I'm putting together a 383 for my 69 Corvette, and would value your opinions on what cam I should use. I want to go with a hydraulic roller. Here is my setup...

69 Corvette, 700r4 trans, 3.08 rear gears
Late model roller block with 4 bolt main, 1 piece seal
3.750 stroke, 4.030 bore, 6.0 rods, forged rotating assembly
Pro Comp 190cc aluminum heads, 74 cc chamber, CNC ported
9.8 to 1 compression
Dual plane intake, speed demon 650 carb with vacuum secondaries
1 and 5/8 long tube headers, 2 and 1/2 dual exhaust
26'' tires

I'm not planniing on going beyond 5500 rpm very often, I'm more interested in good low to mid range torque. Once I know what cam, I'll pick the torque converter.

 

u should check out the comp xe282 roller or for even more low end the xe276....just some ideas

i found i dyno with the 282 cam on a 383 with afr 180 heads, cant be to much different with pro comps



RPM TQ HP


2500 448 223 thats a 383 9.5 CR

3000 459 262
3500 483 326 also it peaks at 5500
4000 501 381
4500 501 429 looks like what ur looking for
5000 488 464
5500 469 491
6000 401 470

 

I'm not sure what cam you are referring to, what is the full part number?

 

heres the part number 12-432-8

heres the link

http://www.compperformancegroupstore...ry_Code=RFHRXE

 

As far as the cam goes, the cam android91chevy suggested would work well. If you want to play around (with Comp Cams grinds anyway) go to http://www.compcams.com/DefaultWide.asp and on the lower right hand corner, download Camquest 6. It's an engine simulator that'll let you simulate what their different grinds should do in a given application. Bear in mind, these numbers are not etched in stone. It'll just give you some idea as to what direction you're going in as fa as component choice. Try it, it's fun!

Anyway, a far as the rest of your combo goes, well.....it may not perform how you hope it will. Those 190 Pro Comp's are a bit small for the 383 as are the 1 5/8" headers and even CNC'd, I'm not sure the numbers will hold up to a non ported AFR (or similar) of comparable size. With 74cc chambers, I'm thinking your compression is less than 9.8:1 with flat top pistons. Probably more around 9.3-9.4:1. I'm not trying to rain on your parade, but just give an objective opinion on what you might expect. It will run, but maybe not up to it's full potential.

 

i can tell you this...beyond cam selection you can totally go steeper in the rear gear dept. i had a 700r4 and 373s in my old camaro and it was still VERY highway friendly...and when i say VERY i mean much above the posted speed limit =)

 

Fast01, thanks for the reply, and don't worry about raining on my parade, if I didn't really want advise from others I wouldn't have asked. What heads would you recomend? I have not assembled the engine yet, and can still make some changes.

Thanks...

 

There are a few questions that need answers to really hone in on the best combo, but I'll give you what I would reccommend. I would use an aluminum head in the 200-210cc range with chambers in the 68cc range. I am partial to the Air Flow Research heads, but there are many other offerings that'll work good too. I'd go with the Fel Pro 1094 gaskets (.015") to bring your quench in line and the reason I say aluminum is for the heat dissipation properties and the ability to run higher compression safely on pump gas. I'd take the compression right to the edge, around 10.5:1. You'll make more power and run more efficiently. The cam suggested earlier should work well, but play around with the program I linked you to. I would also consider stepping up to a 750 carb (not mandatory) and some headers with larger primary tubes, at least 1 3/4". 1 7/8" I think will work better, but again not mandatory. After all is said and done that should put you in the high 400 to low 500 horsepower range with torque in the high 400 range.

I based these numbers on a few assuptions. Has the block been decked? I assumed a light clean up and that pistons will be in the hole .020". That's why I say to use the thin gasket. With the 1010's (.039") normally used, quench will be at .059" or as much as .064" if the deck has not been touched, a bit on the loose side. Quench is real important for detonation resistance. The thin gasket will put you in the .035"-.040" range which is optimal. I assumed 7cc's for valve reliefs in the pistons, which I'm not sure of either. Oh, and I do agree with raped 95Z, 3.73's would work real well and still be highway friendly. Just keep an eye on that 700R4, they in my experience, don't hold up too well. I've broken 3 4L60E's which is essentially the same transmission with electronic controls.

It was real easy for me to sit here and spend your money. This will cost a bit more than what you had planned, but I'd rather put off the build and do it right than just slap something together and not be happy with the result. It ends up costing a lot more in the end doing it that way. Good luck with your project!

 

Thanks Fast01...I need to learrn more about quench. That is the part of your reply that I do not fully understand...

 

Here's something I wrote up in another thread a while back. It explains a little bit about what quench is and what it does.

The newer, more efficient combustion chambers are designed with a large, flat area at the bottom of the chamber called the "quench area". This area corresponds to a flat area on the piston. When the piston is traveling up the bore on the compression stroke the piston forces the mixture out of these flat areas and into the actual chamber where the combustion process takes place. This is done violently and the piston should come within .040" of the head. This creates a more efficient burn and has a cooling effect on the combustion chamber thus increasing your resistance to detonation. In creasing this "quench" much beyond .060" or so will forfeit any of the quench benifits and increase the likelihood for detonation.

I got this from the Keith Black Piston website. It sums it all up a little better than I did. Hope this helps!

Excessive cylinder pressure will encourage engine destroying detonation, and no piston is immune to its effects. An important first step is to set the assembled quench ("squish") distance to .040". The quench distance is the compressed thickness of the head gasket plus the deck clearance (the distance your piston is down in the bore). If your piston compression height (not dome height) is above the block deck, subtract the overage from the gasket thickness to get a true assembled quench distance. The quench area is the flat part of this piston that would contact a similar flat area on the cylinder head if you have zero assembled quench height. In a running engine the .040" quench usually decreases with RPM to a close collision between the piston and cylinder head. The shock wave from the close collision drives air at high velocity across the combustion chamber. This movement tends to cool hot spots, average the chamber temperature, and speeds flame travel after TDC to increase power. On the exhaust cycle, some cooling of this piston occurs due to the closeness of the hopefully cooler cylinder head. The power increase occurs because the shock wave occurs at exactly TDC on all cylinders, every time. It tends to make all cylinders alike and receive more identical flame travel speed. Spark scatter tends to be averaged with the TDC kick received from a tight quench.

The suggested .040" static quench height is recommended as a good average dimension for stock rod engines up to 6500 RPM. Above 6500 RPM, rod selection becomes important. Since it is the close collision between the piston and the cylinder head that reduces the prospect of detonation, never add a shim or thick head gasket to lower compression on a quench head engine. If you have 10:1 with a proper quench and then add an extra .040" gasket to give 9.5:1 and .080" quench, you will likely create more ping at 9.5:l than you had at 10:1. One way to cheat the system is to make sure the piston of choice is light on quench side and heavy on spark plug side. As RPM increases the piston tries to **** away from quench surface, allowing a tighter quench at most all RPM. The suitable way to lower the compression is to use a KB Dish Piston. KB Dish Pistons (reverse combustion chamber) are desinged for maximum quench area. Having part of the combustion chamber in the piston can improve the shape of the chamber and flame travel. The Step Dish is sort of an upscale version of our reqular configuration. It allows some piston weight reduction and allows the quench action to travel further across the chamber. It is especially favored when large dish cc's are required.

 

Good stuff...thanks...

 

Some of the cams listed above with the gears is not going to make a comfortable driver, You need to figure out exactly what you want. 3.08 gears and cam on a 110LC is going to buck while cruising and do to the gears the lowend is gonna suck big time. Puttting in a big cam and looking for the big numbers dont work with low gears and an overdrive trans. Rather than the XE276 look in to XM276HR, this is a on a slightly wider LC and is not a bad driver, with the 383 and the cr you are runnng both of the XE & XM cams would be a good choice even if you where to up the gears to 3.73's. There is nothing wrong wither with the heads you choose, they will help promote the lowend tourqe you are looking for. Another couple of cams might be the 268XFI or the 280XFI, if your not want to really go above 5500 the 268XFI would probably be the better choice, being it is on a 113LC it will be a little bit choppy but will have some descent lowend and some excellant all around power. Sometimes smaller is better.

 

Sting 66, you should probably let the cam company pick your cam for you seeing as how they spend millions of dollars a year in R&D to create a data base for every combo imaginable. All you have to do is email the cam manufacture of your choice or call, they would be more than happy to give you good advice develouped by years of R&D!

 

Thank you for the advise everyone, I'm learning a lot...and have a lot more to learn. I'm anxious too see what some of the cam companies reccomend.

The XM276HR was a cam I was looking at as well, does anyone have experience with this cam?

 

The reason why I mentioned the XM cam is because I ran it in a 413sbc with 10.2cr, 3.73 gears and 700R4 trans, the cam has a lot of low & nidrange tourque and was fun driving around. Also when dealling with these cam companies like comp you can make several calls and talk to defferent guys and each will probally give ou a different cam, but overall if you take to several they should also be close enough for you to make you final choice. Keep in mind being honest of your goals is going to dictate what you are after, if your not and start leading them more into a street strip car then the cam is going to be something complete different from just a driver with some lump to make it sound good. Most guys usually will put bigger cams in and end up not liking it and blaming the guy that recomended it. You mentioned the aspect of not wanting to go over 5500rpm, the 276 duration cams are for shift points in the 6000+RPM point, if you spec a cam where you want to shift at 5500RPM you will wind up with possible 250 or low 260 duration cam which is why I mentioned the 268XFI and wider LC added with the OD trans and lockup converter with the 3.08 gearing will put you very close to your goals, The wider LC will give a broader power band then the shorter which is a little more definind where the power band is. Later if you wanted more performance you can up the gears for even better performance posibly 3.73 but you would also be able to go with 3.23, 3.42 to be a bit more conservative for some fuel economy.

 

Here is the email I sent to camhelp@compcams.com:

Hello,

I need your recommendation on picking a camshaft for my 1969 Corvette, and I want to go with a hydraulic roller cam. This is not a daily driver, but it needs to run well on pump gas.


Here is my setup:

1969 Corvette, SBC 383 engine, 700R4 transmission, 3.08 rear gear ratio
Late model roller block, with one piece rear main seal, 4.030 bore, 3.75 stroke
4 bolt main, forged rotating assembly
Procomp 190cc aluminum heads with 2.02 and 1.60 valves
Dual plane Weiand 8120c manifold
Long tube 1and 5/8 headers
2 and 1/2 inch exhaust
Speed Demon 650 carb with vacuum secondary
26.5 inch tall tires

I still have not purchased the cam, rotating assembly, or torque converter. Once I know what cam to use, I can build the motor with the appropriate compression ratio and select the right stall speed converter.

My goal is to build a street motor with a lot of low end torque and mid range power, to make this car fun to drive with 3.08 gears and an overdrive transmission. But I also don't want a cam that is too small, and that doesn't allow me enjoy the full capability of the motor. The 700R4 transmission has a low 3.06 first gear, which may allow me to run a little larger cam. One of the cams I was considering was the XM276HR, what do you think of this cam?

What cam would you recommend? Is there a custom grind you would recommend? Please provide a desired static compression ratio with the cam you would suggest.

Thanks for your advise...


Here is the reply I got back:

i would suggest using the xe276hr with the 110 lsa. this will provide a nice
low end and midrange cam. set your static c/r at 9.5:1. thanks.



ASHLEY NEWMAN
TECHNICAL CONSULTANT
COMPETITION CAMS
EXT.582