Just got back from the track and am really disappointed. I felt like I had good 60 foot time and 1/8 time but seem to not get any mph. Here is the info looking for some help on improving this.

best et 13.2
best 60 foot 1.9
best mph 98

1969 chevelle
396 bored .030
373 rearend
3000 stall
dynamax headers 1 7/8 3" flowmasters
750 edelbrock
rpm air gap
compression ratio 9:1
comp solid roller cam 246@ .050 .623 valve lift 110 degree lobe seperation
336781 oval port heads stock valves

Your 60 isn't the best, but it's not bad either (but that doesn't have too much to do with your MPH though). Can you post your entire timeslip? It's a bit easier to figure out what's going on when you can see the entire run.

You should start looking at your engine's state of tune. How's the jetting? Total timing? What fuel system are you using?

Check to see if the carb is going full throttle too, this is a very common problem. What RPM are you shifting at?

Overall, a 13.2 isn't too shabby!

60 foot 1.9
330 foot 5.4
1/8 - 8.4
1/8 mph 81
1000 foot 10.9

When I went to rpm air gap came up with a stumble off the line, they suggested going 1 stage richer on power and cruise mode. This did take care of the stumble. Timing is a real issue. I have an aftermarket timing cover that does not have the timing marker. I set timing by initial staight up. I know I need to check the timing and I wonder how much I,m loosing with stock valve size.
Shifting at 6000 rpm, fuel is stock system.

Tis the Edelbrock 750 carburetor,,,a good all around carburetor,but not a choice for all out performance.

Seems like fuel starvation problems to me. You should gain at least 20mph(ideally 22-24) between the 1/8th to the 1/4. Its falling on its face at the top end, probably due to the bowls running out of fuel. Check Fuel Pressure during the run, I'm betting it nose dives to almost 0 in 3rd and 4th. When I was mph 98 in the 1/4 my 1/8th mph was only like 77-78

..something is wrong..as Robert said..must be the carb..too lean of jetting..I would think that combo would be in the mid 12's easily,as about 105+
..what size domes do those pistons have?
I will say thats a big cam for a low compression motor,but you should be in the ET/MPH neighborhood I mentioned.
What kind of timing you running? With that low of compression,easy 20* base/40 total by 3000 would be best.

Don't remember the cam specs real well, but years ago ran a little bigger Lunati Roller in a 10.25/1 396 motor - converter was bigger though at 4000 and 5.13 gears with 13 x 31 Goodyears. That car ran 11.60's - 11.70's. If your compresson was actually higher (close to 10/1) and you ran bigger gears, the ET will dip down by quite a bit. With 9.0/1 CR, you will limited on what to expect from a 396 motor.

Thanks for the response guys. Pulled all my paperwork and cam and intake do recommend a minimun of 9:5:1 compression. I guess that could make a diffence. Far as carb being to lean, it could be, I only went one stage richer on the mains, not the secondary jets. Timing could be a factor seeing I do not have a timing pointer to set MY TIMING AT. Car still pulled, lots of torque in third, just no mph. Piston dome .155.
Mid 12's is really what I expected and 105 mph is right where I thought it would be. Gotta figure it out before it drives me crazy.

rw,
What size tires and what rpm did you go through the finish line at ?

I am running MT ET's, 28 x 10.5 x15, Rpm's at finish is about 5000.

RW,

If you haven't already done so, I would set my intkae lash about .010 more than the exhaust side. This is another of those areas where "less is more ". Try running the exhaust to the tightest lash recommended and the intake to the max. Straighten out the top end fuel probelems. Also, did you degree the cam? Comp probably ground it at 106 ICL, it should be at least that or 104 ICL would be even better with the 9.0/1. Going through the traps at 5K won't need as much top end as you think, you need to get the midrange stronger.

I don't think loosening up the lash .010" is a good idea. Solid cams have lash ramps to take up the lash. If you loosen the lash too much, the lifter can overshoot this ramp and hit the flank of the lobe, causing tremendous shock to the valvetrain and letting the valve slam into the seat on closing. I wouldn't loosen up more than .004". If you loosen up the intakes .004" and tighten up the exhaust .004" you should be OK. Advancing the cam a couple degrees will help.

I personally think you shouldn't make any changes before you get your timing sorted out. Once you verified your timing, then you can re-test and make other changes. If you do make changes now, you'll probably have to change them again once you get your timing set correctly.

As Matt said,sort the timing out before doing anything.Figure out what timing pointer the manufacturer of your timing cover reccomends,and go from there..even the cheap chrome tab might work,as well as getting the TDC locator tool that fits in the sparkplug hole to verify you have TDC correct.I think you'll be suprised at the results graemlins/thumbsup.gif

Pat,

As I said, I don't know the recommneded lash settings for the cam, but I would think the range should be .018 to .028. Coincidence, I ran into a guy on Sat. nite who just went w/ a 496 motor in a '69 Nova, Merlin Ovals, 10.00/1, running the same cam. I believe he had previously ran it in a 427 motor very succesfully. In the 496 motor it sounded very potent. I would be curious to know what vaccuum (if any) this cam produces at idle in the 9.0/1 396 motor.

I really do appreciate all the feedback I am getting from you guys. I agree I think the first thing I need to do is to get the timing tab on and get it timed correctly. The vacuum at idle is pretty good. It is around 5 in. hg from one port and running 10 in hg directly off the manifold.
The valve lash is .022 on both the intake and exhaust.

RW,

If I have it right, this is the smallest of the Magnum Series (these high speed servers at the office are great- hooking up the cable modem and wireless at home tonight -you know what that means - computer and internet in the garage - I may never come out). Back on the topic, I am positive you can run the intake as wide as .028 which would really help the midrange punch on a 9.0/1 motor. What lifters and springs did you wind up installing? The lift rates on this cam should make this rather easy on the valve train.

I'm going by memory but they were the springs and lifters comp recommends for the cam. I believe the springs are 1.550 dual with 420 lb open rate. I am searching in between work and answering for a timing pointer. I see billet has a aftermarket pointer that I am hoping will fit. I need to go home and check the diameter of my balancer. I"m sure it's stock but going to check anyways. I set valve lash right at .022. I guess I'll get the timing straightened out and then look at other options. I won't be happy until I get this fixed.!!

That is a ton of duration for that gear, converter and compression. I'd say you need at least 10.0:1, 4500 stall, and 4.10 gear. The mph is way down at the 1/8 mile mark as well, and the 60' is way off as well. Properly tuned and correct gearing and converter should have you 60 footing in the 1.60-1.50 range. Timing NEEDS to be looked at and if the cam wasn't degreed in who knows what you got. I've seen a couple of comp cams be way off (like 4 to 6 degrees off). And lose the edelbrock carb. Put a 750HP holley on it. Don't even worry about the big valves at this point. There are way to many other issues holding the combo back to be worried about the larger valves. Until you work these other issues out the valves won't make a bit of difference.

A good mechanical pump with 3/8 inch fuel line should feed this combo just fine. However, don't use cheap in line fuel filters as they are very restrictive. Invest in a good high flow filter. Mallory, Fram, BG, or even Summit makes one from $40-$80.

My 67 Chevelle is about the same engine set up as yours, with a bit more compression. Go to my web site and I have the entire setup listed. Good Luck.

rw,
If you do the math, at 98 mph with a 3.73 gear and 28 inch tall tire, your rpm should be about 4400. That means your converter or trans is losing 600 rpm if you are turning 5000. 5000 rpm with a 28" tire and 3.73 gears should be about 112 mph.
Looks like its time to take a look at the trans or converter to me.

http://www.race-cars.net/calculators/rpm_calculator.html

I don't think your timing is the problem, Somewhere you are losing significant power between the 1/8th mile and the 1/4.

Your car should gain at least 20mph between 1/8th and 1/4...a well setup car in the 14-12 sec range will gain 22-25. You are gaining only 17. I run 100.7mphs but mph in the 1/8th at 79.5 or so. If I use the HP calculators for both the 1/8th and the 1/4th using MPH of those intervals ( http://www.smokemup.com/auto_math/index.php ) I get nearly identical Horsepower Numbers which is the way it should be. Plugging your numbers in shows you suddenly lose 30-35HP in the last 1/8th of the track.

Does it feel like it dies at upper rpms in the last 1/8th mile? Cause judging by your times it is. I would be looking at either fuel starvation, valve float(longshot), or maybe some sort of ignition problem.

RW,what rpms are you crossing the stripe at?

What brand of converter are you running? What does the rpm's fall to between shifts, and how much rpm gain do you see in the last 1/8th mile of the run?

I'll try to answer some of the questions. You need to keep in mind that this is only the second time that I have raced at the strip. BillK I am only estimating what the rpm's are at the finish, it very well could have been 4400 rpm. I really didn't notice, just knew that it was up in the rpm range and not topped out. The torque convertor is a Torco, again this is just approximate but I think it is dipping to about 3500 rpm between shifts.
Chad it looks like you really have your chevelle set up good, I do know that this cam is probably too much for the compression and set up that I have. I know that I am not going to get the times you have without a bigger stall and different gears. I am still going to get the timing checked too see where in the world I am at. Having said all that I still think the car should have a better time than it does.

That's the best bet, go back to basics and double check it. I would guees the car probably feels real strong on the street though, at least from a part throttle roll-on. The culprit is probably too much cam and too much intake. The easiest thing to do would be to get an intake with a fully divided plenum (or get a plenum divider made up) and play with the valve adjustment to pick up midrange power.

RW,are you absolutely sure you have 3.73's and not 3.31's ?

The timing could still be an issue, but not more than .1 if it is way off. The fuel issue should be very noticeable in the drivers seat. If it is running out of fuel on the top end you should feel it. My concern at this point is the converter and gears. Your engine is probably making peak torque between 4000-4500 rpm's. YOur converter should hit a couple hundred rpm's above peak torque. I am afraid you are way to far below peak torque with your converter, especially looking at your 60ft. Are you experiencing any tire spin? The effects of this converter may become more pronounced at every interval down track. In other words when you hit third gear and the rpm's fall to 3500 or less and the trans is now 1:1, with a 3.73 rear gear your engine combo has to claw its way back into its power band.

When I was running a pretty solid lift cam with 230 duration @.050 and 540 lift I was using an 11" 2500 stall converter. My car was running 8.0's with a 1.90 60'. Went to a 10" 4200 stall converter and the 60's dropped into the 1.70 range, et's picked up to 7.80's and mph picked up around 1 mph. I know another guy with a 67 Chevelle 396 that was way over cammed like yours. He got the car off of his cousin. It was running 8.0's and teens with a fairly tight converter. He put in the same 4200 stall 10" that I have and the car picked up to 7.60's-7.70's.

Yes, I am sure they are 3.73, I had .331 before I bought the new ones. Power band is as you said around the 4000-4500 range. I guess I should have talked to you guys before purchasing everything that I have. Roller cam, gears, torque converter, intake are all new, so you see where I am at. Here is another question, if I purchased heads with 110cc combustion chambers how much would this increase my compression and how much would it help? (current heads have 119cc)

RW,

Did you CC the heads? A lot of the open chamber heads are actually in the 120+ CC range. I might have miised this, but what pistons are in the motor. I only ask, because I recently did a 408 motor (TRW L2354's .188 Dome), I only wound up with 9.5/1 CR with '290 semi-closed chambers that were CC'd at 104 CC's. Also need to confirm your piston/deck (if not already done) and add this into the compression calculations before changing out heads. If you decide to change out heads-Edelbrock makes a 100CC version of their 290CC Alum head that would make a difference in CR worth doing. Otherwise - get a set of closed chamber GM heads. Compression will help quite a bit, even though the cam will still want to hit peek power in the 3500+ rpm range.

A set of 110 cc heads would put you up to around 9.50:1. The ideal thing would be to find a set of closed chamber oval port heads used. I run the 3904390 which has 96 cc chambers. These heads are bone stock other than, bronze guides, a 3 angle valve job, and race flow manley valves. This would get you to 10.5-10.75:1 based on where you are now. Some other good castings are 3917215 adn 3964290. You could maybe pick some of these up off of racing junk.com or even this board for a good price. Check the guides, put some good valves in and do a valve job, for a bunch cheaper than aftermarket heads. Also, it is possible to mill your current heads to cut the chambers down a bit. However .030 or .040 will only drop you about 5 to 6 cc's. This may gain you .25 or so points of compression, which would hardly be worth the effort and cost.

Originally posted by 67Super Sport:
The timing could still be an issue, but not more than .1 if it is way off. The fuel issue should be very noticeable in the drivers seat. If it is running out of fuel on the top end you should feel it. My concern at this point is the converter and gears. Your engine is probably making peak torque between 4000-4500 rpm's. YOur converter should hit a couple hundred rpm's above peak torque. I am afraid you are way to far below peak torque with your converter, especially looking at your 60ft. Are you experiencing any tire spin? The effects of this converter may become more pronounced at every interval down track. In other words when you hit third gear and the rpm's fall to 3500 or less and the trans is now 1:1, with a 3.73 rear gear your engine combo has to claw its way back into its power band.67Super Sport,

I see you recently became a member here so I just wanted to say, WELCOME! It's always nice to here from someone who has experience from racing regularly and can show us how to approach the 1/4 mile scientifically. graemlins/thumbsup.gif

Your '67 looks REAL SHARP and it doesn't look TOO cut-up for racing which I like.

Originally posted by 67Super Sport:
When I was running a pretty solid lift cam with 230 duration @.050 and 540 lift I was using an 11" 2500 stall converter. My car was running 8.0's with a 1.90 60'. Went to a 10" 4200 stall converter and the 60's dropped into the 1.70 range, et's picked up to 7.80's and mph picked up around 1 mph. I know another guy with a 67 Chevelle 396 that was way over cammed like yours. He got the car off of his cousin. It was running 8.0's and teens with a fairly tight converter. He put in the same 4200 stall 10" that I have and the car picked up to 7.60's-7.70's. Thanks for the real world examples. smile.gif

Rod

Ok here we go again. Most everything everyone has said makes sense and now leaves me the following options.
One- regardless need to take care of timing.
Two- Increase compression, torque convertor and gears. (all that I have just purchased)
Three- Go to a cam with less duration??Keeping in mind I want my car to be streetable (in town driving) but in at least the 12 second range)

RW,

It's a b&^*h, isn't it. For a while, everyone was only running (or at least discussing) big inch motors but there are a lot of us that run the 396/402 based motors. You may want to do some searches on the topic, there is a guy in Pottstown, Pa that posts here, has a 396 and runs a short duration solid roller that he got from Crane - special order deal. Probably 10 degrees or more shorter. The other option may be just go to a bigger gear, that motor may like something like a 4.33. A lot of gear for highway use, but definitely will get more from the set-up with no other changes. Years ago, in the heyday of the 396, anything less than a 4.11 was considered a "cruising" gear.

Believe me I have been in your shoes all too many times. If I knew 5 years ago what I know now I could have saved a bunch of money. Let me put myself in your shoes. Here is what I would do, being that you got what you got for now.

1) Get the timing set correctly. Shoot for 35-39 total.
2) Make sure you are not having a fuel starvation problem. Get a good mechanical pump that will flow at least 110 gph or go with a holley blue electric pump. Also get a good high flow filter.
3) You may be able to throw some more fuel at it as well. If the richer setting cured the stumble it may still need to go richer yet. Just be advised the richer the main circuit is the less streetable you will be.
4) Again, it may not be a bad idea to degree the cam.
5) Another idea would be to back your engine up to your converter and gear. You could go with a milder solid flat tappet cam. This may even pick you up being that you are over cammed for your entire combo now. Your roller will still be the perfect cam for when you decide to go with a better converter, and maybe more gear. I would be more inclined to put more converter in it before a gear. You should be able to put a pretty loose 10" in it and remain streetable. Do you mean every day driver or cruiser?
6)I have heard some not so good things about Torco converters. I can give you the part number for my TCI converter, which has been an excellent converter for me. However, if I ever need a new one I will most likely go with ATI.

Another real world test concerning gears. I have had everything between a 3.90 and 5.13. The weird thing is the 3.90 actually ran as good as a 4.56. However this was with a short duration mild solid lift cam. I then went to a 5.13 and man that made the thing pull. Picked up .1 in the 1/8th, but the car was so inconsistant in the 60' that I am back to the 4.56.

I am also asumming your ignition system is up to snuff.

Good Luck! Let us know your progress.

Well you guys have been great and I'm sure you will here from me again, Matter of fact I think I will check with you all before making any major changes and get your opinions. I definitely will keep you posted on my progress. Guess I will let you go and take things one step at time. Oh one more question, Chad with your 4200 stall how streetable is your car? This is just a fair weather cruiser around town.

Chad,nice numbers with your car graemlins/thumbsup.gif

I have not driven it on the street for a couple of years, and not at all with this converter. However, for cruisin it would be just fine. Just realize that with more stall you will build more heat, so a trans temp guage and good cooler are good things to make sure you don't over heat things.

Heck I have seen guys with 5000 rpm 8" converters that still cruise around on the street.

So, for cruisin I'd say no problem. For an everyday driver, you may be pushin the envelope.

This has been a good discussion, this is a little more relative to what I personally fool with these days. Don't get me wrong, I like the 10 second cars and the guys that run them on the street have brass ones, but to me the guy working on a solid 12 second 396 combo that you can still make a 90 mile drive to the beach for the day is what this is all about.