1970 gs350 camshaft

Hello. I am new to the forum and wondering if anyone could offer a bit of advice regarding an aftermarket cam for a 1970 gs350 motor. Good running smooth motor in 1972 skylark convertible. I plan to do other mods as well, to make a nice quick sbb. Plans include 3.73 gears ( i think 3.90's would be too tall for the highway with a turbo 350 trans) , auburn posi, new carb, ta performance intake. I am looking for a hot street/ strip cam. I had considered a ta310 or 290. Looking to make a formidable and quick buick sbb. I also plan to do a little weight reduction as well, aluminum radiator, lightweight battery and starter, disc brake conversion( i know drums weigh a lot.) , fiberglass pin on hood, fg bolt on trunk lid. Lost the ac condenser/ compressor etc. already ( that stuff weighs a ton!) , don't use it in Colorado anyway ! I plan to have my distributor recurved at a local speed shop. I have already installed a pertronix conversion and an msd blaster coil, which cured my hard start problem and made the engine run much smoother, definitely worth the $150 bucks ! I am curious whether the msd digital 6 ignition box would be worth the money ? I would appreciate any help/ suggestions. I have already gained some useful information here in the recent past, so I thought I would join the forum.
Thanks , Chris

 

my combo exactly - 72 ragtop with '70 SP 350 and TH350.

the SP3 intake was a huge power improve over my TA dual plane even for street cruising. At highway speed from about 40 up, it just keeps pulling almost ridiculously hard all the way up past 90 at which point I usually back off the gas... :laugh:

I'm running a Comp Cam p/n 92-202-4 (their 260h cam), HEI ignition, and mid 70's electric choke 750 Qjet. Also running an open air cleaner and top (K&N style), which feeds nicely on the air coming in thru my GS hood scoops.

Aluminum rad keeps my temps in the 180 range all year long. A board member here sells Delco mini-starters and it's a good choice for easier starts. Running 3.23 posi out back and just now getting into my rear disc brake conversion which should hopefully be finished this week.

don't think I'd do glass body parts on a street car though - you probably wouldn't see enough gain to make it worthwhile and the safety trade-off would make it even less attractive IMO.

 

I have the 310 cam with 3.73 gears in a 70 GS 350. I am actually considering pulling cam/2800 convertor/3.73 gears for 3.42 gears/2200 stall/Crower level 3 cam. 310 makes more upper and I am looking for more low end torque and cruise ability as its a convertible. I might even be pulling ported heads in favor of stockers so I can try the pure stock class. If I get similar times as Steve's high 13s I will be happy.

 

Scott. I appreciate the input. I am not sure what the SP3 intake is.. Would that be the stock intake ? New to the SBB , so I am still learning. I wouldn't go crazy with the glass parts ( and keep the stock ones of course) I know the hood and trunk lid would save a lot of weight, I figure 100 lbs is like adding 10 horsepower.. I wouldn't want to mess with the low end torque, love that low end grunt!! Also contemplating headers, I figure I could make some respectable horsepower with a good cam, and headers. Anyone like to add their two cents in as far the carburetor is concerned ? I am considering a holley 3310 750 , or a holley street avenger 770. Should I just stick with the QJ and tune it ?

 

TA's new 350 single plane intake - just released and soon to be followed by their new aluminum sbb heads.

you can see it in their catalog or look thru the board for prior postings about it. It's a great piece for street/higher rpm even though single planes are typically thought of only as high rpm items.

 

stick with the qjet. check Mark at quadrajet power. he updates and rejets/meters the carb. did mine a few months ago. had him add shaft for overdrive trans incase I go that way.

 

Thanks for all the input. I will definitely check it out.. Kinda thinking of the ta dual plane.. I forgot to mention earlier, if I change the cam , nothing with high of a lift so I can still use stock valvetrain..

 

Thanks for the input on the carb. I like the idea of keeping it simple and cheaper ! The qjet's worked great for the gs back in the day. thanks for not telling me to yank out the motor and putting in a 455.. I look forward to realizing the sbb's potential. I love the grunt and have a great respect for Buick's. I used to race my friends GN back in the day.

 

You mentioned living in Colorado. What is your elevation?

Paul

 

If your going to do much highway driving, I'd consider no deeper than 3.42 gears with a T-350 trans.
The 290-94 TA cam is nice, with the 310 your going to need a higher stall convertor, I didn't see you mention a convertor change.
Stick with the Q-Jet, its an awesome carb, I picked up almost 4 tenths switching from a Holley 750 Vac. Secondary back to my original Q-Jet after Ken @ Everyday Performance redid it for me.

 

I would leave the engine alone for right now and wait a bit till the Ta alum heads are released. Then go with a custom calibrated q jet or Holley 850, sp-3 single plane intake, alum heads, custom roller cam from Ta.

Or if you want to do a mild build on the engine a ta212 cam is a better match for A stock engine.


I like the weight savings idea, my skylark is 2980 pounds.

 

Big cam + single plane w stock pistons in Denver = Poooooooooooooo

 

Now that's the right question. Big cam(relatively speaking) with stock compression(9.5:1 actual?) and high elevation equals slug in the lower rpm range. The nice 3.73's would help but low cylinder is low cylinder pressure. A single plane won't do much for the low end either. I'd stay on the small side of the cam to keep the low end torque up.

.

 

A custom ground cam from Scott at buyracingparts.com would be best but the Crower level 3 should make more cylinder pressure and good low end torque. I don't think the 212 will give much gain if any over a 70 gs350 cam.

 

Hello again. Thanks for the suggestions. I am at 6400' , in Manitou Springs. I realize that the elevation will make a huge difference in performance, meaning that carb tuning / rejetting would be necessary. I considered the holley 3310 because of the metering block and the able to change jets / tune. I failed to mention that I was thinking of a 2400-2800 torque convertor ( so I would be in the optimum torque range for launch ) Gears 3.55 to 3.73 might be a good compromise. Is a mild head porting / polishing DIY job a possibility ? I have read about some folks unshrouded the exhaust valves... As far as cylinder head pressures are concerned , I am guessing a compression test would reveal a lot ? I am sure a baseline dyno would be really valuable info as well. Maybe I'll that stuff alone, install the torque convertor and shift kit, then put the skylark on a weight loss plan.. Sean I would love to know how you got your skylark down to 2980 pounds ! I appreciate all the valuable info. I had considered a 700r4 at the right price, and add a lockup controller, certainly help with lower gears and highway cruising. I am certainly capable of a lot of diy projects, having done axle swaps / engine swaps, etc.. I assume someone out there sells a 700r4 trans crossmember for the skylark ? Then I'll just need a B and M or hurst shifter to finish it off.. Any thoughts or suggestions as far as those ideas are concerned ?

 

Re-jetting for altitude isn't the concern.
It's air density and cylinder pressure.
Higher compression and octane tolerance are affected strongly by those factors.
The relationship between the rpm range of the cam (affected by compression, displacement) and the cylinder pressure curve resulting can be different depending on altitude.
It's already been mentioned, low end torque will suffer.

 

Consider larger ta valves. Not sure why your hearing to unshroud the exhaust valve. With the Crower cam you should not need so much convertor. I had the 700 trans in my convertible. If you get a tail shaft that has mount on it you can slot holes in stock crossmembe. You will need to shorten driveshaft and modify carb for trans cable and modify a cable bracket. Your stock intake may need a spacer under carb for throttle clearance. It also sits very tight in convertible tunnel. 200 is a better option. As far as cylinder pressure what they are talking about is the thinner air in higher altitude with how the camshaft design fills cylinder . different cams can change that pressure and that's called dynamic compression. That's what alters your rpm range/HP and torque range. You want a certain range for street gasoline so not to detonate and damage engine.

 

Instead of messing around with a carb this FI system would be a great addition;


http://professional-products.com/fu...tion-iii-complete-kit-returnless-satin-finish

"Carburetor replica throttle body for that traditional hot rod look.

EMS (computer) mounts directly on the throttle body eliminating most of the wiring found on other systems. No need to cut holes in the firewall for a harness.

Utilizes wideband O2 sensor for optimum tuning feedback.

2.5 BAR MAP sensor integrated into the EMS measures up to 22 PSI boost for supercharged/turbocharged apps.

Only aftermarket throttle body system with this feature."

Idle Air Control, Fuel Pressure Sensor (when utilized), Throttle Position Sensor and MAP Sensor all contained in throttle body assembly.

Version 3.0 Software included with spark timing control"

Or if you don't mind buying it as "remanufactured" you can save about $700;

http://professional-products.com/fu...it-powerjection-iii-complete-kit-satin-finish

Looks like a lot better way to go than a carb and being that high in altitude the self-tuning EFI would seem to be a good way to go to optimize the A/F ratios on the fly incase you drive the car down off of the mountain you're on now some day? GL

 

Sheet metal alum intake weighs about 40 pounds less than stock, turbo kit weighs less than cast iron headers, alum core support, fiberglass fenders, hood, trunk and bumpers, and stuff removed that was not needed.

 

I'm not sure that turbo are the answer in this case.