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I need help with cam selection

814 Views 21 Replies 10 Participants Last post by  trucker1
I have a 64 impala with a 283. I'm running 305 64 cc heads. Stock bottom. I'm looking for a cam to match my motor. Just looking for advice. Also not sure if i want a 2 or 4 barrel carb.
Any udeas or advice is appreciated. I am also runninf a 700r4 transmission and 355 rear gears. I'm open to ideas.
For intake carb and cam. Not a race car. Just a street car witha little bit more than a little. She's bored 40 over. So i guess she's a 288?? Thanks everyone!!!
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I just realized i need a different intake to bolt into the 305 heads. And i haven't yet found a 2 barrel for a 305 intake. I don't know a whole lot about this. Any help or advice please chime in!
I know very little about engines past '73, but I've always known 305 Heads to be one of, if not the worse sets of Heads GM every put on a small block. I would recommend 283 Power Pack Heads which were original in '64. Also, if you want more Horse Power and Performance, put on a 4-Barrel for sure.
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I have a couple sets of power pak. They don't have hardened valve seats. And my machinist guy says it would cost me alot more. He had a set of 305 heads that have accessory holes and hardened seats.
I don't know much about 87 and after either.
I don't want a 350. Before anyone advises that.
Looking for help on a suitable cam and carb and intake. Thanks
Other than for some serious racing, many of us are still running the old style Heads. I had to look it up to verify it, but Lead Gas was banned in the US 27 years ago in January of '96. I've been running small block V-8's continuously since then, as I still am today, and never once had any issues. Back in the early days, I would run a Lead Additive, especially on long trips, but haven't used any in many years now. Are hardened seats better to use, yes, but it something that I'm not that concerned about. Just my opinion now.

Good question to ask the posters on here. How many are still running pre-hardened Heads out there?
I had mine hardened with valve seats when I had it rebuilt in '94.
however, some of the best factory SBC heads are the mid-late 90s, the "Vortec" heads. the 350 heads actually have a ramp to help swirl and they kept the cc small to help compression.
there's more info out there, but I would need to locate it and re-post here. I was looking at doing those on my 80s El Camino about 5 yrs ago
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I know the swirl port heads I'm getting. Are not the best flowing . But i thought it still a good update.
Problem I'm seeing now. Is that the bolt hole angle is different. So i have to get a different one. And i am not finding any 2 barrel intakes.
I had mine hardened with valve seats when I had it rebuilt in '94.
however, some of the best factory SBC heads are the mid-late 90s, the "Vortec" heads. the 350 heads actually have a ramp to help swirl and they kept the cc small to help compression.
there's more info out there, but I would need to locate it and re-post here. I was looking at doing those on my 80s El Camino about 5 yrs ago
Did you have a 2 or 4bb on your 283
Had hardened seat inserts put in my camel hump heads on my 327 (bored /stroked to 383). Not sure how much it is needed, since it is a Sunday driver, so things will probably age more than suffer from miles driven.
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Did you have a 2 or 4bb on your 283
my recollection is that it was originally a 2bb. after rebuild it got an Edelbrock Performer and a Holley
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my recollection is that it was originally a 2bb. after rebuild it got an Edelbrock Performer and a Holley
Did you notice a BIG difference. I'm asking. Because I'm tore at which way to go. 2 or 4bb. I understand from what i read. It wants nothing nothing's more than a 600.
So what would you do? Power pak or 305 head? 2 or 4 bb??
It might be helpful to know the casting numbers on top of that pair of 305 heads you have. Are those iron or aluminum? I was thinking (like Bill) that the early, early 305 heads were just some of the worst flowing heads GM ever made, but now with a little light reading, I'm wondering if there are later model/newer versions of the 305 head that are a small step better. Well, either way we know they're not designed to flow much after 5000rpm so with that ceiling and your engine size and driving/power intent, these will all dictate the cam size you'd want.
Regarding the use of the hardened seats it's really about how many miles you will put on it. I'd personally recommend it but if you only put on 1000-3000 miles a year maybe you can get away without using them. (or use an additive for insurance)

I'm not sure what happened with cam prices but it looks like they've gone up a lot. :-o You always want to get new Lifters with a new cam, and generally new, matching springs as well because the old springs could be fatigued and may not handle the Lift of the new cam.
Do you know if your engine is using a hydraulic roller designed cam, or what the engine came out of? (sorry if I missed another thread on this)
I personally think you need to stay well under 270 degrees of 'advertised' duration due to engine size, heads and how you said you'd use this. No less than 110 degrees of "Lobe Separation".
If possible, I'd try to find a cam that has a 'dual pattern' or 'split-pattern' design, giving you more advertised duration on the exhaust vs the intake. That'll help those heads a little.

Here's a short list of cams that I'd be looking at but take note that 3 kinds are listed here. 'Flat tappet', 'Retrofit hydraulic roller' and 'OE hydraulic roller'. I'm not sure what your engine is using.

I'd certainly go with the 4 barrel intake if you can find one. Keeping a 2-barrel on an engine with a new cam would just seem like a half-step backward to me.
Crunch up the costs of what you're talking about doing here because it seems like you're approaching the same cost of a basic crate motor. (which doesn't have to be a 350, lol)
EDIT: Oh yeah, a 600 carb is definitely a good target. I wouldn't be afraid to use a vacuum secondary 650 if the pricing or availability was better.
Also, not that you asked, but you'd be well served to have an HEI distributor on a cost/benefit basis if you're going to the trouble of a cam change.
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absolutely 4bbl and I would go with 350 vortec heads. I couldn't find the magazine articles I remembered reading about the heads but here are some links that talk abut it.

The Class Of The Heads
Chevy 305s came with only 1.84-inch intake and 1.50-inch exhaust valves. Fortunately, there is an effective upgrade available in the form of '96-'97 Chevy truck L31 Vortec heads with 1.94-/1.50-inch valves. The cast-iron heads' intake and exhaust ports are similar to the late-model Corvette aluminum LT1 heads, but unlike the LT1 heads, they bolt onto conventional small-blocks. The Vortec's greatest improvement is on the intake side, which is why we chose the dual-pattern cam with its slightly larger exhaust lobes.

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Get the casting number and post them here so we know exactly what year heads these are. They must be 1987 or newer 305 head. That is the year Chevrolet changed the mounting angles of the two center bolts on each side of the intake manifold (from 90 to 73 degrees). No 2-barrel carburetors were ever used on the 1987 and later 305 engines. They were all 4-barrel QuadraJet carburetors.
You could modify your 2-barrel manifold by elongating the two center bolts to line up with the heads. I'd probably just go with a Edelbrock Performer manifold 600 vacuum secondary carb. Be sure to get the right one for your heads.
Get the casting number and post them here so we know exactly what year heads these are. They must be 1987 or newer 305 head. That is the year Chevrolet changed the mounting angles of the two center bolts on each side of the intake manifold (from 90 to 73 degrees). No 2-barrel carburetors were ever used on the 1987 and later 305 engines. They were all 4-barrel QuadraJet carburetors.
You could modify your 2-barrel manifold by elongating the two center bolts to line up with the heads. I'd probably just go with a Edelbrock Performer manifold 600 vacuum secondary carb. Be sure to get the right one for your heads.
Thanks. That what i was wanting to know.
I've just been trying to decide which heads to go with. Power paks and i spend 700 or so for hardened seats and a valve job.
Or 300 or so for 187 swirl port heads. Plus a different intake.
Power paks and i can have either 2 or 4 barrel.
305 heads and I'm stuck with a 4 barrel.
I think 305 heads would be a little bit cheaper way to go.....
I had a 283 years and years ago. 2 barrel turd. Took a quart of oil a week. I've never built one so I'm looking for everyones advice.
Wallace cfm calculator says i need a 380 to 490cfm. I've heard the edelbrock 600 is good reliable. Ive been thinking something smaller 400 500 4 barrel. Any thoughts???
The original type 4-Barrel Carb for a '61 283-230 or a '62-'64 327-250 was a Rochester 4GC. Not sure of the CFM's but believe they were in the 400 to 500 range. I didn't research it, but the listings should be available online.
The secondaries of the Edelbrock 600 are vacuum controlled. They will only open as far as the 'demand' requires (like the Quadrajet).
The engine has to breathe. Exhaust needs to complement the intake.

Pete
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Rob, don't overthink the carburetor stuff. You're not going to go wrong with a 490, 500, 600 or even a 650. Just be sure that it's using vacuum secondaries, not mechanical secondaries. I'm using the Edelbrock on mine and I like it, I've also used vac.sec. Holley's a lot in the past and I like them even more.

The calculator you're using is using basic math. The engine isn't going to be forced more CFM by using a carb that is any size larger than that calculator says. The real-world experience is that many engine's see small power increases with slightly larger carbs just do to a better airflow path, not due to flowing more than the calculator says the engine should use.
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here is some reading that may help you selecting a cam:


It's a lot but getting an understanding of how the cam works may help you.

Here's a chart from the link:

Rectangle Slope Font Parallel Diagram


Pete
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I think it's possible to "over-think it" when it comes to cam selection too, especially for a mild street build when all what you want is a step or two above stock. I'm planning to pull the 327 out of my '65 for a mostly stock rebuild and got stuck in "analysis paralysis" for awhile when choosing a cam for it. Best thing is to call a few of your favorite cam manufacturers and talk to their tech advisors. Tell them what you've got and how you intend to use it. Chances are their recommended cams will all have similar duration/lift/overlap etc. specs. Look them over carefully and choose the one you like. Probably best to stay on the mild side. Years ago I would have used a Crane but they're long gone so I ultimately decided to go with Isky, another quality brand I've always trusted. This is the one they recommended for me; it might work for you too, assuming you'll be using a 4 bbl. carb. :
https://www.summitracing.com/parts/isk-201262-27012
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