Can Someone Explain This Too Me??? HELP!!!

[1976 Aspen]

I just put my freshly rebuilt motor in my car and was up at the chassis dyno and it put out 10 HP less than last year with alot of changes. Here's what I had last year: 360 bored .030 over at zero deck. 11.4-1 compression. SRP pistons, Hughes hydraulic roller cam with 236/244 duration at .050 .567/.576 lift, Crane Gold Race roller rockers, MP 4340 crank, Eagle H-Beam Rods, MP Iron Magnum heads that were gasket matched and lightly blended and they flow 214/170 at 28" with no flow tube with, M1 single plane intake, and a 650 Barry Grant Mighty Demon Carb. With that setup it put down 360.5 HP and 440 lbs. of torque at the wheels at 6000 RPM.

My setup this year: Same block with a sleeve in one cylinder, same pistons except for one new one. All cylinders honed for Brand new JE Rings, new cam, main, and rod bearings. I used the Hughes Engines stud girdle on the bottom end otherwise it's got the same crank and rods other than I went with Billet main caps and it was Line Bored to fit the caps. It's got the same cam, lifters, pushrods, and rockers. The block was zero decked again since the line boring moved things up. I bought Edelbrock Performer RPM Magnum heads and had them fully ported and polished by Shady Dell Speed Shop in Pennsylvania and the same intake was port matched to the new heads and the runners and floor were smoothed. The heads flow 276/210 at 28" of water and no flow tube with 60.0 cc chambers. The compression now is exacly 11.05-1 How can my power be possibly down after these new heads and matched intake. I was expecting to gain at least 50 HP at the wheels for $2750 worth of heads and porting. I checked the compression when it was hot and all cyliders were 180 lbs. The pushrod length is right on the money so the valvetrain should be OK. I triple checked the timing and found it was OK. What could be wrong? Any information would be greatly appreciated.

Ryan

[Madman Stephan]

1) Problem with air coming in?
2) Problem with exhaust going out?
3) Fuel issues (quality or supply)?

It doesn't sound like there's anything wrong inside the engine, so, it must be somewhere else. Probably nothing to do with the cooling system and oiling system, so you'll need to check the other subsystems, and my guess is that's where you'll find your problem.

[64dartwagon]

How long has this been back together? Maybe still a little tight. It needs to be run for a little while to get the most from it. Other than that temp, humidity, fuel, etc.. all have a big influence.

[quietdad]

You have .4lbs of compression loss on the new motor......

[ehostler]

I agree with all of the above.

On top of those issues, did you account for different air temperature, barometric pressure, and humidity?

Did you tune the engine while on the dyno, to get the max out of it, or is that just baseline information?

[cudabob496]

The air cleaner, carb, intake, and exhaust have to flow more as well to match the flow increase due to head porting. And the cam has to be matched to the power you want to make, ie if heads flow more, cam would need to be higher lift or longer duration. Just some thoughts. Also, dynos can be inaccurate or out of calibration. When dyno'd, was motor warmed up. Also, proper engine timing?

[Dukes2fast]

Maybe the old heads just matched your setup better

[cudabob496]

Talking to the cam manufacturers is valuable. They can recommend a cam based on your flows and compression, and the power you want to make. I have ported aluminum heads, but they recommended a lower duration cam than what I was going to use based on the compression ratio I had. The Crower guys were good! I would also think the engine needs some break-in period.

[cudabob496]

Also, at WOT there should be less than 1.5 inches vacuum in the intake. If more, then carb may be restrictive. I'd almost think you need a 750 carb. Also, a solid roller cam may be good for another 20 hp.

[DanL]

You said you changed the cam. Is it the same cam? (Same part number, I mean.)

You changed the heads to a set with wholly different numbers.

You didn't even mention what you're doing for ignition.

Is it the same dyno? Temp and air pressure differences between last time and this?

You gave up some compression. Assuming your cam isn't a huge mismatch for your heads, maybe some carb and ignition tuning will bring it around.

[crisser]

Originally Posted by cudabob496

Also, at WOT there should be less than 1.5 inches vacuum in the intake. If more, then carb may be restrictive. I'd almost think you need a 750 carb. Also, a solid roller cam may be good for another 20 hp.

I agree. The head flow went up quite a bit from the last setup. Also, check fuel delivery as the bsfc`s have prolly gone up also.

[cudabob496]

Initially you might think it would be easy to figure the size of carb depending on the head flow numbers, but the duration and lift of the cam will certainly determine if you can use all that increase in head flow due to porting.

[1976 Aspen]

Here are some answers to your questions to get a better idea of things.

Madman Stephen: I have the same air cleaner setup as before. A 14"x4" K&N with and extreme top. The exhaust is the same as before using TTI 1-5/8"-13/4" stepped headers with 2.5" pipe with Dynomax Mufflers. The fuel is exactly the same using Amoco 91 Octane and the air/fuel ratio at the dyno is reading a flat 13.0 I tried adding and taking away fuel with no changes to speak of. I watched the fuel pressure at WOT and it stays right at 6.5 PSI, same as before.

64dartwagon: I have about 20 road miles on it then we did about six light pulls on the dyno and dropped the oil and filter. Then we ran it at full speed on the dyno. Temp and humidity are very close to the last time I ran it. The fuel is exactly the same as far as octane, air/fuel ratio, and brand.

Qietdad: I realize I have .4 less compression than last time but I shouldn't be sacrificing alot with that you wouldn't think.

ehostler: The temp, humidity, and barometric pressure were almost the same as before. I tuned the motor right on the dyno trying different timing and jetting and that's the most we got out of it. NOT a Baseline at all.

Cudabob496: The dyno didn't lie to me because we put another car on it after mine just to see and it hit it's numbers from before by 3 HP. We tried all kinds of timing. Less timing, more timing, it seemed to like about 39 degrees total. I'm going to talk to four cam manufacturers tomorrow and see what they suggest. I'm also going to call Barry Grant and see what they recommend for a carb as well.

Dukes2fast: Wouldn't you at least think you would see a moderate gain from the changes? That's a substantial increase in flow on the top end.

DanL: The cam is exactly the same from before. I didn't change anything as far as lifters, cam, rockers, or pushrods. For ignition I'm running a MSD Digital 6-Plus box, MSD Blaster 2 Coil, MSD Pro Billet distributor, and MSD 8.5 mm Plug wires. It's the same dyno and we tuned the carb for a flat air/fuel ratio and tried all kinds of different timing settings. The conditions were almost the same as last time I was there.

crisser: We had no fuel delivery problems at all. We had a good air/fuel ratio, nice and flat, and 6.5 psi at the carb at all times.

Can my cam be that mismatched to my heads and intake? Carb size couldn't make that much difference could it? I'll call all cam manufacturers tomorrow to see what they recommend and Barry Grant as well to see if my carb is in the ball park. Any other suggestions? Thanks!!!

Ryan

[dwc43]

Your biggest problem is the carb is too small for your set up. Put a stock big block Tq on it and you'll get the 10 back and then some. Also temp and other weather conditions play a part too. IF it's a good dyno set up that should have been controled though.

[1976 Aspen]

I'm looking for way more than 10HP to get back. All that more head flow and no gains? I was expecting big power increase for the product and money I put into it. The conditions were very close to before.

[dwc43]

Like I said, your carb is too small. WE make over 400 hp on our 365 dirt track engines with less than what you have in yours. We also run an 850 TQ on top of it. Your port work wont help any if you can't get the air past the carb. Someone already mentioned you had 1.5 vacuum at wot, and that indicates too small a carb.

[cudabob496]

Also, I think downleg boosters make more power in the high rpms, but annular boosters make the engine more responsive in the lower rpms. I think the additonal 50 horsepower will be pretty easy to bring about once the rest of your engine components are matched to your new head flow numbers. By the way, after your dyno run, how did the plugs look. For max power, I suppose a nice chocolate brown would be a good color.

[cudabob496]

Man, your flow numbers almost look like big block numbers. I have an 850 Holley mechanical secondaries, and I think my intake flow numbers are around 295 cfm. I agree that you need a 750 carb minimum. I'd almost like to see you with bigger header pipes also, as mine are 2 inch with a 3 inch TTI system. Like they say, an engine is just a big air pump. The more air you pump, the more power you make. (I don't know who "they" are, though). Another tip, I run a cold air box over my carb, which is good for about 25 hp. When you feed cold air to the carb, you get about a 1% increase in power for every 10 degree drop in inlet temp. Some engines get pretty hot under the hood. So a 50 degree drop in temp inlet means 5% which means 20 more horsepower on an otherwise 400 hp engine. At about $100, its one of the best bang-for-the-buck mods you can make.

[lilcuda]

I agree about the carb being too small. Howver, your compression should have gone UP a half point rather than down .4 point when switching to aluminum heads. So you are almost a point lower than you should be.

Lee
1966 Barracuda, 340 4 speed

[rumblefish360]

1st up;

quietdad You have .4lbs of compression loss on the new motor......

And 1 point from heat loss.
The aluminum heads are a less heat retaining effceient head than the iron heads. Your loosing power there.

The porting flow numbers are so way off from each other. The iron Magnum is at a lower level of porting. This is keeping the velocity very high.
The Magnum heads. At 276 intake flow, the ports had to be opened up somewhat. The Alum. Mag. heads head volume is very large and possibly making the velocity a bit slow for a cam now to small in duration. Love the lift though.

Also, I would look at another 100 CFM on a carb.

I just re-read the timing. 39*?!?!?!? Realllly

[cudabob496]

Lets see, you're at 11:1 on aluminum heads. You use 91 octane. I was told for my aluminum heads, and the 10.5:1 compression ratio I have, that 92 octane was as high as I can go. So if you are 11:1 and using 91 octane, you may have had some detonation reducing your power output. A longer duration cam may help in that department because it reduces cylinder pressure, and makes more power, I think. The detonation may also have been helped by the 39degrees total timing. Backing off on timing may make more power, or poor in some octane boost.

[1976 Aspen]

I talked to Comp, Crane, and Hughes today about cam suggestions. They all of course had different numbers for duration, lift, and lobe seperation. I don't know who to believe. I'm going to talk to Crower and Bullit tomorrow and see what they say. I haven't talked to Barry Grant yet on a carb suggestion but I need to figure out a duration first before I call. Am I expecting too much from this motor? I really expect at least 500HP from it and still be somewhat streetable. Any cam gurus on here that have any suggestions? I hope to figure something out tomorrow in order of a cam and carb setup. Maybe I need to run open headers on the dyno to see if it will help. Any suggestions. You all know my setup except for the chassis so here it is. 3700 lb. car with me in it. 3200 stall, 4.11 gears, 28" tall tire, TCI 727 trans.

[crisser]

I think you should ditch the hyd. roller and go solid roller. The comp. XR280R
# 20-741-9 or the XR286R # 20-740-9 with a 750 carb. should get you in the 500HP ballpark. 1`st one is 242/248 @ 050, 570/576 lift on 110, 2500-6500 rpm. The 2`nd one [and i think the 500 hp one] is 248/254 576/582 lift on 110
2800-6800 rpm. These cams usually get SBC`s to around 500 hp. So, why not a mopar?

By the way, i`m talking flywheel hp not rear wheel hp.

[cudabob496]

The car setup sure seems ready to rock and roll. For the engine, assuming the intake is not restrictive, the solid roller is the way to go for 500 hp, plus they can be very streetable, and they can rev high!. Carb would have to be a race prep type 750 I would think (mechanical secondaries, down leg boosters), and I would sure be leaning towards some 1 and 7/8 header pipes, if not 1 and 3/4. The mufflers flow real good. Might see what the Mancini boys think about the right cam for a 500 hp small block. Or Indy Cylinder head too. "Victory comes with many advisors" Given the weight of the car, you may want a cam that gives a little more torque/grunt in the lower rpms. In other words, a cam that gives 450 horse and more torque may make you quicker on the street than a cam that makes peak 500 horse, but less torque. All depends how you will drive it I suppose. Those cam recommendations from Crisser seem like good numbers!

[rumblefish360]

3700 is alot of weight.

[345Dart]

Aspen
what fuel octane were you running before with 11.4 Cr and what are you running now?
440 ftlbs at the rear wheels with your 360 combo seems a bit much IMHO.
I have more cubes, more cam and more compression and mine dynoed @ 292ftlbs. @ 3200ft elevation. I know we do not race dynos, but something sure is fishy with the numbers IMHO. My buddies 446BB made 330 on the same dyno and he is running mid11s in a 3850lb car and driver.
What quench distance do you have? if somehow you could gain some compression back it sure would help as now you are in the high 9s at best. I'm running 11.9calculated - less 1 point for aluminum magnum hds, less .4 for elevation so I have in the 10.5 range and it runs just fine on 91 octane. I have the dizzy reworked to delay the all in to 2800 and a 254* cam that helps bleed of some compression but all and all your combo should rock - even with the cam you have. I think the high head flow and 650 carb may be a big part of your concern - borrow a bigger carb and bring the timing back into the 33-34* range and somehow get some more compression . And has been said - you need torque, not hp at 7krpm to get the 3700lbs rolling. good luck

[1976 Aspen]

I'm running 91 Octane right now just like before. My pistons are 4.030 bore .004 in the hole with a .042 compressed head gasket and a 4.180 fire ring and 60.0 cc chambers on the head. How can my compression be in the high 9's when it calculates to 11.01:1??? My elevation is 880 feet. It's hard to tell on the dyno what the real torque is with the converter multiplying the numbers unless you have a 4-speed car. What are your cam recommendations????

[rumblefish360]

static and actual cranking compresion are very different.
Rear wheel HP and crank HP are very different.
Dyno operaters are very different.
Pizza and steak are very different.

[1976 Aspen]

I realize all of the above Rumblefish360. When were we talking about cranking compression? The same dyno operator every time with the same settings and same torque on the straps. Personally, I like steak better than pizza.

[345Dart]

Originally Posted by 1976 Aspen

I'm running 91 Octane right now just like before. My pistons are 4.030 bore .004 in the hole with a .042 compressed head gasket and a 4.180 fire ring and 60.0 cc chambers on the head. How can my compression be in the high 9's when it calculates to 11.01:1??? My elevation is 880 feet. It's hard to tell on the dyno what the real torque is with the converter multiplying the numbers unless you have a 4-speed car. What are your cam recommendations????

your calculated compression is closer to 10.7 unless you have flat top pistons with no valve reliefs (go to http://www.diamondracing.net/cocalc.htm and check with your actual numbers). 10.7 minus 1.0 for aluminum heads minus 0.10 for elevation (1000' = minus 0.10) and you are at 9.60 as a truer CR. at your elevation for your combo is how I calculated it to be in the 9s. Some will say you may loose as much as 1.5 points of compression with aluminum heads and I sorta believe it or mine should ping like crazy. In your case, that 1-1.5 points of compression and high flowing heads may very well be working against the efficiency of your combo.
My cam recommendation is to phone Jim at Racer Brown and give him all the info you can possibly scout up on the engine and the car and get him to grind you a cam in whatever profile you want - hydraulic. solid, roller, etc.
Thats what I did and he ground me a hydraulic that works quit well.
Besides, my grand daughter just phoned and said she had pizza for lunch and liked it very much.

So you went from iron heads with ±55cc chambers to aluminum heads with 60cc chambers - me thinks you went the wrong way for the performance you are wanting.