engine question

[meathead95]

I got this 454 from a guy who said when he got it it was supposed to be a fresh rebuild but they had flattened a lobe on the cam. so I tore it apart today to replace cam, lifters,timing chain, intake, and carb. blah! blah! blah! and the inside was very very clean. and I couldnt find any metal in the oil or anything. but when I took the cam out it had 7 yes 7 flat lobes, crushed lifters/ and bent pushrods. what in the world causes this as I have never seen anything like it before.


also arent the dots on the timing chain gears supposed to be lined up when the #1 piston is at tdc?

[jhow66]

Dots:
1--Dot at 12 o'clock on crank and 12 o'clock on cam = #1 firing stroke.
2--Dot at 12 0'clock on crank and 6 o'clock on cam = #6 firing stroke. .
As to bent pushrods could have floated the valves(to high rpm's) or to much lift on cam for the spring causing coil bind or to much lift causing valve to hit piston on some cylinders.
Lobe problem could be improper break in or to much spring pressure.
(if dots are not lined up someone probably advanced the cam causing valves to hit pistons)

[incoma]

I've also seen folks over tighten their rockers and do this, particularly if they didn't fill the hydraulic lifters with oil before assembly. If they assemble dry, when the lifter starts to pump up, it puts lots o pressure on the cam and voila - no lobe after a few miles.

[arkracing]

JHow...when would you ever put both dots in the 12'o position.
i thought they should always be lined up 12'o on the crank, and 6'o on the cam????

[CHEVYE]

yeah, i always set it to 12 on crank and 6 on cam gear and that is where i set TDC??? i always turn the engine by hand to make sure it lines back up, believe it or not, sometimes it doesn`t. do you know what kind of cam you got in it meathead? my neighbor builds big engines and he has had 2 comp cams flatten out on him and he`s been building engines for 30 years. he says he called comp and they had a bad batch or ??? but now he stays away from them.

[meathead95]

i thought it was 6 on the cam and 12 on the crank. but my question is, is that with the #1 at tdc?

chevye, not sure on the cam make ill check it out tomorrow

[jhow66]

Originally Posted by arkracing

JHow...when would you ever put both dots in the 12'o position.
i thought they should always be lined up 12'o on the crank, and 6'o on the cam????

To make it easier to install your cam right you line the dot on crank on top (12 o'clock) and the dot on cam gear on the bottom (6 0'clock). This is not TDC firing stroke for #1 cylinder but TDC firing stroke for cylinder # 6. If you then turn the crank 1 full turn your crank dot is back at 12 o'clock and cam dot is at 12 o'clock which is TDC firing stroke for #1 cylinder. (takes 2 turns of crank to turn cam 1 turn). To check this out the next time you are installing new timing chain or gear with dots lined up at 12 & 6 start turning engine and watch which lifters or valve starts moving. It will be # 1 cylinder so that cylinder cannot be on firing stroke. Confusing ain't it?

[dwaite72lnghrn]

Personal experience on BBC is if the push rods are bent, (Chances are they are the exhaust valves) you now have bent valves to go with the bent push rods. My factory timing chain went at 60mph at 83,000 miles (D@m plastic gears). When they put it together they probable just tightened them down then started the engine. When you put the new cam in use black moly lube generiously on the cam then pour cam lube (the stp looking stuff) over all of the lifters and valley area so it will continue to wash down with the oil at startup. Be sure to pre fill your oil filter before you screw it in. The Cam should be dowel pinned and the crank should be keyed always install it straight up, Some cams you can advance or retard. With the crank at 12:00 the #1 will be TDC, Put the cam in at 6:00. With the timing still at TDC #1 adjust #1 I/E, #2 I, #3 E,#4 E, #5 I, #7 I, #8 E, crank engine 1 rev(crank 1 rev back to TDC #6) adjust #2 E, #3 I, #4 I, #5 I, #6 E/I, #7 E, #8 I. Then right before you drop the Dizzy in run the oil pump to get pressure in the system ( I took a 3/8 all thread ground a blade on the 1 end and put it in a drill and ran it till the oil hit the valley (oil will start to climb the all thread). Drop the dizzy in so rotor points to #6 make sure you have power to dizzy and go for it.

[GMC AMI]

Turn the motor over by hand past the mark a little then back to the mark to take the slack out of the timing chain if there is any.

[frogsmakr]

improper break in will ruin a cam...........

[68C15]

sitting on engine stand for long time without running WILL in fact do the flat lobe thing. a guy at work here did that to his BB for his mud racer. quick way to loose lots of $. as far as also having bent pushrods it sounds like a spring issue. I recommend some break in springs or low ratio rockers to save the cam from excess lifter pressure.

[meathead95]

so do you think the valves might be bent? can i check without removing the heads?

[dwaite72lnghrn]

If you have a dial indicator you could check the travel on each or a compression test. But the exhaust valves have a clearance issue with the pistons. If the push rods are bent on a big block and it is the exhaust valve push rods most likely the valves are bent.. I have not heard of valve lifters flattening out after sitting, Those things are very hard and every crate motor out there would be bad from the factory if this was true. Most lifters go bad on startup because they are mis-adjusted. Over tight makes them solid with no lash or to much cam and no clearance (springs compress and push rod bends). When you look at a cam you must look at overall lift not just at .050 lift. Any time you start getting above .520 total lift you might start looking at machining the head for spring clearance.

[meathead95]

also this is my first bbc so this may be a stupid question in the very center of the lifter vally it is cut out so you can actually watch the cam turn are all bbc like this? all i have ever had is sbc's and i have never seen anything like it.

[dwaite72lnghrn]

Yep here is a picture of mine when I just did the head gasket. I put a crane HMV-272 cam with crane lifters at 83000 miles, I just did the top end then. I just had it redone at 150,000 and the cam was like new so it was reused. At 156,000 it was drinking water and getting hot so I did the head gaskets.

[meathead95]

this engine i have is that clean inside also

i forgot to mention it pushed one of the pushrods through the end of the rocker.

so do you think maybe the didnt fill the lifters with oil or prime the engine before the fired it to cause something like this?

do you think i should take the heads off and get the valves checked?

what size are the valves in bbc heads i have the 781 oval port heads

[dwaite72lnghrn]

Tough to say what the current valves are now stock would have been 2.06 intake and 1.72 exhaust. The head is a 110 cc 1974 454.
Stock BBC rockers are 1.7 ratio. It doesn't sound good on the push rod through the rocker, You will have to check the rocker stud as it might be bent after that.
Head gaskets are under $40 so it is cheep now to pull them. If you need new valves you might need a grind on the head or at least lap the new ones in. Not sure what a machine shop will charge in your area but you could try just the valves if they are bent. When you pull the head look at the valves and shine a strong flash light in the exhaust port and look for light around the valve.
When you pull it apart take a piece of card board 30"x20" fold it half so you have a 30x10" "V" poke 16 holes in it number them 1 E, 1 I, 2 E 2 I,.......8 E, 8 I. as you pull the rods look at each end and check for broken or rough ends lay it on the end of a framing square and look for straightness, Then put it in its hole in the card board. any sign of something wrong mark the card board hole with an "X" and it will need replaced. This way as you tear it down you will know what valve to look at and what rockers to inspect for damage. I also if I am going to reuse the cam (which you are not) I take a egg carton number the egg holes and put the lifters in the holes so they can go back in the same place. Some say it don't matter where they go but call me anal I like them to go back where they came out.
You will have to pull the pan and clean the oil pickup screen of junk as that is where the pieces are most likely.
In '85 when I did the cam the crane cam was $139 and the lifters were about $70. Not sure of todays market on them. All I can say is the crane cam really woke the engine up. I just changed the cam I got 2-3 mpg increase now with a big block that was a 20-30% increase with that cam and more power than I needed.

[meathead95]

thanks alot i already have a complete gasket set so ill just pull the heads and have them checked out. i also already have new rockers for it also. i dont know why i have been debating pulling the heads i am pretty anal about stuff too, plus i have so much money tied up into it right now i want it right when its done. thanks for your help
dwaite72lnghrn
and everyone else

[dwaite72lnghrn]

One other thing to check is make sure the plastic oil pump shaft sleeve has been replaced. When I did mine there is a short shaft from the oil pump up to where the dizzy connects factory used a plastic sleeve. After market I used was metal sleeve.