200ci Seriously disappointing dyno numbers

This applies only to 200ci
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datac

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I grenaded the camshaft on this engine about ten years ago, rebuilt it shortly thereafter, and finally got the rest of the car reassembled late last summer. The new build has a bit over 1000 miles on it now, runs and feels good, no driveability problems other than a fairly lopey idle.

200ci .030 over, Comp 260H cam, small-chamber 170ci head, Winona bronze valve guides and stellite seats with standard 3-angle, oversize valves (80's vintage spec, need to look up the dimensions, it's been a long time ago), light port+polish, Clifford dual-coil valve springs and tubular pushrods, Mallory Unilite distributor and Promaster coil, 13deg initial + 38deg total advance, Clifford long equal-length headers w/port divider, 1.75" true dual exhaust, Offy 3x1 intake w/Pony Carbs modified Autolite 1100 (spec'd by John Enyeart specifically for this application). Standard trans.

Feels a bit softer than the last time I built it, which was with a 272H Clifford cam and Rhoads lifters, but drives out nicely.
I was absolutely shocked to see the dyno numbers (it's a reliable dyno, reports reproducible numbers on other cars). I thought I'd be anywhere in the 110-130 range, but instead...

Pink is first run, blue is after some tweaks. Dyno operator reported that jetting looked good, engine seemed to run strong, but to my eye something's clearly off. To save your eyes, that's 79.87 hp, 137.5 tq

Dyno_hp.jpg


The dyno operator delayed the opening of the secondaries a bit to smooth out the A/F ratios, again blue is second run...

Dyno_af.jpg


It's a daily driver, so I'm certainly not after maximum performance, but I sure as heck expected better than this.
Guess it's back to fundamentals, check compression, etc., etc., but hard to imagine how something could be that far out of whack on a fresh engine without introducing driveability issues.

photo.JPG
 

bubba22349

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Very nice looking engine (y) What compression did you end up with? Also what timing chain set did you use, was cam set straight up or advanced?
 

datac

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IIRC Comp cams ship w/4deg advance, I installed it straight up.

Block hasn't been decked, standard Fel-Pro head gasket, head very lightly surfaced. As long as it's been I don't recall my compression, should be slightly less than stock due to the gasket. I'll need to run a compression check, no doubt.
 

64falconsix

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very similar to my set up , I am running the comp 260 on my large log Tri-power backed by a c/4 auto. numbers look low and the torque curve seems to fall off after 2,300 rpm.I have'nt dynoed mine yet but with the cam set at 106 ICL my setup is still pulling strong at 5,300 rpm and feels like the torque curve is broad and flat. running my numbers through the Wallace racing 1/8th mile to HP converter I come up with 135hp. The dyno sheet is hard to read on my screen but if the second sheet are the AFR numbers they look way off. I normally run an AFR of 13 throughout a WOT run according to the narrow band tapped into the header collectors.
 

datac

Active member
Yeah, that's the AFR in the second, along with the hp. The forum limits to 600px high images- I'll link to bigger stuff if it's helpful.
How lopey is your idle? I'm wondering if I've got valvetrain problems. Not certain what else could account for such a big drop- poor fuel pressure maybe? I'm grasping at straws.
 

64falconsix

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The comp 260 gets a bad review on this site but in my opinion is a performance cam for the 200 and smaller engines. with 30 more degrees of duration @.050, 12 more degrees of overlap and.068 of lift over the best stock 200 cam it is a decent street performer and does have a nice little lope. mine is fairley lopey when first started up but smooths out just a little when warm. could start be readjusting the valves to rule that out as a contributor. but the AFR shows the mixture going from dangerously lean then way too fat towards the end of the run, the one run looks like it follows the same path until close to the end then spikes toward the lean side. I would look at the jetting first. you said you originally lost a cam in the first build, did you wipe a lobe? to help protect the flat tappet cam and distributor gear run a bottle of Comp cams breakin lube at every oil change. this advice comes from a friend who is a speed shop owner and nostalgia racer who recommended it and says all the flat tappet cam racers do this to help protect from lobe failure due to the lack of ZDDP in modern oils, plus it's cheaper than one of the specialty flat tappet cam oils. here is a vid of mine at Idle with the comp 260. http://youtu.be/lVlo4vn0-kY
 

datac

Active member
Yeah, differences in exhaust aside your idle sounds much like mine.

I did take out a lobe, but it was ten years ago before the demise of zinc. With about 10k miles on it, I had an umbrella seal come apart and a piece wedge in the valve spring on the #1 exhaust- broke the rocker arm shaft between the intake and exhaust. I didn't realize the culprit at the time, replaced the rocker arm assembly, checked the pushrods, and bolted it back together. The impact must have damaged the bottom of the lifter, 5k miles later I'd lost a lobe. All new since then.

It felt considerably stronger (although I hadn't dynoed it, and it was ten years ago) before with the same jetting- I wonder if I've got a float level issue or something similar. Might explain the big swings in AFR.
 

CobraSix

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I loved my Comp Cam 260H.

While I never dyno'd my tripower, by the seat of the pants it had similar power as the OZ250 I ran with a 390 Holley and it dyno'd at 147 at the wheels. The Offy had more top end though and pulled like a mofo after 4000.

So, you numbers do seem really low and the AFR drop is the likely culprit. Figure +-20HP based on the dyno itself. Sure, it may be repeatable, but is there is an offset, it'll just show up each time.

Have you verified the outer carbs are actually coming and providing fuel (I know, obvious, but still)

Odd part is that on the first run, your AFR jumps up to 16 above 4k. I wonder the condition of the fuel pump, filter, and floats in the carb.
 

wsa111

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Very clean engine compartment. Craftsmanship excellent.
However, zero deck the block, get rid of the 170 head its strangling the engine.
Need a head with a large log & modfy from there. Get the head cc's between 50-52 & run a victor headgasket, its .006" thinner than the felpro.
If you stick with the tripower disable the power enrichment system & just richen the main jets on the end carbs only.
Eliminate the idle circuits on the end carbs.
As a matter of safety you should use invertered flare fuel line fittings instead of compression fittings or go the AN route.
The 260 comp cam is weak, very slow rate of lift. Any camshaft that requires only 50# of valve spring seat pressure is not giving you the best performance. Yes its a lot better than stock, but there is room for improvement.
Get a set of at least 1.6 or better 1.65 rocker arms to get more lift, rate of lift & more duration @.050" lift. The advertised duration however remains the same.
The best power is an A/F ratio 12.8-13.1 WOT. Cruise should be 14.2-14.7 for best ecomomy.
The 36-38 degree total advance is fine, but you need to shorten the centrifigul advance so you can at least run 18 degrees initial. Won't help your dyno numbers at the top end, but will definately enhance your low end performance.
Doing the above recommendations will get you close to 140-150 HP at the rear wheels.
Cobra Six has a great idea in making sure your fuel pump & lines are up to the job.
At least for the present get your A/f ratio's in line & do a little distributor work.
As i said your workmanship is above the norm, just do what you can afford. Good luck.
 

FalconSedanDelivery

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What is the casting number for your 170 head wsa is right for most of the 170 heads , BUT there is one that is good ( its the one on my 250 ) and the one AK Miller recommended back in 1971
 

chopperman69

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Did you degree the cam? You could have a timing set that is seriously retarded and even with the built in 4* advance from Comp, it may still be retarded.

I think this is the only conversation we can have with the "R" word and still be politically correct. :LOL:
 

datac

Active member
Miller recommended the late Maverick 170 head for its combination of small combustion chamber and 200-sized valves. My head came from a '63, and I modified it to accept oversized valves (IIRC, 1.75 intake, 1.45 exh, but it's been a long time). I know it's silly, but outside of my soon-to-be-replaced coil I've tried to keep everything on the car visually period correct, so no big log head for me. I didn't degree it, that's probably coming if I don't make any progress.

It's a 20+ year old, 150k mile fuel pump that's spent the last ten years sitting under my workbench, so that's probably as good a place as any to start. Before reassembling the car I inspected the fuel lines for possible replacement, flushed with solvent and blew out with compressed air. Tank, sending unit, etc., are all new. I'll check my float levels while I'm at it.

Here's the rest of the car, still a lot of work to do:

P3160236.JPG


P8170350.JPG
 

JackFish

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datac":1rl558n5 said:
IIRC Comp cams ship w/4deg advance, I installed it straight up.

Block hasn't been decked, standard Fel-Pro head gasket, head very lightly surfaced. As long as it's been I don't recall my compression, should be slightly less than stock due to the gasket. I'll need to run a compression check, no doubt.
You probably have a compression ratio that's hurting performance.
Did you CC the head?
 

xctasy

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Our gruped together knowledge will help you find out why your combo seams not to be making the power you expect.


wsa111":8mz8p7n2 said:
Very clean engine compartment. Craftsmanship excellent.
However, zero deck the block, get rid of the 170 head its strangling the engine.
Need a head with a large log & modfy from there. Get the head cc's between 50-52 & run a victor headgasket, its .006" thinner than the felpro.
If you stick with the tripower disable the power enrichment system & just richen the main jets on the end carbs only.
Eliminate the idle circuits on the end carbs.
As a matter of safety you should use invertered flare fuel line fittings instead of compression fittings or go the AN route.
The 260 comp cam is weak, very slow rate of lift. Any camshaft that requires only 50# of valve spring seat pressure is not giving you the best performance. Yes its a lot better than stock, but there is room for improvement.
Get a set of at least 1.6 or better 1.65 rocker arms to get more lift, rate of lift & more duration @.050" lift. The advertised duration however remains the same.
The best power is an A/F ratio 12.8-13.1 WOT. Cruise should be 14.2-14.7 for best ecomomy.
The 36-38 degree total advance is fine, but you need to shorten the centrifigul advance so you can at least run 18 degrees initial. Won't help your dyno numbers at the top end, but will definately enhance your low end performance.
Doing the above recommendations will get you close to 140-150 HP at the rear wheels.
Cobra Six has a great idea in making sure your fuel pump & lines are up to the job.
At least for the present get your A/f ratio's in line & do a little distributor work.
As i said your workmanship is above the norm, just do what you can afford. Good luck.

I'd add to FSD and wsa111.


In one Hot Rod article, Ak Miller and Jay Storer said any closed chamber 52 cc 170 head with the small chamber is up 30% on the stock (105 cfm intake) flow rate,

http://www.invectivus.com/hrm_mustang3/ ... 20copy.jpg

bringing the CFM flow 15 cfm above the ~120 cfm intake flow a big log post 1975 big valve engine makes. When you then add the big 1.75" valves to it, the small chamber 170 head then flows well over the 42 mm port 2V 250 heads intake flow rate, and more than any stock 75- 83 ~120 cfm flow rate head by a country mile. It's all about the quench and squeeze of air flow around the valve, and the ability to then get a better combustion chamber shape. Just getting the air flow right means you can then get more hp with the other standard head plane and porting modifications...the extra size of the later log head doesn't help fix up the triple carb flow rates, but opening up the carb holes and running fixed, simultaneous opening carbs helps control the rampant air fuel ratio swings. And swing it does, like a drunk mans wife pouring the hooch down the sink.. first lean, then rich, then lean again. Kevin showed us that a well set up combo on a calibrated dyno should get 140 rear wheel hp, even if the air fuel ratios are not ideal. The Offy and Edelbrock trip power intake isn't consistant fie air fuel because the porting is so varied, and you have to do dyno time to find out the sweet spots for ignition and air fuel. wsa111, Kevinl1058 and Falcon SedanDelivery know what advance curves work on a modified Ford six, and its heaps of inital advance and then a flattened delivery past 2600 rpm. Very important to dial in just the right amount or you'll be loosing power on the dyno andplug hole

It was the same with Kevins 206 with triple ICTs Weber Aftermarket 29mm ( a humble 138CFM @ 1.5" 34-ICH Replacement for old Land Rovers). The wild swings in air fuel are factor of the poor porting, a feature of the large diameter log, see his posts. Kevinl1058, viewtopic.php?t=64712

FSD decked his block and head over 100 thou each, and that makes a 250/170 head an ace in the hole. Invectivus can read the finer detail, and provided this as evidence.


See the invectivus supplied details in http://www.invectivus.com/hrm_mustang3/Cover.jpg


any 170 head is with the trip power is the bomb, but they show the large log 170 head.
 

Gene Fiore

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datac":2kvly4s2 said:
I didn't degree it, that's probably coming if I don't make any progress.
I think I would start with degeeing the cam...this is a must IMHO. ;) Great looking setup!
 

wsa111

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Very interesting on the 170 head. Never knew it existed.
Is the log as large a an 80 log???
With the small chamber & a lot of quench you probably need only 34 to 36 total advance.
 

datac

Active member
Thanks for the advice- I'll start with the fuel pump, float level, maybe try a valve adjust before I pull the front cover for a cam degree. I'm surprised that it seems to sound, run and drive so well, considering how far amiss something clearly is.

I first built this engine pre-innerwebs back in the late '80s, when info was much harder to come by. Old Ak Miller articles were pretty much all I had to go on.
Here's the same engine in the same car last time around, some time in the late '80s-early '90s (heck, same fuel pump too):

ford200r.jpg


ford200l.jpg
 
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