290hp 350 Cam Replacement

[fallguy]

Ok, the gutless wonder has finally pushed me too far. All my research shows basically the engine is a problem from day one due to GM grabbing mismatched parts etc etc...so my first step is a new cam.

Comp Cam XE256H is apparently the way to go...I know jack about this stuff but that seems to be the general consensus.

I know I'll also buy the kit with new lifters as I'm told I need to do them too.

My questions...do I just pull the valve covers, radiator, fan, timing cover, chain & pulley...and that's it? Or what do I need to be looking for here? Any special tools or road blocks I'm going to hit?

I hate reinventing the wheel so any help/advice would be groovy.

TIA!

 

[Driver4r]

for a camswap, assuming its a NON-AC truck.

1.Remove Fan shroud and Fan.
2.Drain water/coolant
3.Remove the radiator
4.Remove front acceseries
5.Remove the Distributor
6.Remove the intake
7.Take off the valve covers
8.loosen up all 16 rockers
9.Pull out all 16 Pushrods
10.reach into lifter valley and remove all 16 lifters(bag and tag each if you plan to save)
11.Unbolt and remove the timing cover
12.Unbolt the cam timing gear, then remove
13. take the timign chain off
14.Depending on if it comes off easy or not, you might need a claw/hook puller for the crank timing gear
15.Might have to unbolt your fuel pump from the block to let the drive rod fall
16.Pull on the bolt on the cam, mabey wiggle it and the cam should start to slide, youll have to guide it thrue the holes.
17.Clean

Reasembly:
(get a tube of white lithium grease or some engine assy lube)
1. Get the cam out of the box
2.apply slight lube to all 5 bearing surfaces
3.Help guide the cam into the block, making sure it seats completly against the back cap.
4.Grab your lifters, apply lube to the bottoms of ALL lifters, then individually drop them into their holes. They should slide under their own weight.
5.Apply assy lube on both sides of all pushrods and insert.
6.Line up each rocker(apply assy lube between the rocker and the rocker pivot) and slightly, snug them(watch for the lifter colapsing).
7.Install your crank timing gear
8.Bolt on your cam gear(to line up the 2, i recamend turing the crank to line it up)
9.Once the 2 timign dots are lined up, remove the cam gear and install the chain with the gear.(I dont remember if timign chain sets have thrust washers or not. My gear drive did)
Everything else is basically Dissasembly in reverse. When you go to reinstall your timign cover, on the front pan set there are 2 metal tabs, trim them off to get it to slide onto the engine.

As far as setting rocker lash, everyone has their own opinions.

if i forgot anything, someone feel free to add

(while typing this my eyes kept telling me it was bedtime and a couple times it kept getting blurry lol)

 

[rich weyand]

That cam is the 12-234-2. Nice cam for that engine. 302hp at 4500 and 415lbft at 2500. That's right about at the limit of what you can do with those heads. You can get more horsepower, but with less torque; you can get more torque, but with less horsepower.

You must be registered for see images

(I just happen to have my setup saved in Camquest from recamming my 350/290 last year, so I have all the parameters for that engine in there already.)

That's with a dual plane manifold and long-tube headers, of course. And you are correct: you MUST replace the lifters, because they bed in in the first few minutes. Put the old lifters back in and they will destroy the new cam.

Having re-cammed my 350/290, I will tell you that you will be overjoyed the first time you get on it with the new cam in it. You'll keep asking yourself if it's worth it while you're doing it, but when you punch it that first time, all doubts will disappear.

One note on the steps above: it's easier eyeballing the alignment of the cam when you insert it, and getting the timing chain right, if you remove the grill, the hood latch and the vertical brace from the radiator crossmember so you can look straight at the engine from the front. Only takes a couple extra minutes to pull that stuff.

And of course, once you have the new cam in it, you get to go through the engine break-in procedure again. ZDPP in the oil, change the oil and filter after the first 30 minutes, no running for extended periods at constant speed the first so many miles, etcetcetc.

 

[77 K20]

I need to find that thread with my dad's truck I have... I finally heard an update with him last week.

He also has the 290hp 350. HATED it as it wouldn't pull his 5th wheel up hills. He changed the cam. Better, but still not good enough. Re-geared the truck. Better, not good enough.

I finally talked him into some Edelbrock aluminum heads. This raises the dismal compression ratio up to a "normal" level.

MUCH better. He went on a trip last week and went up several big passes. Truck has enough power to maintain speed up the long hills. He can even accelerate up them if someone slows him down. He was also much happier with going down hills. Before the truck would just go into "runaway" as an engine with very low compression has nothing to hold it back. Now it is more controlled going down passes.

And his gas mileage has improved. Before the heads he was getting around 7 mpg towing. On this trip (same as many before) he got 11 mpg.

 

[fallguy]

What heads are recommended?

I have edelbrock performer intake and edelbrock 1406 carb.

 

[rich weyand]

If you want to change out for new heads, you should look at the Dart heads with the Comp Cams 12-238-2 cam:
http://www.summitracing.com/parts/drt-127121/overview/

My simulation gets 415 lbft at 2500 rpm and 360 hp at 5000 rpm. Probably rev to 6000 or so. Use the recommended lifters.

The 12-238-2 cam has more duration, with a later intake valve closure, which you can do with the higher compression ratio (64cc heads) without killing bottom-end torque.

The secret of these heads is .202 intake and .160 exhaust, instead of .194 and .150. Bigger valves make for more flow, and horsepower is all about how much mixture you can get through the engine.

Intake manifold and carb are fine. People argue carbs, but any carb that is properly tuned will do better than any carb that isn't. Learn the carb and make sure it is tuned properly and it's fine.

 

[fallguy]

http://d9581292.u130.isoaxishosting...ams-262-Extreme-Energy-Camshaft-12-238-2.aspx

Or

http://d9581292.u130.isoaxishosting...Cams-256-Xtreme-Energy-Camshaft-34-255-5.aspx

 

[rich weyand]

Comp Cams 34-255-5 is for Ford 429 and 460 cubic inch engines with an ECM.

All the SBC cams will start with 12-, I think.

12-242-2 wouldn't be bad. 400+ lbft from 2500 to 5000, 250 lbft coming off idle at 1000, and 415 hp at 6000. Yowzah.

Re-running the 12-238-2 with actual flow numbers from the Dart catalog, I get 400+ lbft from 2200 to 5000, with 260 lbft coming off idle at 1000, and 402 hp at 5500.

You should download the Camquest software from Comp Cams (google it) and run these yourself. Not too hard to set up. It will only show you the cams that fit. Google dart catalog to get the pdf of the catalog and get the actual flow numbers.

Setup down the left side is:
Usage 5
Hydraulic
4500 lb vehicle weight
Carbs
Chevy 350
2-valve, wedge, low/perf/ported, large valves
enter the actual flow numbers
2.020 in
1.600 in
9.50
Dual plane high flow
600 cfm
None
Gasoline
Large tube headers, mufflers without cats

When you run simulations, make sure you give due deference to the torque curve from 1500 rpm to 3500 rpm. Wind-up horsepower is nice, but you have to get the truck moving first.

 

[HotRodPC]

Just passing the word for you Jamie, and I can't remember the name of the member now, but his dad had the same problem with a GMPP Crate 290 engine. He first did a cam swap to no avail and still no major help. He recently updated his heads to Edlebrock E street heads, and finally it's running like a raped ape, or at least to the point they are satisfied. Just want you to know, not to get your hopes up to high.

You know, I think we can all agree the 882 heads are not all the impressive at all, and then with dish pistons, and as said, who knows how low the slugs are sitting in the holes, compression is just to low on these motors. I've heard from mag articles I've read, the 290hp crate doesn't even put out 8:1 compression. Now I don't think you need to go as far as getting E Street heads, but I bet some Vortec heads will wake that motor up. 2 reasons, 1 bigger port runners, 2 and the main reason, the raise in compression I think is going to be the hot ticket.

I must have the 260hp Crate motor in my truck because for one of these crate engines, with an Eddy EPS Intake, Eddy 600cfm carb, and headers, I think it's got plenty of power. My expectations weren't that high of course, but I've not experienced any severe power loss issues. No, it doesn't run like a late model truck, but it'll at least get out of it's own way and had no issue getting up to speed to jump on the freeway and not hold up traffic.

 

[HotRodPC]

I need to find that thread with my dad's truck I have... I finally heard an update with him last week.

He also has the 290hp 350. HATED it as it wouldn't pull his 5th wheel up hills. He changed the cam. Better, but still not good enough. Re-geared the truck. Better, not good enough.

I finally talked him into some Edelbrock aluminum heads. This raises the dismal compression ratio up to a "normal" level.

MUCH better. He went on a trip last week and went up several big passes. Truck has enough power to maintain speed up the long hills. He can even accelerate up them if someone slows him down. He was also much happier with going down hills. Before the truck would just go into "runaway" as an engine with very low compression has nothing to hold it back. Now it is more controlled going down passes.

And his gas mileage has improved. Before the heads he was getting around 7 mpg towing. On this trip (same as many before) he got 11 mpg.

Aha, here he is.. Glad you jumped in here at @77K20. I guess I just retold your story in the long version since I remember your long ongoing thread about being dissatisfied with the 290 Crate engine.

Here is your dad's towing woes thread. http://www.gmsquarebody.com/forum/showthread.php?t=7860

 

[rich weyand]

Yeah, I bought the 350/290 engine when my 135,000-mile stock engine started blowing antifreeze. I was hoping to get more go than a stock engine, and it does -- above 3500 rpm or so. Wind it up and it does pretty well, for having something like 8:1 compression, as HotRodPC accurately says. But off the line it was a dog. No torque in the bottom. That was the trade-off, and with that compression ratio, you are going to have to deal with trade-offs.

So I went in the other direction. You don't need high compression to get low-end torque. I re-cammed it with the Comp Cams 12-300-4, which has the highest torque numbers from 1000-3500 rpm in that engine, with those heads, of any Comp Cam I looked at. Pull to 3500 rpm is much better than stock, and it has a great hole shot. At 4000 rpm it runs out of steam, which is OK with me because I don't drive it that way.

But the performance is much better than stock, much better than the 350/290 engine, and I have driven all three, in the same truck, within a relatively short time period. I could pick another cam, and go with high-compression heads like the Vortec or the Dart, and get the same torque curve in the bottom but with lots more horsepower up top, but I just don't see the need. It's the torque curve in the bottom that I drive every day.

 

[HotRodPC]

Yeah, I bought the 350/290 engine when my 135,000-mile stock engine started blowing antifreeze. I was hoping to get more go than a stock engine, and it does -- above 3500 rpm or so. Wind it up and it does pretty well, for having something like 8:1 compression, as HotRodPC accurately says. But off the line it was a dog. No torque in the bottom. That was the trade-off, and with that compression ratio, you are going to have to deal with trade-offs.

So I went in the other direction. You don't need high compression to get low-end torque. I re-cammed it with the Comp Cams 12-300-4, which has the highest torque numbers from 1000-3500 rpm in that engine, with those heads, of any Comp Cam I looked at. Pull to 3500 rpm is much better than stock, and it has a great hole shot. At 4000 rpm it runs out of steam, which is OK with me because I don't drive it that way.

But the performance is much better than stock, much better than the 350/290 engine, and I have driven all three, in the same truck, within a relatively short time period. I could pick another cam, and go with high-compression heads like the Vortec or the Dart, and get the same torque curve in the bottom but with lots more horsepower up top, but I just don't see the need. It's the torque curve in the bottom that I drive every day.

You've got the right idea. Many times guys don't know how to pick a cam, or they go to big and lose that bottom end torque. Or they may even get the correct Lift and Duration, but get the wrong LCA (Lobe Center Angle) and the torque curve be more in the mid range. Of course if that happens you can compensate by advancing the cam timing and bring the torque band down to a lower rpm or if you want you can even retard the cam timing and move the torque band to mid or top end range. With todays technology and the various cam grinds available, I see no reason why someone needs to get into all the logistics and technical bs of retarding or advancing cam timing. Just choose wisely, set the thing in straight up and rock n roll with it. You get you a cam with a 112 - 114 LCA you're going to have a good low end grunt. 110 LCA more of a mid range and 108 or so going to give you top end. So anyone interested, in the Low End grunt, along with MPG, IMO try to choose a 112-114 LCA cam. Also on these low compression engines, you can't afford to be giving up or leaking off any compression, so try to be looking for a cam with no valve overlap, which pretty much means it's probably going to be a lower duration cam. Those are all the ingredients for good low end daily driver or towing torque and keeping the mpg in the better range.

 

[rich weyand]

Here's an article about camshaft selection that I found helpful:
http://www.crankshaftcoalition.com/wiki/How_to_choose_a_camshaft

I put the 12-300-4 camshaft on the 350/290 engine (same as 350/260 engine other than the cam), and I like it a lot. 420+ lbft of torque at only 2500 rpm, with 320 lbft coming off idle at 1000 rpm, and I am getting 12 mpg highway/10 mpg city with a K-10 and 3.73:1 gears with the hubs FREE and the NP203 unlocked.

My biggest worry with it is I am at (or over) the limit for torque with the stock drivetrain. TH350 + NP203 + G80 Gov-Lock in the corporate 12-bolt would not be hard to break with that much torque if I started doing brake-torque launches and burnouts and the like, so I don't drive it crazy.

Interestingly, it has 108 LSA with 108 ICL, so it's ground "straight up", but not as low an LSA as you and I would think necessary for those bottom-end torque numbers. I think modern, quick ramps help there.

I picked it using the Comp Cams' Camquest software to do simulations. And yeah, simulations aren't that accurate, but simulations are useful for comparing one cam to another.

 

[77 K20]

What heads are recommended?

I have edelbrock performer intake and edelbrock 1406 carb.

I haven't been around much as I was traveling out of state.

Different heads can be very nice but can be costly. The cast iron vortec heads can be found for much cheaper than aftermarket but then you'd need to get a different intake manifold (bolt pattern is different).

The Edelbrock e-street heads are cheaper than other heads I had priced out at the time. They were fully assembled and were made in the USA. There was some chinese made ones that were cheaper, but no thanks. At the time I think the 64cc heads were $935 or so thru Summit Racing.

 

[fallguy]

I called comp cam folks and told the tech support guy what I had, my issues and what I want to achieve. He told me I needed the ex256 with springs to match. Found that to be interesting because I've heard that suggestion a couple times before. I told him I'd eventually be doing a head swap for higher compression and didn't want a cam I'd regret at that time....he didn't change his mind and stood by the ex256 suggestion.