[mgarblik]

I agree with Cliff and others I am reading here. I would just add that although I love the look and the no hassle installation of factory ram air exhaust manifolds, they are no match whatsoever to tube headers. Especially on the larger engines. Recent back to back dyno pulls on the engine dyno, 462 Cu In engine. Optimized tune with ram air manifolds with 3' long 2.5" pipes. Removed them and installed a set of lousy 1 5/8" primary headers I had laying around from a 74 GTO with a 350 engine. No other tuning. Engine picked up 28 ft. lbs. of torque everywhere between 3500-5500 RPM. Also picked up 22 HP in that range. I don't like long tube headers on a street cruiser, but they work.

[jhein]

A couple things. Having dealt with "dyno disappointment" myself...

I'm a street guy, not a track guy. Sounds like same for you. Regardless of what my actual power numbers are, with my street setup, I can't use all of it due to loss of traction. The way to fix that would be caltracs and drag radials. I've toyed with the idea of going down that road but then you have to worry about breaking other parts, etc. My point is that in its current configuration I can't really use any more power than I have and since I'm not racing, tenths don't matter, just driving feel. And from that standpoint my motor is a 100% success.

I know you haven't had your car on the road enough to see what it does, but from what you describe so far it sounds like you may be very happy with it's street performance. So just forget about the numbers and see how she drives. I bet you'll be happy.

[mgarblik]

We call our Mustang Chassis dyno the "Heartbreaker". Most of our young students are driving imports with cold air induction and a loud "Can" for an exhaust. Couple that with a slightly slipping clutch and you have a super loud Honda Civic with a B-16 engine making 39 HP at the drive wheels!! The heckling from their classmates is priceless. I am not making this up.

[Verdoro 68]

What I'm picking up here is that the numbers don't seem all that bad for a conservative cam, 9.5:1 compression, unported cast iron heads and manifolds. When you step back, the build is basically a 455HO with a little more compression and a roller cam. I would like to bring it back to the dyno and tinker with the timing to see what that can get me. I'm certain 32 degrees total didn't do me any favors as it feels a lot punchier with 36.

Overall, it sounds like I've done just fine considering my constraints of a stock-ish appearance. As pointed out, the unported heads and RA exhaust manifolds likely wouldn't support a bigger cam and the 8.2 HD rear end is on the fringe of what it can take as far as torque anyway.

A set of headers and maybe some bigger head pipes would be the easiest way to grab some more power. I've stayed away from headers due to the maintenance, ground clearance and because I think they'd interfere with the stock trans cooler lines (my cheap old ones did).

I don't consider myself a dyno racer, but all you know how it is. There is a part of me that wants to impress when folks ask how much power it makes. Maybe I'll just take them for a ride instead.

Originally Posted by mgarblik

We call our Mustang Chassis dyno the "Heartbreaker". Most of our young students are driving imports with cold air induction and a loud "Can" for an exhaust. Couple that with a slightly slipping clutch and you have a super loud Honda Civic with a B-16 engine making 39 HP at the drive wheels!! The heckling from their classmates is priceless. I am not making this up.

Ouch! That's a reality check for sure. Back when I was involved with the '04-'06 cars the guys around here would avoid shops with Mustang dynos and favored DynoJets because the results stroked their egos a little better. At the end of the day, dynos are just another tool for tuning and I think that's easy to forget.

[steve25]

I agree with your third paragraph above fully.

Don't say anything just take them for a spin and then ask them to make a guess at the HP.

[srmmmm]

I am a little surprised at your RPM at peak horsepower as well, and would agree that air flow limits are being encountered. In comparison, my 413 (350 block with Butler 4.25" stroker kit) HP peaked at 5600 RPM running 6X-4 heads and a Comp XR275HR that has a duration of 224/230 @ 0.050 running through headers.

[Cliff R]

I didn't see it mentioned but at 9.5 to 1 compression and those heads there would be a pretty big dish in the pistons.

I've only built one dished piston 455 variant here and it was considerably down on power from the same basic engine build with flat top pistons. I chose none of the parts for it, just hired to assemble and dyno it after the owner had a falling out with the machine shop/engine builder he was using. It was your "basic" Eagle 4.25" stoke 400 build with the long rods in it, and was originally going to use #48 heads but they ended up being cracked. So small chamber CNC ported KRE heads from Dave at SD were used instead.

That engine had trouble busting the 500hp mark on the dyno and after a long afternoon of tuning and making a lot of pulls on it we ended up about 520-530hp/540-550tq. A near identical build with flat top pistons a customer did a few months earlier netted 552hp/604tq.

I remember the dished piston engine wanting quite a bit more timing than I usually use on those builds to make best power, so something you may want to experiment with before the next dyno session. I'd also arm my self with a few sets of secondary metering rods as well a few thousands in either direction of what you are using now.......

[Verdoro 68]

Yes, the dish is pretty large on the pistons - a little over 29cc. Good tip to not be afraid of timing with them. Like I said, it seemed to really improve when I bumped it from 32 to 36.

[napster]

To OP,

I think we have had replies back and forth in the past. I'm going to do the 461 with RA II heads like you. The project has been put on hold for a few years and will continue that way for a while. However, I don't have the exact same setup in a '70 T/A , but it is a 433 with 722 heads unported heads. Has the Butler custom grind roller cam of 230/236 @ .0500 and 112 LSA.

Dyno numbers are at uncorrected. The dyno guy my mechanic uses is a real Richard. Here it goes anyway:
RPM HP TQ
2500 247 520
3000 295 516
3500 356 535
4000 400 525
4500 431 503
5000 447 470
5500 436 416
5800 402 352

This is thru RAIV Manifolds with the 2.45 inch outlet. I think the corrected numbers are around 460HP and TQ 545. Compression is a little over 10 to 1.

Hope it helps. Ask questions if you like. I will try to answer the best I can.

Jim

[Stan Weiss]

Originally Posted by napster

To OP,

I think we have had replies back and forth in the past. I'm going to do the 461 with RA II heads like you. The project has been put on hold for a few years and will continue that way for a while. However, I don't have the exact same setup in a '70 T/A , but it is a 433 with 722 heads unported heads. Has the Butler custom grind roller cam of 230/236 @ .0500 and 112 LSA.

Dyno numbers are at uncorrected. The dyno guy my mechanic uses is a real Richard. Here it goes anyway:
RPM HP TQ
2500 247 520
3000 295 516
3500 356 535
4000 400 525
4500 431 503
5000 447 470
5500 436 416
5800 402 352

This is thru RAIV Manifolds with the 2.45 inch outlet. I think the corrected numbers are around 460HP and TQ 545. Compression is a little over 10 to 1.

Hope it helps. Ask questions if you like. I will try to answer the best I can.

Jim

Jim,
Do you have a dyno sheet you can post, or are those numbers all you got?

Stan

[napster]

Stan,

That is all I have.

Jim

[steve25]

With the stock intake flow of those 722 heads and that level of camming 450 to 460 hp is what I would expect.
And so is that rpm where the Hp nose dives what I would expect, in comparison to the OPs 5700 rpm nose dive where his motor has lesser flowing heads and those heads have to feed at least 25 more cid.

[Skip Fix]

My stock "computer tune" '04 GTO is heavier than my 78 TA with an E head motor, the same as iron heads! 3880 with my 150 lb body in it. Not sure which chassis dyno it ran what on but same shop 284 HP on one, 292 HP on the other dyno. It had to have sticky DOTs at the track to hook.

[Skip Fix]

I'll throw this out to you as far as cam selection since you have the smaller D port intake ports and the better flowing round port-although into manifolds- your exhaust/intake ratio is going to be way off! My RAIV heads are close to 85% with a better intake port and the last motor they were on picked up with more intake duration !

[Gach]

85% is really good.

[ponjohn]

Chassis dyno question...

A car weighs a certain weight. So under acceleration it has X load and the combo responds accordingly.

How does a chassis dyno "know" what load to apply?
Too little and the power is low, too much and the power is low.

[Skip Fix]

My question on chassis dynos is since your rear gear ratio multiplies TQ why does that not affect it?

[Steve C.]

This will be of interest to some....

468 with iron 670 heads ported by Dave at SD Performance.
Paul Carter did dyno testing with headers and then with Ram Air restorations H.O. manifolds to see the differences between the two.

Numbers with headers in the first post. Post number 49 has the numbers with the RA manifolds, and then a following conversation about them.

https://forums.maxperformanceinc.com...+Air+manifolds

Two more tid bits of interest...

https://www.motortrend.com/how-to/hp...-vs-manifolds/

https://www.sdperformance.com/moreTech.php?newsID=39


.

[mchell]

Originally Posted by Verdoro 68

Prior to the last go round I had with the rear main on my car, I had taken it to get a baseline pull on a local chassis dyno. The results were a little milquetoast, but I kind of expected as such.

This pull was done with about 32 degrees total timing and all accessory belts in place and 91 octane. Basically driven off the street onto the dyno. The operator said to add about 18-20% to estimate crank output which would put it around 420hp and 510 ft/lbs torque. Decent torque, not so great HP. When I tore down the engine to replace the rear main I discovered a fairly substantial mismatch in intake ports so I'm sure that contributed to the results.

That said, I'm less worried about the actual numbers because I know they don't mean a lot with an automatic, but I am more surprised about how it peaked around 5k. I expected it to peak higher.

Unfortunately we didn't get a chance to play with the timing and do any more pulls because the Taylor wires and Pertronix weren't playing nice with their timing equipment. They did say they the A/F ratio was the best they'd ever seen on a Q-Jet so kudos to Ray Klemm. When I get some time I'll bring it back and do some more pulls now I've got the intake and ignition upgraded.

Mustang MD-750 dyno
4.25 Butler stroker kit
9.5:1 compression
236/242 114 roller
Port matched R69A heads
1.5 HS rockers
Ram Air Manifolds
2.5" exhaust
TSP 9.5" converter

Doesn’t seem out of line given the combo……think I got to 370 or so rwhp with an old iron headed combo I had at one time..

[Stan Weiss]

Originally Posted by ponjohn

Chassis dyno question...

A car weighs a certain weight. So under acceleration it has X load and the combo responds accordingly.

How does a chassis dyno "know" what load to apply?
Too little and the power is low, too much and the power is low.

Car weight has thing to do with how the dyno works. I don't know about a roller chassis dyno, a hub dyno uses different rotation mass (weight) based on the engines output.

Stan