Wendell Allen

Scenario:
1) '72 350, stock block (.030 over), carb (Q-Jet) that's for the most part dialed in, stock intake, and exhaust, stock points distributor (30 degrees dwell, 6 degrees initial advance with vacuum advance disconnected, all 36 degrees comes in by 2500 rpm or so).
2) Aftermarket cam of unknown specs (loppy but consistent idle at 600-700 rpm), hydraulic lifters, flat top pistons, light bowl porting on otherwise stock heads, 145lb (I believe) valve springs, MSD 3 coil, Accel 8mm wires, 15 inches of intake vacuum at idle.
3) stock TH400, not sure about the rear end, but I think it's 3.06's.
4) unsure what crank is in the car, but I believe it's stock.

Car will scream when kicked down a gear and secondaries open. Ususally works best at when kicked down at about 2500 rpm. But then it only runs to 4000 to 4500 before it shifts. The shift point makes sense considering the point at which the hp peaks. Over all, the motor runs fairly smooth.

Problems: I'm getting 195hp at the rear wheels @ about 3700 rpm dyno verified. Car will scratch for about 3-5 feet in first gear on 255/70R15's, then not much after that. Can't even get a chirp in second gear. Car runs hot (230 to 250+ degrees) in the summer months, even after complete cooling system overhaul and component (thermostat, pump, and radiator) replacement.

I dunno. I hear about other Sharks really doing a lot better than this with no more set up than I have. I'm thinking something's wrong.

Need any more info?

Care to speculate? Is it possible the cam's flat spotted? Timing off a tooth? Am I worrying needlesly and just need to sink more bucks into parts before I complain?

QuickVet

the only thing that i first noticed was you timing seems really low at intial. i would bump that to about 12-14.

how do the plugs look?

how does the car feel under full throttle?

does the car make any weird noises?


[Modified by QuickVet, 3:42 PM 1/8/2002]

Wendell Allen

1) Just to verify: I should bump the initial timing to 12-14 with the vacuum advance disconnected? I'll give it a try if you that's what you're saying.

2) The plugs are a light tan on the elctrode, with no oil, gas (wet look), or carbon (but they don't have enough miles for carbon).

3) At WOT, the car feels fine. Especially once it gets up to the 3000 rpm+ range. It sounds awsome.

4) No noises that I can put my finger on, but it doesn't exactly sound like most Chevy small blocks I've heard. Kind of has that "slapping" sound when it fires each cylinder. Like I've heard from some Fords or Mopars at the drags. I don't know if that's just characteristic of my cam, exhaust, or both though. No metallic or hesitating noises though.

I just got no grunt off the line. :cry :cry :cry :cry


[Modified by Wendell Allen, 5:35 PM 1/8/2002]

QuickVet

i run my car at 14 INt. timing with no vacume advance. works great.


I have no idea why the car runs that hot but i bet that is also affecting HP. my car runs at 180 all the time. have you taken the intake and heads off and checked those parts and just looked to see what is under there?

68shark

Seeing you don't know what cam you have, but it has a "lopey" idle...you may have "too much" cam given auto trans. and highway gears. That would explain nice sound and pickup at 3000+ rpm's, but not much off the line. My 327 has a Comp Cams XE262 that really would probably be similar if I had automatic and your gears. Seeing a fairly stock '72 I don't think the RWHP is the problem, but more where the torque curve hits and it appears to be not where you need it (that being off the line).

I'd bet a cam geared for lower rpm, auto trans and highway gears like the Comp Cams XE 256 or the copies of the "300HP cam" or similar, would be helpful to you.

Suggest you check with Ganey or one of the other experts. I'm an amateur by comparision...but just my opinion!

Matt Gruber

Doug is right, you have a 6000rpm cam and are shifting by 4500 :lol:
Get the kickdown circuit working!

FeedVaal

Wendell, I notice in your sig pic you're missing your front spoiler. This is what directs air to the radiator allowing it to cool the heated water. It would definately be a good idea to stick one on if your running without one.

:cheers:

QuickVet

have you shifted the car yourself at high rpm?

even if it was a big cam i would think he would get more then 190 hp at 3K+ :confused:

Les

You state you have 195 RWHP at about 3700 RPMs...the big question is- did your horsepower peak at that RPM? If so, that's way too early even w/ a very mild cam. I'm assuming it's not missing since you make no mention of that. Either you have a much milder cam than you think & your lopey idle is caused by other issues......or you have a problem w/ poor fuel delivery, low compression, worn cam, or something like weak valvesprings. Have you done a compression test and or leakdown test to determine the health of your engine? I'm hoping you can find something easy to fix like fuel delivery & that your internals are all good.

Wendell Allen

Quickvette Q#1: I'll give it a shot then. Hopefully that'll help. With the vacuum advance connected, it's at the 12-14 area though.

Doug: I didn't want to say it up front, but I'm wondering if you're right. Because of the mods before I got the car, I was thinking that the motor had been pretty well modified and the owner took all the bolt on stuff off when he sold the car. So maybe the cam was used in conjucntion with other stuff. I'm going to keep this in mind as I try other things and change the cam out if they don't work.

Drives: Given the HP peak is at or just below the shift point, isn't this the right thing to do?

FeedVaal: I hang my head in shame. You're right about the chin spoiler. I'll save my lunch money for one.

QuickVet: Since the motor peaks so low, it runs out of steam before the current shift point. It just doesn't make sense to shift higher. And the tranny is dropping down a gear if I'm on the fly.

Les: You got it. The motor is peaking out at that point. Pretty low, eh? Crap. And man, the rest of the stuff you're talking about echo's the myriad of other things I've thought about. I get confused every time I to thought it all. I've really worked the carb issue in line with Lar's stuff, and I'm increasingly confident that's not the problem. I know it's not 100%, but I think it's about 90% there and I don't think the other 10% is the difference on the fuel delivery issue.

Is this a big key though? I was thinking about this after my initial post. And Doug's reply is making me think about it more now. The factory "conservative" torque rating was 360 lbs/ft (you may recall - GM change their method of rating HP and torque in '72 to the more conservative estimate). My dyno'ed rating was 244.

Puhleeze! Keep the suggestions coming!!!!!! :yesnod: :yesnod:


[Modified by Wendell Allen, 5:56 PM 1/8/2002]

ZD75blue

about the scratch if first... your not holding down the gas long enough... or power braking near hard enough...

sorry thats the extent of my knowledge

ZD :jester

Les

Wendell,
IMHO it helps to start w/ the easy stuff & go from there as needed. Forgive me but, due to several similar posts by others, I can't remember if you've changed the fuel filter & tested your fuel pump for output. If you feel that your carb & ignition are in good order, I think the next step would be to check the filter & pump. I'd also check fuel lines for crimps & cracks along w/ the sock in the gas tank for blockage. External parts are alot easier & cheaper to test/fix than internals & lack of fuel can certainly cause your symptoms. Best of luck.

GWHITE75

Your cooling system really needs the deflector installed and make sure you have all the proper rubber seals installed around the radiator shroud and between the radiator housing and radiator at the bottom. You want as much air being pulled in through the radiator as possible. You did not mention your clutch and fan. Are you running a flex fan? Does the car recover at all when you get up in speed for any length of time?

If you up the initial advance to 14 degrees, make sure you keep your total to around 36-38, if possible. I would think that if you have a 3:08 rear gear, your acceleration will be a bit weak. IMO, a rear gear change might pep up your combination, but you will need to get the cooling issue solved no matter what you do.

Wendell Allen

Les: The fuel filter and pump (mechanical AC replacement) are both new. But I'm wondering now. I was forced to put an in line filter in when crap from the gas tank kept blowing by the filter on the carb, and causing the needle and seat to stick open and the car to flood. The additional filter solved that problem, but now I'm wondering if there is in fact blockage in the line or at the tank. Hmmmmm...........

GWhite75: You're right on the cooling issue. The bottom part of the shroud is missing, and I'll be replacing that soon. And I'm probably going to get an auxiliary electric to help it out. Or maybe just take the belt driven fan off all together. I have a flex fan with a spacer on it now since the factory clutch died last summer. The car does best on city streets and heats up most on the highway. I'm told this is because the fan blades flatten out with the higher rpm.

GWHITE75

Wendell, I wouldn't recommend removing the fan. In theory, there should be enough air flowing through the radiator to cool the motor at speed, but the fan helps to create a low pressure area in front of the radiator, so the air will pass through willingly. Once you replace the air dam/shroud, you should re-establish the proper air flow to the radiator. We live in a climate that needs all the cooling possible in the summer and I have made every effort to seal anything that would allow air to go around the radiator. I also use an aluminum fixed fan to pull as much air as possible, at the expense of some HP. I am thinking of putting my clutch back on. You might be onto something with the carburetor. I wonder if you are not leaning out the motor at speed? Is all of your exhaust equipment functioning properly?

Wendell Allen

GWhite75: Thanks for the suggestion on the radiator. I'll keep it in mind. As for the exhaust, it's the stock pipes, what ever diameter they are. I think 2.25". Of course the exhaust manifolds are stock and there is no heat riser between them and the pipes. The only other restricting factor is the mufflers, which are old, blown out, GM factory replacements. Not much resistance there.

My only other concern is the factory heat shielding around the tranny. It's obviously old, and has begun to kind of shred and expand itself in a way that fills in the air space between the floor pan and the tranny. I'm wondering if this isn't letting the warm air in the engine compartment evacuate itself completely.