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Old 01-15-2004, 09:37 PM
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Heads

My brother has a 67 camaro with a fairly stock motor. Right now he has stock 64cc heads. He is looking to get some high performance heads under a grand. He was looking on ebay and found a set of pro topline 200cc 2.02/1.6 cylinder heads for I think around 700 bucks. The heads are 50cc heads though. Right now he has about 9.1 compression ratio with stock dish pistons. With the 50cc heads he'll have around 10.5 compression ratio. His question, and I guess mine too, is are those heads ok? Do you think the fact that the heads are 50cc wouldn't be a good idea? He says he would like to up his compression ratio and go with a better performance head. Do you think these heads are ok, or is there something else you might recommend? Thanks!

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Old 01-16-2004, 01:31 AM
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First the Pro Topline heads are excellent (especially for flat top or dished pistons), BUT (big but), I think his compression will be higher than you think going from 64cc to 50cc. What size engine are we talking about? (327 or 350)

I set up a 327 with 64cc heads and a compression ratio of 9.22:1 by switching to 50cc heads the compression went to 10.9:1 (this was assuming is was a standard bore and tat the pistons are .020 in the hole with a 5cc valve relief). If it is bored oversize the compression goes up even more.

Now if it is a 350 and starts with 9.3:1 with 64cc heads, by switching to 50cc head you get a compression ratio of 10.9:1. If the heads are aluminum and he has a healthy cam he "may" be able to get away with pump gas. If he has a mild cam he won't be able to get by with pump gas. If the heads are iron the compression is way to high for pump gas.

When you say "about 9:1" that is not close enough if you are on the edge, you need to know exactly what you are starting with. If you can get some more details (deck height, bore size, type of piston), then you can get close. If not I would stay away from a head with that small of a chamber and by some with 64cc chambers to be safe.

Royce
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Old 01-16-2004, 06:44 PM
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This is just my personal opinion, but if you have $1000 for a set of heads, I would save up the extra $300 for a set of AFR's. Those heads are the best bang for the buck.
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Old 01-16-2004, 07:32 PM
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I can remember doing some measurements when the motor was apart. The pistons are .020" down the cylinder, the pistons are dished 4 valve reliefs with 11.5cc, the motor is a 350 with a 4.060 bore. I did the formula on a web site to figure out the compression ratio and with the 64c heads he has 9.29:1. With the 50cc pro topline heads he would have 10.83:1. He has a comp cams xe-268 cam with 224/230 duration at .050" and about .480/.490 lift. The heads are iron heads. Do you think this will be too much for 92 octane pump gas?
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Old 01-16-2004, 07:37 PM
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i have 11.5 to 1 and i run it on 93 octane the only thing is you have to keep your timing lower.
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Old 01-16-2004, 07:46 PM
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I dont think that it would run on pump gas with that much compression and iron heads. Another thing, I see that you are looking at a set of Pro Topline 200cc heads. Those heads unported flow pretty well above .450 lift, but below that they arent too good. For your application, if you ran the cam you have, and used a set of Vortec heads with the high lift spring upgrade from Scoggin dickey for $630, your motor would make more hp and more torque than if you had a set of the 200cc Pro toplines. Plus the Vortecs have a 64cc chamber which would put you where you needed to be on compression. You will have to buy a new intake manifold with the Vortecs, but I would think you would be getting a new one any way. I have seen accurate flow numbers on both Vortec heads, and pro topline heads, and under .450 lift, the vortecs out flow the pro toplines. The thing that makes this even more impressive is that vortecs have a 30cc smaller runner and smaller valves. This means that the Vortecs produce way more port velocity, which is what is important.

Good luck,
Adam
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Old 01-17-2004, 12:41 AM
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Excellent point/s Adam. I agree 100%

No you will not be able to get away with that compression with iron heads and that cam.

Retarding the timing is a band aid. Why build the extra compression if you can't use it? You don't gain much from a small amount of compression and you take what you gain away by retarding the timing. You gain about 4%of output for every full point of compression (do the math).

Royce
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Old 01-17-2004, 09:24 AM
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go with the high compression and use what they used in the sixties (period correct) WATER INJECTION.It will stop the detonation caused by high compression.
I dont know how to do this, but it has been done and works. ask some of the older rodders, they probably be able to set you straight.mike
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Old 01-17-2004, 11:49 AM
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mikeweyman, you can't be serious. Water injection "helps" to reduce detonation, it doesn't eliminate it. We don't have the same gas that was available in the 60's so you can't build engines the same way. What happens as he is cruising down the highway and runs out of water/alcohol in his injection? Save the water injection for race cars and forced induction.

They were not going anywhere near as fast in the 60's as they are today (and they had better fuel), this is because of technology.

You best bet is talking to people that have cars that run the way you want to run, see what works for them (in todays world). The older guys have tons of good info and you can't beat a guy that went fast then and still knows how to now (kept up with technology).

4% of 300HP = 12HP
4% of 400HP = 16HP
4% of 500HP = 20HP

Is that little gain worth the chance of detonation. The 1 point is compression is often not worth it. This will depend a lot on the cam you want to run (longer, bigger cams require more compression to make power). Without taking DCR (dynamic compression ratio) into account the general rule is 11:1 is the limit with pump gas and ALUMINUM heads.

10:1 with IRON.

This will greatly depend on how well the engine is built (tight quench), and what cam you are running. You have to account for cylinder pressure as well. Too much to explain here, but do your research before you buy the heads.

Royce
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Old 01-17-2004, 02:22 PM
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vortecs have great intake flow numbers, but, the exhaust sucks... im sorry campers but its the naked truth!! if you get a set of vortech heads you are going to have to port the exhaust to get the same performance as a set of toplines, also your friend will heed a new intake manifold, so in my view the vortechs aren't very cost efficient in your/your friends case... go with the toplines, and if you are going to spend the extra buck, don't do it on the vortech manifold, upgrade to pro topline aluminum...

my 2 cents
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Old 01-17-2004, 02:27 PM
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I agree with camaroman7d. Definitly no more than 10:1 with iron heads. I'd probably go 9.5:1 just to be safe. Aso, I'd say that the runners on those 200cc heads are a bit big for that cam. Like some of the other guys said, they will not have the low lift velocity that a smaller runner head will. Therefore, they will not run as good at lower rpms. Best bang for the buck would be the iron vortec heads. I've seen a bunch of dyno tests using vortec heads and the cam you are running. It's good for a little over 400hp, with good torque too. I also have to agree with firestone about the AFR heads, they are good stuff.
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