I am on a quest for lowend power, here is what I have currently:

350 crate engine (truck engine)

76 cc heads (good for lowend, right?)

TPI intake (low-mid range, right?)

melling torquer cam with 4 degrees advance (shifts the power down low, right?)

1.6 roller rockers and matching springs

edelbrock headers, and a cutout.

During the cam swap, we replaced the coil, cap, rotor, plugs, wires, and cleaned out the entire intake plenum, manifold, runners, and TB with oven cleaner.


I still can just bearly break the tires loose from a stop. the tires chirp in 2nd gear, and thats all. Shouldn't a 350 (even stock) be able to break the tires loose with ease?

I am not looking to break the tires loose all the time, I am just using that little "test" to see how much lowend I have gained after the cam swap. I can feel it alot more in the low/mid range, but it seems like there should be more.

Is there something in my current setup that is hindering my lowend in vast amounts, or something? The rockers and timing were set by a performance shop, so I am confident about that.

What else short of a blower, no2, and a stroker crank, would help my lowend out? I am probably going to get my intake ported out, but I don't have the money/time to port the heads just now.

thanks for replies and suggestions!

 

roots type blower

 

 

76cc heads?

What pistons are you running, and what's your final compression ratio?

If you ran the stock dished pistons, and 76cc heads, you have about 7.5 to 8:1 compression. Not good for performance unless you have a (dare I say it) blower.

 

the compression of the crate engine is labled as 8.5:1

I'm not sure what the pistons are.

It has been mention in both replies, a blower... I'd LOVE to get one, but what would that do to my MPG? I finaly inched up from 10 MPG to 14 MPG... what would the blower do to that for normal driving? And I assume a blower isn't to cheap, and I don't have money for $2000+


Anyway, would my compression ratio really be why I don't seem to have lowend power? I mean, the engine was built as a truck crate engine, so I would assume that it would have good lowend.

I'm going on a dyno December 20th, and I'll beable to see how much power I really have. Idonno, maybe I just hook up good? I do have new tires... but I doubt new tires would make it hook up that good.

Speaking hypotheticaly now... if I were to get the compression up to 10:1, would I really see a huge difference in the low end? And having said that, what would be the best way to raise the compression? I assume sticking with the 76cc heads would be best (to keep the low end power), so would different piston heads be the best way? any suggestions as to which piston heads to look into? And if piston heads are on the order, then I might as well have the heads ported... I guess?

thanks for any info!

 

first why are you so worried about getting all low end power?
second cc of the head doesn't mean your going to get low end power

if anything you would be better off going with a smaller head though and some dish pistons and go with about 9:1 compression at least


the reason you want to go with small heads is for better burn of the fuel


second go with a smaller cam I would say no more then 205* duration and about 114* of lob seperation

 

Well, I got a couple things for ya...

First off those heads are probably smogger heads, they won't support much power even with porting. Check under the valve cover for the casting number and post it up here then we can tell you what kind of heads you have. You probably have dish pistons in the motor, so you could either go with a set of 305 heads (58cc chamber) or a set of 64cc 350 heads and flattops. Either one would raise the compression to a reasonable level (9.5 to 10). I don't know what the specs are on the Melling cam, but I would imagine it's pretty mild and would make the most power if it's installed straight up, or even a few degrees advanced.

 

I'll see what I can find out about the heads.

As for why I want lowend? well, aside from the fact that I don't ever race or drive in the upper RPM's I remember riding in an older chevelle back home in Louisiana, and he built up a big block specificly for lowend torque. I don't know anything about the engine accept that it was 454 ci. DANG it was a fun ride, it pulled SOO hard once the tires stopped spinning out.

Because I don't race at all, I would like to have the power down low in the RPM that I normaly drive.

 

are you running a stock torque converter? if you are that would probably explain why you can spin tires from a stop... would also make your low end pickup kinda ****ty... just a thought since you didnt say..

 

ah, forgot to mention that. my 700r4 has been rebuilt with stronger parts, a custom shift kit (it's kicks hard!!) and a heavy duty 1800 stall torque converter. I'm not sure what the stock stall is, but I believe this is a bit higher.

 

somethin doesnt sound right
do you have high gears or somethin?

 

I have the gmgoodwrench crap 350 and the low end torque and off idle powerband is the only card that motor has to play. With the small runner heads and tpi it should have great torque around 2k-3.6k or so. With the torque and power curves so low in the engines operating range im getting around 24 mph and being able to break the tires loose from a dead stop even with 2.77's is definatly not a problem. Come to think of it, cant even hook up in first. Have you gotten into prom burning yet? It sounds like it might just be a case of a mistuned motor if your getting poor fuel economy and it lacks decent torque. One thing that will definatly need to be done is to add more timing in certain spots of the engines operation. Those large cc heads like to have extra timing in order not to bog down. You wont get much power out of it but you should be able to get some decent torque numbers with the tpi when its all set up right.

 

the computer is still stock... maybe that is my problem?

I'll look into that, thanks!

 

that isnt much better then a stock converter..

 

If the melling cam has realativly low durations then the converter he has is probably ok. I still have my stock 1200 rpm stall with mine.

 

I'm not really sure whats going on. I have 3:23 gears, and people are telling me with my combo I should beable to roast the tires easily even from a roll.

Maybe I need to get a chip burned for it.


Anyway, this Saturday I am going to the drag strip, and the saturday after that I am going to a Dyno with the local F-body club. I'll see whats up then.

If I pull a low 14, I guess I'm in good shape then, and I am somehow getting traction like a ****.

 

If your going to burn a chip do it yourself. Avoid the 'snakeoil' mail order proms that everyone else claims will improve performance. No one can tune your car but yourself or someone who has direct access to your car to do the tuning since some of the most valueble info comes from your five senses and not someone's guesswork. It might also be worthwile to check your base timing again and, if you ahve a scan tool that can display knock counts, experiment a little and see if it responds to a little extra timing. The low CR of that engine will want more timing then a similar engine with a higher CR. Maybe around three or four more degrees of base time over what is called for stock. Make sure you follow the recommended procedure for setting the timing and that the curb idle speed is within spec or your base time will be off.

 

Ok, just got back from the Dyno, 200HP and 285 Torque. I didn't pick up the printouts because they emailed the results to us (I would loose the printouts), I got home and looked at the results with the Dynojet Viewer, and All I can see is the HP and MPH, no Torque or RPM's.

I think I'm going to change my injectors sometime, when we did the cam swap, we noticed 3 different types of injectors, some were yellow, and some were black. I have no clue what the specs of the injectors are What size should I go with?

 

Ok, I found out how to change the settings, here is my torque curve in 3rd gear (2nd looked almost identical, but I can't view both gears at the same time, probably because the RPM changes between the gears)

Is the torque curve supposed to slope down like that?

 

uh... a while back CHP ran an article on a 350 build where they ran vortec heads and a comp 262 (i think that was the one) and they got some bada<x>ss torque numbers out of it.... i'm sure that it was at least 400 ft lbs maybe you might want to check that out

 

your lack of power is probably coming from the low compression, no-flow smogger heads. go find some 416's from a junkyard, or go with vortecs either or will give you much better low end torque numbers.

 

I'm not going to do any more major work on the engine for a while, I just don't have the money or the time (it's my only vehicle). After I graduate I'll probably pick up a "beater" car just to get around town and then start working up this engine.

A guy I met in my local F-body club might burn a chip for me, before that I'll get 22lb injectors to replace my multi sized injectors. I'm sure both of those would help a little bit. 22lb sound enough?

Thanks for the cam and heads reccomendations guys, when it comes time to seriously build the engine, I'll probably go with a combo like that for monster torque, stroke the engine, and also raise the compression with flat-top piston heads maybe?





What would be the best combo (if money were no issue with in reason) for monster torque from a 383? And then with that combo in mind, what would be cheaper alternatives to those parts? (intake, heads/cam, pistons, and anything else)

When I graduate I'm not exactly sure if I'm going to be makeing big money in the computer graphics area, or if the money will come in slowly. If it's there real good real fast, I'll get the best. if not, then I'll go for the cheaper alternative.

 

It's not the heads, smog heads and low compression pistons arent going to keep you from burning the tires. That ones going on one of my lists, sorry guys.

Your heading in the right direction tunning will solve most of your problem, but you should have left you cam *-* Melling cams are cut with a slight advance (dot to dot) plenty of umph (dot to dot), one more time (dot to dot).

 

And yes even my stock 350 TPI would lite thm up from a dead stop my record without brake torqing is 91 feet and on a good day my car would even lit them up at 25 mph if I pound the gas.
P.S. it is an automatic with no shift kit either thant is juct putting it in drive and letting it do its thing so somthing aint right with your stuff!

 

so, is it a problem that we advanced the cam +4 degrees? What happens with to much advance? I'm not sure what "dot to dot" means, how many degrees advance is cut in the cam?

would it be worth it to back the cam advance back to 0? or would that really do anything?

 

Did you degree the cam? What's the LSA? What's the ICA?

If you don't know what "dot-to-dot" means, then (to be blunt) you don't need to be playing with the advance.

Tell me the above specs and I'll use them to explain how many degrees of advance are ground into the cam.

 

Looks to me like you have the classic TPI torque curve, with the peak at 3600 RPM and it craters after that; the actual peak torque value is just low. The motor is just weak, pure and simple.

I'd be inclined to think it's from having no compression, from those crappy heads. Plus your cam is probably not a particularly good match to TPI, as it tends to require somewhat specialized grinds, rather than one of those ancient generic carb profiles.

I don't think messing with the cam timing is going to do much of anything one way or another. You just have a bad combo, that'll basically never run good.

 

What part#number is your cam? If its an MTC-1 its perfectly matched to your TPI power band, if it were me I would have used a roller cam. The MTC-1 is cut with 3-4* advance with the dots on the timing gears aligned dot to dot or up, up on the marks d to d is just easyer. So in actuality your probably @10* advance which will hurt your bottem end AKA TPI power. The low compression small valve combo hurts your HP but tq isnt as effected with these parts.

 

I think It ended up in mine it sucks

 

I think It ended up in mine it sucks

 

yes, I have the MTC-1 cam ($85 for cam and lifters!!), so I should bring the cam back to 0 degrees, and that would help my lowend? What else will that effect? will it effect my MPG at all?

Anyway, I wasn't the one who set the timing advance, A friend of mine was there and actualy slid the cam in and put the aligned the gears. asked me if I wanted it advanced (and explained that it would give me more a bit more lowend, I believe he said), so he did that, and we put everything else back together.

I wonder if just one tooth counter clockwise would put it back to 0 degrees? I can't remember exactly what he did to advanced it

Here is the info on the cam:

http://www.melling.com/production1.htm It's the first cam listed.

I don't see LSA or ICA specs anywhere on this chart... so... I'm not sure what to tell you guys :-\


I would like to know how you have come up with this? The engine is a GM crate engine designed for a truck (76cc heads, thats good for lowend, right?), with a lowend cam and the TPI intake which shines the brightest at the low range RPM. So how is this not a good setup? I realize that I could have replaced the crate heads and pistons for better flow and compression, but that was not within my budget.

 

TPI shines teh brightest at mid rpms, not down low. Oen of the early complaints was the lack of low end torque from the runners being out of the range that theyre in tune. The truck heads wont really help low end that much, other then the fact taht they have small runners. The low compression probably hurts, too. Id degree the cam and set it straight up and see how it works then. That cam has almost the same specs as the edelcrap one I have. Torque comes on real strong off idle, peaks around 2.5k, and then the power craps out around 4k. Should work ok with the stock tpi.

 

Will the rockers need to be adjusted at all to turn the cam back 4 degrees? I just want to find out how much work is going to be involved to correct our mistake.

 

That cam has an LSA of 112* and an ICA of 107* If the LSA and the ICA matched (both 112*) then the cam would be "straight up". But it's already advanced from the grinder.

112* - 107* = 5* advance already ground into the cam.

If your buddy used the common 'crank keyway' way of adjusting the cam, then it's now advanced 9* to 103* ICA. That's not horrible, but maybe a bit much. Most SBC's respond well to ~4* advance. Any more than that and it just doesn't help anymore unless the cam is way too big for the engine. But that's not likely with that cam. It's pretty mild as it is.

The problem with that cam is the SLOW acceleration rate of the lifter. Although it has short duration at .050", it's advertised duration is extremely long. It allows the cylinder to bleed off too much of the intake charge which is horrible for cylinder pressure.

And yes, the torque curve is supposed to drop down like that. As RPM's increase, torque goes down, and HP goes up. The unfortunate part is (as RB is right again) if the graph were to go as high as 5200 RPM, you'd see the TQ and HP lines intersect. But since TPI runs out of breath before 5000 RPM you can't tell in that graph.

And no, 76 cc heads aren't good for anything except Emissions and using domed pistons (which was found to not be as great as once thought). They're not made specifically for low RPM grunt.

Overall the graph isn't surprising. It looks like a typical low compression TPI dyno graph. Sorry. If you want my advise, get Comp Cam's XE250. That will help get your cylinder pressure back up.

 

Ok so were working with the same cam I have in my truck 350 (I miss my 402) and have used in plenty of engines over the years.
It makes plenty of power just installed the way I described in my earlier post. The TPI should respond very well to this mild grind and the current heads will not be as much of a factor with this TPI since smog heads are restrictive for higher flow rates then the TPI in (stock form) is capable of. Guys on this board are always complaining about head......... flow

I'd very much suggest you pull the cover align the marks reset distributor timing and see what happens. If you have a sprocket on the crank that has mutiple keyways run down to Checker/Azone and pick up a Cloytes chain with a single key and use it for refrence or replace the one you have on it now.

 

so would a chip and equaly sized injectors be of any help? I'm not going to dive into the engine again untill I have money to do some major work, which probably won't be till I graduate (a year or so).

Thanks for all the info, looks like this cam wasn't quite the cam people told me it would be :-\ oh well, it increased my MPG by 4 :-D (along with the ignition)

(edit)

I'm afraid I don't know what a key away is, I guess I shouldn't be doing all this to my engine (well, I did have help )

 

The keyway is the slot in the crank gear where it slides over the Woodruff key in the crank, which is what holds it in exactly the right place on the crank. The usual way of altering cam timing is to have multiple keyways cut in the crank gear, with each one at a slightly different angular relationship to the teeth. Typically they have 3 keyways: one at "nominal" timing, such that if that one is used, the intake centerline will be as the cam card specifiess; one that advances the cam 4 degrees with respect to the crank, and one that retards the cam 4 degrees.

You've got a motor essentially identical to all those pigs that put out about 165 to 180 HP all through the 70s, with a TPI stuck on top of it. Go take a look at the L98; look at its compression ratio, and the flow characteristics of the heads. The L98 long block, with minor variations, is the same thing as a 345 HP ZZ4 long block. Granted, by the time you put it in a chassis, it's less than that, maybe down to 300 HP or so; but the comparison is still valid, namely your 180 HP long block vs. a 300 HP long block in the stock L98. That's why you're getting so much less power than a stock L98; not the cam timing. You're not going to suddenly rewrite the laws of physics by taking a 180 HP motor and sticking a TPI intake on it, and think you're somehow going to compete with a 300 HP long block with a TPI stuck on it.

And, the cam you have (while a decent choice for a competent if not spectacular carbed street motor) is still a mismatch for TPI, no matter at what timing it's installed. You need a cam that's tailored to the specific RPM characteristics of TPI, otherwise you're going backwards from a stock L98 in that area too. TPI's RPM characteristics aren't that "it favors low RPMs"; in reality, it favors RPMs between about 3200 and about 4000. Open your mind, look at your dyno graph, notice the peak at 3600 RPM, and accept the fact that 3600 RPM is the target RPM to optimize your motor for, just like the factory did with the L98 and LB9. That's kind of what dyno runs are good for: they expose the true torque vs. RPM curves of your engine, and allow you to plan the rest of your car in co-operation with that characteristic of the engine, instead of blindly guessing or fighting against the engine's nature.

Basically, your combo is simply inferior to a stock L98; and is a mismatch to TPI besides. That's why it's a disappointment.

 

Looks someone messed up someplace. Have whoever did it fix it. Or have a friend fix it.

As for lighting up the tires. Ive got a 83 t/a with what I assume is LG4. Dunno if any mods. Itll light em up in 1st. I havent done it lately though to find out exactly.

Nate

 

this is where I get confused, some people tell me this cam "matches" a TPI intake, and some people tell me it "mismatches" a TPI intake.

I think I'm just going to leave it alone for now, I keep getting conflicting information on this.

Thanks for the replys yall, Next time I go for lowend power I'll get a set of heads and a cam that will work good with those heads and my TPI. To bad I don't have the money to do that right now

 

While it might be able to be made to work with tpi with some tuning, its a much better match for carb/tbi applications where resonance isnt an issue like it is with the tpi intake.

 

RB touched on a lot of the problem, but the other major issue (as I've said) is that cam. It's being used on an engine with low compression.

Don't be fooled by the .050" duration numbers. The advertised duration is where the intake valve opens and closes. Where and when the intake valve opens determines how much cylinder pressure it made. With a low compression engine, you NEED more cylinder pressure.

Have you ever noticed that long duration cams have a suggested comp. ratio on them? Crane cams is better than any company about telling you this, but that's because of the loss in cylinder pressure from using a long duration cam. The longer the duration, the higher the comp. ratio needs to be.

Either raise your compression or use a cam with less advertised duration.

 

It's power band "works with TPI" Is it ideal? No, is it better then the GM 350 crate grind? Absolutly!

 

your worried about your low end torque because it doesnt spin tires from a dead stop... pretty much any car can if its set up close to properly... are you sure you tv cable is adjusted properly? I know when the bracket that holds mine came loose before I lost pratically all low end grunt..

 

AJ's definatly right about that. I ahve the same engine as you and I spent alot of time needling away in literally 10ths of a degree at my timing curve to get the engine to not bog down at real low rpms with the stock stall tc and 2.77 gearset. Ive overcome it and, most of the time, have very good low end response above 1000 rpm but without the tuning it was a real dog down low.

 

You know, have you considered putting together a mpfi system? With an old BBC throttle body and a good carb intake with injector bosses machined into it you could ditch the crappy stock tpi intake and not have to worry about the whole 'tuned port' thing getting in your way. The only downside is that youd have to switch over to one of the later 730/749 ecms and go speed density to do it. But, since your only after torque you wont have to worry as much about vacuum signal so having the SD instead of maf wont make any difference. Another plus is that the 749 is set up for boost so you can run power adder. Tuning not inluded, of coarse but if I had a tpi system id definatly consider converting it over to mpfi instead.