KJL

I am looking primarily to increase the CR of my stock 8.5:1 engine by going to 64cc chambered heads. Going with aluminum interests me because of the lighter weight, good flow and cooler combustion. The Edelbrock Performer also have a new design combustion chamber for improved performance. I am more interested in lower end torque than top end horsepower. I will probably go with a mild cam like similar to the one that comes with the Performer package. I have been told I will need studs for aluminum heads and the spark plug threads will strip out at some point...... Plus they are not cheap either. My stock heads are 487's. Would a set of iron 64 CC heads do the same thing? I know large flow area can hurt lower end performance so big valves are not required for lower rpm applications. I just don't want to pay for more perfromance than I will or can use. But I have no problem paying for quality. :confused:

TedH

Your 487's have an intake port volume of 161cc and exhaust volume of 65cc's with 76cc combustion chambers and 1.94/1.50 valves in stock form.

John Lingenfelter in his book "John Lingenfelter on Modifying Small-Block Chevy Engines" states "... The 993, 487x and 441 used heads offer not only the most flow potential, but also the most durability".

Having said that, your heads can be safely ported to flow greater volumes of air, resulting in greater power production without impacting compression ratio. You can also opt for a better cam shaft to boost the combustion PRESSURE to boost performance; again without increasing CR. Another option is to go with flat-top hypereutectic pistons with valve reliefs. Moving to a better, higher compression head can put greater stresses on an engine that has yet to be rebuilt. I'd recommend a rebuild with the cylinder heads and include the cam and pistons in the mix (whether you opt for porting or heads replacement).

Air Flow Research produces an emissions legal iron head with intake volume from 180-230cc's. I'd storngly recommend that head for durability and quality. I suspect they offer 68 and 72cc combustion chambers.


[Modified by TedH, 10:59 AM 12/31/2002]

theandies

If you want to increase your CR and want to go higher than 9.5:1 then aluminum is the way to go above that without pinging on 93 octane. I would not run iron heads higher that 9.5:1. You do not need studs to install aluminum heads and as far as the sparkplug threads go....who is changing your plugs....Bubba :lol: . You would have to remove and install your plugs before and after driving you car everytime to wear out the threads........to me that is a non-issue on this subject. IMO the benifits of aluminum heads outweigh (or not :lol:) the lower cost of iron heads.
John


[Modified by theandies, 10:23 AM 12/31/2002]

VegasJen

if i had the money, i'd go with aluminum. i haven't heard about the head studs though. i don't believe studs were used on the L98 or LT1, but i could be wrong. if your looking for an inexpensive way to boost compression and increase low end power without going into the short block, then i have one thing to say--305. not the entire engine, mind you but the 305HO heads will boost your compression by about a full point and they're fairly common (read cheap). the HO heads have 1.84" intake valves so you don't loose that much flow, in fact, the factory SBC heads flow is not limited by the valves as much as by the intake ports. the 305HO heads will flow as much volume as most factory stock 1.94" heads.
in case you think this sounds like voodoo or something, i just installed a set of these heads on my factory original short block back over labor day. i re-ringed the pistons with a slight hone and installed a blue racer cam, everything else is pretty much as it was before. no changes to the exhaust or intake. i netted 40+ hp at the flywheel. i had a couple strings about this little swap and the results on the forum back then. if this sounds interesting, you can do a search and find it. there are others who have done this as well.

KJL

Clutchdust,
What are the specs on the blue racer cam?

lason

You dont need studs with aluminum heads and they weigh less and I have NEVER stripped a spark plug hole in a aluminum head, and I have had 4 sets in the past and about to have another set on my vette.

gkull

I believe in fully studding aluminum heads.:)

10.5 and aluminum heads works even with mild cams. My buddy just purchased the AFR 190 cc milled to 56 cc to get his compression up.

KJL

I know a performance cam will lower the dynamic CR, My current warm cranked compression is 155-160 per cylinder with my stock set up. If I go with the 64cc heads and a mild cam (256H or 260H for example) will the cranked compression increase much? My engine has been rebuilt in the past but I don't know what was done to it. Some say it sounds like it has an after market cam but the vacuum at idle is about 19"hg which is high for any kind of performance cam. Is 160psi about right for the stock set up?

Ryan77

I plan on buying a set of AFR 190cc aluminum heads in the spring, they flow excellent :yesnod: . The have them in 68cc and 76cc combustion chambers, but you can ask for smaller chambers and they will make them for you for about $150. They also make custom heads for specific applications, I'd give them a call and tell them what you are looking for. Also, check out their website: http://www.airflowresearch.com





[Modified by Ryan77, 3:29 PM 12/31/2002]

Vetterodder

I'm also a fan of aluminum heads. They will cost more than a comparable iron head but be sure that you are in fact comparing similarly equipped heads. Many of the low priced iron heads you see at bargain prices don't include guide plates or quality valves and springs. By the time they are brought up to the same specs as the Edelbrocks you're considering the price difference may not be so dramatic. Also, don't just compare the cost of the heads themselves. Good gaskets, bolts, etc., aren't cheap and will cost the same regardless of the heads you select and the labor involved is also the same. The Edelbrocks have heli-coils in the spark plug holes but most others don't. While "Bubba" can screw up anything if he tries hard enough, I don't think stripped threads are that common a problem for any of the aluminum heads.

I wouldn't worry too much about the effects of those mods on your cranking compression. While smaller combustion chambers will raise dynamic compression along with static, cams with more overlap than what you already have will have the opposite effect on dymanamic compression. Both of the cams you mentioned are pretty mild though and I wouldn't expect a drastic change in cranking compression. You could get a lot more power by stepping the cam up a notch or two to the 268H or one of the smaller XE series. You'd still have plenty of vacuum for accessories and be able to use a stock converter.

72Shark

I recently switched to TFS Aluminum heads from 76cc small valve iron heads, and I now sing the praises of 10.0 to 1 compression and aluminum heads. I went to a "bigger" cam at the time too, from a 265 DEH (211deg/221deg) to a 270 Magnum (224/224) and still pull 14+ inches of vacuum. I would worry about too much cylinder pressure with a small cam like the Performer (only 204 degrees on the intake!!!). For easy driving, try 64 cc aluminum heads with approx. 190-200 CFM intake ports and the CC 268 High Energy cam. Good vacuum, relatively smooth performance, but will run hard to 5500 rpm.

The Money Pit

If you're interested in a stock type cammed engine,stay with the stock heads and run a torque cam like the Comp 260H with headers and duals. This combination will keep the flow requirement well below what would require upgraded heads,ans will provide a kick in the pants engine. It's all in the combination. Another trick would be a gear change. It's amazing how different the same car runs with different gears,and everything else the same.
I've run in the 300-350 hp range for years with many different engines,and when I decided to go for much more,I needed the heads to help pull the extra hp.

nunus79

The following thread has my $.02 in it: http://forums.corvetteforum.com/zero...823573#4823573

In essence, if you are eventually going to rebuild your motor, go with aluminum. If you are just interested in hot-rodding it a bit and want to just bolt something on, go with iron.

redwingvette

You don't need to use studs for aluminum heads but you will need to buy new bolts and washers for them. Never instal aluminum heads without the washers. I just bought Performer RPM heads and the bolt kit was $50. you may need push rods to fit the heads as well. Depends on which heads you get and what rockers you use.

chewy

Your stock engine isn't 8.5 to one it's probabily a lot closer to less than 8 to one. For what you have (stock cam etc.) use a set of iron 64 cc heads with moderate runners you will really notice the torque increase.

Ironcross

Most of the time you will not get any advantage with after market aluminum heads and a hydraulic camshaft combination. They are normally profiled for high RPM`s. With what you have,a good choice of camshaft would be the 327/350HP # 3863151 GM cam. It`s really a nice cam with excellent power and good torque. It works fine with all compression ratios and has a nice desirable lope. The best for the buck. :thumbs: :)