Runs better with vac advance unhooked (Help)

[73 C10]

I got my plug wires and threw them on with no change. I haven't had time to try them one by one yet.

I also bumped the base timing to 14*-15* BTDC (off the tab). I expect to get the centrifugal and va stuff today.

Anyone know what the desktop dyno numbers are for my set up (see signature).

 

[rich weyand]

With a stock crate engine, stock cam, 4bbl carb and headers, you ought to get about 260 HP and 350 lbft. Which isn't shabby. I mean, more is always nice, sure, but that isn't bad.

Modern camming can push those numbers up. With the 76cc stock heads and a cam change to a modern grind it is pretty easy to get about 315 HP and 385 lbft (or 275 HP and 420 lbft, at a lower (more useful) rpm -- there's a trade-off there). The higher horsepower cam requires different valve springs, the higher torque cam does not.

To go higher than that, you have to change the heads. Higher compression Vortec heads (or Dart or other hipo aftermarket heads) can go lots higher. Normally aspirated 400 hp and 500 lbft is doable. At that point you also start looking into beefing up the stock drive train so you don't punch it and leave parts on the ground.

The next step after that is to blow on it, with either a supercharger or a turbo setup. Sky's the limit there, both with hp numbers and out-of-pocket costs.

 

[73 C10]

Are there perimeter bolt vortec heads? Sorry. Stupid question. Do all vortec heads bolt up to my block? I suppose they require a different intake manifold and valve cover? Whats the best bang for the buck head replacement for more power. I want to incrementally add power over the next few years, breaking up the expense.

Any advise?

 

[rich weyand]

Other people will have more input on heads -- I'm running the stock ones.

I will advise to replace the cam at the same time. Pick the cam to go with the heads. You will be deep enough into the engine at that point that there will be less work involved than doing the jobs separately, and a cam and lifters isn't that expensive.

One fellow on another forum is running the Dart aluminum heads with a nice cam. I think the Dart heads are expensive, though, especially compared to a used set of Vortec heads. Of course the Vortec heads also require a new intake manifold, so it adds up.

Read this whole thread through. Pay attention to LTZ C20's build. That thing is a land missile. For all that, though, you can get the same peak torque low down with just a cam change. He's getting 425 lbft low down, but 360 hp up top. You can get the same 425 down low with 275 hp up top with the 12-300-4 cam and no other changes. And torque is what you drive, not horsepower. Also note that he is breaking transmissions.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=28581.0

 

[350runner]

Speaking of heads... It really depends on what you want to spend for them. Vortec are great for hp you'll have a higher revving engine. That will have better top end then your current heads. Back when I was thinking of my next carbed project my mind was set on AFR heads. But the price goes up^^^ and so does the hp

Sent from the dust in front of you!

 

[pat]

My vac advance was adding to much timing. it would get up towards high 30's. I disconnected it. Timing goes to 30 now.

 

[350runner]

My vac advance was adding to much timing. it would get up towards high 30's. I disconnected it. Timing goes to 30 now.

It just needs to be limited is all

Sent from the dust in front of you!

 

[73 C10]

I guess I want cheap fun till I ware it out. If it made sense to rebuild the engine when the time comes and reuse vortecs then maybe that. Or crate 350hp 350? I don't know how to keep the smile on my face for a few years with this truck. On the cheap. I plan to have for awhile.

 

[pat]

Carbed LS!!!

 

[350runner]

If funds were a concern I'd stick with your current block and get some vortec heads from your builder. Mine sells em rebuilt but unmodded for $150

Sent from the dust in front of you!

 

[73 C10]

I like carb'd a lot. Is an LS $$$$ or a budget alternative?

 

[73 C10]

I'm splitting my $ between 2 cars and 5 bikes, so each ones on a tight budget. I spend what I have to to keep the smile.

 

[350runner]

Here engine, trans, and computer, is not $1300. + those new engine mounts from the member here that allow you to use your current cooling setup and such your good to go

Sent from the dust in front of you!

 

[73 C10]

I been forgetting a symptom. It seems to have a odd sounding cylinder on deceleration compression. I would call it the same jug but not every cycle.

 

[350runner]

Kinda hollow sound? With a pop?

Sent from the dust in front of you!