Maybe this cam needed to have more lift on the exhaust. I also think it is ground on a 110 LSA so maybe the cam should have a 113 LSA The cam I run has a LSA of 116 and it did keep the vac up and I do get good bottom end takeoff The downside is the cam starts to give up at 5700 and I have spun it to 6200 lots of times but I usually shift at 6 grand. It does not sound like there is a vac leak since Reidk gets around 14 vac on the gauge and has the same cam. That 284 is very close to the Comp Cam 268 I used years ago. Back then all I had was the stock intake and 650 DBL pumper I would work on the carb more to get it dialed in I have to wonder now if it is the correct Q-Jet on the 350
I don’t normally suggest this however I think it’s time to remove the engine and go through it again, something is physically wrong.
Dont worry about the choke for now, its not important, you dont drive on the choke after warm up. That leaves you with two issues, yes? Running hot. Rough idle. I'd suspect a leaky intake or exhaust valve for the rough idle issue. Describe or post a video of the idle, a cam with a lope will idle with a rumpita rumpita sound. A leaky valve will idle duh duh duh, it will be rythmic You can tell alot from how an engine sounds It wouldnt be the first time a "rebuilt" head leaked Try the suggestions on the running hot issue, but FIRST, get the engine running as it should. Thats not bad idle vacuum with a cam. Remove the rocker shafts and do a leak down test. What is your lifter/pushrod set up like? Heads milled, block decked?
I'd try working on the carb & cooling system 1st, esp. since there was a difference bet. the QJ & QFT and nothing obvious he knows of internally plus the comment thylat this cam likes a lot of fuel at idle. If anything, pull the valve covers while running and make sure there’s nothing obvious like a wiped lobe & not saying it couldn't be internal but what else besides checking/changing cam timing would it accomplish?
Agree. I was just throwing that in there in lieu of tearing it down when there's no obvious signs as far as we know or the OP has indicated of it being an internal problem.
I would definitely be interested in this to rule out the valley pan gasket being the issue. I have never like that pan gasket, I would always prefer a paper gasket, just feel like the composite gaskets seal much better. I have checked for Vacuum leaks in the past by unplugging all vacuum lines , plugging all ports on the carb and it didnt make any difference that I could notice. I can try to put a hand over the carb. I think ive tried this but dont remember what the results were
Haha pulling the motor and dropping it off at the machine shop. In my mind, it's never run right since. Ive been chasing my tail for going on 6 years with this rebuild. changed cam timing, water pump, the radiator, multiple cabs, replacing valley pan gasket, etc. Nothing I have done has hurt the running, but nothing has been the ultimate fix.
I had previously done a compression and a leak down test. Leak down showed only 5-7% leak down per cylinder. Compression test all 154 Plus/minus 4 psi Heres a link of it running during a walk around. https://youtube.com/shorts/GWAIclZh9Yk?feature=share and here is an old video I took showing the shaking at idle: Disclaimer is this is an old video and the cam timing has been changed since then, however the shaking at idle remains very similar https://youtube.com/shorts/SWC-sl0id30
I actually have had the engine out of the car and gone through because I was burning a quart of oil every 2 tanks of gas. There was an issue with how the valve seals were installed, engine builder fixed it for free, verified the cam is in good condition as well. No wiped lobes according to him Someone else asked about the rocker set up, they're stock rockers that came with the 68 heads, using the 70 style original length push rods with the hole through the middle for oiling the rockers. I assume the head has been decked, but by using original length rockers I would also assume it hasnt bene decked significantly, or the builder used a thicker gauge head gasket to compensate.
Looking at the vid of the engine it looks typical for an engine with a non stock cam. Your walk around vid the exhaust sounds typical of an engine with a non stock cam. Your compression and leak down numbers look good, don’t see an issue there. That leaves you with a running hotter than you want it too issue. What type of converter you have?
With proper rtv on water holes & copper coat or high tack on remaining surfaces, those embossed valley pan gaskets seal well, just the same as steel shim head gaskets. Don't think that's the issue. Maybe fuel, ignition or timing.
Are you sure that you aren't chasing something that is normal? 13"-14" of vacuum and a rough idle could just be characteristic of that cam. That cam shows RPM range 2-5000 so if you're trying to get it to idle @ 800, the idle will be rough. 220* isn't at all hot under certain conditions. I was trying to measure the height of my car with it running and the height was varying 1/8"+at idle with my engine only having 11" of vacuum. If you want a smooth idle, maybe install a different cam.
I suppose you could be right, I've just seen this cam run in other engines that have a very similar build to mine and seemed to run alot better with no heating issues. the coverter is a 2400 stall ( which I think is probably too high, kinda want to kick it back down to like 1600-1800) Believe me, when you're sitting at a stop light after this thing is warmed up, you would think something was wrong based on how the car shimmies at idle. The heating issues are a concern still. Never had heat issues before the rebuild. I understand its no longer a stock engine, but I feel like it should manage the heat better than it does.
if this truly is the characteristic of this cam and not anything else, do you think changing the cam would also fix the heating issue? or is that still more likely related to the fuel/ignition? Heres a video of another 350 with a 284 cam, very very similar build from what I can tell and the description, and his is idling around 650 RPM and seems to run a lot more smooth than what I am seeing
The rough idle in gear is probably the engine tugging on the trans. You say it’s a 2400 stall, but is it really? 2400 stall may be behind a big block that developed more torque. Is it an off the shelf converter?? A custom converter from JW would be the ticket! IF you went down in stall, the issue would get worse, NOT better, 1600 rpm stall is like a stock converter.
