I have a 1970 350 with
268h comp cam installed strait up not retarded or advanced
set of 193 heads with the lt1 z28 valve spring with a install height of 1.700 i think at about 110 ft/lb of seat pressure
i was using the push rods form the 193 heads
im using stock 1.5 ratio rockers the heads do not need the self alining rockers i checked
Now hears my problem its a fresh rebuild never started but it bent all the exhaust push rods whats wrong i have the old push rods form when it had the 882 heads on it whats going on???
HELP

 

Possibly the retainers hitting the guides?

 

Thats what im thinking i think i bent a Valve i here a hissing when i crank it over with none of the exhaust push rods in

 

I'm no expert here, but ...

Your heads are from a roller motor, but your motor should have a flat tappet cam. Did you use roller lifters or hydraulic lifters? The 350 should have had hydraulic lifters, but the newer valvetrain (ie newer heads) is expecting roller lifters and a roller cam. Might be a pushrod or lifter issue - the pushrods from the 882 heads might be the wrong length.

But as I said, I'm no expert here with these matters.

 

ya that's what im starting to think,So my 882 heads where rebuilt last year they have about 4,000 miles one em you think if i just put new valves and springs ect and just lapped them with compound they would be ok i lapped one valve and it looks perfect,and i did bend a valve i have crap for compression on cylinder 4 and on others im sure

 

I have noticed this is a bit of a trend lately - did you actually measure anything before the rebuild, or just throw some parts together and hope for the best?

 

I did measure every thing out but i didn't measure retainer to seal clearance i figured that my cam wasn't that radical that i needed to go that far

 

Agreed, what lift has that cam got, 454? Should have been ok, but evidently the parts had other ideas. Gotta be either a valvetrain interference or piston/valve. Sure you got the timing set aligned right?

 

It is a .454 lift cam
so today i took it apart all the exhaust vavles hit the pistons
so did i put the heads together worng i uses the 882 heads valves in the 193 heads because they where like new are the valves differnt lenghts?
i used the 193 push rods
and stock style lifters
can the 193 heads ne used on my 1970 block with all 1970 parts or did i need some special parts or differnt lifters and push rods
i send my old 882 heads to the a expert and hes going threw them with all new parts
what should i look for

 

bump

 

any one

 

I have never bothered switching around valves to different types of heads, but I was under the impression they were pretty standardized. A lot of aftermarket valves are +.100 inches tall or something like that I think. Even if the pushrods arent the ideal length, it doesnt change how far the valves open, pushrod length is set to encourage the rocker to walk across the valve during engine rotation. Basically, the ideal pushrod length causes the valve to rotate when its not being held against the valve seat. This constant turning and landing is part of what keeps the valve seats sealing after hundreds of thousands of miles and the reason you have to lap valves into valve seats during head assembly. It all plays a part.

The roller cam pushrods would be a lot shorter than the flat tappet cam pushrods, but even then, you have to set valve lash the same way you always do. It wouldnt cause the valves to open so far they would hit the pistons when they otherwise wouldn't have. What I wondered is if the pushrods are that much shorter, you'd have the rockers much farther down on the rocker studs and you might end up in a situation where you were low on clearance between the rocker arm and various points on the cylinder heads.

But as you've said, the valves it the pistons, so I dont think any of those things are necessarily relevant.

By the way, the only heads more worthless than 193 heads are junk 70s smogger heads. You can do better.

 

Nevertheless, even worthless smogger heads should fire up and run just fine if the motor is put together correctly. My embarrassing 624's certainly do.

Agreed, the valves can only open as far as the cam lift allows. Given that they start in the closed position, and you haven't got like 1" exhaust lift or 4.0 rocker ratio, it's unlikely to be valvetrain causing the interference. More likely, the pistons are in the wrong place at the wrong time, ie the valve timing is way off.

Again, are you sure the timing set is installed right? Dot-to-dot at no.6 tdc firing? Did you turn the crank by hand at least 2 full revs by hand to feel for binds anywhere?

I take it this never fired yet. I've never bent a pushrod - I'm surprised they can bend from the starter alone - thought it would have just locked up. Is there any other damage - bent valve, damaged rocker studs etc?

 

the valves look ok all the rockers are fine looks to just be bent push rods, i just put the cam in dot to dot thats how its done right?

 

Ok so took it apart i put the crank gear on worng i put it on the the retard postion and lined up the worng 2 dot so now i have it dot to dot and it looks to be right the crank key way is in line with the the #1 connecting rod and the pin on the cam is in about the 3:00 postion sound right?

sorry for the bad splling on my cell phone

 

Sounds about right. Although, I'd have thought you should still have been able to use the advance or retard positions without bending pushrods; that cam doesn't have THAT much duration. Maybe you were a tooth off in addition? Also - cant remember if you can put the crank sprocket on back-to-front, probably not but bears looking at.

Exactly right:

Find #1 tdc.

Crank keyway should be pointing 1:30 to #1 cylinder.

Install crank sprocket, using the key position that allows the dot or 0 to point exactly straight up. Not - or + for straight-up install.

Stick on the cam sprocket, rotate cam till dot point straight down, and cam pin is at 3 o'clock.

Get a straight edge like a ruler or string, and run it between the cam and crank centrelines. Sprocket dots should be exactly in line.

Get the chain on without losing this relation.

Now the motor in at #6 firing position. Rotate the crank by hand exactly one full rev, to get back to #1 firing, for setting your timing. Then give it 2 more full revs to chev for any binds. Do this again once the valvetrain is in.

 

I put the gear on the crank in the retard position and lined up the dots for strait up instillation.

so it looks like i have it in right i should have my heads back next week end,i used a cloyes racing timing chain there's tons of key ways in it for advancing and retarding

 

'Straight up' is a confusing general term meaning - not advanced or retarded. Not that the dots are pointing straight up, thats a given. You can't install 'straight up' in the retarded position.

You've got me a little concerned here - you aren't putting the crank sprocket on retarded, and then rotating the crank until the 'straight up' dots are aligned, are you?

Are you intending to install retarded to shift the powerband?

 

At first i was going to install the timing set strait up no advanced or retarded
But i accidentally installed the crank gear in the retarded position and lined up the strait up marks ''no advanced or retarded'' marks causing the valves to hit the pistons and bend the push rods
So now i have it lined up in the retarded position i lined up the retarded mark on the crank gear''the square''with the 0 on the cam gear

the cam has a 4 degree advance built in and i have the timing set installed to retard by 2 degrees
they way i have it installed looks right form what the books say and the cloyes web site

 

Cool, so long as it's where you want it! Just make sure you crank it around by hand this time to feel for binds.

I would also definitely degree it, to make sure you're getting the valve timing you think you are.