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What are your thoughts on this cam? I really wish I had found this forum before I started the rebuild on my 71 Olds Cutlass with a 350 but since I’m here now I thought I would have you guys check my work.
Here is the rest of the build also:
Cam is installed on a three key way timing set on 0 degree.
Flat top pistons with .030 bore - somewhere around 10.5:1 compression
Crank turned .010 under with new rod and main bearings
Original block bored .030 over, chromoly rings on pistons
cast iron #7 heads milled for smoothness with new valves. 30 degree back cut on valve seats
edelbrock 7111 intake, blocked off heat crossover ports in intake
Holley street demon 750cfm carb
HEI distributor
Factory valvetrain with new springs and lifters specced to the cam
2300 stall converter and trans go shift kit in turbo350 fully rebuilt by a local shop
It runs pretty nicely not a whole lot of trouble with the idle, not much vacuum at low rpms (power brakes tend to empty the booster during hard braking)
Saving for headers but have the factory cast iron log manifolds installed at the moment.
thoughts on the build? Any suggestions for improvements?
Last edited by markvii1; September 10th, 2020 at 07:39 PM.
The stock cam (400084) for a 350 4 bbl automatic rates 201/210 intake/exhaust at 0.050" with 0.400" lift.
The stock cam (393859) for a 350 4 bbl stick rates 222/222 with 0.472" lift.
I used the 393859 in a 350 build with a switch-pitch T-400 and a 2.78 axle. It was down just a bit on power off idle, but it had very good power once the revs built. There was a nice note to the exhaust.
Factory cam 400165--W30 automatic--specs out at 223/223 and 0.472" lift.
I hope this gives you some background to help you judge the suitability of your cam for your application.
Unless there was some head and block deck milling, flat tops pistons will give around 9.8:1 compression ratio.
Anyway, that cam seems short on lift for the amount of duration compared to other grinds, but it should work OK.
The cam in my engine gave a similar issue with vacuum and brakes - it had around 15" vacuum at idle and was very bouncy. After adjusting the distributor (HEI) for higher initial advance (set to ~18º) and connecting the vacuum advance to manifold vacuum, there is now a strong, steady vacuum signal and the brakes work fine under all conditions.
222/226 on a 111 lobe separation should work fine with power brakes, especially if you have legit 10.5:1 compression. I have a friend running a 231/239 duration on a 110 lobe separation (way more overlap) without issue on his 350 with power brakes.
Not degreeing the cam means you are trusting the accuracy of the timing set. The cam is a bit short on lift, as noted above.
Follow Fun71's advice above to get yourself a bunch of base timing and it will help out the idle vacuum tremendously.
I will adjust the timing on the HEI this weekend and move the vacuum advance to the manifold, I have it run of the carburetor base currently but there is a spot to tie into for manifold vacuum. I still have the 2.73 rear end, so I won't be winning races but it has enough power to stay out of trouble. The ultimate goal with the car was a modest power increase without killing the fuel economy completely (aiming for 10mpg city and 13 highway). I plan to take it up the blue ridge parkway next month for our honeymoon and then daily drive it around town and to work.
FYI, the vacuum canister on my HEI was stamped "24" which is 24º of vacuum advance, which is way too much. I modified it by slipping a bushing over the end of the rod to shorten the travel in the slot and that dropped it to 16º, then later I made an adjustable stop and set it to 10º which is where it is now.
Before digging into the rest of the drivetrain get the distributor straighten out. A little more initial timing will really wake up the low end. Unfortunately, bumping up the initial leads to excessive total timing.
Shot for 14ish initial, and 32-36 total. You can usually get away with another 15 or so of vacuum advance.
If you get creative with vacuum advance limiters, you can limit the total and also adjust the vacuum needed to make the advance start. If you flip the stop around the other way, you have changed the starting position of the rod. You still limit the advance, but since the spring is compressed more than the base drying, it will take more vacuum to overcome the spring.
Is it a new HEI? If so the vacuum advance should be adjustable. I find the aftermarket vacuum cans have 20 degrees max. What brand timing set is it? Hopefully not a Comp Cams, they have accuracy issues. As said the cam should degreed in to check the cam and timing set accuracy. Sounds like a nice cruiser. A tuning kit for the Street Demon will also help power and economy. The 750 might be a tad rich for your set up.
Is it a new HEI? If so the vacuum advance should be adjustable. I find the aftermarket vacuum cans have 20 degrees max. What brand timing set is it? Hopefully not a Comp Cams, they have accuracy issues. As said the cam should degreed in to check the cam and timing set accuracy. Sounds like a nice cruiser. A tuning kit for the Street Demon will also help power and economy. The 750 might be a tad rich for your set up.
Yes it is a new HEI - made by summit racing. I bought a new engine wire harness from American Autowire to convert it from the points distributor that was in it, and also deleted the TCS system.
The timing set is a comp cams double roller chain set with a three key way chuck, but you are correct I did not degree it before install (I would like to check it but it ran fairly well after full build and I am trying to avoid tearing back into the engine at this point).
The carb does run rich but the plugs stay dry and mostly clean - a little gray around the edges but no soot or oil buildup on them - compression runs about 145-155 on each cylinder. What would be your recommendations to get the carb more in line with my build? I was worried it was overkill but the carburetor was highly recommended and other than having to run a custom Lokar bracket and bicycle brake cable for the throttle it was an easy install.
September 10th, 2020, 07:37 PM
