350 TBI Cam

[496blaze]

I am freshening a bone stock 350 TBI that will go in my daughters 1990 Blazer. It has to be California smog compliant and I really don't feel like going through a bunch of hassles with burning chips to get it to run right. My plan is to use good stock replacement parts and keep the stock swirl port 193 heads and focus on improving the cam and exhaust to increase power while retaining good mileage.

My question is: is there a shelve grind hydraulic roller cam that will increase power without causing fits with the stock tune? I figure upgrading to a roller cam should be a good improvement in power. I have read that the RamJet cam 14097395 is a good choice but I'm leary of the 109 lobe separation. I think something in the 112 range would be a better choice. Any suggestions?

[pdq67]

Might call Mike Jones, Camking and ask him.

pdq67

[donforeman]

Its possible to get a cam that works without burning a chip, but think about it, you are choosing so bad of a combo that the VE of the engine is not changing enough to mess anything up. If you must keep the stock tune, you might as well keep the stock engine. The only way the stock tune is any good is with all the stock parts. Even then there is drastic improvements to be made. I put vortec heads on mine and the baby ram jet cam. It required a lot of changes but the changes were not hard. The biggest trick is not to go hacking up the tables like you know more than the engineers that made the thing. I have seen so many tunes that have huge mistakes in them and people are driving around like that. Most mistakes only show up under part throttle. WOT tuning is the easy part.

A few small tips.
1)The VE tables from the factory are very rough, smoothing this even with a stock engine will help.
2)There are some forums that state setting PE and AE very high or with short delays. You can but expect your mileage to take a hit. I tried it then went back to stock settings and ended up with a very minor changes and much better fuel economy.
3) Most recommended timing curves pushed on other forums are way too aggressive for towing safely. Watch your knock counts. I did notice improvements changing the tables, but make small changes and try to get some dyno feedback.
4) The 94/95 tbi computers are a lot better with speed and options. I have heard my ramjet cam causes idle problems but with the later computer, it will run OK on the stock chip. Its far from the Ideal situation.
5) Stay away from TBI Chips, a few of his chips have been audited on different forums and he does sneaky stuff when he is stuck on a customers tune. Common complaints include limiting the block learn range so your chip shows perfect fueling and he gets out of his responsibility while the chip runs worse than stock. Not all are this way, just the customers he is tired of messing with. The equipment to burn is fairly cheap and its fun to learn and see the improvements. The Jet chip I bough was audited by myself. Its changes when compared to the stock file were so minor, its a joke, that and a lot of changes were posted in the 5000rpm and above range when the factory fuel cut off rpm was left unchanged so you can never use it. If you look up that exact chip on Summit, there are a lot of great reviews, placebo effect!
6) Factory GM code was never released to the public. Semi Freeware like tuner pro is done with a few glitches. If your not careful it can mess stuff up, one other reason to be conservative with the tune changes.

I don't know it all, there are much more experienced people, but I am pleased so far with the 40hp and 50ft lbs I gained on my 5.7 van so far without moving the rpm range one bit. It actually makes more torque below the torque peak than stock. It still teeters out about 4500 but I don't care, its a towing van not a race car. Its still in progress though.

[prairiehotrodder]

I know guys that have attempted to put cams in those engines and its nothing but grief if you are trying to use the stock TBI.
Brian

[donforeman]

Since you have a 1990 this guide is really pretty good. http://www.gmcmi.com/wp-content/uploads ... System.pdf
I messed with burning chips long before messing with the engine. Redoing the shift points alone made a pretty big difference in the way it towed and drove. It was always up shifting too early into 4th, all my other gears are delayed a bit too. I don't think you have full ecm controlled transmission in 1990 though. Switching from 3.26 to 4.11 also made a noticeable difference. Those two things and a little altering of the timing and fuel tables will make a lot bigger difference than swapping in a cam that's crutched to work with the stock computer programming.

[donforeman]

I know guys that have attempted to put cams in those engines and its nothing but grief if you are trying to use the stock TBI.
Brian

Its actually more the person and the choices they are making not the system. There are some things the tbi system is good at and somethings its not. It does take some patience and technical knowledge, compared to ripping it all off and putting a carb on there. One person I know had a very similar system on a 2.8 TPI stock eliminator car that was running way below index. They decided it was all junk and ripped it all out to power the system with Holley's ECM. It had been refined with years of R&D, by a previous owner. When they first tried to start it with the Holley, the car would not even run. I did some work on the Holley system this summer and its getting close to the same ET, not even close to the same part throttle in the pits though. It could be better, but I don't get paid to work on it, so I just got him close. If I am working on stuff for free it had better be mine. My point is some people just are not technical. They will struggle with things that require you to think, learn and make careful choices no matter what brand ecm it is. I wish they have saved the old gm computer, all those hours, dumped into the trash. At least the info on it would have provided a really good starting point for the new Holley.

[496blaze]

Wow, thanks Donforeman for taking the time to provide such great information. Your right, how can I expect the stock tune to deal with a drastic change in the combo. I will be reaching out to you when it comes time to start messing with the tune.

If you had it to do over again, would you still use the same cam if you had a choice? Also, do you think the vortec head swap was well worth the cost and effort? I know from reading your post about your project you have had some quality issues. Great thread by the way.

I plan to just reuse the stock intake manifold since its been stated its only worth like 5 hp. Not enough verses the cost of it.

[donforeman]

I like the cam a lot for a truck. I also like the fact that the torque curve is so flat for towing. It's not a high rpm cam. I am not sure if it will pass California emissions though. Its barely bigger than the stock vortec truck cam so it may be fine. I am sure there may be better cams, but I picked up a crate motor take out for $85 shipped. For that I would do it again. In California, I may just try the stock vortec roller cam as its very close in duration with 111 Lc where the Ramjet is 109. Neither one is going to set the dyno on fire. It does tow the small enclosed trailer and the chassis dyno I have noticeably better than the stock L05 did. My block was drilled and tapped for a roller cam even though it was a flat tappet. Not all are.

If i had to do it over, for under 4500 rpm like my van I would use the swirl port heads and stock intake. The Jegs vortec heads are imported China crud for quality and at 4000 rpm on a 5.7 I think the swirl ports give up very little. Live and learn, my reasoning for them was if I did do a 383 kit later, the vortec heads would be a better match.

If you need help, holler. I think it's interesting working on TBI. I am not as familiar with the older pre 93 computer, but i will be soon. My uncle has drafted me to fix his 4runner with a tbi 4.3. It's a mess, tune wise.

[donforeman]

Here is the VE table difference between what came from the factory in 1995 and what is needed with a small 196 duration hydraulic roller and vortec head swap. The very rough table on the left is factory GM tbi for the LO5. Some of the table past 4500, past the "V" doesn't matter really as its limited to somewhere in the mid 4500 rpm range elsewhere in the program. I only bumped the fuel cut limit by a few hundred rpm. The smooth table makes a difference as a lot of part throttle driving is spent on the edges of the individual data points not in the exact centers. So a smooth table helps, because when you happen to be between data points its sort of an average of up to four cells in that area. My fuel table is not done, but its close. The big hump in the mid range is because the combo is pulling more air through the engine with the new parts at those points. You could run the engine on the stock chip, but it would not be wise. The block learn numbers are very close to 128 across the table now. Some parts of the ve table are less developed than others though and need more work for best result. Its not anything to copy, each vehicle has different needs, just an example to show what you can do with the factory computer, minimal equipment and some time.

[Walter R. Malik]

I am freshening a bone stock 350 TBI that will go in my daughters 1990 Blazer. It has to be California smog compliant and I really don't feel like going through a bunch of hassles with burning chips to get it to run right. My plan is to use good stock replacement parts and keep the stock swirl port 193 heads and focus on improving the cam and exhaust to increase power while retaining good mileage.

My question is: is there a shelve grind hydraulic roller cam that will increase power without causing fits with the stock tune? I figure upgrading to a roller cam should be a good improvement in power. I have read that the RamJet cam 14097395 is a good choice but I'm leary of the 109 lobe separation. I think something in the 112 range would be a better choice. Any suggestions?

I have used a Chevrolet factory 305 H.O. cam and 87 Corvette cam, having great success with those heads.
Probably because it stays within the range of the factory ECM.

EDIT: Looked-up the part number; #14093643 ... 202/206@.050" - .403"/.415" valve lift - 115 separation.

[CGT]

The ramjet cam is a bargain.

[makin chips]

Doesn't Ed Wright do TBI cams? If anything, you could always go to him. He posts here fairly often, as well. That's the first person I would likely call if I was in that situation and ended up needing a custom tune.

[496blaze]

i wanted to provide an update to this project. I ended up using the stock swirl port heads and a very mild Comp flat tappet cam. 202/206 @.050 and like .400 lift, 111 sep. I have to say I could not be happier so far even with the stock computer chip. I did bump the timing up 4* from the stock spec of 0*. It really woke it up. Put about 100 miles on it and took it down for the smog check so I could complete the registration process. The smog tech went over the engine with a fine tooth comb and spent about 45 minutes testing it. Passed with flying colors..

I want to put a custom chip to complement the cam swap but need to learn more about doing this. As Don said in his post, I believe the shift points alone can use some help before messing with the engine parameters.

I used a 192* thermostat to ensure it close to stock for the emissions. Is there any benefit to running a colder tstat?

[mt-engines]

The LT1 B-body cams work great with no tuning in the TBI engines. If California emissions allows a EBL modded pcm, you can run just about any camshaft you want, 2 widebands. And it will pass with a camshaft in the 210@.050 will pick up almost 50 hp from stock.

I highly recommend the EBL flash from dynamicefi.
I still burn chips or I have to, but I charge more to burn chips than to install and tune with an EBL flash.

[dfarr67]

LT1 cam- there were more than one, vortec cam (96+)