put my flathead on the dyno today

With the help of a friend, we mounted the flat on a dyno, trying to understand why it seemed so underpowered.
First reading was 67 hp at 2500 rpm, and 62 at 3000.....not very promising. The engine was losing power at higher rpm. We found a leaking coil, so went to a junkyard and got a good one. Things improved slightly, but not much. Engine was acting very strange as rpm were incresing, like misfiring and rough running. We tried to retard lightly , seemed to run better, but horsepower was lower. We changed spark plugs, because found some short plugs were mounted in place of correct ones. We picked up 10 hp with this change, but still very much underpowered.
It was late in the afternoon and had to come back home, but problems are still not solved. Maximum reading was 85 hp at 3000 rpm, and after this ho went down like crazy.
Engine is a new french flat 239 with about 300 miles on it, dual intake, Mallory dual point ignition, Isky MAX 1 cam and lifters, Edelbrock heads. idle is very nice, and till 2000 rpm everything seems ok. When rpm go up, there is misfiring and backfiring. Max rpm we could get was 3500, but power was way down.
I have ordered new spark plugs, new points and condenser, and new cap. Any idea on getting some power back?
Here are some pics, will post the graphics as soon as I get them.

 

I dont know much about flat heads yet but what about valve springs? I had a race motor that the springs were going weak and it would act like that.

 

New Isky that came with the cam

 

Are the valves to tight?

 

Might check the 94s and see if they are supplying enough fuel after 2000 rpms..
Weak springs could also be the issue..
See if spark is losing volts..
Let us know what you find..
Good Luck.
Duane.

 

what compression ratio are those heads?

any relief work done on the block?

advance curve might be off, with all the additions. Or it could just be off period. I would think lack of fuel would just bog, not really pop and backfire.

 

8.5 compression, no porting or relief to the block

 

Check to see that you don't have a stuck mech adv. weight or broken spring. sounds timing related to me.

 

Have you tried manually adjusting the timing while under load on the dyno?

 

Smells like ignition to me...

 

Don't know about the Simca for sure but look out for this. The early Ford's here in the USA were positive ground as were most of the Imports of that era.

Coils have polarity. If you have a positive ground coil such as an original Ford or the old Lucas hot coil, and have connected it to a battery that you are using the negative as a ground, those are exactly the symptoms you will have.

Or if you have bought a more modern hot coil it is most likely negative ground and if for any reason your battery is connected as a positive ground for whatever reason, same deal.

This can also happen by someone charging a battery from a flat condition and hooking up the charging cables in reverse.

Just a couple of traps you'll play hell figuring out if you're unaware, chasing everything under the sun. However very easy to check out and make sure before doing any other chasing.

 

hey ADVENTURER...man i ran a mallory duel point dist. on my 327 sbc. and believe me, you have to keep a close on the points. adjust and run, then check gap again. man their unrully. also i couldn't see where the coil is, could be shorting out on metal. my first time to see a flathead dynoed...COOL...POP.

 

What's the cranking pressure (hot, open throttle, plugs out), in psi?
Sounds like voltage loss.
What does the fuel curve look like when it craps out?
If it's just low secondary voltage, an easy test is narrow the plug gap to .015". If it picks up, suspect the oil or plug wires.

 

you people that need points should just walk
it will save you a lot of time

 

Out of curiosity, when Ford advertised 100 hp, what method did they use to get that figure? I suspect modern testing techniques yield lower values.

Casey, I have to agree with you about points. I replaced my dizzy with a MSD ready to run, a spark box, and a hotter coil. It really perked up the engine.

-Stefan

 

some replies:
distributor is new, so would rule out something wrong inside.
coil is 12 volts neg ground,
Will surely do a compression check as soon I am ready to work on the engine again (when parts arrive....)
next time at the dyno will try to manually change advance under load. We tried with different settings, but the misfire was there at all the settings we tried.

Thank you for the advice, please keep on.....

 

Ditch the dual point dizzy or have GMC Bubba fix it up for ya...it's definately timing related...

 

New doesn't mean it works...trust me, quality control at a LOT of companies sucks...never trust something because it's new, all it takes is a loose screw on the advance plate to make something not work properly...

 

+2 I was thinking a timing issue as well...

 

i'm putting my money on the dizzy having issues. i have chased problems in brand new motors that had brand new dizzy in the and ended up being the new dizzy. talk about pulling your hair out and wasting time. when i was selling parts we had box of bulk gm condensers and orders were if anyone came back thinking the condenser we sold them was back you handed them 2 new ones out of that box. the extra one was for their trouble.

 

I personaly have never had good luck with mallory, yet I have had impeccable luck with MSD.

JMO ditch the points and go electronic. I have a stock crabstyle on my flathead now but if it takes a shit again it's shit canned.

FLIP

 

Tried plug leads?

 

Had the same problem on my 51 Merc. flatty. Repalced plugs, coil, condensor, plug wires, and had GMC Bubba send over one of his distributors. No problems since!

 

Hello italian Friends

Mallory dual point are not really reliable, and don't work well even new...

My experience is if you want a good ignition, buy a HUNT magneto or modified a chevy/Mopar distrib, put a pertronix or similar inside, and here you go.

FYI, 239ci adn 255ci french block are factory relief.
You should get 120hp with this set up.

My 2cents...

;-))

 

Disagree CheatersPete. A friend of mine just got a brand new Hunt mag for his hemi, and it's an un-useable piece of crap. It looks as though it's made in china. The shaft floats 1/4" and has no way of locking it in place, the plastic bushing will last about a 1/2 hour, and the advance weights just flop around. Sorry to go off the topic, but I feel it has some relevance.

BTW: my father was Swiss, from Wintertur.

 

Bad news, I was lucky with mine so...
last things to do is buy an old distrib, and rebuild it with the good parts...

 

If the French Block was not Ported on the Intake or Exhaust in the valve seat,guide and intyake runners, you will never get any RPM or HP out of the engine.

The port are is so restrictive as manufactured it will physically not flow any air or fuel.

They were used as military type and stationary applications with very low rpm etc.

We have done a lot of these blocks and there is a substantial amount of port work necessary to make them street useable.

Max Sr @ H & H Flatheads

flatheads-forever.com

 

The condensers that come with the new Mallory dizzys have been known to be a big problem. Order an IH200 from NAPA and change it out!

Oops! Just noticed you're from Italy maybe you don't have any NAPA's there.


Jim

 

Stuff: Retorque heads...not the problem, but DO IT.
"...man i ran a mallory duel point dist. on my 327 sbc. and believe me, you have to keep a close on the points. adjust and run, then check gap again. man their unrully. also i couldn't s" Mallory (recent) points are not unruly, they just have rubbing blocks made of Chinese cardboard! I have seen service life WELL below 1'000 miles and MULTIPLE other minor problems. I can talk you throught the issues and good points. DO check the curve with a timing light! Basically, if it hits very roughly 20 crank by 2,000 UPM, it is good enough to tune from there. It will probably be too slow and too much advance!!
ALSO!! Look at the wires/strips connecting the points inside. I have seen new ones with the connectors so close to case the case showed electrical burns!! Assembled by IDIOTS! Everything can be fixed, but as sold it may be close to junk. Thank you, whoever bought the best distributor company in the world and KILLED IT.

Debug the Mallory, OR get antique Mallory or a Chevy reworked by Bubba.