Torque Converter to help 60ft.

[Steve]

Steve here with the 68' 4-door Dart (273 cu.in. engine).
Need your help with a torque converter choice. I have a 904 with a 9" 4000 stall converter. The car runs 2.07 60ft times, but chases down the quarter in 13.9 seconds. I don't know if my problem is the converter or the M-1 single plane intake. The cam I have in the 273 now is a 234/234 @50 .522/.522" (with 1.6 rocker) solid cam, 10.5:1 compression, 360 heads (1.88/1.60 valves) milled 40 thousandths, 600 Holley dual feed, and 4.56 gears. I shift at 6800 RPM's and go through the traps at the same. My best run was a 13.91 at 98 MPH.The only thing though since the change to the 360 heads, the car misfires the whole way down the track and turns the back plugs black each run. I think though the guides are worn, and the heads will be ported and rebuilt this winter.
All I wanted was the car to go into the 13's, but now I want to see the 12's bad!!!!!
Turbo Action said about running their 4600 stall 8" converetr, but I'm not sure.
Here are my questions:
1.What converter?
2.What intake?
3. What size carb.?
4. How much can you safely mill your heads(about a third of the piston sticks above the deck about a 1/4") I need compression.
5. Do you think 12's are possible.
Thanks, Steve

[Christopher]

Use the Turbo Action converter that they recommended.I live in the same city where they are located,and I'll tell you,their stuff is not junk and what the recommend can be taken as gospel.Keep the M-1 intake,increase the carb size to around 650-700 cfm,port the heads,and install bronze wall valve guides.I don't know a exact number for the head milling,but you need to check the clearance that you have now,then figure how much you can mill.With a positive deck height,it won't be much.

[Tim_K]

Hey, Steve, what's new? I saw that guy with the white '66 Satellite run at keystone last sunday, and he ran pretty well with his 273. I saw him go in the 12.80's at 102 mph twice. After talking to him, it seems his car weighs about 3770 or so with him in it, and he has a 3000 stall converter and 4.56 gears. And, I think, a wide-ratio setup in his 904. He showed me one of his timeslips, which showed a 1.76 60 foot time. He said he shifts it at 6400 rpm.

I'm curious as to why you're not getting better times (60' and 1/4 mile) with your lighter Dart. A few ideas I've had on it:

You say you have 10.5 compression, but was that an actual measurement, or what it said on the box the pistons came in? I thought you said Ray Barton set it up to have an actual 10.5 . I'd check the cylinder cranking pressure, because no matter what compression you have, changing camshafts will change the compression pressure. And you've got a pretty good size cam in that 273. It's a 276/.490 purple shaft but with 1.6 rockers, right? Do you run pump gas or racing fuel? Will it ping on 93 octane? What kind of spark advance setup and total number do you have? For that 273 to make power, I'd guess it would have to have at least 150-160 psi on a compression test. 93 octane is said to be good to 160 or 165 psi. I don't think going to a higher stall converter than 4000 rpm will help your situation. It seems, from what I've read on this site so far, that there is a general lack of bottom end power, which is costing you in the 60 foot. Get back to me on the compression test stuff, so we can analyze this situation further. Do you have a wide ratio setup (2.74 / 1.54 / 1.00) gearset in your 904, or is it still the stock 2.45 / 1.45 / 1.00 ratios?
According to my Chilton book for Aspen / Volare, 1976-1980, fouled rear plugs can be caused by the oil drain holes in the back of the head being partly or totally blocked. This will let oil sit around the valves and get sucked into the engine. With 145,000 mile heads, I'd guess that the guides were pretty loose anyway.
As for an intake, I think you might be better off with a dual plane. Yes, everyone says you need a single plane for high rpm power in a small block, but you're running a 273, not a 340 or 360. Even at high rpm's, you simply don't have the same volume of airflow requirements a bigger smallblock would. So that single plane might be hurting your bottom end more than it would hurt the bottom end power of a 340, and you're not flowing enough air at 6800 rpm to really need the single plane. I could be wrong, I don't remember what all dual planes you've tried, but it's an educated guess. I spoke to Dave at Hughes engines recently about my 273 project, and he was saying my idea about using an LD-340 wouldn't be good for a small street engine because of too much plenum volume for the engine at lower compression and rpm's. However, I think an LD-340 might be good for your higher compression engine spinning at higher rpm's. Have you tried one yet? They must be good for something to be in such high demand.
That carburetor might be a little on the small side. If you want to stick with Holley, maybe a 650 or 700 double pumper would work better, or maybe a 625 AFB Carter. A Thermoquad would probably be too big (and hard to get parts for to fine-tune it). I think small block heads can be cut 60 to 80 thousandths safely. Remember to pay attention to head gasket thickness, most gaskets are about 0.040" thick, but you can get thinner ones for more compression. Stock steel shim gaskets were 0.017" to 0.022" thick.
I think 12's are very possible for your car, there's just some more parts experimenting and fine-tuning to be done. If you went to a dual plane intake, I would think a 3000-3500 stall converter would be better.

NOW, let's talk about my plans for my 273 I'm getting. I'd like to hear opinions from everybody on this.
It is a 1965 273, 81000 miles. My use of the engine will be in my daily driver '71 Valiant, but I don't mind a few compromises for performance. Doesn't have to be smooth and quiet like a 318 family car, that's what I'm trying to say. I'd like to keep compression in the 9 to 9.5 range, about 150 psi cylinder pressure, so it can easily run on pump gas without being on the ragged edge of pinging all the time. I know this is a power limiter, but it's a 'mostly street, some dragstrip' engine. I'm probably going to use stock 360 heads, cut for compression, stock 1.88/1.60 valves, with some mild pocket porting.
The bottom end I'd like to build up pretty good to be able to handle high rpm's whenever they might occur. I would like to be able to safely rev it to about 7000 or 7200 rpm. Not that this will happen often, but a little overkill in the building process wouldn't hurt. I'm planning to use a 6 quart oil pan, HV oil pump with 70 psi spring, and full-groove tri metal bearings. Has anyone ever heard of half-groove ROD bearings? Someone told me once that they will allow more oil to be kept in the rod bearing surfaces, which decreases chance of failure at high rpm. If I can't find any, I can always get out my Dremel grinder set and make some. Carefully! Since '65-'67 273's came stock with forged crankshafts, we're ok there. I'm going to use 360 press-pin rods with ARP bolts. Bigger and stronger for the rpm's I expect to turn with this engine. I want to use main studs also, but with a windage tray. Milodon has a kit for it, but I'd prefer ARP because of their reputation.
I insist on using a solid lifter cam because that's what I want to use, 273's had them stock, and no pump-up problems as with hydraulic lifters. As for pistons, that's the tough part. I'd like some forged flattops with valve reliefs, but I'm not gonna pay $600.00 for them. I've heard from Ray Barton and other engine builders that hypereutectic pistons are junk (brittle), so I won't use them, either. That leaves cast pistons, which aren't usually recommended for performance engines. Tough choice. As for an intake, aluminum. I don't want to use an Edelbrock Performer (because so many shivvys use them) and I think they are kind of a generic intake. Like I said before, an LD-340 has not been recommended for my application, so I'm open to suggestions on an intake manifold. Carburetor of choice so far is a 625 AFB. For exhaust manifolds, I'm not planning to use headers on this car, so B-body iron manifolds will probably be used. There's no need for the expensive A-body manifolds if you have manual steering, and I've seen B-body manifolds fit power steering cars (like mine) if some careful fitting and grinding is done. 2-1/4" dual exhaust is the choice there. I'm planning to build a 904 transmission to 999 specs, with a wide ratio gear setup, good bands and clutches, and a 3.23 rear gear, possibly a 3.55 if I try the 3.23's and find them to be too high. About 2800 to 3000 for a (Dynamic) converter stall speed, with a BIG aftermarket trans. fluid cooler working after the stock radiator trans. cooler.
I've always been kind of paranoid on revving engines up pretty high, but that happens when you've been around too many Slant Sixes. I've heard many times that 273's are good 'screamer' engines, like 383's, so I'm going to try to get over this low rpm thing I've had to live with for way too long. When it is all built and running, I'd be happy to have low 15's or maybe high 14's out of it. I say that now, some day I'll be trying for 13's probably, but seriously, If I can get 14.8 to 15.4 with the initial setup, that would be good. Let's hear some other opinions on this, so I can develop this engine BEFORE buying parts.

[Christopher]

How is the rear suspension set up on this car Steve?? Springs,tire size,etc.

[Steve]

Tim K, My cylinder pressure in the 273 is 145psi all the way around so I don't know about true compression since the 360 head change. The engine was originally set up by Ray Bartno to be 10.5:1 compression with JE forged pistons and with the 273 heads. I don't know though if this is an actual number. The piston like I said though rises above the deck about 1/4" on about 1/3rd the piston. I talked to Frank with the white satellite and he said that his also has about the say rise above the deck and his bottom end was setup to 10.5:1 compression. His heads now have been milled, to what he doesn't know because they were used and he is using the thin 22 thousandths head gaskets. To take up some of the change in combustion chamber size, I milled the 360 heads 40 thousandths just to be safe while I saw if they would make a performance difference. I picked up 3 tenths with these old heads compared to the mildly worked 273 heads. I am planning on Tim Bowman to do head work for me this winter and I am going to check with him on how much more I can mill the heads. As far as timing, this solid Mopar cam I installed staight up, but as I found out this year it needs to be degreed in. I amruning my timing at 48 degrees full advance to make up the slack. This is where it runs the best and has no pings running 94 octance pump gas. Next year the cam will be degreed in. The intakes I haven't tried yet. Money, need more money. I do have a 340 cast intake that I am thinking of trying just to see if it would lead to better 60 fts.
Now with your engine.
I ran a 15.68 with my car a few years ago with very minor changes to the engine. Mine was a 2-barrel A/C car to start out that ran 17.60's. First, I changed the cam to a Mopar hydraulic 260/268 duration cam. Then, I put on a 340 cast intake and a 600 Holley dual feed with stock Holley jetting(probably too much). Lastly, I installed an 8 3/4 rear with 3.55's and Mobil 1 and ran the number. No piston change No head work or milling, just bolt ons. I used to shift the car at 6000 even then with no problems.
Oh lastly, my tranny will be rebuilt this winter for the first time in its life, but then again it has 38,000 miles on it now with hardly ever any buildup of clutch dust in the pan. Also stock ratio in the planetaries.
Thanks Steve

[Steve]

Christopher,
my rear suspension is basically stock. Stock springs and a pinion snubber. The tiore are 235/60 series M&H 14" , but I've never spun yet. The gear ratio is 4.56.

[Christopher]

The gearing is correct as you should go thru the traps at the same RPM you shift at,which you are.I think the Super Stock springs that Mopar carries would help the 60 ft times.I still would go with Turbo Action's converter,or see what Dynamic says.You say this engine misses at the top end.How is the fuel system?? Electric pump?? 3/8" fuel line???

[Tim_K]

Steve:
Yes, that 145 psi compression pressure is definitely on the low side. Cutting those heads another 0.020" or so would probably make a noticeable difference. Although most people concentrate on what their static ratio (9:1, 10.5:1) is, I believe the dynamic compression test (135 psi, 165 psi) is also very important. Also, you didn't degree in the cam? That could be a problem too. Whatever the recommended centerline is, advancing it 4 degrees will move the peak power rpm down, as well as help the bottom end. Be sure to check valve to piston clearance, though. Try that stock intake again, and see how it goes. Might be an improvement even though it's heavier. The dual plane part might make a big difference.
Interesting that we're both planning similar 904 buildups. We'll have to talk about that some more.
I was glad to read your 273 went in the 15's without much buildup. Gives me hope for my low 15's goal.
I'm going to have to put up a seperate posting title to try to get more feedback on piston choices. I want to build the short block ONCE and RIGHT. No tearing it down for quite a while. Talk to you later.

[Steve]

Christopher, I am running a Carter strip pump and 3/8" line for the fuel setup.

[Steve]

Tim K,
Do you think also that a lower gear set in the 904 tranny would help me even if I am running a deep set of gears as my 4.56's.
Also, Turbo Action said that running their 8" converter would be no problem with a tranny cooler , but what do you think about running their manual valve body on the street. Would it hurt thge tranny to much and how much would it help me at the track time wise?
Thanks, Steve

[Christopher]

I know you directed your question to Tim,but I'll throw in my 2 cents worth anyways.The manual valve body will work fine on the street,I ran one for years.I'd run a cooler,it does make a difference.The valve body will quicken and really firm up the shifts,especially the 1-2 shift.Once you get used to driving with one,it's kind of fun!!And I'd use the lower(2.77) gearset also.

[This message has been edited by Christopher (edited November 15, 1999).]

[Tim_K]

Steve:
Yes, I think the wide-ratio gearset would definitely help, especially on the bottom end. Do the math on it, each transmission ratio times rear axle ratio for both regular and wide ratio sets. It can make quite a difference. You may even find that with more gear down low, you might be able to change your axle ratio to something like a 4.30 or 4.10 and still get good dragstrip numbers, only now with better street driveability.
No matter what converter you run, even a stock converter, run the biggest trans. fluid cooler you can buy after the radiator's stock cooler (which will then serve as a pre-cooler to the bigger one).
As far as running a manual valve body on the street, I don't see any problems if the trans. is built with good parts, but do you want to have to do all the shifting all the time? It would be like a manual trans. but with no clutch pedal. Also, I think manual valve bodies are set up for the hardest shifts possible. If that is true, expect each shift to go SLAM! regardless of speed or driving conditions.
Just cruising around - SLAM!
Taking your girlfriend somewhere - SLAM!
Taking your parents for a ride to show them you are a responsible driver - SLAM!

Point is, they may have the quickest possible shifts for that last tenth or so at the track, but do you really want to have to live with it all the time? I guess it depends on how much you drive the car. And I think most manual valve bodies have a reverse pattern, too.
For the 999 I'm planning to build, I will be using only a mild 'Stage 1' type shift kit. I might give up a tenth or so at the track, but it's the daily driver car, so it has to be something I can put up with all the time.

[PRO]

2 MORE CENTS WORTH. 2.07 60 FT. THAT IS YOUR REAL PROBLEM,I SUSPECT YOUR CONVERTER IS GOING AWAY, YOU SHOULD BE CAPABLE OF 1.8 OR SO EASILY.TURBO ACTIONS ARE FANTASTIC.IF THIS IS STRICTLY A RACE CAR ,4600 STALL IS FINE AS LONG AS YOUR TRANS IS BUILT TO TAKE IT . THATS A BIG DAMN CAM,REMEMBER YOUR ONLY 273CI ,COMPARED TO A 440 YOU'D HAVE TO RUN .836 LIFT TO EQUAL THE SAME(BASED ON LIFT VS. CUBIC INCH)DROP THE 1.6 ROCKERS TO 1.5 AND SEE IF IT HELPS, IF SO RETARDING THE CAM WILL HELP BUT YOU REALLY NEED 11:1 OR BETTER COMP(180-190PSI) TO MAKE THIS CAM EVEN BEGIN TO WORK. MP CAMS ARE ALWAYS WITHIN A 1/2 DEGREE OF PERFECT, I'VE CHECKED OVER 100 DIFFERENT ONES OVER THE YEARS.650 HOLLEY WILL HELP AFTER YOU RAISE COMP. I MIGHT CONSIDER SMALLER CAM, SOMETHING AROUND 480/ 230@.050.BUT TO GO TWELVES KEEP THE CAM AND RAISE COMP.A COMMENT TO TIM K,KB PISTONS ARE AN EXCELLENT PIECE, NEW TECHNOLOGY SOMETIMES SCARES PEOPLE THAT HAVE ALREADY FOUND A GOOD THING AND DONT WANT TO CHANGE OR NEED TO.OH YEAH .060 IS MAX MILL ON 360 HEADS(SAFELY) IVE SEEN MORE BUT IT TOOK A COUPLE SETS TO GET ONES THAT WOULD SURVIVE(NO WATER LEAKS)....PRO...

[340king]

Hi Steve,

Just a few coments on convertors. I help on a '70 duster drag car. It has a 12.2:1 360 engine with stock unported heads. We use a Dynamic 8" convertor. Stall is around the 4500 rpm mark, I don't know, cause I aint looking at the tach during the launch when I drive.

We had a lower rpm stall convertor in the car when we transplanted the 360 in. We noticed on video tape that there was a very prominent change in engine pitch near the 60' mark. We went from 1.88 60'time to 1.57 and from a best of 12.18 to 11.75 with a convertor change and lighter wheels.

For this reason I think you could use the higher stall speed to build up your torque.

On the engine I did some checking with CR. If RB set up at 10.5:1 with composite gaskets, the new CR would be 9.3:1 assuming a 72cc head volume. Changing to .018" steel shim gaskets would raise the CR to 9.8:1.

If you change to the higher stall, you could use a little more cam. The limit would be around the 242° @ .050". I do have one question though. I assumed your cam was a single pattern cam. This would yield a .557" lift intake with a .522" lift exhaust. This probably isn't a big deal, but the flow ratio of the stock 360 heads isn't great as the exh lags from ideal.

Also, the peak torque looks to be around the 6450 rpm range, so your shift point is really close. One final question, What lobe sepration does your cam have

[Steve]

PRO,
Do you think that if I mill my heads to 60 thousandths that they would clear everything. The heads now are milled .040" and clear fine. They compression test was 145psi. The pistons do come out about 1/4" on the one side but I don't know if it will clear everything like piston to head on piston to valve. Any thoughts? I know the piston will clear the walls of the combustion chambers because of the 3.66 bore on the 273. As far as the converter going away, I don't think so. In fact with the small solid cam the times went from 2.15 with the old hydraulic to 2.05 with the solid. What do you think of the .060 mill plus thin gaskets ( good idea or bad?) How can I raise compression other than new pistons? If you have any suggestions on this or a better converter I would appreciate it.
Thanks, Steve

[Tim_K]

Steve:

Like PRO was saying, that is a big cam you've got there (276 / .490" purple shaft) right? But with 1.6 rockers. Duration at 50 is always something to consider, but it's important to remember that a 273 won't need as big a cam as a 440, for example. A 276/.490" cam could be near full-race in a 273 and only mild street in a 440. I know, I'm having a hard time deciding on a cam for my 273. I wanted to put in a 276/.490 to get the high lift, but I'm sure the duration at 50 would be way too big for the milder 273 I'm building. I want to stay with a solid lifter cam.
Since you've already cut your heads .040" and want to go to .060", I don't think that would be a big enough change to get 180-190 psi. If you haven't degreed in and advanced your cam yet, you might try that to see what kind of change it will make before cutting the heads. Do you have a cc number on those 360 heads at the .040" cut?

[Small Talk]

Steve
I've run small blocks for along time & I am still learning & I except there are no set rules. I've never run a 273 but 340's yes. I'll try to be breif. I'm in total agreement with Torque Converter change. I run a 69 Dart. What you are discribing on your engine setup there is some overkill on cam maybe under compression this will inturn drastically reduce your low end torque & hp. I have tried many converters Turbo Action is a good choice to be considering. Don't be intimidated by the hi stalls. Its doubtful your engine would stall 4600.(I've run a similar setup in a 340 W/640 lift W/11.0 comp, W/single plane manifold) W/a 2.07 60 ft your 273 is struggling until it reaches it optimun RPM for good torque & hp. I've run as hi as 6500 stalls & you would never know by feel W/a 5.38 gear.You need to compensate for this condition W/ a looser converter to elevate & transfer the power quicker & shock the suspension & tires. Small Block's love RPM's Good Luck/I love Pa. vfv

[340king]

I have some food for thought.

What RPM was your compression test run at? What RPM was Tim's run at? What RPM was PRO's run at?

I base my cam duration recommendations on full race, no holds barred engine performance. Therefore the size may look on the large side. I did however say that you could go up to a size, but did not say you should run that size.

The lobe separation of your cam is very important for optimum performance. With a small displacement engine you need to maximize your torque potential. The lobe separation is a big factor in where the peak Volumetric Efficiency(VE) is achieved. Peak VE=peak Brake Mean Effective Pressure(BMEP) also refered to as dynamic compression. Selecting a cam to provide peak BMEP at the right RPM will make your car peform better.

So, what we want is an easy method to predict if a certain combo will work, what the engine wants is a certain pressure to produce power, and what we get may or may not be a true indicator of that.

All I'm saying is that since compression testing occurs at about 200-400 RPM, using that information to determine performance at 4,000 to 6,000 RPM may or may not work.