5,7 tbi roller rockers

[JeremyNH]

The Ramjet difference is straight ratio change. Full roller reduces friction and that is worth even more. There is a reason the LS engines use factory roller trunions and the newer 4.3s had the same style. Moving from a friction causing 1.42 stamped to a 1.6 full roller realizes torque gains everywhere. My 350 TBI even idled more smoothly.

There's also a reason why GM doesn't put the Ramjets full rollers on the HT383e. Because for a low revving high torque truck motor it wouldn't do anything.

 

[L31MaxExpress]

There's also a reason why GM doesn't put the Ramjets full rollers on the HT383e. Because for a low revving high torque truck motor it wouldn't do anything.

Actually that is false, they just don't want to add more cost to an already expensive engine. Look at some of the results from the HT383 build. 1.6 rockers added considerably to the torque even down at the 2,500 rpm throttle hit.

 

[JeremyNH]

Actually that is false, they just don't want to add more cost to an already expensive engine. Look at some of the results from the HT383 build. 1.6 rockers added considerably to the torque even down at the 2,500 rpm throttle hit.

If you could pay $6800 for a motor rated 343HP/464tq or $6600 for a motor rated 323HP/444tq which would you choose? Come on. GM would sell a few more HT383e's if they had those numbers at that price point. But they don't have those numbers so they can't sell them.

 

[351FUN]

it's too complicated, I'll skip this.

how about just putting a tuned tbi like this:

46mm PORTED 5.7L TBI Package Deal 650CFM | eBay

THIS IS 650CFM! 46MM TBI /Adjustable Reg Cover. TBI are known for leaky throttle shafts. 5.7L TBI as described above and below. There are multiple casting numbers used. Not all the TBI units have all the available vacuum ports as shown in the photos.

www.ebay.com

along with the vortec fuel pump, otherwise stock engine.
will i gain anything?

Not from my understanding. The stock TBI is enough for a few mods, dumping extra fuel in won't help any if you're still stock.

 

[PlayingWithTBI]

Not from my understanding. The stock TBI is enough for a few mods, dumping extra fuel in won't help any if you're still stock.

^^^This but, as long as you keep the same 13 LB pressure regulator spring, you won't add any fuel. If you add more mods, the original TBI pump won't support much more than 230 HP (EP381 supports ~450). If you wanna rev it up to ~6K, you need the 650 CFM advertised for this TB and a stronger spring.

Anytime you add flow from top to tail pipe, you'll realize gains - just how much is determined on how well each mod works with the other(s) - and a tune

 

[kenh]

O.k., Now back to "my buddy" he shouldn't be allowed tools and if you find him fix him up with my ex-wife!

I prefer to just weld his tool box shut......

Ken

 

[Frank Enstein]

I prefer to just weld his tool box shut......

Ken

With him inside!

 

[Schurkey]

it's too complicated, I'll skip this.

how about just putting a tuned tbi like this:

46mm PORTED 5.7L TBI Package Deal 650CFM | eBay

THIS IS 650CFM! 46MM TBI /Adjustable Reg Cover. TBI are known for leaky throttle shafts. 5.7L TBI as described above and below. There are multiple casting numbers used. Not all the TBI units have all the available vacuum ports as shown in the photos.

www.ebay.com

along with the vortec fuel pump, otherwise stock engine.
will i gain anything?

There are two enormous bottlenecks with the TBI engines as delivered by GM.

1. The cylinder heads are a disaster for mid-to-high RPM. "I guess" they're ok for low-rpm use, at or below 2500--3000 rpm.

2. The camshaft is beyond mild. It's super-mild. It's what I'd have expected to see in 1940, not 1990.

Until you fix those two things, most everything else is going to be a disappointment IF EVERYTHING IS WORKING PROPERLY. Fix an actual failure, such as a plugged catalytic converter, or mis-adjusted timing, or low cranking compression, or a worn-out cam lobe, or a faulty sensor, things can perk up considerably.

 

[L31MaxExpress]

There are two enormous bottlenecks with the TBI engines as delivered by GM.

1. The cylinder heads are a disaster for mid-to-high RPM. "I guess" they're ok for low-rpm use, at or below 2500--3000 rpm.

2. The camshaft is beyond mild. It's super-mild. It's what I'd have expected to see in 1940, not 1990.

Until you fix those two things, most everything else is going to be a disappointment IF EVERYTHING IS WORKING PROPERLY. Fix an actual failure, such as a plugged catalytic converter, or mis-adjusted timing, or low cranking compression, or a worn-out cam lobe, or a faulty sensor, things can perk up considerably.

While the TBI swirl ports only flow about 180 cfm, that is still more than capable of 350 hp. They will stay ahead of most other heads including vortecs until 4,000 rpm.

Won't argue on the camshafts in cars. The cars got the 305 peanut cam unless it was a 9C1 which got the L98 roller cam. The truck cam is the same old generic small block cam GM always used. GM 929 or Melling 274 equivalent. It was used in the 300 hp 350s. The old 300 hp 350s had a 10.25:1 compression ratio, a better flowing intake manifold with a quadrajet and were not having to breathe through a cat and y-pipe that flows horribly.

The biggest power robbers on the TBI engines are intake manifold, exhaust and tuning to me out of the gate. I have made 208 hp at the rear tires and 300 ft/lbs at the rear tires with the stock heads and stock cam and that was on an 8.75:1 compression 18cc dished piston 1-ton engine. I swapped to a 96 production LT4 roller cam and 1.6 rockers. Picked up 40 hp without losing any torque. I then ended up putting ZZ4 heads and a ZZ4 cam on that engine and picked up about 30 hp over the LT4 cam/TBI heads.

 

[wb292]

I purchased a set of Speedway split ratio self aligning stainless steel roller rockers from fleabay. I used the 1.6 ratio in the intake valves and the 1.5 ratios on the exhaust. I paid $180. I was going for fuel economy more than extra power. I used a stock vortec short block with TBI heads, Edelbrock intake and JBA shorty headers. I had Harris burn a chip for it. It ended up having a lot more power than I expected. Although I have never put it on a dyno so I don't know how much. I can tell you that it pulls a lot stronger than the stock 350 I pulled out. Its a K1500 RCSB with a 5 speed. I rarely shift higher than 3500 because It seams to loose power after 4000. I wanted it to make more low end so I don't have to down shift as much climbing the mountains. It's my daiy driver and I do 136 miles a day round trip so fuel economy was my first concern. I have 18K on these rockers so far with no problems,