Taijutsu

Bee Jay; Please do some expensive before/after testing and share it w/us.
I want to benifit from your extensive and expensive research! lol
I want to be able to cruise at low rpm w/.68 overdrive w/carb!
I know EFI works best in that situation, but my 650VS Demon will have to do. The improved mpg by being able to run a gear higher around town isn't bad either.
You still haven't commented about the before/after unsprung weight reduction? Yours looks like #80 less than stk. That should be felt?

Your efforts are appreciated!

R

Bee Jay

Will do.

What 80# weight reduction? I've done a few weight loss mods. If you mean the Wilwood Brakes, I did a thread on that. Just search Bee Jay threads.
Bee Jay

Gordonm

You will get all but the women with the Z06. C6 cars are like belly buttons, everyone has one and they are all the same to me. The C3 is much more of a women magnet than the C6.

Bee Jay

You know, I owned this car since new, I was only 21. I'd go into the disco, party all night, and when I left, there would be phone numbers on my windshield. The car could only do 14 second quarters then, but the women didn't care. Little kids would look at the speedometer just to see how fast it could go. 160 mph, wow! I bought just in time, becasue they came with 55mph speedometers later.
Bee Jay

Bee Jay

I just drove the car to Santa Maria and back. About a 50 mile trip round trip. I think I have it dialed in idle and low throttle. My throttle scale is 30 to 230, where 30 is idle and 230 is wot. Most in town driving and highway cruising is below 70. 60 throttle in OD is 85 mph cruising. You rarely go over 100 throttle unless you are hot rodding. It's actually amazing to me how little time you spend with anything more than small throttle openings.

The car is not running very well over 100 throttle. It feels fat. The AFR is rock solid on 13 and 13.5 to 1, but it feels fat. It will pull to 6000, but when it shifts, it bogs. I'll take 10% out of the fuel map tonight and see if things improve. I had already taken 20% out of the map from where the 1105 was very happy. The vacuum still sucks, pardon the pun, 12" max at idle. A good healthy non tire burning acceleration has the headlights popping up after two gears. Admitadely, I have no battering ram vacuum reservoir any longer, but I didn't have this problem before. The headlights only popped up at wot around 120-140 mph previously.

Maybe I am overcammed now. I really thought that the smaller duration of the LT4 Hot Cam would offset the huge increase in lift. Maybe I could try 1.5 ratio rockers and see if that makes the cam sufficiently smaller. Any thoughts or ideas?
Bee Jay

Bee Jay

Matt may have something there. Here is a picture of the Z28/LT1 intake manifold with Q-jet mods I was running before. The center divider goes to the top.

Here is a picture of the top of the RPM Air Gap:

Matt Gruber

BJ
if u r clever with a die grinder and other hand tools u could make a slide in piece to fill in the slot. Then it could be removed at the drags for comparison.
I'd make a pattern with a piece of styrofoam and then find a scrap of steel to hand fit. aluminum clogs up sandpaper etc, so that is why i like steel, but use what u can find that is strong and won't fall out and be eaten by a valve.
.
i don't think it is overcammed. C5 & C6 use weenie cams so they don't need a fully separated dual plane. Sure u could try 1.5 rockers as u have a set. That will cost it more power than fixing the slot. I'd do that and advance the cam only after u have the slot fixed, as they both may not be necessary. U may have to lean it out some too.
.
anyone interested in having a powerband like a c5 should read my article http://community-2.webtv.net/mattgru/carb

rham

BJ
Sorry to high jack but can you tell what rpm this cam starts to pull at?
I was looking at it also for my 78 but I have 3.36 gears and dont know if it would work. Summit lists the operating range from 1800 but GM lists it at 1500 rpm.

Bee Jay

I drove the car in to work today, and you know what, it was still running like crap. This intake isn't that big and this cam isn't that big, something else is wrong. So I pulled the plugs, a few looked really rich, and I did a compression check. Check it out:

With the Summit 1105 my compression was between 165 and 175 lbs. It was 185 to 195 lbs with the stock L-82 cam. Now it's between 120 and 130 lbs. WTHeck over? One or two low cylinders would mean bad lifters, but all of them are low. So something is wrong with the camshaft, right? I bought it used, but it had the Hot Cam numbers your supposed to look for stamped on it. Help.
Bee Jay

DRIVESHAFT

Its either bigger than you think it is or you installed it in a retarded position.

Bee Jay

Here is a picture of the crank and cam gear installed. I put it in straight up. I used the 0 keyway and the 0 crank mark.
Bee Jay

DRIVESHAFT

BeeJay, you are the first guy I have ever seen that has been able to produce a picture like that when it was suggested that the cam might not have been installed in the correct location. Good job.
From what I have been able to find the .050" closing point for the 1105 cam is 41 abdc and the hot cam is 39 abdc. Based on that, I would expect your cranking compression to be very similar or higher.
You mentioned having installed the 1105 4 deg advanced. Was that 4 deg on the timing set? Based on Summit's specs, that cam is ground 5 deg adv, so if you advanced it another 4 it would have been 9 deg advanced. That would have accounted for some of the extra compression before.
Still your current compression seems low. I wonder if the cam might have been ground retarded. Maybe thats why you got the chance to buy it.
Harold Brookshire has a technique that he refers to as his "Quick and dirty" method for checking the installed position of a cam. It goes like this- (cut and paste to follow)
I recommend my 'Quick & Dirty' method for verifying that the cam was installed correctly. The reason being, IF the cam is installed even slightly retarded, one of the obvious indications is that the engine takes more timing to run right, and there is a lock of bottom-end power and response.
You have this, so it is worth checking it out.
You only have to remove a valve cover.
Turn the engine up to TDC, and look at #1 cylinder's valves.
If BOTH valves are closed, you need to turn the engine one more turn so that both valves are off the seat at TDC.
Check the heights of the top of the retainers to the spring seats. The intake valve should be .030" to .060" CLOSER to the head. If the exhaust valve is closer, the cam is retarded and you have to take off the front cover and install the cam correctly.
The most common problem is that you have lined up the keyway with the dot on the keyway. The correct mark is on a tooth a couple of teeth counter-clockwise from the keyway. The cam does not have to be taken out to fix this problem.

Bee Jay

Thanks Driveshaft.
I thought the max I could advance this cam was 2 degrees, but that is cam degrees. I can advance this cam 4 degrees. So do you think that will bump my compression up about 40 psi? I can do that this weekend.
Bee Jay

Eddie & the Cruisers

Hi, BJ
I have a '94 LT1 Vert w/ otherwise stock engine that has a LT4 hot cam installed and a custom tune on the PCM. I know nothing much about cams and their lobes and such, but I understand that the LT1 engine has a 4* built-in advance and the LT4 hot cam, I believe, is ground with a 2* advance and gives the engine a mechanical 6* advance. Then the PCM on the LTx engines takes over for a 20* advance at idle and around 38* to 40* advance at wot. I could be all wet on this.

I am running a MSD ProBillet optispark distributor and the stock heads and intake have been ported to match each other and cleaned up to give better flow as well as the heads and shorty headers ported to match. With the A4 OD trans and 3.07 rearend, I have lots of low end torque and pulls all the way up to around 6500 rpms. Shifts nicely in all gears. On the 1/8th mile track (have not been on a 1/4 mile track), I run a 8.8 sec on 315 street tires. It would be much better if I had drag radials because I can't hook up and spins the tires half way down the track and a duck waddle every time it shifts. If I could hook up, I think it would lift the front tires up a little. Runs like a scalded ape.
It is an original Vert and weighs in at 3400# and I add an extra 100# more than most drivers, I'm old and not much on R/T.

I also have 12 in. of vacuum at idle and my P/Bs suffer from this. I am thinking about putting a vacuum pump on it to assist.
I'm just learning about my '73 C3 big block and would like to get some umph in it, too.

Bee Jay

Thanks Eddie. You are confusing spark advance and cam advance a little. But if you get only 12" of vacuum, and it runs like a scalded ape, that is good to know. I think I will adjust this cam for another 4 degrees of advance and see if my cranking compression goes up.
Bee Jay

Matt Gruber

BJ
i always final adjust the valves engine HOT, idling.
i use a cut open valve cover so it won't make a mess. Any chance they are too tight? The #1 mistake on cam swaps where it "runs like crap" is too tight valves.
.

DRIVESHAFT

That cam is supposed to be ground 3° advanced from what I am reading. It has a 112 lsa, with the intake being installed at 109 lca.
You should be able to advance it another 4° without any problems, assuming adequate intake valve to piston clearance.
Your compression numbers will increase from this, but Im not sure exactly how much. If you try it, you will have to let us all know how much it was good for.
Before I went tearing down the front of the engine though, I would pop a valve cover off and see if I could tell if the cam is advanced or retarded now using the Quick & Dirty method.

vstol

I have a LT-4/6spd Hot Cam in my GSR and runs extremly well. I contribute that to having PCMFORLESS reprogram a OBD-1 PCM for me. Like Eddie in the previous reply it pulls strong to 6500RPM. If you are running the stock PCM I am told you will have many issues with it running right. I am also running 96 GS master cylinder and big brake package with no issues.


My Bust did not see Intake and Carb set up so my response is OBE. Work email sucks

larrywalk

Short comment about the "Quick and Dirty" method...
It is even easier to put a 6 inch rule (straight edge) across the tops of the retainers when the engine is at TDC overlap. Judging from the tilt of the straight edge, if the exhaust is more open (depressed) than the intake, the cam is retarded; if the intake is more open than the exhaust, the cam is advanced; if both are even, the overlap is split. In the latter case, if the exhaust has longer duration than the intake, split overlap is considered correct (advanced).

__________________
1978 Corvette
406 SBC AFR heads Lunati roller Quadrajet TH-350 3.08
11.59 sec / 118.9 mph 1/4 mile

Taijutsu

Bee Jay: You and everyone else on this forum are smarter than I. It looks like you are doing all the right things to sort your mess out.
I can't help but think that a used cam unless it came from a known source is a big? Perhaps it is time to go back to the basics and see if you can get it to work w/carb? There are so many variables and unknowns that it is easy to chase your tail in circles. A known carb would eliminate your FI
as the problem. JMHO

R