Fonz

an aftermarket Elgin high lift cam .470" lift , has Smaller "Base circle" on cam lobes to be able to fit into the block. so the lifters go .085 "deeper" into the "lifter bore". So,longer pushrods are needed because of the "non adjustable" valve train. Has anyone ALREADY gone through this ?? (I know, i need to measure for pushrod Length with a "checker") Got one coming. I'm just trying to get SOME insight on how you did it and what you ended up "using". Thanks. I don't know WHY the cam manufactureres don't SAY " longer pushrod required" in their ads !

cutlassefi

What’s the duration on that cam? What are your rear gears?

Fonz

204/214 .440/.478 2.56 going to 3.08 - not concerned with power right now , just want it to RUN Right. pushrods too short are surely not helping it

cutlassefi

Not concerned about power, more concerned about it being a pig with that gear and 8.0:1 compression.

Fonz

have used that cam in pontiac 350's with 8.5 comp and they were fine. I WASN"T ASKING ABOUT POWER, I was asking about" valve geometry" because of the "smaller Lobe circle". car had plenty of power with the STOCK 189/204 degree .400/.400 lift cam. More Lift .440/.480 is NOT going to make it slower.

Firewalker

Here is what I would do, and you don't need a pushrod checker if you have a pushrod that is close and know the length of it. but here goes. Install lifter and pushrod tighten down the rocker all the way. Make sure the lifter sits on the bottom of the lobe. Now is there any up and down play in the pushrod, that would mean it too short if there is. Now start putting different thicknesses of feeler gauge blades between the lifter and the bottom of the lobe When the pushrod has no up and down movement by hand, then that is zero. Now take the thickness of the blades used to get to that point and add that onto the pushrod length and now add another 50 thousandths for preload, nd now you have the length needed.

It simpler with a pushrod checker, since it is marked and you just screw it longer or shorter, to hit that zero with no up and down then add the 50 thousandths, and no feeler gauge is needed. .

dragline

I think since you're dealing with a circle it would be .0425" or half of the .085" that was reduced off the base circle. Have you considered and adjustable valvetrain and possibly stiffer springs for the added lift?

joe_padavano

Simply changing to adjustable rocker arms doesn't fix the problem - the geometry of the rocker on the valve tip will still be wrong without the correct pushrod length.

cjsdad

Cutlassefi is in the camshaft business and always tries to get an eye on the entire vehicle combo to maximize what you have. Getting the engine running right is a great place to start. You seem to have a decent grasp of the mechanical interaction so hope this isn't to basic. The rocker arm tip moves in an arc so it scrubs across the tip of the valve stem when in use. You want the rocker tip to be in the exact center of the valve stem tip when it is half way through its arc movement. There are some great videos about how to check this on youtube so you end up with the correct length pushrod. Best of luck with your project, getting things to fit right can sometimes be frustrating.

Fonz

turns out 8.300 pushrods was the ticket, EXCEPT #5 intake valve. using a compression gauge to check everything before buttoning it up) the Intake on #5 would not Shut all the way ! had to put a .050 shim under the pedestal for that valve to get it to shut ! ( before starting all this, I used a steel straight edge to make sure all the valves were the same height, and they are.) COULD the 1 LIFTER on that valve be locked in the "topmost position" ??? how would I tell ? when the lifters are full, you can't try to collapse them.?? LOL

olds 307 and 403

That cam will be OK with a 8 to 1 350, just not ideal. I had no issues running the generic cam with stock pushrods. You should be able to move the lifter plunger with the pushrod.

Fonz

apparently another problem ! the engine was rebuilt about 18 years ago, but only has about 5000 miles on it. compression check is 130-135 PSI Every cylinder, but a shot of PB Blaster and it jumps to 150 PSI. thinking Rings Never properly seated ! what do ya think ??

Firewalker

I would put aome Mystery oil in each cylinder, and let it sit up for a few day after rotating it once, if it has sat up for years. Its not unusual for rings to stick or to get some rust up in there over long periods of sitting. Once you start driving it then it should improve,.

Fonz

has NOT "sat" for years, sits in the garage and gets "run" about once a month for half hour or so.

Firewalker

ok

Dynoking

130 -135 PSI is considered a good reading. In my 40 + years of professional auto repair I have found compression will always increase 15 - 25 PSI when performing dry and wet compression tests. Part of my engine diagnosis is testing engine vacuum reading at idle speed, 1500 RPM, 2000 RPM and 3000 RPM. The suggestion of adding Marval Mystery oil to each cylinder may be helpful. I have used AC Delco Top Engine cleaner with good results. I would recommend an overnight soak. After performing either (or both) recommendations if engine performance doesn't improve I would perform a running compression test at idle speed and 1000 RPM recording and comparing readings.

I have to ask; your original post was questions about push rod length. Has that issue been corrected?

Fonz

"

push rod problem has been corrected. this engine, From day 1, I have never been able to get a vacuum reading of more than about 16-17, no matter how far I advance the ign timing. every other engine I've ever built/ worked on I could get 18-21 with a stock cam, but Not this one ! this RV cam(204/214) is installed straight up, as was the orig "factory cam". (186/204) And trying to set the ign Timing at factory sticker (12 degrees at 600), never wanted to run right either. has to be around 18 with vac advance disconnected. tried 3 different style carbs, no vacuum leaks. (was wondering if I shouldn't have installed the cam 4 degrees advanced). never had to before. The last time I did that ( a long time ago in a chevy 283) I ended up with too much compression ! is there something "Peculiar" about an oldsmobile ???

cutlassefi

By straight up do you mean dot to dot?

Fonz

by "straight up", I mean dot to dot , not advanced or retarded. (it's a 3 keyway crank gear)

cutlassefi

Actually since you didn’t degree it you really don’t know if it’s advanced or retarded. That could be at least part of your problem.
Just an FYI, the term “straight up” doesn’t really mean dot to dot.

Fonz

I know how to install a cam. at 12 & 6 or 12 @ 12, all the difference is, is turn the engine 1 revolution (360 degrees of the crank= 1/2 turn of the cam gear) + and 1 will turn into the other. it's all about where you drop the distributor. I'm thinking since the car has sat in the dampness for a few months, maybe my advance weights may be stuck in the dist. have to look at that tomorrow

Dynoking

Running compression test?

cutlassefi

Actually based on that statement you don’t have a clue. It may not be the bulk of your problem but it’s always nice to be able to cross things off the list.
We’re just trying to help you know.

Dynoking

Try a power balance test. With the engine at a fixed curb idle speed; If you have point type distributor, In the firing order, pull one ignition wire at a time out of the distributor cap while watching for an even RPM drop on each cylinder. If you see no or uneven RPM drop you have found the cylinder(s) that are not firing. With HEI attach a test light to ground and pierce each spark plug wire through the boot at the top of the distributor cap while watching for a RPM drop as described. If you are concerned about compromising the boot(s) a dab of dielectric grease in the tiny hole left by the test light probe will prevent any leakage problems from occurring.
I know some people may not agree with my method for cylinder shorting with HEI, but I have performed this since '76 with no problem. (haters please keep your comments to yourself, unless you can provide an alternate method a lay-man without electronic cylinder shorting diagnostic equipment can perform in their backyard, I'd love to learn something new)
Since this engine has a history of mechanical issues with the pushrods, I can't help but feel you may have damage to the valve train. I would run the engine at a fixed 2000 RPM (on Q-Jet carbs I always use the second highest step of the fast idle cam) With a vacuum gauge connected to manifold vacuum I cam looking for a rymthimic bouncing needle which may indicate a valve not closing. You can isolate the cylinder(s) using a timing light connected to each cylinder by firing order aimed at the vacuum gauge. The timing light will "freeze" the bouncing needle when connected to the bad cylinder(s)

olds 307 and 403

Pretty sure that vacuum isn't far off especially if your carb is in the rich side. With a super lean idle mix, I pulled 19 inches maximum with a 8 to 1 403 with the 204/214 cam. That cam is also a compression bleeder, I got 140 to 142 psi with a very good running 76 350. As Mark said, your cam timing could be anywhere without being degreed. I advanced mine 2 degrees on the timing set, which should help cranking compression. I later verified that timing set when I degreed my next camshaft using that timing set. Still my 204/214 or your 204/214 cam could be improperly ground, mistakes happen. If I do use it again, I will degree it, it ensures your cam timing events are actually what they should be. I use Kleenflo Combustion Chamber Cleaner, very effective to unstick rings. If you fill the cylinders and let sit, remove the spark plugs before cranking it over. I did it many times but last time I got bit. I gained back 15 to 25 psi on the cylinders but wondered why my oil pressure was down. I actually bent the soft factory connecting rod in #8 and no doubt destroyed the rod bearing. This motor owes me nothing just makes me get my *** in gear to finish my 424.

cjsdad

In theory, that is the correct way to install a camshaft. I have done it too, but I have been schooled by more than one engine builder on the need for more accuracy. There are a few other things to consider when installing a cam. Core shift, manufacturing tolerances, different manufacturers (cam and timing set ), and probably a few others. There have been documented cases of camshafts being as much as 8° off when using the "straight up" method. If the dowel pin is off a couple degrees and the cam sprocket is a couple degrees off and the cam gear is a couple degrees off, it all adds up to a huge discrepancy in the valve timing in relation to the crankshaft/piston position. The reality is that just installing the cam "dot to dot" can have the cam advanced or retarded as much as 6~8°. Again, there are a lot of very informative videos on how to degree a cam. Once it has been "degreed", you can be positive about your cam being "straight up" or 2° advanced. Youtube is your friend!

Firewalker

Yeppers

Fun71

That is exactly what happened to me. I installed the cam dot-to-dot and the engine didn't have the power I had expected. Then years later when I did a cam swap, I checked the old cam before pulling it and found it was 8º retarded. So the lesson I learned is always degree the cam.

ajr2820

Same here. Installed mine and had a helluva time getting it right. If I recall correctly, I had to use the retard keyway, then advance the cam 2 links on the chain to get it right.

Inline

Howards cam aswell was 6 degrees off "dot to dot". If i remember right it was retarted.

ajr2820

Mine was a Howards as well.

Fun71

Mine was a Crower from around 1993.