305 performance?
 

Hi, I´m in the process of dropping a 305 LG4 out of a 1985 Camaro into a 1974 Firebird(originally equipped with a 250L6). The 305 I´ve got has about 100k miles and still runs great. Still, i will be replacing the timing chain and gears and the valve seals while the engine is out.

I´ll be using Summit G9001 full length headers (1 5/8 primaries), a Edelbrock Performer Intake and a Holley 600 cfm carb with vacuum secondaries. I also have a HEI distributor with a Accel SuperCoil.

Is this a good combo? I know the 305 wont make killer power, but since it has 9.5 compression from the factory, I guess it could take a bigger cam.

I´ve read several posts about using a cam like Edelbrocks Performer (204/214) or similar with an engine like this. Since this wont be a daily driver, I was thinking about using a Crane 274H06 cam (218/218, .450/.450 @ .050). Is this too much? Any other suggestions? Maybe down the road I´ll swap this engine for a .040 350 with Vortecs I´m building, but that will not be soon.

BTW, the engine will be backed by 700r4 and maybe, if needed, a S10 torque converter I have.

Re: 305 performance?
 

The 204 cam, or the Summit equivalent, is definitely the better choice, along with the S10 TC.
Any idea what rear gearing is in the 1974?

Re: 305 performance?
 

I'd pull a plug and confirm you have flat top pistons over dished to verify that comp ratio.

Re: 305 performance?
 

I used a k1103 Summit cam, a good intake and 650 Holley in an Lg4 once and it ran fine. I should have put a torque converter and gears in it would have done much better still it put the 87 Formula in the upper 14s. IIRC Lg4 had dish pistons but I have heard the 87s had flat tops. My 87 Formula had an 86 engine transplanted in it before I got it and im pretty sure it had dish pistons.

Re: 305 performance?
 

Thanks!, As far as I know it has a 3.08 non-posi, but I´ll be installing a posi with 3.90 gears before the car is drivable.

Re: 305 performance?
 

Thanks for the tip, went out and checked, and it has dished pistons :( .

I was under the impression all 85 LG4s had flat tops too.

Re: 305 performance?
 

How much did you rev that engine? Any idea what gears you had in the Formula? Was it too sluggish in low end? MPGs? Sorry for asking too much questions.

Re: 305 performance?
 

5500 RPM. I may have been over-revving it a bit.Best I could tell it had 273s 0r 308s. 16-17mpg. My stock Lb9 auto was a touch stronger actually. With gears and torque converter I think it would have made mid or maybe lower14s on a good day. Best time was 14.88

Re: 305 performance?
 

Pull the heads and shave them .030

Re: 305 performance?
 

Sounds like a fun cruiser! I´ll most likely install the 3.90s in the back so I hope it has some punch to it.

Re: 305 performance?
 

To raise compression? Maybe I could do that, I really don´t want to open the engine, save for the cam install, but it that would give me a little more power maybe I could.

Re: 305 performance?
 

Heres some info for you on cams in that range ....an accidental lower compression build by car craft - they chose the wrong pistons but ran with it ,,,you have a full point more compression - so you should be better but theirs is a 350 ,, 8.4 :1 350 cid /350 iron heads -3 summit cams - 304 hp 343 tq / .

"We flipped through our latest Summit Racing catalog and checked out the company’s line of in-house grinds. Skipping the first three weak-suck profiles, we found

SUM-K1103, a cam with 214/224 degrees of duration at 0.050-inch lift, intake/exhaust lifts of 0.442/0.465 inch, and a lobe separation angle of 112 degrees.

SUM-K1104? 224/224 .465 That’s got 10 degrees more intake duration and a 0.465-inch intake lift; the exhaust profile is the same, so it’s a single-pattern cam. Sounds better, but wait! There’s also

SUM-K1105, 224 /234 a bigger split-pattern ’stick with a hearty 224/234 degrees of duration at 0.050 and 0.465/0.488 lift. That sounds aggressive without being too radical. Since they all cost the same $79.95, why not get a little more bang for the buck? You can see the quagmire we’re quickly spiraling into: Some is good but more is better, and before too long, we’ll be pulling 9 inches of vacuum and sounding like we’re running in Pro Stock Eliminator.

Conclusions
We ran all three cams on Westech Performance Group’s SuperFlow dyno with a Holley 650 carb, a Holley Street Dominator dual-plane manifold, a stock HEI ignition, and a set of Hooker 1¾-inch primary headers (see dyno chart, top right). The headers are larger than we would probably use for this engine on the street and likely gained us some top-end power at the expense of torque (we bought a set of 15/8-inch full-length headers from Summit (PNG9001) to use later). All three cams produced peak power with 12 degrees of initial timing (38 degrees total), and, interestingly, all three produced peak horsepower and torque at basically the same rpm points. As you might expect, the smallest cam produced good peak torque, the flattest torque curve, and the best idle vacuum. The middle cam produced 5 more horsepower at the peak with about the same torque curve and a little less vacuum— even so, we’d choose the smaller 214/224 cam over the 224/224 unit.

Although it generated the least idle vacuum, the biggest cam produced the best peak torque and horsepower of all three cams tested: 343.6 lb-ft of torque at 3,900 rpm and 304.3 hp at 5,100 rpm. That’s a 15hp gain over the smallest cam with only a small low-rpm torque loss, primarily under 3,500 rpm. As far as we’re concerned, the small loss in area under the torque curve would have a marginal effect on driveability and is more than offset by the hefty increase in power at the top end, especially since it produces peak power and torque in the exact same rpm range as the smaller cam. Also note that the 224/234 cam is identical to that used in our El Cheapo car, and we think it runs plenty good enough for daily driving. In this case, we’re not afraid to say that bigger really is better."


LG4 Ohv V8 155 @ 4200245 @ 20004-bbl.9.5:1305/5.0Z*,SC,B

Re: 305 performance?
 

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