OK, how do I get my '72 Skylark from 12.20's to 11.80's?

The transmission is scheduled to be shipped out on 12/1. I'll be pulling the engine over the weekend to get the heads off and ready to take to the machine shop. My brother and his G8 are going to be in trouble come spring. :laugh:

 

12-14 PSI in radial tires? I thought I'd read somewhere that they shouldn't be run that low, but I could be mistaken. At any rate, wheelspin does not seem to be a problem at this point, so I figured running them at the highest pressure I could without spinning would get me the best MPH.


I'd be afraid to shift mine higher than 6000 given I'm running cast pistons. My son keeps telling me I should have gotten forged but at the time I never imagined I'd be trying to run 11's. :laugh: I've never had it on a dyno but given the parts I have I would think my peak HP would be somewhere in the 5800 range too.

 

You know what, my mistake. At the track I have a 26x10 slick. I run that at 12-14 psi. Man my brain is really starting to fry now that I'm 52 years old today.

 

I noticed your cam is 5 degrees advanced, from what I understand this moves your peak hp and torque down 500 rpm or so. My 430 has ported heads w/ stage one valves, hemi killer cam, sp-1, 850 demon carb, bottom end has some forged sealed power replacement pistons. It will rev to 6000 all day long, and it feels good doing it but it is definitely not where the power is at with this combo.

 

Its your Birthday? Well, happy birthday Phil.
Wow,52, you still look pretty good:laugh:
At 52 you should be getting close to 25,maybe the drop program?
Get set up then retire and spend more time with the family and the GS.
gary

You're shifting 6000-6200? I guess we did something right,when was that mill redone,I forget.

 

I suggest locking up your converter as soon as you hit second gear which is always good for something. That's why you get a multi-disc, to hold up to the HP. At least a tenth and 1 mph or more with a 3500 stall. Every car I've had a lockup converter in gets locked up and is always worth a noticeable performance increase. You don't need to use it every run. At the very least you only need to do it when you need that extra push for a low ET.

IMO if you are short shifting an engine and it is running faster there must be something wrong with instability in the valvetrain or some other system which won't allow the engine to rev to its maximum power peak. Back in the day when I ran stock cammed engines they ran the fastest shifting around 5000 and Stage 1's a bit higher. The biggest factor is what rpm does your engine drop back to after you shift. A 200 R4 is like a wide ratio manual trans compared to a T350 which would be closer to a close ratio manual because of the internal gearing therefore you should shift at a little higher rpm. A looser converter will alleviate some of this because after the shift it is slipping more at low rpm compared to the rpm it was shifted at.

When I first got my '76 going I had a TA RV12 cam in it and I shifted at 5300 for best ET. Any cam bigger than that probably should be shifted at even higher rpm. On the face of it short shifting doesn't make any sense. Why would you put a bigger cam in an engine and then shift before it hits the power peak. You may as well install a smaller cam and keep it in its' power band. Generally speaking most cams are installed a few degrees advanced to make up for timing chain stretch when the valvetrain is loaded especially as the miles add up. Don't quote me on this but I think 5* advance would only shift the power peak 2-300 rpm.

Definitely go after getting the heads opened up. That will add more power but also it will widen the engine's rpm power band. More compression always helps. I'd consider 3.73's to make sure you are getting up in the rpm range as you are nearing the traps. Think about it, what good is building an engine that makes peak power at 5800 rpm and then it is only at 4800 in the traps(Same as short shifting). The O.D. will work great with the 3.73's. Get rid of the vacuum secondary Holley. Try getting a cold air system on there. There's not much power to be found with the bigger cam until everything else is brought around. When everything is right you'll be in the power range where the 2.5" exhaust is starting to slow you down. Consider a 3" system or open exhaust and 3.5" collector extensions. If you get the better gears and converter the 3* bigger cam would help slightly.

 

Before removing the 3.23 gears, look at your starting gear ratio based on 26" tires.
* You have a 2.75 low, 3.23 rear = 8.825 starting ratio (lower than my TH400 and 3.42 rear)
* I have a 2.48 low, 3.42 rear = 8.48 starting ratio...factor my 28" tire and you get = 7.886, that is high, but add a 3500 stall... blows tires away like a lower gear.
* Many guys use a 2.48 low, 3.73 rear = 9.25 starting ratio...add 28" tire and you get a 8.55 start ratio.
* I love a pure 10.00 to one starting ratio, done that, but it's hell getting traction and NO fun on the street.
On the SHORT SHIFTING...(LOW GEAR ONLY) I think a turbo 400 has the most to gain becaust of the severe internal weight and mass. However, check in with the 200r4 guys and you may find that the converter stall may be a big factor with those lighter mass tranny's.
MT Street Drag Radial, try 18 lb air.

 

Have a "track" 3.73 rear axle running lightweight rims disc brakes, and "track tires".

You will want to upgrade your "street" axle to rear disk for this to work. You don't need to have rear disc. But it is a lot better to slide calipers off then bleed your brakes each time.

Put the car on jack stands, remove your tires, hang up the calipers, slide a jack stand under, unbolt the drive shaft, u bolts, shocks, traction aids, pull the old axle out, slide the new one in, bolt everything up then drive down to the track. Pull your runs then slide the "street" axle back in.

If done correctly you should be able to pull out the "street" and swap in the "track" axle in under 2 hours. That number will drop the more you do it. Cost is not huge if your able to hit the junk yard for a 3.73 or find one for next to free. Disc brakes upgrade should be done for around $700 for both axles using basic calipers if done yourself.

Lightweight "sticky" rims and tires(better traction) for the "track" axle is going to cost you and is the next step. But, your driving to the track on your street tires and bolting the "stickies" at the track so they should last for a while.

It is not perfect fix.
But, it keeps your car as street friendly as it currently is, does not cost a ton, and will knock your track time down.

 

Update:
The transmission has been shipped back to Extreme Automatics. Hopefully it won't be too long before I get it back. I took the heads to my local machine shop a few days ago; the head porter there and I had a good conversation and he's going to let me know what he can do with them early next week. In the meantime, I'll use this opportunity to clean the engine up, including the replacement of a timing cover gasket that was seeping a bit of coolant around the driver side water passage.

 

Hey everyone,

The transmission came back from Extreme Automatics a week and a half ago, and my new TSP 10-inch lockup torque converter arrived Friday. My son and I got the transmission back in the car yesterday and started it up and took it for a drive today.

During the first drive, I noticed the shifts were coming a bit late and the torque converter wasn't locking up. We took it back to the house and fortunately the torque conveter issue was quickly resolved by reconnecting the wire that had come off my TCI lockup controller. I also played around with the TV cable adjustment to see if I could resolve the late shifting issues and I was able to improve it a bit but I'm still not happy with it. Unfortunately I'll have to wait until at least next weekend before I can have another look at it.

The new torque converter feels just like the old 12-inch one under normal driving but when I get on it even a third of the way in first the rear tires start to break loose. Forget about punching it in first - there is no traction whatsoever. I can't wait to see what happens with my 60-foot times at the strip when I have the drag radials on it.

While the transmission was out for repair I also had the heads ported and shaved .030" by my local machine shop. The new compression ratio worked out to 10.5:1 and I noticed a little detonation at full throttle. I'll probably have to dial the timing back a bit on the street and run race gas at the strip to get the most out of it.

Hopefully I can get it to the strip either later this month or early March. I'll let you all know how it goes!

 

You can slow up your advance curve and use a 160* thermostat to help with your det. problem.
It should still want 36* total. Maybe 4000 rpms or so for total advance.
If your hearing it from the driver's seat, it's more of a problem than you think.
I hate to ask at this point, but there wasn't a sharp edge left around the chamber from surfacing?
Definitely read your plugs closer or try a few different ranges on one bank.
Brands don't always cross-reference quite right.
You should be able to tune out det. issues with your cam/compression.

Trans shift might feel soft from the converter flashing a bit higher than the shift recovery rpm.
You'll lose torque going to a huge diameter collector extension. Type your engine and cam specs into the header calcs @ Wallace racing.
Should be closer to 2.75" x 18"(?) length. OK to neck down from the 3.5".
Leaving a lot on the table with a vac sec carb.
Uncontrollable wheel spin is a good improvement.

 

you might need to jet up carb alittle also. to help clean up detonation.

 

Every 455 I have ever built and dynoed, with specs like yours, want's 33-35* of timing, as the best balance between torque and HP.

Set the timing at 34* total, and work back from there if you have to.

JW

 

Thanks for all the continued tips guys!

8ad-f85, you're absolutely spot on when you say if I'm hearing it, it's worse than I think. There weren't any sharp edges left after surfacing; the shop polished the chambers after surfacing as part of the porting work I had done. I like the idea of trying a different heat range on the plugs - I may be able to go a bit cooler on them. As for the vacuum secondary carb - can you explain exactly why you think I would be leaving a lot on the table with it? I am considering replacing it with fuel injection (if I'm going to spend a bunch of money replacing a carb I already spent a bunch of money on, I really don't want to get another carb).

Alec296, I actually had to jet this carb up quite a bit in the secondaries from what it came with. I've done quite a bit of tuning on this carb (jets, power valve, power valve channel restrictions, air bleeds) using my A/F gauge and the drag strip. Originally it had 80 primary, 86 secondary. I don't recall exactly what I have in it right now - I think 81 or 82 primary and 94 secondary with the power valve channel restrictions completely removed. This gives me a cruising A/F ratio in the 13.5 to 14.5 range with WOT around 11.5. The 11.5 seems rich to me, but that was producing the best MPH at the track with no detonation the last time I ran it.

Jim, I'll have to check the timing again, but I think I'm maxing out at 32 or 34 right now.

 

Interesting that you have detonation issues.

If your heads are around 66cc, your compression is just over 10-1.

I would suspect that either the cam is advanced (did it get degreed in?) or that .020 on the deck is the culprit.

Those two variables are the only thing different between your motor, and a know combination that we do here, with 1/2 a point more compression. Had that build in may cars, and never experienced a detonation issue.

Your right, if your O2 feedback gauge is accurate, 11.5 is on the rich side for a Holley type carb at WOT. Although the difference in power between that, and the optimum tune, might not be able to be seen on the drag strip, there are so many variables. Also, your motor might not be as efficient as it should be, certainly the deck clearance is not helping that. So it may need to consume more fuel that "it should" to produce the best ET.

Run that cam at 106-107 ILC for best results.

For a plug NGK FR-5 will work just fine for you.

JW

 

You almost can't get the secondaries to open quick enough with the vac carb.
If you lighten up on the spring so it screams out of the hole, it might open too quickly in top gear when flat footing it from a cruise.
Might be a factor the 60 ft. time.
There's different vac carb builders with different methods and abilities. Some Qjet guys eliminate the dampening dashpot altogether.
On Qjet's, I set the spring tension a bit differently in summer vs. spring/fall. I'm not a carb expert, but it works better for me that way....
Lower gears like yours make these carbs more sensitive to changes like that.

People are concerned with dumping too much fuel with a dbl. pumper.
Just by reading your last post I bet you wouldn't have a problem tuning one.

I re-read the beginning of this post, I did overlook the Quick Fuel carb.
Some Holley vac carbs won't open up all the way without mods. I can't say that for the QF. I don't know.
Might borrow a dbl. pumper and see for yourself.

Some plugs require different timing, best to creep up on things. The plugs and performance will tell you what it wants.
I also just noticed you are at a lower elevation.

 

The heads are only 62 cc after the work I just had done on them, so I believe that puts the compression closer to 10.5:1.

The cam was degreed in and it is installed 4 degrees advanced.

 

Need to look at the heat range and timing indications left on the plug, and go according to what the plug tells you.
That will tell you a lot more.
Verify timing with another light if not already done.
You already know that dial-backs can have issues.
Anti-seize messes with the heat transfer and creates detonation if it's in the chamber.

I'm not disagreeing with JW's fantastic info and experience, just making sure the simple things aren't overlooked.
They usually are.

What's near the edge of tune-ability in MN might not work where you are.
It should, that's why I think something simple is at play.
ECR might be one full point higher and +20 psi on cranking compression depending on DA, added to your .5 point.
(Not a be-all-end-all, just another tool in the box.)
I didn't see what coolant temps you ran, outside air temps, or hot underhood air maybe?
Those can matter.
Good luck

 

Thanks for the continued advice. One question though - what do ECR and DA stand for? I'll guess the CR is Compression Ratio, but I've only heard of static and dynamic compression ratio, so I'm not sure what the E is.

One other note about the detonation: it doesn't seem to happen at part throttle; just full throttle. Does that mean anything to you guys?

Coolant temp is a steady 180. Outside air temp was about 60 the day we took it out for a drive and heard the detonation. Underhood temps don't run too high on this car; the VHT header paint seems to do a very good job of keeping the heat from bleeding out of the tubes and my 4500 CFM electric fans really keep the air moving.

 

Here is my suggestion, call Pro-Systems Carburators and tell them everything about your car and you intensions, they will tell you your exact carb size you need for your application. My buddy bought one after telling them what his doing and he only had to adjust the air/fuel mixture screws only and that car ran almost a half second faster at the drag strip and ran like a charm on the highway If you don't have the proper carb., you'll never get your plug reading rt! Sincerely Gary M.