Gutless Wonder

[MrMarty51]

RV cam should work real good in these engines.

 

[HotRodPC]

RV cam should work real good in these engines.

I'm pretty sure they're 1.94 / 1.60 valve heads. RV cam and 1.72 / 1.50 valve heads would work even better. They might be 1.94 / 1.50 valves too which won't be to bad.

 

[77 K20]

I'm pretty sure they're 1.94 / 1.60 valve heads. RV cam and 1.72 / 1.50 valve heads would work even better. They might be 1.94 / 1.50 valves too which won't be to bad.

They are 1.94/1.50s

http://www.chevroletperformance.com/EngineShowcase/tech_specs.jsp

 

[HotRodPC]

They are 1.94/1.50s

http://www.chevroletperformance.com/EngineShowcase/tech_specs.jsp

That's good for RV Cams. Everyone seems to want bigger valves and pay big bucks to get them put in. That's all fine and dandy for the upper rpm band and racing, but for low end torque and pull power, the smaller valves are better. This is why many truck heads have the small valves.

 

[MrMarty51]

That's good for RV Cams. Everyone seems to want bigger valves and pay big bucks to get them put in. That's all fine and dandy for the upper rpm band and racing, but for low end torque and pull power, the smaller valves are better. This is why many truck heads have the small valves.

What kind of lift~duration would be good for such an application, do you suppose ????

I too, someday, may get one of these engines for My 93 and would want to recam before the installation into the pickumuptruck, probably have to have the dealer install the cam for warranty purposes, I suppose huh ????

Well, since I use this pickup for dragging My trailer, I always use the D range of the transmixer so it runs a bit higher in the rpms but, I do`nt know just what RPMs it is running, maybe still not enough to utilize the band of the cam that comes in these engines, I suppose, probably the RV cam would still be better for the RPMs and pulling the load. I suppose ????

 

[Jims86]

Leave the stock cam in, and change the exhaust valves to 1.7.....look out jack! works good on 4.3s too. TBI heads even wake the **** up.
Stock 1.94 intakes are fine, its the 2.02s that bring intake velocity down. SBC heads have always suffered in the exhaust area.

 

[HotRodPC]

Leave the stock cam in, and change the exhaust valves to 1.7.....look out jack! works good on 4.3s too. TBI heads even wake the **** up.
Stock 1.94 intakes are fine, its the 2.02s that bring intake velocity down. SBC heads have always suffered in the exhaust area.

Still not sure about that myself. Exhaust ports not breathing the best is true, but it doesn't do a damn bit of good really to open the valves up if you don't have the ports to take advantage of the bigger valve.

Maybe some else will chime in on the factor I'm looking for to explain this low end torque factor with the smaller valves. I'm wanting to say "Quench" And this is especially true on a lower compression motor. You're wanting to hold some compression back to have a head start making power on the next power stroke. Alot of this has to do with VALVE TIMING and the lobe centers also, so a cam swap with better specs for low end torque can certainly make a difference. Also, if you're real good with #'s and theory, you can keep the same cam if you like the lift and duration of it, and degree it in to time the valves a little different in relation to the piston and do the same things. IIRC, and don't quote me, it's been a long long time since I was into degreeing cams, but if you retard cam timing, you can get more low end grunt, if you advance the cam timing you're putting more power to the upper mid range and top end, but losing on the bottom end. Some guys don't get that technical and you don't have to these days since you can just buy the cam you want with the spec you want and put it in straight up, but many times some will buy a new a cam and it's virtually the same specs just on a different lobe center which they could have accomplished the same thing, with the same cam by just degreeing it in with a degree wheel. Now sometimes, Lobe Separation between intake and exhaust can be to far apart or to close together too, in that case, you'd want a new cam.

 

[fallguy]

What about this cam??? Would it do as well as the suggested XE250H Comp Cam?

Parts #24502476

Hydraulic flat tappet I: 212 E: 222 I: .435 E: .460 112.5

Used in 350/300 HP and 350/330 HP special performance engines.

http://www.gmperformancemotor.com/parts/24502476.html

 

[77 K20]

Have an update on my dad's truck. He did have an RV style cam installed a few years ago. He said it helped a bit, but wasn't too impressed.

About a week ago he had some Edelbrock E street aluminum heads installed. These were 64cc chambers which boosted the compression ratio by about a full point. The heads do have the .202 intake valves but they have pretty small intake runners that keep the velocity up and are good for low end torque. He also got rid of the stock exhaust manifolds and went with 2.5" ram horn exhaust manifolds. So far he loves it- but has put his 5th wheel trailer away for the winter. There will not be any towing testing done until this spring.
But with just running around he has noticed several things. He lives up in the mountains and parts of the road were he had to slow down a bit around a curve and then be faced with a long uphill area are better now. Before the truck had to downshift to 2nd then it would accelerate then with a shift to 3rd then it would barely accelerate. Now around the same corner at the same speed it just stays in 3rd and can accelerate up the hill with no problem.

Gas mileage is much improved. He has put on about 200 miles so far, and he hasn't had exact figures yet and is going out of his way to find any/all big hills to charge up but he said gas mileage has improved 40%. So instead of around 10 mpg he is now getting 14+.

I haven't driven it yet. In the next few weeks I should be down there and will hopefully drive it. If nothing else I'll take some pics of it. The truck is in great shape and I guess even the valve covers were painted to match the truck instead of chevy blue.

 

[Jims86]

Have an update on my dad's truck. He did have an RV style cam installed a few years ago. He said it helped a bit, but wasn't too impressed.

About a week ago he had some Edelbrock E street aluminum heads installed. These were 64cc chambers which boosted the compression ratio by about a full point. The heads do have the .202 intake valves but they have pretty small intake runners that keep the velocity up and are good for low end torque. He also got rid of the stock exhaust manifolds and went with 2.5" ram horn exhaust manifolds. So far he loves it- but has put his 5th wheel trailer away for the winter. There will not be any towing testing done until this spring.
But with just running around he has noticed several things. He lives up in the mountains and parts of the road were he had to slow down a bit around a curve and then be faced with a long uphill area are better now. Before the truck had to downshift to 2nd then it would accelerate then with a shift to 3rd then it would barely accelerate. Now around the same corner at the same speed it just stays in 3rd and can accelerate up the hill with no problem.

Gas mileage is much improved. He has put on about 200 miles so far, and he hasn't had exact figures yet and is going out of his way to find any/all big hills to charge up but he said gas mileage has improved 40%. So instead of around 10 mpg he is now getting 14+.

I haven't driven it yet. In the next few weeks I should be down there and will hopefully drive it. If nothing else I'll take some pics of it. The truck is in great shape and I guess even the valve covers were painted to match the truck instead of chevy blue.

Sounds like that truck my benifit from th next step higher gear ratio...less stress on the engine means better all around performance...especially in that area.

 

[77 K20]

Sounds like that truck my benifit from th next step higher gear ratio...less stress on the engine means better all around performance...especially in that area.

Sadly he already went thru that once. It had .308 gears and he asked what I thought he should have. I said 4.10s. He then went out and had 3.73's installed.

But at least he is just running stock sized tires and not something larger.

 

[Jims86]

Sadly he already went thru that once. It had .308 gears and he asked what I thought he should have. I said 4.10s. He then went out and had 3.73's installed.

But at least he is just running stock sized tires and not something larger.

Sounds like a tired bottom end. Was there ever a compression check done after the new heads went on?

 

[foamypirate]

Sounds like a tired bottom end. Was there ever a compression check done after the new heads went on?

If I recall, the truck has a relatively new GM crate 350 (20k miles or so?).

 

[Jims86]

Ahh, ok, i am going through too many threads at once here, getting confused.
Is Pop's truck the one with the 290 hp 350? I have always considered that more of a car engine, cammed for higher rpm performance. Cam duration is 222/222
most trucks are Around 190/195
higher cam duration, moves the useful torque up the RPM band.

 

[77 K20]

Ahh, ok, i am going through too many threads at once here, getting confused.
Is Pop's truck the one with the 290 hp 350? I have always considered that more of a car engine, cammed for higher rpm performance. Cam duration is 222/222
most trucks are Around 190/195
higher cam duration, moves the useful torque up the RPM band.

There are a few threads with my current project on it (not to confuse people, but it just happened). One of them was about a head gasket problem, then I was going to put on upgraded heads. Then decided that $$$ is better spent elsewhere for right now.

I hate to just leave threads "hanging" in case someone searches in the future and was looking for info or answers.

Yep- pop's truck has the 290HP 350 that he didn't like. And it is not recommended for towing, or for heavy vehicles. Information that he of course found out after the fact.