290 HP 350 anyone used before?

[K5owner]

Originally Posted by nekkidhillbilly

http://losangeles.craigslist.org/sgv...411379590.html

ill play

I already posted that link up yesterday in post number 41 and said it was a great deal if it is what it claims to be. Hey if i can help a fellow gearhead out great. I on the other hand have my reservations as I have been through that route and bought a 4.8 that had hidden issues that necessitated scrapping it. So buyer beware... But what isn't a crap shoot these days. The third one I linked out of Fontana is typical for the going price for a complete with computer and harness but no pedal or accessories usually. Actually I get them for more like $1450 ish.

[nekkidhillbilly]

that still less than 3k man..........and if you cant find the rest of the stuff for 1500 i would be really really shocked. but we will disagree.

[68c10owner]

Had a 65 el camino a few years ago with the 290hp engine. Actually ran pretty good for what it was. I was surprised. The magazines did a dyno shootout on it and the 290hp engine actually made closer to 325hp. Its the same exact engine as the 260hp version with just the cam change and the higher price. If your planning to change the cam anyway best bet is to get the 260hp version and save yourself some money. The cam in the 290 hp engine is ok, was the same cam that came in the 350hp 350 engines in the vettes.

The compression is low but compression doesnt have anything to do with camshaft selection. You`ll make more power with more compression or course but to say it is too much cam for the low compression is wrong. The smog heads are hurting it more than the low compression.

[MikeB]

Originally Posted by 68c10owner

The compression is low but compression doesnt have anything to do with camshaft selection. You`ll make more power with more compression or course but to say it is too much cam for the low compression is wrong.

Compression ratio has a LOT to do with camshaft selection! That's because more duration means the intake valve closes later on the compression stroke. That's why the 1960s GM high performance engines had 11.0:1 compression or more. That's why cam companies' descriptions of their cams will say something like, "likes 10:1 compression" or "works well with 8.5-9:1 compression.

Too little cylinder pressure will reduce torque and make for "soggy" performance at lower RPM. You also need good heads to work with a bigger cam, and the 290hp engine certainly doesn't have them.

Modern cams like the Lunati Voodoo series have less seat-to-seat duration for a given amount of duration @ .050" tappet lift. So they will bleed off less cylinder pressure than a 70s technology GM cam. I'd say the smallest Voodoo cam (#60100) would work great with a 260hp or 290hp crate engine -- certainly MUCH better than the 290hp cam.

[68c10owner]

Originally Posted by MikeB

Compression ratio has a LOT to do with camshaft selection! That's because more duration means the intake valve closes later on the compression stroke. That's why the 1960s GM high performance engines had 11.0:1 compression or more. That's why cam companies' descriptions of their cams will say something like, "likes 10:1 compression" or "works well with 8.5-9:1 compression.

Too little cylinder pressure will reduce torque and make for "soggy" performance at lower RPM. You also need good heads to work with a bigger cam, and the 290hp engine certainly doesn't have them.

Modern cams like the Lunati Voodoo series have less seat-to-seat duration for a given amount of duration @ .050" tappet lift. So they will bleed off less cylinder pressure than a 70s technology GM cam. I'd say the smallest Voodoo cam (#60100) would work great with a 260hp or 290hp crate engine -- certainly MUCH better than the 290hp cam.

Yes the timing events will bleed off cylinder pressure low cylinder pressure will make the engine feel weak like you said but thats why you dont put a 40yr old grind in a engine today.

I know it sounds crazy and I thought the same thing for a very long time until recently after a conversation with a very intelligent camshaft designer. Let me ask you this, what is the job of the camshaft?

[Jake Wade]

Originally Posted by 68c10owner

You`ll make more power with more compression

Then why crutch it with a paltry CR? Isn't "more power" what we all seek?

We all want snappy, off idle, seat of the pants, response, feel, torque.

Cylinder pressure is one of the keys to performance.

Up the compression ratio or tame the cam in the 290 HP version.

[68c10owner]

Originally Posted by Jake Wade

Then why crutch it with a paltry CR? Isn't "more power" what we all seek?

We all want snappy, off idle, seat of the pants, response, feel, torque.

Cylinder pressure is one of the keys to performance.

Up the compression ratio or tame the cam in the 290 HP version.

Because the compression ratio isnt the problem. Its the 40 year old camshaft with lazy ramps and bleeds off too much cylinder pressure. Dont confuse what I said. Camshaft timing will absolutely effect cylinder pressure. What I said was compression doesnt have anything to do with camshaft selection.

On a 4 stroke engine, like the 290hp crate engine, we have INTAKE, COMPRESSION, POWER, EXHAUST

Now what does a camshaft do? It feeds the engine with air and fuel on the intake stroke, right? What is the camshaft doing on the compression stroke?

[Jake Wade]

If you change nothing but the CR, and it runs better (which it will), has more power(which you admit), then it does make a difference, which is all that matters.

I do agree the cam is old tech and the heads are not the best choice either.


I am not a cam guru, intelligent cam designer so I don't have the credentials to argue with you other than I have been building small and big block chevy's at various power levels for over 25 years. All I know is I aint building a 8.0:1 motor for nobody with a 222 @ .050 cam.

[68c10owner]

Originally Posted by Jake Wade

If you change nothing but the CR, and it runs better (which it will), has more power(which you admit), then it does make a difference, which is all that matters.

I do agree the cam is old tech and the heads are not the best choice either.


I am not a cam guru, intelligent cam designer so I don't have the credentials to argue with you other than I have been building small and big block chevy's at various power levels for over 25 years. All I know is I aint building a 8.0:1 motor for nobody with a 222 @ .050 cam.

I've been doing this for 25yrs myself and always was told to match the can with the compression. Until recently when I didn't talk to a can designer about this exact question. Since you didn't want to play along I'll fill in the blanks. On the compression stroke the camshaft has the valves closed so its not really doing anything for that particular cylinder so if the engine is 8:1 or 13:1 it doesn't matter because the camshaft has nothing to do with that cycle of the engine. You don't can a engine based on compression, you can a engine based on desired rpm range.

[Jake Wade]

Originally Posted by 68c10owner

you can a engine based on desired rpm range.

That sir, is a correct and true statement, I could not agree more. This is where so many foul up, over camming.

[68c10owner]

I need to clarify that I'm talking about static compression. 8:1, 9:1, 10:1 ect. This has nothing to do with camshaft selection. You can design the camshaft to create more cylinder pressure, have the same rpm range and make more HP and be just as street able with the lower compression.

[MikeB]

Originally Posted by 68c10owner

On the compression stroke the camshaft has the valves closed so its not really doing anything for that particular cylinder

Not true. Even on a stock cam, the intake valve is still closing at the start of the compression stoke, and doesn't fully seat until the piston is well on its way to the top.

Here's a a great explanation from CompCams, beginning just past TDC exhaust stroke:

We have now passed through overlap. The exhaust valve has closed just after the piston started down and the intake valve is opening very quickly. This is called the intake stroke (figure 3), where the engine "breathes" and fills itself with another charge of fresh air/fuel mixture. The intake valve reaches its maximum lift at some defined point (usually about 106 degrees) after top dead center. This is called the intake centerline, which refers to where the cam has been installed in the engine in relation to the crankshaft. This is commonly called "degreeing". We will talk about this later also.

The piston again goes all the way to the bottom and as it starts up, the intake valve is rushing towards the seat. The closing point of the intake valve will determine where the cylinder actually begins to build pressure, as we are now into the compression stroke (figure 4). When the mixture has all been taken in and the valves are both closed, the piston begins to compress the mixture. This is where the engine can really build some power. Then, just prior to the top, the spark plug fires and we are ready to start all over again.

Complete article here: http://www.compcams.com/Pages/416/va...-tutorial.aspx

[68c10owner]

Per the article you listed,

The last point in the cycle is the intake closing. This occurs slightly after Bottom Dead Center, and the quicker it closes, the more cylinder pressure the engine will develop. You have to be very careful, however, to make sure that you hold the valve open long enough to properly fill the chamber, but close it soon enough to yield maxi mum cylinder pressure. This is a very tricky point in the cycle of the camshaft.

Seems its closed a little sooner than you think.


For 25 years I was told you needed to match the cam with the compression until a few weeks ago when I had a discussion with Chris Straub. He is the one who told me you dont cam for compression, you cam for the desired RPM range. Since its his job to design camshafts its hard for a hobby builder like myself to argue with a man who is very well known for his camshaft knowledge.

[Jake Wade]

I fiqured that was who you was talking about. I saw where he brought that up over at Team Chevelle, pretty much left everyone hanging.

Whether he is right or wrong, fact is, If you have chosen the optimal camshaft for your desired operating RPM range, have the optimal cylinder heads, it makes no sense to have less than optimal CR .. even though it doesn't matter to the cam.

That's all I got to say. over and out.

[68c10owner]

Originally Posted by Jake Wade

I fiqured that was who you was talking about. I saw where he brought that up over at Team Chevelle, pretty much left everyone hanging.

Whether he is right or wrong, fact is, If you have chosen the optimal camshaft for your desired operating RPM range, have the optimal cylinder heads, it makes no sense to have less than optimal CR .. even though it doesn't matter to the cam.

That's all I got to say. over and out.

He did leave everyone hanging which is why I pm`ed him to find how what he was talking about. I mean, makes sence to me. Valves are closed in the compression stroke, no way to build cylinder pressure if valves are open even the slightest bit. So on the compression stroke it doesnt matter what the compression is because the cam isnt doing anything on that cycle. Now cylinder pressure is something else all together and that is easily fixed with the right cam. Sure a 40yr old grind is not going to build proper cylinder pressure. But a modern grind with similar specs will make more cylinder pressure with the same compression and make more power in the same rpm range.

I was just trying to help out here and clearly my opinion is not very popular so with that I wish you good luck. The 290hp engine is a decent engine, I was happy with it for what it was and should bring you plenty of trouble free miles.

[Jake Wade]

Anthony, its all good, it was good discussion. I would like to hear what Mike Jones or Harold Brookshire had to say.

[MikeB]

Originally Posted by 68c10owner

For 25 years I was told you needed to match the cam with the compression until a few weeks ago when I had a discussion with Chris Straub. He is the one who told me you don't cam for compression, you cam for the desired RPM range.

Both statements are correct. However, if you are replacing the cam in an existing engine, and have to live with the CR, then you MUST take that into consideration when selecting a new cam. Otherwise, you MAY pick up some RPMs and horsepower, but you WILL kill torque and throttle response. This is especially true for an engine that already has VERY low compression, like both Goodwrench engines. In fact, they have been measured at closer to 7.8:1 than the advertised 8.5:1. You may want to Google "Goodwrench 350 actual compression".

Originally Posted by 68c10owner

The last point in the cycle is the intake closing. This occurs slightly after Bottom Dead Center, and the quicker it closes, the more cylinder pressure the engine will develop.

Seems it's closed a little sooner than you think.

Well, "slightly" is a relative term. And it's very easy to know EXACTLY when the intake valve closes. Looking at CompCam's 268H, which has been very popular over the years, you will see the Intake Closing Angle at .006" tappet rise is 60 degrees ABDC (After Bottom Dead Center). I don't know about you, but I wouldn't call 60 degrees a "slight" part of 180 degrees. And this cam at 268/268, 218/218 has less duration than the one GM puts in the 290hp crate engine!

[76stepside01]

I just got this motor, and now I'm wondering if it be worth it to upgrade the cam?

[68c10owner]

Originally Posted by MikeB

Well, "slightly" is a relative term. And it's very easy to know EXACTLY when the intake valve closes. Looking at CompCam's 268H, which has been very popular over the years, you will see the Intake Closing Angle at .006" tappet rise is 60 degrees ABDC (After Bottom Dead Center). I don't know about you, but I wouldn't call 60 degrees a "slight" part of 180 degrees. And this cam at 268/268, 218/218 has less duration than the one GM puts in the 290hp crate engine!

I know what the compression is listed at and what its actually was measured at. This isnt my first time.

Your not going to find many shelf cams that are going to be able to build cylinder pressure in a lower static compression engine and still make more power. You can change the valve events to increase or decrease cylinder pressure but your still going to need the correct duration to make power.

Originally Posted by 76stepside01

I just got this motor, and now I'm wondering if it be worth it to upgrade the cam?

If your looking for a nice daily driver hot rod leave it alone. If your looking for serious power from it you should have started with a different engine. Its a fun engine for what it is, drop it in and enjoy it.

[JPsChevy]

Originally Posted by 76stepside01

I just got this motor, and now I'm wondering if it be worth it to upgrade the cam?

I'm not touching my 290H.P. I'm just installing it in the truck if it ever shows up, should be here thursday.

[85Bowtie]

Originally Posted by 68c10owner

The compression is low but compression doesnt have anything to do with camshaft selection. You`ll make more power with more compression or course but to say it is too much cam for the low compression is wrong. The smog heads are hurting it more than the low compression.

This is completely wrong.

CR has everything to do with camshaft selection. CR extracts power from the fuel mixture and with proper quench forces complete burn. A lumpy cam with a lot of overlap is going to be a complete dog and run like crap with a low CR.

Smog heads are synonymous with low CR...that's why they're "smog" heads...lower CR means less NOx.

[flashed]

I have one of each ,a 290 HP in my wife's 72 Malibu convertible and one 260 HP that was just installed in my 72 Chevy truck ,Im happy with them both . Both of mine are completely stock and both have plenty of power .

[rich weyand]

New to these forums, not to these trucks. Been lurking for several years and finally signed up.

The static compression ratio matters because the cam closes after BDC, when the compression stroke is under way. The compression from full valve closure to TDC is the dynamic compression, and this determines performance more than static compression. Since the closure point is in degrees, at higher rpms a later closure helps fill the cylinder, while at low rpms it hurts. So a later closure will benefit horsepower up top and hurt torque in the bottom.

My truck originally had the 260 hp block in it. I replaced it with the 290 hp block. I have since recammed it, so I have run all three options in the same truck. Carburetion is Edelbrock 1406 through air-gap manifold with Hooker headers and H-pipe through dual Flowmaster 40s.

The 260 hp block is a solid engine with nice torque in the bottom end.

The 290 hp block has less torque at low rpm than the 260 hp, but it gets nicely feisty when you get some rpms under it. The 50-90 passing times at "war emergency power" were great. This engine made the truck a two-lane terror, but it's slower off the line than the 260 hp.

After a year I re-cammed the 290 hp engine with a torquier cam. The 260 hp and the 290 hp cams are both 50 year old grinds with slow ramps, which hurts dynamic compression on the compression side of the spark, and dumps the charge early on the power side of the spark, hurting mileage and power. Modern fast-ramp grinds give the cam designer more options on duration and overlap without being intake-late and exhaust-early.

When re-camming, I consulted with engine designers, engine builders, and street rod guys. The consensus: horsepower is what you race, but torque is what you drive. If you are building a circle-track engine, where you will be full-throttle and near-redline all the time, that's a lot different than building a street engine, with lots of 0-30 starts and motoring around in the mid-range. Torque is even more important in a 5000-pound truck to get the darned thing moving.

All that said, the Comp Cams 12-235-2 was the most recommended cam for the low-compression stock 350. 12-300-4, 12-231-2, 12-235-2, and 12-238-2 are four cams that have fast ramps, high torque, and work well with the low-compression heads. I listed them there in order of increasing lift, increasing horsepower, and decreasing torque.

In my situation, with no Interstates even close and lots of country road uphill and downhill, I went with the torquiest of the bunch, the 12-300-4. It runs off the torque curve at 4500 rpms or so, so I increased one weight in the tranny governor by one size so move the shift points down about 500 rpm.

Best all around, though, for cheap power in a new-out-of-the-box engine is to get the 260 hp crate engine and put the 12-235-2 cam in it. With decent induction you can expect 290 hp at 4000 with 415 lbft of torque at 2500.

Of course, if you are handy at engine rebuilding and have access to the tools, you can build yourself up something really nice. BTDT when I was younger. Also, if money is not an issue, you can buy a GM Performance Connect & Cruise powerplant that will give you up to a 556 hp LSA with 4L85E.

But if you just want to drop a stock-ish 350 in with a little sweeter cam for under 2 bills, the 260 hp crate with the 12-235-2 is probably the way to go.