I bought a rebuilt 350 to install in my 76 Century. It was built to install in a street rod with a lumpy cam so I was told. Problem is valve train noise on start up sounds pretty bad with a lot clatter as though the lifters leaked down. Most of the noise clears up in the first minute it never goes away intirely. I’m wondering if this cam requires longer push rods. Springs, rockers and shaft looked brand new and when I pressure lubed the engine during final assembly the push rods seemed tight. Anyone have experience with this camshaft? Sorry, it’s a Comp 268H10 camshaft. Lift .469/.469, duration 268/268, rpm range 1,500 tp 5,500. Numbers stamped on the front of the block are 49H629393.
What oil filter are you using, may have a weak drain back valve. You should check for pushrod length with appropriate tool. Preload should be around.030. If you used Rhoades lifters they don’t get quiet. Comps lifters never seem to quiet either in my experience.
I buy Purelator oil filters. What brand do you recommend? I did some homework after I posted my problem that explains the process of checking pushrod length. It’s something I should have done but I have reassembled several SBB 350’s and I’ve never had this problem before. Still wondering if the 268 cam is the problem. Does oil filter drain back cause the lifters to loose their prime?
Wix filter seems to work best. It will cause drain of oil when engine off. You really need an oil pressure gauge on engine to confirm oil pressure . Then see if noise occurs at particular times, and compare to oil pressure. You could pull valve cover and check engine when running. Check rockers for lash or loose .
I used that cam in my '76 Buick 350, had no problems with it. My top end was clattering... due to no oil pressure. I wouldn't run it anymore until you get a gauge on it. I used bosch 3423 oil filters, never had a problem with them. They're small in diameter and longish. Are the rocker buttons the stock ones? They could've broken.
The Comp cam ramps cause the valves to slam shut. They will erode the valve seats if hardened seats were not installed in the heads.
It has 40 lbs. cold and 15 lbs at idle. Engine now has over 100 miles on it, pressure has dropped slightly. I changed the oil to Castrol 10w30 aft the 20 minutes at 2k cam break in period. I will change the oil filter to a Wix I bought today and see if it helps the noise level. If still there I will pull the drivers side valve cover for inspection. AC car so the compressor is on the passenger side. Thanks for the advice.
when you pull the valve covers off check to see if the lifters are mushy when you push down on them. when cold they will push easily and what I did was use the Comp Cam pro Magum lifters. They use a check ball in the lifter and they will not bleed down when the engine is off. Ever since I used these the engine never makes noise on startup. Put a 2200 stall behind this cam and it should run fairly good I used this cam back in the 80's and ran well but needed more stall in the convertor. I was using a stock convertor.
With that cam you also want better flowing exhaust, headers will help a lot as well. If in you want to stay with ex. manifolds with single ex. then this cam will be a lack luster turd and run embarrassing 15s in the QM if you ever take it there. With headers with dual ex. you might be able to get in the high to mid 14s with that cam if your compression is closer to 9:1 and you have better than a 2.56:1 rear gear in the car, like a 3.08 or better would help. And like what Guy wrote, a better converter will also be very helpful to get your car moving. Guy, what compression were you running with that cam and didn't you have headers with duals on your car with a 3.42:1 rear gear with a better converter? That cam isn't the best choice to run with ex. manifolds especially with an single exhaust system because of it being a single pattern cam is a sbb engine. That cam grind was engineered for a sbc and put on a sbb cam, comp did NOT do their homework to make a Buick cam. If in they did the cam would have a dual pattern with more exhaust duration to compensate for the sbb head flow ratio that is less than 70%.
I had headers with duals No convertor Comp was whatever a 71 engine had. I started with the 256 gear only needed 1st and 2nd for that gear, ran 373 gears and 28" tall tires and ran best of 14.80. cam was ok for the time brut there are better ones now. This cam is from 1980.
The lifters are not mushy but some of the rockers are not centered over the valves. The plastic buttons that keep the rockers centered have problems. Some have slots worn on the edges and some are coming out of the holes. I picked up a new set today and will install them Sunday. I look forward to starting the engine with the valve covers removed to see if they are getting the correct oiling.
The car has 2 1/2” dual exhaust with stock exhaust manifolds and turbo mufflers. It runs 100% better than the original stock single exhaust with cat converter. It’s not ment to be a drag car with the stock 8 to 1 compression. It’s a 1976 Buick Century Custom with TH350 with only 40k miles. The original motor had really low oil pressure and spun the thrust bearing on the crankshaft ruining the crank and block.
There are left and right hand rockers, make sure you have them on correctly or you could run into problems down the road. The easiest way to make sure they are on right is to look at the pushrods, those are closer together than the valves are, so the offset on the pushrod side goes next to each other and on the valve side are farther away from each other. GL
The stamped steel rockers dont have any markings iirc... are those the ones you have? The aluminum rockers have an L and R on them. So, the problem was a broken rocket button?
Update: replaced the rocker guides and started it up without valve covers. Lots of noise and no oil for 30 seconds or longer. Checked the gauge and it had 40 psi but this was after waiting a long time. When the oil finally came up the pushrods it is foaming. No there is no antifreeze in it. Shut the motor off and the puddles of oil clear up after awhile. Where is the air coming from? The machine shop did a poor job of cleaning the pickup tube so I cleaned it and replaced the tube to block gasket during assembly. Any suggestions?
. That’s the only thing I can figure out. I spent a bunch of time on the pickup tube since there was a build up of crud in the pickup.
I removed the engine and I’m replacing the cam with a smaller Comp cam. The timing cover is warped and I’m pretty sure it was sucking air at the port where the cover meets the block and loosing prim with the oil draining back into the pan. I’m lucky to find the problem. After scraping off the RTV everywhere but the oil pump location I knew something was wrong. Putting the cover on without a gasket showed there was a gap that area. I would never expect to see the cover warped but heads warp so timing covers can too.
