Hey small block guys - HP & TQ estimate??

[Gam Man]

Guys (340 King/Sanborn? )

I have a 360 combo planned and am wondering what sort of output I would be looking at with the current parts that I have stashed. Specs are as follows:

1971 360 0.030 up bore & hone with TQ plate, line honed and studded t'out.

Floater HD Mopar rods, KB pistons, plasma moly rings, cast 3.58 crank, all balanced, convertor neutrally balanced.

Compression measured at 9.5:1 (street use as well), O-ringed/ported/milled 915 J heads, 63 cc chamber. Intakes flow 270 cfm@ 600" lift at 28" H20; (2.02/1.60 11/32 valves) welded exhausts flow 205 cfm @ same measurement. Intake port volume is 182cc.

Cam is Hughes max Velocity solid HEV 4550 with 245int and 250exh @0.050 / lift is at .560" int & .575" exh.

Pipes are 1 3/4" x 35" x 3" collectors merging into 2.5" mandrel bent dual system.

1.5 Needle roller rockers, one piece pushrods, dual springs and moly retainers finish off the top end.

Intake is either (have both) Edelbrock Performer RPM Air Gap or M1 single plane and carb is 780 Holley.

Ignition is MP Chrome box/ blaster coil with elec dist all in by 2000 rpm with initial 16-18 and total 36-36 deg.

Trans is 727 TF, full man reverse pattern valve body with 3500rpm stall. Rear end is 9" with 4.56 gears and 29x15x12" tires.

Car is a tubbed A body @ 3250 pnds and will be street/track.


What do you guys think of this combo in terms of TQ & HP and where (if any) can any improvements be made?Have I left anything out? Which intake would be better? Would 1.6 rollers better feed the the heads? A heap of queries to be sure!!

I'd really appreciate some feedback as I want this engine to kick some brand X butt and you guys sreally know your stuff!!!

Thanks in advance.....

The Gam Man!

[Gam Man]

Sorry, I forgot to mention,


Mid lift flow is 195 cfm @ 300" of lift and 238cfm @ 400" of lift. Hope this info is useful !!

[sanborn]

There are computer programs available that are fairly accurate to predict HP/Torque for combos like yours. I use a seat of the pants "rule of thumb" that a properly prepared single four barrel engine will produce 2-2.1 HP per CFM of intake flow@28" provided the exhaust flows 70% of the intake. Said another way, your engine should produce 540-570 HP using my "rule of thumb". That's a pretty stout SB Mopar.

One area you might look at is the cam lift, if your heads flow 270 CFM @ .600" you might consider a higher lift cam or 1.6 rockers. With the combo you described, your cam will never get you to max flow of the heads.

Another area to consider is the heads, W2s will flow better than "Js". Flow of 310-315CFM for a modified set of W2s is very achievable. But 600-620HP is the limit a stock block/crank combo can take under any conditions.

Above 600 HP will require serious race parts; crank, rods, block, etc. Heads(W7,8 and 9) are available that flow 360-385CFM @.700" but those engines are a whole different story.

Enough talk about HP! The real question to answer is driveability and the ability to put the HP to the ground. There are plenty of 550HP engines that out perform 600HP engines because of the way they are driven or the ability to put the HP to the ground. You must think about that subject as much(or more) than the engine.

Hope my comments are helpful!

[Gam Man]

Thanx for the feedback Sanborn. I guess I already had considered 1.6 rockers to get that cam lift up with a slight increase in duration to match the head flow, its something to consider. We have also gotten about 292cfm at 0.600" out of these heads with a 2.08 valve and welded exhausts with a flow ratio of 72%, but I am reluctant to go this way b/c of the increased port volume affectinting the VE of the engine and the rpm Id have to turn to get "it happening"!

I'm reluctant to go W2's or W5's as they cost a fortune Down Under (look at our dollar) and I already have the rollers and headers to suit the J's so I'll refine what I have & see how we go.

I am also considering grouting the block to ensure round cylinders for max ring seal at high rpm. What do you think of this for street/ strip use? I understand that grouting will not affect cooling if it is kept to the level of the side/front core plugs! Yes ??

Will the engine be realistically able to make that HP level with the compression that I'm running though??

I understand that having all this power is useless if ya can't put it to the ground too! To that end, I have just installed springs, shocks and a pinion snubber and i will be running slicks when I hit the track. A matched
"system" is what counts and that's what I'm trying to achieve!

I'd be happy if I could achieve a REAL, weight shifted figure of 500 RELIABLE HP or so nat aspirated.

Thanx once again for your input!

[Rich33]

Hey, Gam Man what about circle tracking racing down under? I went to a great 1/4 mile track just out of Hobart, Taz. a couple of years ago when we made a port visit there (Navy). It was a blast! The owner showed me around and there was a quite a bit of great late model and sprint hardware there. Unfortunately, no Mopars...Maybe you could change that, hey? Sheeez, they thought that Chebby stuff came from heaven or something.

I realize your a ways from Hobart, but I'm sure there's some tracks near you, right? I also saw a bit of the A.M.C.A. stuff that was begging to grow. Modifieds with Holden V8's. Get a hold of one of them and put your Mopar Small block in it. That'll give 'em a show!

[340king]

G'day mate, I plugged your specs into the old pentium processor and assuming it didn't miss a divide somewhere, this is what it came up with and also what I know from my experiences with a very similar combo. Engine Pro came up with a predicted output of 428 ftlb of TQ @ 5100 rpm and a HP of 478 @ 6300 rpm. It also predicted a maximum cam duration @ .050" of 252°, before both torque and HP dropped with increasing duration. Engine Analyzer 2.51 came up with slightly differing numbers. Peak TQ of 499 ftlb @ 4500 rpm and peak HP of 481 @ 5500 rpm.

So what would I change? I like the idea of the 1.6 rockers to pursue the sweet spot in the flow. A slightly larger cam might work OK. I might use a slightly larger intake and carb also for the track.

I have wrenched a '70 Duster drag car for several years now and have learned that your convertor will work well on the street, but will be lacking at the track if you can hook it up. The first indication is that the stall point of the convertor is below the peak torque of the engine. This can lead to a lazy performance off the line or worse, a bog. We ran a 3,500 stall with 12.5:1 compression, 252° @ .050" intake, stock "Z" cast heads and had poor 60 foot performance. On the video tape, it seemed like we were hitting the nitrous or something at 60 foot. The car came to life like a two-stroke coming on the pipe. We were running 1.76-1.90 60 foot times. We switched convertors and went immediately to 1.56-1.57 60 foot times. We run a Dynamic custom built 8" convertor, $840 U.S. before duty.

Possible reasons why the output may be lower than expected. Both computer programs use the airflow, cubic inch displacement, bore to stroke ratio and other pieces of info to calculate performance. The critical area that they look at is the bore to stroke ratio. In small blocks, longer stroke is the kiss of death according to the programmers. They look at it like there is not enough displacement gain, due to the increased stroke, to offset the parasitic losses accompanied with it. In EA 2.51, I have seen HP losses of over 175 @ 7,000 rpm predicted by the program. A similar bore 340 shows only about 150. That is a 17% increase with only 20 cubes to make it up.

So how does this stack up with what I have seen? Pretty closely unfortunately. The rpm range required to get the most out of the flow you have listed is a little past the optimum for a typical 360 combo in my opinion. Don't get me wrong, your car will really rock! It could just use a little more stall and a little more lif

[Gam Man]

Hey 340 King, thanx for info too pal....

I was a little concerned about the lift as well, I figured around .600 - .620 " lift would be better with a duration of about 250-255 @ 0.050. Would this duration be a problem with the compression I am currently running?
I also have an MP .590/312 solid but that would be way too much for the compression I am running. I don't want to bump up the comp too much as this is a dual purpose car.

I also guessed that I would need more stall, as the maladies you described in your post have been identical to what I had experienced out of the hole at the track in the past. I'd guess a stall of around 4500-4800 rpm would do the job. What's your opinion mate??

[340king]

I think that you should probably stay where you are in duration and increase the lift if easily accomplished. If you increase the duration at .050" lift, you will raise the rpm where peak torque is made, hurting the situation with the convertor. From the dyno predictions, your peak torque is probably very near the 4600-4800 rpm. EA 2.51 runs at 500 rpm increments the way I have it setup. Therefore there is a little error possible in the exact rpm where peak torque is made. The farther you are from the peak torque with your stall speed, the harder it is keep from wallowing out of the hole.

I have dynoed several engines. Right at the break point, where torque is coming up close to the peak, they can be real fickle to modulate the water brake for steady rpm pulls. The engine wants to rev up and down erratically around the desired rpm. I think this is the cause for the variable 60 foot times when there is insufficient stall in the convertor. Bracket racing is all about being consistent. The convertor is one of, if not the most important, single component of this combination. So, I would look long and hard at trying to come up with a good quality higher stall convertor.

[Gam Man]

340 King,

Timely and accurate info I'm sure.

If the torque peak is at 4600-4800 rpm, then will a 4800 convertor be OK? The reason I ask is that I have a mate who has this convertor handy and I may be able to twist his arm to let me use it!!

If I went the 1.6 ratio route, would I be able to get way with only 1.6 on the intake side?

Thanx for your advice to us novices of the SB game....

[340king]

I think I am going to do some thinking on this before I answer. What has gotten my attention to the 1.6 ratio on the intakes only deal is pulse tuning, overlap scavenging and intake reversion. It takes me some time to figure out what is going on with these components of flow when we are making unusual changes. As for the convertor, go for it!

[Gam Man]

Hi 340 King,

Once again your knowledge & expertise is greatly appreciated across the BIG POND !!

Frank

[SDDuster]

For what it is worth. 340King does my work, and he is talking about my car. When I ordered my convertor there were two prices. One was around $620 and the other was $960. I took the $960, since that convertor allowed me to put more horepower to it. The first thing I changed it paid for it itself. I added a transbrake and called the company. They said, if I had ordered the $620 convertor, I would have needed to send it in and have it worked on, but since I paid up front I did not need to have it rebuilt. This is a case, pay me now or pay me later. I am glad I did what I did. You can't believe the difference the convertor made. My last eleven runs, with the old engine, I was within .02. Therefore, I believe you get what you pay for.

[Gam Man]

Hi SD, what convertor stall were u running & what 60 ft/1/4 mile times did you end up with (before & after) the convertor swap?

Frank

[SDDuster]

I have some slips when 340King drove the car.

A total of five passes and they ranged from:
60' 1.58 1/4 mile 11.87
60' 1.67 1/4 mile 12.007
This was with the old convertor at 3000 to 3200 stall.

This is with me driving the car:

A total of four passes with the new convertor, using the foot break:
60' 1.57 1/4 mile 11.88
60' 1.58 1/4 mile 11.83
The convertor is a Dynamic 5000 Stall. I did make some othe passes but were about the same.

I had my transmission worked on with the same covertor but with a trans break, with eleven runs:
60' 1.56 1/4 mile 11.65
60' 1.57 1/4 mile 11.64

As you can see they are right in there.