Aamer Sattar

Hi I'm going nuts with my c5 automatic.
I installed heads and cam.
texas speed prc 227 heads
and their 224/228 112 lsa cam.
Everything else is stock, except a cai.

Problem is the car is gutless now lowdown.
You stomp on it and it'll get going, and showed 370 Ps to the wheels on a dyno.

but it's crap to drive everyday. The low end and lot of the mid is really gone.

I shouldn't be really be losing that much low down with this combo should I. Texas speed says I shouldn't.

I've tuned my ve tables. And done maf calib using ltfts and am within 1 to 2 % of zero mostly rich.
(waiting to install wideband)
I have generally mediocre acceleration all round except Wot, where it goes like a demon.

I have a huge dead spot, cruising in 4th around 1200 to 1800 rpm, any kind of throttle movement there gets no rpm change, just a change in engine tone totally bogged down and lugging.
A sharper stomp on the pedal gets me a lower gear and back to mediocre acceleration.

I've been told that it's just too much duration and too little lsa,and told the only way to get back my fun to drive torquey car is to swap out the cam as its too much.

A 224 228 112lsa with the 227 heads isn't too much cam is it?

I"d appreciate any feedback and help.
Is this combo really not going to be able to make decent low mid power?

Help!

sstonebreaker

Is your torque converter still stock? With that cam, I'd install AT LEAST a 2500 stall converter, preferably a 3000 stall. That will improve your acceleration and make it easier to drive around the streets, although it won't feel like stock.

If you want stock-like driveability and lots of power, forced induction is the way to go.

feeder82

3:15 rear gears or 2:73? And a stock converter with that cam I don't think it will have anything till you get above 3k

Aamer Sattar

The TC still stock.
Texas speed assured me that this cam would be fine with the stock converter.
And shouldn't lose much down low.
I see lots of other posts of ls1s with bigger durations and lsas claiming to run great.
What I've seen on the dead spots is it goes into high maf pressure boonies of the spark and ve tables, real low spark advance areas towards the bottom of the 1200,1500 rpm columns, where the timings like 9 or 13.
I can't advance spark down in that region, it'll knock.
But it shouldn't be going down in there in the first place right?

​​​​This is with like 20ish% throttle in fourth, coming up from about 1200rpm..
Dead.

Aamer Sattar

It's the stock ratio. A 2.73 I believe.

feeder82

Never seen a cam recommended with a Lsa less than 114 for a stock cube auto car.

MadMax96

Gear change should have been your first mod IMHO.

walleyejack

and exhaust. without a doubt

Aamer Sattar

I'm thinking I made a mistake with thi cam and head 'upgrade'.
..
​​​​​The cars no fun to drive any more. I need to figure out how to get that drivability back without going back to stock components.

Reduce lsa? Duration?

Kubs

Those heads are too big for that cam. That kills low rpm air speed and hurts torque. Moves a lot of air at high RPM though. I would have gone with like 215cc head. Bigger is not always better, especially with a stock intake and exhaust.

Autotragic

Kind of a dumb question but since you have an auto, did you reset all the torque management to a higher number across the board?

LilNutSac

Agree with the others, a few issues with this setup. First, I've never seen a heads/cam C5 with stock exhaust manifolds. Those are holding you back quite a bit. Then the tune, guess you're waiting on the wideband to really see the detail you need and dial it in. Then, yeah, rear gear change would be in order and/or a different converter. Should be a stout setup, but I feel you've put the carriage before the horse. Cam/heads selection is good. I've run a larger cam than that in my daily. But it had rear end gears, headers, M6, intake, etc.

Dbl_D718

What's your tuning experience? You might want to have a professional tuner take a look before you swap hardware again. I'm not a tuner myself, but I could tell a huge difference in street manners and drivability between a bad tune and a good one after my cam swap.

dskinsler83

Heads are way big for that little cam. And why do all that and run OE exhaust and manifolds? What year is the car, or did I miss that? Running a OE intake manifold and TB too? Choking/starving it for air with those things and the cam.

grinder11

Did you degree the cam? It sounds like it is installed with the valve timing retarded. That would give a boost to high rpm power, but reduce the low speed torque by closing the intake later, reducing compression. TSP may say it's OK with a stock converter, and it might be, but NOT so much with a 2.73 gear. Did you tell TSP you have a 2.73 gear? I agree with the other guys, a gear change to a 3.42 and a different exhaust system would make it a totally different car. But if the cam isn't ground or installed correctly, it'll never reach its potential. Could it be the cam was ground "straight up", with out any advance? A lot of cams have several degrees of advance ground in, and are installed straight up. Obviously, there is something wrong with either the tune, the cam, the cam install, or, possibly, you're expecting a lot from a 2.73 gear with a stock converter and stock exhaust. Hope this helps, and good luck........

Aamer Sattar

Thanks for all the feedback.
1. Can't change the intake exhaust. Cause it needed to be undercover, the regs here would catch those.
2.my tuning experience is limited, but I have good online help, I'll work through it with him once my wideband is in.
3.i didn't change the torque settings for the tyranny. Will ask my online tuner bout that.
4. Someone said the heads are too big! That is the last thing I wanted to hear! Xpensive. And a lot of work.
I was thinking if all fails with the tune I'd swap out the cam again for lower duration less lsa. But if the heads are an issue. Crap! How do I determine that the head is the issue?
The seller recommended the combo so I went with their advice. They're reputable by all accounts.
5.dont know what else to do right now. .

Aamer Sattar

No didn't degree the cam. Installed it dot to dot.

Kubs

It sounds like tuning may be the biggest factor, but yeah large port heads are for high air flow high RPM applications. Youre going to sacrifice low end for high RPM.

sstonebreaker

Those guys who say the heads are too big are holdovers from the gen 1 smallblock/carburetor days. Back when vacuum created by intake port velocity was the mechanism to suck fuel into the engine, big ports were a problem on daily drivers because the slow flow at low rpm was so different from the high flow at high rpm, that it screwed up the fuel metering. That's why they had to invent 4 barrel carbs - two barrels for low speed and then all 4 barrels for high speed. Since fuel injection actively meters the fuel into the engine, rather than passively like carbs, port velocity is much less of a driveability issue. plus, the difference in cross section between a 215cc intake port and a 227cc intake port is minuscule. the difference in volume is only about 5%, which means the difference in cross section is going to be a derivative of that - something like the square root of 5% or something similar, depending on the exact shape of the port cross section.

What you did was what 75% of first time hotrodders do - you threw the big sexy parts on the car without the supporting mods. Ever hear the term 'blueprinting'? It means to build with all matching parts. You need to change the rear gears as everyone was saying, and think about putting a bigger torque converter in as long as you're in there. That will cure most of your driveability issues at low speed.

walleyejack

IMO it is all for naught, if you don t have exhaust.