Went to Runday Sunday at Bradenton to see what the new converter did for me. I was happy that my 60's dropped 2 tenths to a 1.75. I foot braked on the two passes I made to about 1500 for the launch. The thing that puzzles me is that I am still running 12.70's but my MPH is down from my previous best of 108.53. The engine seems to be pulling hard all the way through the traps. From memory, the best timeslip yesterday was something like this.

60' 1.756
330' 5.27?????
660' 8.09 @ 85.??
1000' ?
1/4 12.755 @ 104.93

If you need more details I can look tonight and fill it in futher. Anyway, what I know is different between then and now is that I have 28" slicks versus 26.5" street tires. I think my trap rpm was about 5400. Could this account for the drop in MPH? The other thing is 2" headers vs. 1-7/8" headers. How much is this going to affect it? The weather was comparable at about 1200'DA. I also have the solid CAM and new fuel system but I would think it should make more power than before. I really think the carb is too small but it should still make at least the same power to get me back to 108.5 mph right?

Should I be gaining more than 20mph in the 2nd 660'? What do you think?

I was going to make another pass with my street tires on the car to see what it did for MPH but I threw a alt belt on the 2nd pass and didn't want to run too much until I got another one on there.

Thoughts?

Troy.

Troy,what carb and what is your jetting

Not to be picky, but this is why you oughta do one thing at a time if you really want to know whats going on and why. Otherwise, its hard to tell what did good, and what didnt. One guess is that your new solid camshaft likes to spin a little higher than the previous camshaft, yet you added taller tires(which effectively reduces gear ratio) without a complementary change in gear ratio to go along with the taller tires. You might be keeping the engine out of its best rpm range with the taller tires, new cam and current gears. That wont help MPH. Looking at your signature though, I dont exactly think thats it though cause your drivetrain specs and buildup sound pretty well matched enough that your not way off base.

Another possibility is that new converter. Even after the stall speed of any non-lockup converter you will have some degree of slippage. The new one is a looser, higher stall converter and it might just slip a little more at the big end of the track.....effectively burning off a little bit of mph.

Finally, whats with the 2 inch headers? Id say they are a little unnecessary with your buildup. Id say step back to your old ones and see what happens. I cant imagine a great difference in horsepower, yet the smaller primaries will provide a little more grunt and pull you harder. Id say you definitely want to spin that motor harder than you are(along with building it a little more radically) to make use of a 2 inch primary tube.

And finally, with all the new mods it just may simply be in the tuneup. All the changes you made are going to affect the air and fuel flow charactoristics of your setup and if you havent already, you will need to thoroughly go through the tuneup to get it to perform optimally. If your running with the old timing and carb settings and such, that could be the answer.

What is your shift rpm. You may need to adjust it.

OK - Here goes. The headers are 2" because Hooker doesn't make a smaller coated header in the Comp line. you have to go to Super Comp and they are twice as much (over $600). This is primarily a show car and I was going for looks but may have inadvertantly hurt my performance.

The carb is a Holley 3310 750vs. I don't think it is large enough and I have a proform body for it but I wanted to leave it alone until I got the other things worked out.

Greg - you are correct about the amount of changes. I agree - "one thing at a time". My problem is I can't get to the track very often with this car. I coach three hockey teams (my kids) and crew for two Top Alcohol Teams so my time is limited on the weekend. That's why I made more than one change between trips to the track even though I know it's wrong. graemlins/clonk.gif

I shifted at 5800 or so on the 1-2 and about 5600 on the 2-3. What do you think I should do, go up? The converter slips less than my old one, another reason the tires may be more of a factor.

I think I am inclined to agree that this thing likes to rev a little higher. I can feel the difference over 5K. I think I will play with the carb the next time I can get out there. I will also make a pass with the street tires and just look at the MPH.

Oh and one thing I ought to mention, my valve lash was at .026 across the board. I am going to try it at .018 and see what it does. Harold said this cam was good from .018 to .030.

I wish I could get back out there immediately but it isn't looking good for at least a month or two. Cool air will be gone.

Thanks guys - anything else as far as suggestions?

Troy.

I would change the jetting.
If thats a 3310 stock out of the box w/72's primaries and the rear metering plate,there is some MPH sitting on the table..the carb might not be too small,just jetted lean.
Read this:
http://www.chevelles.com/forum/ultimatebb.php/topic/9/17241.html

10-4 - I'll take a look. I will say this, last time I was out - back in September of '04, I went from 70 to 72's and the car didn't pick up at all. I took that as a sign that more wasn't going to help. Was I incorrect in that assumption?

Thanks for your help,

Troy.

70 or even 72's are lean..good for cruisng but not for all out performance.
That thread I posted will give you a good idea on where to go.
Swapping to 73's/74's on the primary side and running 82 to 84's in the rear will certainly help.

Thanks - I will give it a try. I have a metering block in the back. What do I need to get to change to a plate with jets? Just the plate and jets or do I need a PV blockoff and some other items?

What are your thoughts on tightening my valve lash? I'm starting to have 2nd thoughts about that.

Troy,if you have a rear metering block,you're all set.Make sure the powevalve on the secondary side is blocked..it might not even have a provision for one either.

I would leave the valve lash alone.
You're hooking pretty good with the 1.75
remember,one thing at a time.

Troy,
I think that the first thing you need to do is make a few more passes, but this time instead of worrying about times, pay real close attention to the shift points and trap rpm.
If your trap rpm really is 5400, then something is wrong. At 5400 rpm, with a 28" tire and 3.73 gears, you would be running almost 121mph. Even with a little converter slip, it should be way higher than 108 ! Are you certain that your tach is correct ? What type is it ?
Before you start making changes, you need to know exactly what you are doing now as a baseline.

Troy, not to offend you or anything, but for a big block with good heads/cam, those times seem really slow to me... something doesn't seem right.

that 104mph trap speed indicates probably only around 320rwhp, give or take a few, which translates to maybe 380-390 at the crank.

You aren't offending and I agree. It should be running better. Maybe the tach is wrong. I can verifyu it with my timing light but have never crossed checked it. The 121 MPH would be assuming no slip right? What do you think is reasonable slip? I was thinking 8% or 10% The Tach is just a small Autozone special. I don't even remember who makes it. I'm really at a loss for exactly what is going on. I triple checked the CAM placemnt when installing. I'm positive it's on a 104ICL. The fuel system is solid. The timing is 36º all in by 2800RPM. 16º initial. Good distibutor, wires, plugs etc. Maybe the carb has something major wrong. I just can't figure it out. I know I need more track time. It's just not that easy for me to get the free time.

I'll see what I can do about getting to a T&T on Thursday or Friday nights maybe.

Thanks for all your suggestions guys. It makes me think.

Troy.

I'd try bumping up the timing a couple degrees. Several years ago on the engine I had at the time, we found 28 more HP by increasing the timing 3º. That is a noticable increase.

That should be the same cam I'm running in my 439- duration @ .050 of 243/251 and lift of .586/.601 right? If so, as long as your bottom end is built right you're shifting somewhere around 1000 RPMs early. Harold told me my power peak would be around 6500, a good shift point would be around 6800, & it would pull 7000+. It may be a bit earlier for you with the extra cubes & longer stroke but I think if have the rest of your combo dialed in you should consider trying 6500 as a shift point & see what that does for you. Best of luck.

Wow - I didn't know the peak power would be so high! Am I safe to spin this thing up that high? I have a cast crank(-.010) with truck rods and ARP bolts. I have had the Crane Hi-6 limited at 6200 but that's easy to change. I just don't want to scatter this thing. I can't afford to put it back together right now if I do. My boys' hockey fees are killing me.

Troy.

Do you have 2.19/1.88 valves or 2.06/1.72 ?

I still have the stock size valves. I have priced getting them recut and the heads massaged by the same guy that does our head work for the T/AD teams. Is this going to be my savior?

I'm sure that the bigger valves would help.
But in the meantime,the reason I ask is,your shift point might be lower with the 2.06/1.72 valves (this is just an educated guess)
I would shift @ 6000-6200 max. and try that,then change the jets.

I shift my combo @ 5500 and my specs are 223/231 @ .050

mr 4 speed asked an important question. Bad assumption on my part that you'd gone w/ bigger valves. I'll bet his shift point recommendation is right in the ballpark. Bigger valves & some porting should net you significant gains. Depending on your budget you may want to just optimize your current set up & see if you're happy before you take the plunge.

By the way that's a great looking car- my favorite color combo for your year. graemlins/thumbsup.gif

you might want to make sure you're getting full throttle and that the vacuum secondaries are opening before you get to carried away. it has to be something simple like that, because your combo is not way off or anything and it should be running much faster than 12.70's. i would think it should probably be running 12.00's or maybe even a bit faster. also i see no reason to be shifting it above 6000rpms, unless the cam is in 8deg retarded or something. i had a much more radical camshaft in my 454 and i would shift it at 6200, but it usually reached 6500 before it went to the next gear. tried higher and lower shift points, slowed down a bunch when i shifted higher. i had a single plane intake and 2" S/C headers too.