I just bought an 87 ta which has a 305 carved with the following mods: 059 Vortec heads, comp cams 258 cam ( I think that’s what it was I don’t have the paper with specs right in front of me, ) Edelbrock manifold and carb, hedman headers. Guess I’m just not sure about how much more power those heads would give me over stock? What kind of power should I be expecting once dialed in. I figure stock is about 165 hp so something like 240 maybe? Being conservative

 

~270-280 hp at the crank. The Marine 305 Vortec with dished pistons and a 196/206 @ 0.050 cam makes 260 hp crank and that is net rated with marine log manifolds, accessories and restrictive marine flame arrestor in place. Your engine should do better with its headers, larger 206/212 @ 0.050 cam, and flat top pistons provided the rings are still sealing well.

 

Pffft... Those numbers are underrated.

Whatever happened to actually putting an engine or car on a dyno, or taking the car to the track to actually gauge the performance instead of trying to make some educated guess? I can appreciate what you're trying to do, but do these threads ever really reach any kind of logical conclusion? You could factor everything under the sun, and ultimately you're still just guessing.

It'll probably pull like 450hp because the 267cu in. V8 in my 1980 Malibu was rated at 88hp, I think, but the 305s were underrated on account of how they were going to use them in the 1983 ZR1 F150 Corvette, and GM wanted everyone to think the 350 used in 1982 was stronger because collector edition, and you can't have a 305 competing with the Corvette. It's only logical.

 

lol @ Drew

He makes ALOTTA really good points in there. Above all about the factor. While it's REEEEEEEEEEEL EEEEEEEEEEEEEEZY to say "numbers don't lie", it's also REEEEEEEEEEEEEEEL EEEEEEEEEEEEEEEZY to "create" them (aka fabricate, pluck out of the Millenium Year Application Software System - YOU work out the acronym - , make up, consult astrologers, etc.) and tell people "my car makes xxx HP" even though it runs 15.9 @ 81 mph in the 1320. Or WORSE YET, "interpret" them. Which with dyno numbers, is DEATH to anything resembling reality.

That said, assuming there are no hidden bottlenecks elsewhere in your car (LG4 or L03 Y-pipes for example) and GOOD TUNING which is by no means an automatic given, I'd give it about 250 at the crank. "Fast" 's 275ish would apply with a better cam. For example, one 305 I know of put 237 HP to the wheels, in California emissions trim; but it had better heads, a better cam, better air cleaner, carefully optimized timing curve, a number of emissions-transparent modifications to the Q-Jet, and better headers. Probably 285 - 290 at the crank (5-speed car). OTOH I knew more about the parts than the brand ("Edelbrock"... covers a MULTITUDE of sins) and I consider myself an accomplished carb tuner, from experience garnered over the 30 or so years prior to the dyno test way back when (those numbers were from 15 yrs ago or more, maybe 20). If your carb is the Edelbrock branded Carter AVS you won't make the full ability of the rest of the motor. Also the cam you have will force the motor to peter out at around 4800 RPM, even if the rest of the motor (heads, intake, exhaust, carb, air cleaner, …) is capable of more. It's simply not designed to go over that. And since HP = torque x RPM x 2 x pi ÷ 33000 (2 x pi ÷ 33000 is usually abbreviated as 5252.11, I'll let you non-physicists out there figure out how & why for the moment), it's not hard to see that if you're RPM limited, that puts a MAJOR constraint on "max HP". Remember, that equation uses torque AT THAT RPM, not just some random "peak torque"; meaning, HP at 4000 RPM is related by the equation to torque at 4000 RPM, HP at 4500 RPM is related by the equation to torque at 4500 RPM, and so on. If your motor makes no torque at some arbitrarily high RPM, it will make no HP either.

Regardless, WITH GOOD TUNING, your combo should run just fine, and might well surprise a few folks. Don't be as worried about "dyno numbers" as you are about RESULTS. Meaning, the Fun Factor.

 

While the Comp 258 cam is small it is still bigger than the 260 hp marine 305 cam as I pointed out above. I will stand with my 270-280 HP estimate. It will definately be well above the 250 hp mark. The 305 Vortec heads flow alot better than any stock GM 305 head prior to them.

 

Well, ya know, track times will tell. Then, it'll be eeeeezy. We can predict the past. Ya never know until ya KNOW.

Predicting is hard, especially about the future.

 

We can't assume the engine was in as good health as it was when it left the factory. Just because it has Vortec heads and a cam doesn't mean the pistons aren't dished, the rings aren't worn, the cylinders aren't worn, etc. You can't just say 'these heads are good for 80hp over stock, and this cam is good for 15hp". There are variables and intangibles that make any guess as plausible as another. The only way to REALLY know is to measure exactly what you've got.

If I had a quarter for every thread I've read on here where someone had a list of mods and a wicked slow time slip from the drag strip, or dyno, I could eat like a king off the value menu. Unfortunately the reality is that a lot of people 'figure' they're building XXXhp, only to find out the real result falls short of their expectation. Heads and a cam on a given displacement engine doesn't ensure a specific result.

 

Always fun to bring a new toy home. My suggestion is take it to the drag strip, get some numbers, and have a lot of fun doing it. Drive it for a bit and get familiar with the car. And then decide how you want it to change. Make mods, go to drag strip, get new numbers, have fun, repeat!