I have a 383 in my 1972 corvette. 3.36 rear end, 5 speed, 3.37 1st, and .67 5th. I am in the process of replacing the top end. I am leaning towards the Comp Cam xr264hr, roller kit. Duration: 264/270, Valve Lift:.325/.330. RPM Range is 1200 to 5200.


1. What assembled heads on the market will work with this cam?
2. Will I need to replace the valve springs on the assembled heads?
3. Will this give me ok vac?


Thank you
Cal

 

that cam should give you ok vacuum .what intake will you be using .you can order most after market heads with the proper springs for a roller cam .competition products offer sells most after market heads .they offer the dart with several spring options .what rocker arms will you be using ?if you don't have rocker arms yet ,order the heads with the bigger rocker arm studs .

 

The rated rpm range listed for most off the shelf cams assumes a 350 ci engine for the sbc, keep this in mind when choosing for any other cubic inch displacement.

If you're buying rockers too consider 1.6 ratio to help feed your 383.

I'm guessing this isn't a budget redo so you may consider the best - AFR. Call them with your needs and have them spec your cam too. You can never go wrong with the best !!

 

you have the gearing for a bigger cam/ higher operating range. A 350 to a 400 drops your operating range 500 RPM so when selecting a cam keep this in mind. AFR is the best and they will set the head up with the exact springs you need. Power potential is all in the heads.

 

Are you sure the lift is accurate?

 

OOps can't type, that was lobe lift. Below is correct.

Duration: 264/270, Lobe Lift:.325/.330. Valve Lift: .487/.495, RPM Range is 1200 to 5200.

Thanks

 

Running a hydraulic roller the springs on most heads are good to go. Vacuum at idle depends largely on camshaft duration/overlap and intake/carb combination. First unanswered question is what is your budget? Doing a CNC porting job will pick up the power on any head and even out the port flow inconsistencies ( modern casting cores are already far superior to any technology from the last century anyhow...CNC will give you that extra 10% if you feel the need) CNC combustion chambers are nice too but this all costs money. I tend to like heads with 180/195cc intake port volume for a 383 but, there are many " experts " on here that will tell you to go bigger 200/210cc runners. What do I know? My cars have a reputation of always being decent runners and always in contention for a trophy whether it's competition or a show event. Answer some more questions on budget and what you going to use the Vette for and you'll get better answers.

 

Thanks
I am fairly flexible on budget, I will spend the money if I need to, however I plan on making this a driver, no racing except I want a little when I get on it. So I may accept a Modern Sportsman head over a AFR if I saved several hundred and had to give up a little. But unless there is a significant savings I will spend a little more. This forum really helps me figure out what I want, you guys are great, all info helps me. This cars not for racing, but I want it to work well and sound good, I will not be over 6000 much. That's why the Comp Cam roller 264 looked about as much as thought I could go. Learning more here however.

does this help a little more
thanks again
cal

 

Look at this link:
http://www.compcams.com/Pages/401/dyno-sheets.aspx
and scroll down to the roller cams. Figure dropping about 400 RPM on any cam on this chart since you going 383 instead of 350. The bigger CI will also increase vacuum with a given cam. The cam you selected flattens out @ about 4000 RPM. This converts to about 3600 in your engine. It is restricting the ability to fill the cylinder at upper midrange RPM due to the lower duration. You buy good heads to increase power production. Don't restrict the heads ability to make power by restricting flow. Good heads will make more power across the entire RPM range. I would shoot for around 10 to 1 or a little under compression and, with your 5 speed and 3.55 gears go with something like the XR276HR on this chart. Remember to figure the difference of about 400 RPM less across the board. See the power difference @ 2500 RPM? (2100) in your build, Also look at the torque peak and rpm range above 400 ft lbs, again backing everything off about 400 RPM. The 276 is noticeably higher and gains from 2000 to redline over the 264 exponentially. Also notice the point where power flattens out, even the 276 will hit the wall at a little over 5000 rpm in a 383. Do not be afraid of a loss at the bottom end. The 383 combined with the 3.55 gears and 5 speed will allow you to have good bottom end, get into the powerband quick, still pull decent vacuum and be very docile in everyday driving yet make good use of your upgrade heads and make increasingly more power as it accelerates. I would recommend the AFR 195 eliminators for your combination. No replacement for quality heads, they make more power everywhere. Also 1.6 rockers will not change the operating range but will help good heads fill the cylinders, they will like the extra lift and increase power from off idle and up. The Dyno charts are actually misleading because all are on a 350 with 9.25 to 1 compression. As you go bigger on the cam you can increase compression making more power across the board hence the 10 to 1 recommendation. The engine used is actually losing DCR (and cylinder pressure) as they upgrade cams so your results will increase compared to theirs. Take it for what it's worth.

 

As others have stated, AFR 195 Eliminator heads will get you max power from your 383 combo. But if budget is a factor, I've found Trick Flow Specialties 195cc heads to be a very good "runner up" decision. Good bang for the buck, a few hundred less than AFRs, but good horsepower. I had Trick Flows on my 383 when first built, then later went to AFRs after hearing recommendations. They performed similarly to 5000rpm, then the AFRs walked away with an extra 25 horsepower at top end.

 

Thanks I confirmed I will have 10/1 compression with 64cc heads, and I will go to the larger cam, that info really helps.

I am still checking out heads, I have found a set of Sportsman 11 heads assembled (the new technology) with the correct springs for several several hundred dollars less than the AFR's. Based on my needs is the savings worth it over the AFRs.



thanks
cal

 

Thanks I confirmed I will have 10/1 compression with 64cc heads, and I will go to the larger cam, that info really helps.

I am still checking out heads, I have found a set of Sportsman 11 heads assembled (the new technology) with the correct springs for several several hundred dollars less than the AFR's. Based on my needs is the savings worth it over the AFRs.



thanks
cal

 

Flow @ .300 lift
AFR 195.....................211 intake 175 exhaust
Sportsman II .............182 intake 128 exhaust

Flow @ .500 lift
AFR 195 CC.................285 intake 219 exhaust
Sportsman II 200 CC ...257 intake 160 exhaust
AFR Aluminum, Sportsman II Iron
Your call. I would go AFR no doubt. Flow on the exhaust side is as important for making power as flow on the intake side.

Edit: Add Trickflow 195
Flow @ .300.................196 intake 135 exhaust
Flow @ .500 ................249 intake 186 exhaust

Here is head flow info: http://users.erols.com/srweiss/tablehdc.htm#Chevy

 

The AFR heads are probably 25-40HP more than most other offerings not cheap but you'll get what you pay for.....free HP!

 

I always wonder why builds 500 hp and under always get the AFR nod and not the Fast burn nod .. IMOP the GM fast burn is all the head of any so far talked about and it surpasses most mentioned in a lot of areas

Flow being only 1 area of importance. And it seams all anyone ever goes by and that is not the end all of which head is better.

I suggest the fast burns , shop for them the prices can be really good. I got a new set in boxes off racing junk for 850.00 shipped ... And on my 350 i get 383 hp/ tq all day long and the only 383 i have lost to was in a 2700 pound S-10 truck..

The new GM 383 is rated 450/450 with what many would call a mild cam that says a lot , the cam in my 350 is mild as well , she idles like kitten screams like a lion and that is all because of these heads.

 

If budget is not an issue than the question is what do you want out of the car? What do you want it to do? Good running engines are good combinations of parts. One must figure out what he wants out of the engine, then select heads to achieve that. Cam is second to the last component.

For a 425 to 500HP you can spend around $1800 for a kit. For 550 plus you will spend around $2500. Just note the more HP the less "manners" the engine will have.

 

The fastburn 7712 has a 210 CC port. It is a raised port design.
Flow numbers on the 210 port fastburn:
Flow @ .300............... 177 intake/124 exhaust
Flow @ .500................223 intake/166 exhaust
What intake are you using that matches the ports and fits under the stock hood?

GM performance parts testing shows substantially higher flow numbers.
http://www.hotrod.com/techarticles/e...ylinder_heads/

 

To add to what Mako has posted, if you have a head with smaller CSA and flows more air, that simply put is more velocity. Velocity on a street engine that needs to see power in a wide rpm band is king.

 

get a copy of the cam card ,to find out the needed spring pressures .then call who ever you get heads from ,and make sure the springs that come with the heads you decide on ,have the proper springs .

 

This is where AFR excels. Their 180 eliminator flows more than most 200+ cc Heads on the market. Port velocity helps bottom end torque. I/E ratio is another strong point as well as lightweight valvetrain components. If budget is not the primary driver buy AFR. If budget has no bearing at all buy the AFR Competition ported 195 eliminators for about $2000. They flow 300CFM and are capable of close to 600 HP with a 195 port. If budget is the primary driver look at the Straub heads. They seem to be the best bang for the buck in a budget aluminum head.