GoldOlds

OK, here's what I want; mid-13s on pump gas for the 350 SBO in my 3,700 pound (that's a guess) '69 Cutlass. It has true dual 2.25" exhaust and a 12 bolt Chev rear with 3.73:1 posi gears. Tranny is a TH350 with what feels like a Stage 2 shift kit. Right NOW, motor runs great and is stock except HEI ignition.
What would I need in a hyd. flat tappet cam? I like Comp, but I'm open to other suggestions. How much cfm for the carb? I'd like something in the vac. sec. variety. I'm pretty much a carb idiot, the lone reason I'm wary of sticking with the Rochester Q-jet and leaning more toward a more user-friendly choice like the Holley Street Avenger.
This will mostly be a crusier that sees the 1/4-mile 3 or 4 times a year. I'll probably put W31-size valves in the heads (#5) and deck them for about 9.5:1 compression. I still haven't decided between Performer and Performer RPM; leaning towards RPM.
Thanks in advance!

- GoldOlds

Redog

A Mondello 18-20 or a 22-25 cam would work pretty good, but you should change the torque convertor with any cam work. Be sure to get the street cam. Some don't make enough vacuum to operate the brakes

5 heads are actually pretty good to start. I'd leave them alone, maybe put in hardned valve seats, stainless valves and a 3 angle valve job if you're going to do anything. If the heads have air bosses, get them grinded down.

You can't just throw in a cam. You have to get the pushrods, rockers, and springs to make it work correctly. Unless you get a cam that is just a little bit better than stock, but is that really worth all the work then?

You really want to high a higher compression. 9.5 is good, but 10.1 to 1 or 11 to 1 is better. You just want to stay below the 11.5 range, becuase then running on pump gas becomes harder to impossible. If you are going to do a rebuild in the future, get higher compression pistions

captjim

I have a 9 to 1 355 in a G-body wagon with 3.42 gears. Here are the specs;
http://72.22.90.30/phpBB2/viewtopic.php?t=28012 The car is very fun to drive, reliable and durable. If it was me, I would use that cam or the new Voodoo; http://www.holley.com/60801.asp 213/219 with 9.5- 9.7 to 1 compression, RPM intake, and a 770 Street Avenger carb. I agree with reddog that you will want a little more converter. I will STRONGLY disagree with the cr recommendations. 11.5 on pump gas?????? Ask most builders or cam grinders and they will say that realistically, high 9.xx to 1 is it on pump gas, unless your cam/tune is perfect.

GoldOlds

Thanks for the responses; much appreciated! I'm starting to think the suggestions on the aforementioned cam guide might not be 100% accurate. Anyway, what stall speed would you recommend for the cams you've suggested? I know it's possible to have too much cam for your converter, but can you have too much converter for your cam? Would 2500 work well? I'm 99% sure the 3.73s would be enough gear for those cams . . . right? What about the 2.25" exhaust? Thanks again!!!!

- GoldOlds

captjim

That is plenty of gear, if anything a tad much. Use a tall tire. Also, 2500 sounds good, but instead of guessing, call a converter manufacturer and give them your specs. I really like Coan, great service and product, but there are other good companies out there. For $350, they will build you a custom, quality unit. IMO, this is not the place to save a few $. My nitrous race converter has a 2600 stall, does not slip at all on the street, cost $650 and is worth every penny.

GoldOlds

Right now, the back tires are 255/60/15 (27"?). . . is that tall enough? I've also heard many good things about Coan converters and I agree, it's not something to cheap out on (kinda like an oil pump; spend the money!!). Would one of the cams you've suggested work better with a Performer or Performer RPM manifold? I've got a brand new Holley 770cfm Street Avenger (vac. sec.) sitting in the box, which I originally bought for the 454 Chev I was building - that was BEFORE I bought the Cutlass. Is that too much carb? Thanks again... you guys have been very helpful!

- GoldOlds

captjim

I did a little RPM/Performer test, not really scientific, but here if you want to read it. http://72.22.90.30/phpBB2/viewtopic....performer++rpm The car was quicker with the Performer, but faster with the RPM. This at 9 to 1. I think at 9.5 and with that gear, the RPM would be better. If the cr ends up being 9 to 1, it is pretty close. Although, the throttle response was better with the Performer in my car. #5 heads with 65cc chambers, 6cc dish Speed Pro pistons, and .050 quench gives you 9.8 to 1. Use that with the RPM, 770 carb, and a cam in the 215-220 @ .050 range and you ought to be just right. This one, http://www.holley.com/60802.asp maybe, or one like it. And with the Speed pros you can spray it if you want, those things are strong and durable. Those tires should be fine, but there are guys using 275/60/15s, too. They are 28" tall, IIRC.

Olds64

I mentioned an article in Popular Hot Rodding that gives really good paramaters for determining carb size for an engine. Check it out.

https://classicoldsmobile.com/forums...4433-carb.html

I wouldn't suggest a Holly carb if you are carb stupid. I have used them before and I prefer an Edelbrock carb. They are much easier to tune and are more tolerant if you forget to change carb settings as things wear and the seasons change. Of course, that is just my experience, I am sure you can find plenty of guys that will swear by Holleys.

88 coupe

3 angles = Basic valve grind

Pushrods: Only if the base circle, on the cam, is smaller.

Rockers: Stock assemblies will handle .550" lift easily. The potential problem is not the rockers, it is the possible interference between the valve retainers and the seals/guides.

Springs: Should always be matched to the cam profile.

These type formulas show a balance between power and "streetability". On the same engine, a smaller carb will have better "off idle" response, while a larger one, will have more power.

I swear by whatever carb I'm using at the time. An "out of the box" Q-jet, on a Torker, put my 3900# Grey Coupe into the mid 12's.

Norm