i know thats a real vague question, but i've got my 350 rebuilt and it's runnin 16.1's in the mid 80's.

the block is a 30 over blueprinted decked block with 4 bolt mains
the crank was turned 10/10 and polished
the rods are 5.7 wheeler forged profiled i-beams
the pistons are flat top speed pro hypers
the cam is a comp 268H with comp lifters and comp stock pushrods
the heads are port matched gm casts from a 300hp crate engine, 64cc chambers, 1.96's
right now it's got a 650cfm edelbrock on a performer intake
rotating assembly was balanced
the engine was compression tested and every cylinder was between 178 and 183psi

i can't for the life of me figure out what's wrong, it's the first time i've built an engine, but i went by the chiltons book, everything was torqued to specs. just fyi the rear is a 3.08 one legger and the trans is a rebuilt th350 (the swap resulted in .2 slower et's, but i read that thats common).

first thing i thought was that it was just the carb because only two barrels were opening, i fixed that and then blew the 700r4 and went to a th350. Now i'm wondering if i incorrectly adjusted the valves or if i installed the cam wrong or what...what's it sound like to you guys...i feel stupid as hell spending 6 months and several grand on an engine thats only grossing 16.1's...any suggestion is welcome

one stupid question...i don't have the pics anymore of my engine buildup, and i can't remember if the dots on the timing gears were both at the tops of the gears or if the crank was at the top and the cam was at the bottom like it's supposed to be....so the question is, the engine wouldn't even run if the cam was installed 180 degrees off, would it? i don't think i made such an obvious mistake, but the thought has crossed my mind

i guess in retrospect, it should also be mentioned that the headers are flowtech 2.5" collectors into a single 3" all the way back to a flowmaster 40 series with 3" out, the distributor is an accel billet HEI with an accel coil, no computer and no emmissions in my car

 

It is not possible to install a cam "180° out". For each half-revolution of the cam, the crank makes one full revolution; that is, at each 180° point of the cam, the state of the crank is induisinguishable from the other 180° point of the cam. So forget that.

I'll assume that you've done the usual tuning things, i.e. setting up the carb jets and distributor curve (or at least tweaking the static timing adjustment) for best results.

Power lives in the heads. If you aren't getting what you should out of it, that's where I'd start.

What is the head casting #? I suspect you don't have what you think you have there, whatever that might be.

 

What makes you wonder? If they are to loose you will here them for sure. lots of clacking under the valve cover. If they are to tight it will run like you have a miss because what ever cylinders you have them to tight on will not seal and the motor will be unbalanced. But you did a copression test and it turned out ok. So it sounds like you adjusted lash correctly.

Are there any other symptons besides lack of power? Like stumbling or poor idle quality?

 

Jimmy: nope, only reason i'm wondering is because i can't see anything obviously wrong and i'm guessing and double checking everything...

RB: head casting numbers are 14101083, i've advanced and retarded the timing +/- 5 degree either way to no avail, adjusted the carb, engine runs strong, just not fast

 

Are you able to watch your fuel pressure during the run.

 

Did you degre the cam when you installed it? Even if the cam was made "right on spec", the timing set may not have been, or you may have missed the sprocket alignment by a tooth. It happens.

 

vader, nope, thats what most worries me, it was a pete jackson timing set, but doesn't exempt it or the cam from being off...how many degrees off would that put the cam if it was off by a tooth? 10? would that result in the lack of power i'm experiencing?

jimmy, fp isn't a problem, it's got a holley blue pump and a magnaflow rising rate reg set at 6 psi

i guess i should mention that it also gets **** poor fuel economy...like in single digit range

 

ttt

 

So what do your spark plugs look like? Are they consistent from cylinder to cylinder? Is one perhaps fouling or maybe not firing?

 

they look fine, going by the spark plug pics in the back of the haynes manual, they're between normal and a little rich, and i'd rather be a little rich than lean

 

ok, so the motor runs strong, just gets bad mileage and runs poor et's. Could you possibly be having tranny problems. Is it slipping in third gear or something? I run a T-5 so I could be way off base here. But it sounds like the motor is fine by what you are describing. I would think if there was an issue with the motor causing the horrible gas mileage the plugs would show it. Maybe it's something else in your drivetrain causing the issues.

 

Most timing chain and sprocket sets (except the XHD single row true-roller rollers) use a 22/44T arraangement, which provide a difference of 17.75° per tooth. One tooth off puts you almost 18° off in cam timing - more than enough to kill performance, mileage, and starting.

Of the few "cheater" gear drives I've seen (the ones with idlers, like Jackson's) I've counted the same 22/44T arrangemement. That still equates to a 17.75° per tooth timing. The "true" gear drives (requiring a reverse-rotation cam grind) use a 28/56T arrangement, which still affects timing in nearly 13° increments. I don't know about the HTD belt drives' pitch and tooth count.

In essence, one tooth makes ALL the difference. Hell, my bone-stock 305TPI does better than that, although it does have the advantage of a posi axle (2.77:1). You really should verify the cam timing, if for nothing else than to eliminate the possibility.

Incidentally, the last one of those I had (a tooth late) also ended up with an exhaust valve being bent by the late timing and piston interference. Not to alarm you, but you really should check it out soon. Got a degree wheel?

 

There too is the possibility that the cam may either be defective or was broken in wrong...

Did you follow the cam break-in specs properly? It happens...

Did you degree the cam when you installed it to verify it was ad-advertised?

 

yea, i broke the cam in once i got it running long enough to do so, and if i had a degree wheel at the time, i seriously doubt i would have installed it a tooth off, but i didn't and so im not sure...

 

ontogenesis,

I understand your furstration! I too recently did a rebuild, 1 1/2 yrs ago. AFR 190 heads, zz3 cam, compression chekc is 168-175 in all 8 cylinders! I checked the sproket on my cam to make sure it didnot jump a tooth. I'm lucky if it can run a 14.0. I ran a best of 12.6 with my paxton s/c @ 8lbs of boost both befor and after the rebuild! I should be able to run that time with out the charger with my new setup! IF I find out anything, I will definately let you know, maybe I can help ya out/visa-versa.

good luck!

 

And not to question YOUR work, but degreeing a cam will verify a couple of other things as well as the installation.

You have to wonder if the cam was ground correctly. There is also a possibilitiy that the dowel was pinned in the wrong place. And that's just in the cam timing.

There are other places where things could have gone wrong, as well. Mr. Jackson could have drilled the cam gear dowel hole in the wrong place. The crank gear could also have been keyed in the wrong place. Mr. Jackson might also have stamped the timing mark on the wrong side of the gear, changing the timing as well.

All five of those possibilities, plus the two possible errors in the cam manufacture, make it a good idea to check the intake LCA of the cam. That's especially true now that you have mysterious issues.

 

On the 1st incarnation of my 400 (carbed, stock-type), I used "good" stock valve springs and my performance sucked...I could barely spin the tires and the engine didn't respond well throughout the powerband...I was never 100% sure what the problem was, but I can tell you that when I swapped the cam and did new valve springs, I was much happier...

Good luck...

 

What kind of performance gain did youget once you changed the springs? Waht kind of difference from before/after? Also, Vader is exactly right! I ended up taking off the timming chain cover to see if the dots on the t.c. were on AND verifed the cam with a degree wheel! Definatley get a degree wheel and verify the cam is in correct!

 

Pretty good change...I also put in a different cam as I thought that my Summit cam may have been not right...

I guess for troubleshooting purposes, I could have only replaced the springs, but I wanted it fixed....

The cam I put in is actually my current cam and works well...