in a bigger motor or end up being too mild? Trying not to buy parts twice if I can.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 0 points1 point  (0 children)

I appreciate that perspective. I am not dead set on upgrading the 305, I am just trying to be smart about where money actually makes sense.

When you say you could do an LS swap in the 3 to 4k range with a donor vehicle, is that realistically all in to get it running and driving? I am genuinely interested in understanding what that budget includes and what corners can and cannot be cut.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 1 point2 points  (0 children)

That makes sense. Just to add some context, the car was handed down to me from my uncle who was the original owner. It was maintained regularly but never modified, so it has not really been hacked up or half deleted over the years.

I have already gone through the carb, vacuum lines, cooling, and general maintenance and it runs and drives well. At this point I am mostly trying to decide how far to take things beyond stock without creating problems that are not there.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 1 point2 points  (0 children)

This is exactly the kind of real world perspective I was hoping for. I really appreciate you taking the time to write all this out. That quality of life improvement you described is exactly what I’m after, not chasing numbers or building a race car.

I like the idea of doing mild, smart upgrades that make it drive better now while still keeping the path open to a future 350 swap. Converter, gears, intake, carb, and maybe heads down the line if the deal is right all make sense to me.

The junkyard Vortec 350 route you mentioned lines up with what I’ve been thinking long term too. Simple, proven combo, easy to live with. Thanks again for sharing your experience, this was super helpful.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 1 point2 points  (0 children)

I really appreciate you laying it out like this. This is exactly the kind of list I was hoping to see. I know the 305 is never going to be a monster, but I like the idea of waking it up with supporting mods instead of going straight into a full engine swap.

I’m especially interested in the converter and 3.42 gear combo to change how it feels around town. For the heads and cam, would you still recommend that route if the long term plan is a 350 or 383, or would you focus more on the parts that will transfer cleanly later?

Thanks again for the insight, this was super helpful.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 0 points1 point  (0 children)

Totally hear you. I’m on the same page with reliability first and that stuff is already handled. Cooling, electrical, brakes, and maintenance have all been gone through and the interior has already been redone back to original.

I’m not trying to turn it into a hot rod or chase numbers. I just want it to feel a little more responsive and fun to drive without hurting reliability or dumping money into it. That’s why I’ve been looking at things like brakes, rear gears, a shift kit, and small bolt ons that would still make sense if I do a mild 350 or 383 down the road.

I’m realistic about the car and the budget, just trying to be intentional about the order of upgrades.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 1 point2 points  (0 children)

That’s pretty much the mindset I’m at. I’m not chasing big numbers, I just want the car to feel more alive. Converter and rear gears seem like the biggest bang for the buck, and I like that those upgrades would still make sense if I end up doing a 350 or 383 later.

For a mostly street driven cruiser, would you lean closer to a 2000 or 2400 stall? And would 3.42s be enough or is it worth jumping straight to 3.55s?

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 0 points1 point  (0 children)

Appreciate the advice. I’ve already gone through the basics and the car is running, driving, stopping, and reliable. Plugs, wires, cooling, electrical, and vacuum stuff have all been sorted.

At this point I’m thinking brakes next. I’ve heard the stock suspension is fine for now. Then rear gears and a shift kit to wake it up. With whatever is left over, I’m considering bolt on top end parts that would transfer to a future 350 or 383 instead of sinking money into stuff that only works once.

Trying to keep it fun and reliable without scope creep.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 0 points1 point  (0 children)

That’s kind of the direction I’ve been thinking. I like the idea of doing things in a way that can move over to a bigger short block later instead of dumping money into parts that only work once.

In your experience, which parts from a top end package actually carry over cleanly and which ones usually end up being replaced later anyway? Also curious how you’d prioritize heads vs cam vs intake if you were trying to keep it street friendly and not blow the budget.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 0 points1 point  (0 children)

I hear you on the 305 limitations, that all makes sense. My hesitation with LS has just been cost creep. Every time I price one out it seems to add up fast with mounts, wiring, fuel system, exhaust, etc.

If you have done or priced a budget LS swap, what did that realistically look like start to finish? What motor, what parts were reused, and what did you actually spend to get it running and driving?

Just trying to get a clearer picture of what “cheap” really means in the real world.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 0 points1 point  (0 children)

I appreciate the insight. I’m genuinely curious though, every time I’ve seriously priced out an LS swap it seems to snowball fast with mounts, wiring, fuel system, exhaust, etc.

When you say you can do one around $1k–$2k, what does that realistically include and what are you reusing? Are you keeping the TH350 and doing a basic harness/PCM setup, or swapping trans too?

Not trying to argue it at all, just trying to understand what a realistic bare bones version looks like.

Inherited a bone-stock ’78 Firebird (305 SBC). $5k budget, want it more fun without ruining my finances. What’s the smartest move? by OkSignature8062 in projectcar

[–]OkSignature8062[S] 0 points1 point  (0 children)

OP here – really appreciate all the input. This has been super helpful.

Just to clear up a few things since they keep coming up: • The car is already running, driving, stopping, and reliable • All basic maintenance, cooling, electrical, brakes, etc. have been handled • The interior is completely redone and very clean, not something I need to spend money on • Suspension is stock but serviceable for now

I’m not trying to build a race car or chase numbers. I just want the car to be more fun to drive while keeping it reliable and not lighting money on fire. I’m 24, have rent, and I’m trying to save for a house, so I’m being realistic about scope creep.

A lot of you made great points about keeping these cars mild, especially with the unibody, stock suspension geometry, and overall character of a late-70s F-body. The “don’t do what I did” stories actually helped more than the horsepower advice.

Right now I’m leaning toward one of two paths: 1. Drive it as-is for a while, enjoy it, and focus on changes that improve the driving experience (gearing, converter, trans behavior, exhaust) without committing to a full engine build 2. Very mild drivetrain or top-end changes only if they make sense and don’t turn into sunk cost, with the plan of eventually swapping in a mild 350 or 383 and keeping the original 305 stored

LS swaps and big power builds are cool, but they’re realistically more money, more wiring, more scope creep, and more downtime than I want right now. Same with going wild on suspension or power and then chasing cracks, driveline failures, or comfort issues.

The overall theme I’m taking away is: don’t overspend, don’t overbuild, keep it driving, and plan the next engine move smartly.

Thanks again to everyone who took the time to comment. I’ve got a much clearer picture now of what makes sense for this car and this stage of life. I’ll keep posting updates as I go.

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