I went to the dyno session with Jim Wiese yesterday. I had never been to the dyno and I had the time, it was a pretty cool experience. I wanted a street strip engine for my GS that my wife could easily drive. That means it has to have enough vacuum to run the brakes etc. I also want the car to be able to run in the mid 12's. Some of the parts used were my '70 block .038 over to 464 cu in, a set of '73 heads with Stage 1 valves and a porting job to 270 cfm. I think the cam Jim used was the TA 288-94H, the mildest of the three he regularly uses. I have 1 7/8s ceramic coated headers, MSD, a performer intake with a Holley 870 vacuum sec carb. The engine perfomed perfectly. The morning runs didn't show the power we were looking for. The HP was peaking too early at 4800 rpm. Over lunch Jim and Mike moved the cam back to only 2* advanced from 8* originally. That woke it right up! Much of the rest of the time was spent trying to get the carb right. I think the top numbers for the day were 484 HP at 5300 rpm and 550 lb/ft at 4000 rpm:laugh: I was pretty darn happy with those. In addition it will idle nicely with a slight lope at about 900 rpm and makes 13-14 inches of vacuum. All of the goals were met on this engine, now if spring would just hurry up and get here so I can DRIVE it. The engine made over a dozen pulls yesterday. The first and the last showed the same 70 psi oil pressure, it held together nicely.
Cool! sounds like a great street motor! Pretty good numbers for iron heads and that small of a cam. :TU:
Brent - Gotta like those iron-headed numbers! Hope you didn't mind me sneaking in for a peek yesterday.:beer C'mon springtime!:Brow:
455 Nice numbers, what compression are you at? I have same motor i am building. Jim has said to set this cam at 4 adv any reason he went back to two? good luck with motor thanks
10:1 compression. When the cam was at 8* advanced the power peaked at 4800 rpm. At 2* it peaked at 5300-5400 right where we wanted it. The difference Jim noted was the extra head flow as compared to previous similar combo's. The ONLY way you are really going to know is to run it on a dyno. Had we not done it, I would have given up at least 25hp and had the power peak too low. I also forgot to mention that we made a pull with a Q-Jet on top. It was too rich but still turned in a 475hp number. Nothing wrong with a good old Q-Jet at this power level
Brent.. Good thing we got it thru the dyno yesterday.. would have been an ugly drive down in the snowstorm today.. By the way.. thanks for picking up lunch! Steve, Brents motor is right at 10-1.. and I had to work the head chambers quite a bit, and use a .060 thick gasket to keep it "safe" for pump gas. That prolly hurt us a little in quench area, but the reality of the job was that we had a set of take-off converted Stage 1 heads to work with, from another customer, and could get him more power, for less $$ than converting and fully porting his heads. The cam change deal was interesting.. that cam ran really well in smaller port/ valve- higher velocity cylinder heads, in a 470 HP motor. And that was at a 107* installed centerline. But in this particular motor, with the larger valves, and bigger ports, changing the timing events via cam advance hurt it. It was making only 445 HP, and 525 torque, before we moved the camshaft. I attribute this to cylinder filling issue, with the same ci motor, but with more cylinder head volume. Moving the cam picked it up 40 HP, and 30 ft/lbs, and put the motor "right where it should be", considering the various different motors that have been on that dyno recently, with very similar parts. Now, I almost moved it back 4* instead of 6*, and feel that results would have been very similar, had I moved it 4*.. but we were testing, and I am happy with the change. I will still say that this cam is best installed 4* advance, as every motor and set of cylinder heads/intake/ carb is gonna be a bit different. That is why we test every one of them. We also did extensive work with his 870 Avenger Series Holley, as I have been looking for an alternative carb to the manual choke/parts non-existant TQ's, the harder to work with and keep fuel in the bowls, divorced choke Q-jet, and the $650+ chokeless HP series Holleys. This carb has an electric choke and fast idle system, and we worked the vacuum secondaries, to get them to function correctly, on this size motor, and the primary jetting. Now we have a nice street carb, which will provide good cold start/ yet run right with the 950 HP carb, which this one did. JW
Now that I have a dyno sheet in my hands, thanks Jim!, the part I like the most is the torque hitting 500lb/ft at 3000rpm and staying above that until 5000 rpm, peaking right in the middle at 550. No peaky race motor here, smooth and strong:bglasses:
No problem faxing the dyno sheet Brent... well at least as soon as I figured out how to run the new fax machine that George Gave me.. That was test number 17.. front and back of the sheet. On test 16, it made 485 Hp... at 53 and 5400... oil was getting a little hot right at the end there, and that can bite the numbers a little. I would call it a 485hp/550 TQ motor. With 13.5 inches of vacuum, 800 rpm, in gear. Of course, on pump gas. Love that little cam. Just got a new variation of that cam in today.. for Brian's motor. Tighter lobe centers on that one should make some more power, but still idle within reason. He lives in ST Louis, so choke and cold driveablity are not as big an issue with him as it is with you. And with the choke working right on that 870 carb, should be a super driveable mid/low 12 second car. Under all conditions, including cold start, since you live up near the arctic circle.. :laugh: And easy for your better half to drive... ya right, your gonna let her drive it... Better not.. you might not get it back. Mike is working on the car today, and as soon as the roads clear again, we should have it all buttoned up, and ready to deliver.. so you can sneak it out for a "test drive" on one of those clear winter days, when the roads are good. I've got my nose back to the engine grindstone, till I have to put my bodyman hat on this evening.. JW
Brent, Nice engine.... With a good exhaust system you may just see an 11.99!!!!! OH... and I love the part about this combo is something my wife could drive. Thats thinking!!:Brow: Jim, With all your time spent on the dyno have you ever seen an engine that likes the camshaft advanced 8*? Usually advancing a camshaft creates the effects of a smaller cam thus lower power band. Thanks
Yep.. Not at all uncommon to run a lot of these cams 6* advanced. I know Scotty runs everything at 106*, and most of the cams he put in were on a 112 or even 113 lobe center. I have run this cam, 114 lc, in at 107, several times. But that is with less porting in the heads, and smaller valves. Typically, all it does is move the power band down, and clean up the idle. The interesting thing about this move, with this particular engine, is that we only sacrificed about 12 lbs of torque at 2700, and I did pull the motor from 2700 rpm, just to see that difference. Made 493 ft/lbs at 2700 with the cam in at 106*, and and 481 with it in at 112. With the cam in at 112*, it caught the 106* install pulls torque at 3100, and then made more power as it climed in the RPM range. Since he has my 3200 stall vp converter, there will be no downside to moving the cam where we put it. And he likes the idle too.. There was a huge difference in idle quality, when we moved the cam 6*.. a full 2" of vacuum, and from a barely discernable lope at 800 rpm, to a much more pronounced one. Not objectionable, and still plenty of vacuum, but it did make quite a difference. Not something to worry about on a race motor, but with the all important idle quality issues of a street motor, it's a big concern. If we can advance the cam, yet make more power with the longer duration, and have the idle quality of a smaller cam, then we have our cake, and eat it too.. JW
Hi Jim In the photos I see your running an electric water pump. Will that stay on the motor, and will it be reliable for a street driven car by his wife? I bought one and in the destructions it said for race use only. Thanks Mike
Since Jim is likely working pretty hard, I can answer most of the question for you. The electric w/p was just for the dyno session, it is not going in the car. I think the destructions are correct, they are not meant for daily drivers or street cars in general.
Jim, What is "extensive" modification to make an 870 holley street avenger carb run right? The electric choke, and vacuum secondaries in addition to the the large flow capacity, seem like this would be a good setup for our motors. Thanks, Brett Schmahl
Would also like to know about the 870 mods. Trying to figure out what to do about carb this spring and have been looking at the Avenger.
Hey guys. Secondary opening timing is the big issue with this carb out of the box, as it is set up for a motor flowing a lot of air. We have a good baseline on what it's going to take to make it at home on a 485 HP motor, and after some tweeking, it ran right with a 950 HP. But I don't have the full story as of yet, prolly won't until the car hits the track, this spring. JW
