Pormance on my 408

Hello everyone !

I would need your comments on the performance of my Indy headed 408.

I've been quite happy with the pleasure and fun my 67 Barracuda for the past 2 years. But some questions are left unanswered concerning performance.
First, here is the set up:

67 Barracuda 3000lbs with me in ti
ladder bar with Dana 60 , 4.56 gear
5000 stall conv 904 trans, low gear set
408 cid 10.8 cr -1 heads 343 cfm int 275 exh
Mopar W2 tunnel ram with a pair of Proform main body (750cfm) and billet metering block around

My 60ft are pretty good, yesterday I made a 1.29sec 60ft with the dual quad

Last year average 60ft was 1.32sec...

Here is the problem: I run on an 1/8 mile track, and I feel et's are not what they are supposed to be....

If I had a 60ft of 1.32, et was 6.42
If I had a 60ft of 1.30, et was 6.30
If I had a 60ft of 1.34, et was 6.34 and so on....

I scratch my head and say to myself: heck with that 60 ft, I'm supposed to run faster et's !!! right ????

I feel something is wrong here......but what ???????


Yesterday, with a 60ft of 1.29, I ran 6.50 sec no power valve and 75 jets....Ok it is a new set up, needs fine tuning etc.......But still !!

What is going on here ??
I'm supposed to be faster than that !!

Need any idea you can throw....

Dan

You can only go as fast as the power available and those 60`s indicate a good working suspension........Not to say the carbs don`t need attention though..............

What's ur mph?

I don't have the mph.....sorry

MPH is definitely some needed info, did the time slip not print out correctly?
Have you had time to jet the carbs up or down or move the timing up and down?
Your 60 foot is pretty awesome.

No mph at this track.....

No I didn't have time to play with jet or timing...

I'll try to lower my jets to 72 next week end

I would never run an engine with a tunnel ram without first dyno tuning it!
That said, you should be closer to 80 jets with no power valves...OOTB around 72-80 jetting with PV in front, so more like 80's square but I would try 78 jets square in both carbs first.
If it's really lean it will pick up a ton with jet...if 78's work, try 80's square and so on...
Brian

I agree with Ou812, I never dyno my engines buy I definitely think you should try the 78 jets and then 80.

I was hoping you jump in Brian...

The plugs are a bit dark and the wideband says rich a bit....

But I should really be faster than just a jet change ?

Dan

My Demon will 60 ft 1.29 and go 6.15 at 110 mph, and 1.26 60ft and 6.09 at 111mph. Sometimes 1.42 60ft and still a 6.10 in the 1/8th mile but looks like the picture below. 360/418c.i.--587 production heads--flat tappet cam-Racer Brown STX-22--727 trans--Dana 60 w/ 4.56 gear-- 13x31 goodyear slicks. Your ET should be way better with the 60ft you have, and with indy heads your mph should be a bit better than mine as well as the ET. My intake port flows your exh number of 275

Ok your car looks awsome !

So where do you see my problem ?

Dan

You start out great then it losses power...
check your fuel supply... are you looking at
the plugs right after you shut down or driving
back to your pit.. sounds like your fat at low
rpm(when you get back to your pit and pulling
the plugs then)... on a 1/8 track its hard to
pull them right after you turn off.. if you have
to drive a bit

408 cid 10.8 cr -1 heads 343 cfm int 275 exh

I personally would like more compression and what are your cam specs? With that 60 foot your car SHOULD be flying.

Cam specs are 255*/285* int
263*/293* exh

?????

I second that?????????????

285/293@.006
255/263@050
I'm sure this is what he's trying to say

It looks like the first spec is advertised duration and the second is @.50 guys.

Sorry, thought it was obvious....

Can you record and look at the wide ban readings for the entire run? If so is it a little rich for the entire run or just the first 100 ft. or so? If so try making it better the entire run I had fuel delivery issues that I found with my LM1 and once it was fixed I could jet the carb. up enough to slow the MPH down in the 1/4 mile and 1/8, that was on pump swill and it would leave te starting line at 14.3 and lean out to 15.8 It didn't miss or break up at all, the plugs look good also
You have a lot faster 60 ft than my car ever did, my car ran 9.99 ar 134.+ MPH in the 1/4 mile and low 6.3s at 99 MPH at the local 1/8 mile track I had to slow it down at both tracks do to the roll bar only and no NHRA certs for me or the chassis

If I recall, this spring I had 13.5 in the middle of a 1/4 mile track....

I' llcheck again this week end

Let us know, I think it will run quicker and faster with AFR in the 12.4 to 13.3 at WOT, especially in the last 1/8 mile in the 1/4 mile Have you treid jetting it up yet? If not, test, test and test some more

If you are starving it for fuel (either by jetting or fuel supply) you can lose 1-200 HP! You basically kill the engine.

I'm not saying this is your problem, but typical 750 carbs with no PV's are jetted around 78-80's...and you have 2 carbs so think about it...it's an easy test. If nothing gets worse or better, it might be fuel supply.

Make sure you check everything else out too...I still say dyno testing is the best way to start with a new combo to get you close on tune up, and also easy way to make sure engine is healthy and happy...i.e. valve train issues is one that comes to mind.
Brian

I was thinking the converter might be in fault.........

What's it flair to?

This is where MPH data would help tremendously but also lack of fuel or fuel supply will show low MPH too....

I dont think its a conv issue.. its got a strong
60'... what are your rpms at the line.. if its
slipping hard up top the rpm will tell you... I
think its all a fuel issue.. either jetting or
supply
EDIT
You might want to change the needle and seats
to .120s... but normally with 2 carbs the .110s
work fine.. but something to think of

I recall last year going richer without success........the reason why I got myself a wideband

That's why I'm not sure going this direction will help, but I will keep an open eye on that this week-end....

Dan

You need the MPH... if you jet up 4 sizes and
if nothing changes or if it doesnt slow down
(MPH) then you have a supply issue... could be
a needle and seat being to small also... do you
have a fuel gauge you can see during the run...
and dont use a oil filled gauge... if its under
the hood and filled it will show a lower pressure..
thats the oil heating up and pressing back on the
gauge

Needle and seat could be an issue....I don't have a fuel gauge I can read during a pass: I can keep an eye on the fuel bowl and look the level trough the side glass ! lolll

Like I sais before, I have had that problem for the past 2 years. I went pig rich with plugs pitch black with no results...This on a single carb that went on a dyno...tested rich or lean....

What can happen on tunnel ram setups is they can pull a ton of fuel at high rpm causing performance loss in excess of 100HP and even pull enough fuel to sometimes cause the engine to rpm limit!

Hard to see when your trying to drive the car, shift, and all. Might be why the plugs are black?