Poor performance, anybody got any ideas?

This is my first attempt at a BBB, so forgive me for my lack of mechanical know how.
I recently got my engine broke in and have been working on tunning it. However, the performance so far has been pretty ddissapointing It is a '70 455, .30 over, TRW pistons, GS118 cam, MT headers, performer manifold and a '70 carb built to stage one specs. TCI 2,400-2,800 stall convertor, I believe. I know our altitude here (Denver 5,300ft) can be a problem, so the carb has .68 primary jets, .42 rods (?) and secondaries are AU rods.
The problem is the car doesn't seem to have any guts to it at all. From a standing start it acts like it wants to go, but no wheelspin at all and it takes forever to reach 3,000RPM, then it really doesn't want to go past it, starts to spudder bad. Under part throttle cruising, the car does ok, no overheating, etc.
I have checked to make sure to throttle is opening all the way and it is, as are the secondaries. Timming seemed a bit odd to me. With the vacuum advance pluged, the balancer mark was on the 12+ mark on the timming cover for about 24 degrees on the timming light, but it started at the touch of the key. If I tried to bring the distributor back to 12-14 degrees, the car was very hard to start.
Am I a tooth off on the distributor gear, or is their something else I need to look at?

 

Having lived in Reno NV and played with cars in altitude, my first reaction to your description was late timing. But the starting scenerio killed that thought.

I have only dealt w/ stock Qjets but my biggest beef with them is lack of accerator pump squirt on take off. Lack of fuel at tip in would cause a lean condition all the way through the power band. Bolting a good double pumper on any car i have ever played with is like adding 30 foot lbs of torque to the motor.

How are the plug reading after a hard run?

Your altitude is good for 15% loss of horsepower but what you have described should still be frying tires at will.

My guess is late fuel delivery and a flub in the carb rebuild.

 

Thanks guys, I am going to take a closer look at timming this morning and then move on to the air/fuel ratio on the carb.

 

Was the cam properly degreed when the engine was assembled?

You can't trust these timing sets......If the cam is off you could cost yourself BIG power.

With traction,It should runs mid 12's I'm guessing,Even at your elevation.

 

OK, I reset the timming to 12* initial, from 24* prior, as it appeared that I was a tooth off on the distributor. Total advance is about 30* before 2,200RPM. From that point up there is no change. The cam was installed straight up. I did not degree the cam. Just took it for a drive and still no change. It take forever to get to 3,000RPM and then it struggles to get over that. If I downshift it will go to 4,000RPM but at a snails pace. From a standstill, it won't screech the tires, not a wimper. Any other thoughts?

 

Gotta be the cam. Either not correctly installed or lobes knocked off during break-in.

Good luck, man, you got a lot of fun in store once you get it sorted out.

 

Couple of ideas for you Scott.

1) Dumb question but how about the float level / fuel level in the carb? Did you set it according to the instructions?

2) Restrictions in the fuel system> A blocked fuel filter in my kids beater Chevy wagon with a 307 Olds and Quadrajet made it a real dog.

3) Restrictions in the exhaust system? I know you aren't running cats but replacing a blocked cat on that same wagon picked up a ton of HP/Torque and milage.

4) I'd check that cam timing. When I was just out of high school, a buddy of mine had a 70 Camaro. Sounded pretty nasty with a huge by large cam in his little 327. Headers, intake and carb to go with it all. Wouldn't spin the tire even on a wet street! Based on the way it sounded, it should have been a pretty quick ride. Nope. Also had some issues with the timing marks on the balancer. Well, another buddy's dad was a long time drag racer and after some real basic checks, said the cam was installed incorrectly. Sure enough, he spent a couple of nights with the car in his garage with us helping/getting in the way/generally being 17 year old pains in the butt and when he was done fixing the mess the kid that owned the car had made, it really was a screamer. Ran 12.00's on a stock converter. Remember now, this was back in 1977 and in a 3500lb car. This was way before 1 hp per cubic inch was so easy to do.

Check that cam timing and let us know how you come out.

 

Thanks for your thoughts guys. I am starting to lean toward it being the cam also. Bummer, I just got it painted and looking great.
If the carb and timming aren't making any difference, then it's got to be something else that controls the valve timing - that leaves the cam. Anybody ever have any experience with a cam with the lobes ground off?

 

seems the most critical advice I have been given over the years is to properly lube a new cam and static time engine, have water in it and get it to 2000 rpms and hold it there for 15 minutes on initial start up. The cam being the most likely piece to fail on a new motor.

 

Scott give use a call and we should be able to help you out 303-857-9064 or cell 720-323-5994

 

Scott, first thing I thought of when I seen you where from Colorado, is that you should get hooked up with the Strube's. I pitted next to Jeff and his father Larry in B.G. this year and I have full confidence that they'll have you fry'n tires in no time.

Good luck

 

Thanks for the thoughts.

I haven't rejetted the carb yet, I'll see if I can do it tonight. I have had a vacuum gage on the car - tough to read at idle because it bounces so much, but something like 12-14 inches of vacuum. I've played with the timing and can't seem to get anything below 12-14 degrees of initial advance or the car will not run. It seems to like higher initial advance (20-24 degrees). Could the cam be installed advanced? Or a gear tooth off?

The exhaust is a set of MT headers and 2.5" dual with Walker mufflers. Good thought, but I think we are good here.

 

Check push-rod length. If the heads were milled and the block decked, the push-rods will be to long.

 

Scott, I've been reading along and just wanted to chime in and give my .02 worth. I lived in Denver for a long time with my GS, stock and modified. Stock it would scare you and it would lay rubber pretty much on demand and as far as I cared to stay on the gas. So you definitly have a problem and I'd lean towards a timing\cam\distributor problem. I didn't see anything on your ignition setup? Stock Distributor? I couldn't run more than 10 deg of advance stock without having problems. When I finaly got a performance ignition setup it really came alive! That said I have battled power issues even now and when I finally figured it out it was the carb, I would ensure the secondaries would open in the garage then take it out on the road and it would feel slow. The problem turned out to be that my secondaries would not open with the aircleaner on when it wasn't totaly warmed up. My point is that it may just be something little that you would never think of. Good luck!

 

I'm with LEO455. Same exact symptoms years ago. Tried everything for many years before swapping to adjustable pushrods...problem solved.

 

Thanks for all the ideas. I am putting in a set of adjustable pushrods as we speak. This seems to make sense regarding the symtoms. I'll let you know.

Rick, I thought the secondaries were a problems as well, but I have had the lock out removed on this carb. Secondaries open in the garage for sure. If these push rods don't cure it, then I've got to be a tooth off on the cam timing.

 

OK. Installed the adjustable pushrods and the car performs the same. After I adjusted the first one I pulled it out and compared to the previous solid pushrods, there was about a 1/16 difference in that the adjustables were shorter. I think I am going to have to tear into the engine and get a better look at the cam cam/timing. - bummer.

 

Tuning

I think you are jetted pretty lean - 68's with 42 rods might not get it.

Also, degree the cam before you do anything else.