1.78 vs 1.88 intake valves

[69 Cuda 440]

Teak,

The upgrade (Step 1) in the Cylinder Head that we performed as compared to the above post.

A) Install Mopar #4876397 Stainless Intake Valves (swirl-polished). The 1.88 Head
was cut down to 1.84", and the valve also had a 30* back-cut @ .025" wide.

B) The intake bowl area was opened from (1.52") to 1.61" with a cutter-tool.

C) The valve guide area in the port pockets were smoothened out.

D) Intake seat cut = 30* - (Seat 45*) - 60* - 70 * (Seat Width .040")

E) Exhaust seat cut = 37* - (Seat 45*) - 60* - 70 * (Seat Width .060")

F) All sharp angle adges were radiused and smoothened.

* That upgrade knocked (-.16) off the E.T.

 

[MOPARoldtimer]

I don't believe anyone has discussed charge velocity at low RPMs. The 1.78" valves would work better at low RPMs because the charge velocity would be higher, especially with all that porting in a low-compression motor.

Of course you then have to weigh in the other changes that 69 CUDA 440 is going to make if he installs the 1.88" valves, but the low charge velocity might make the motor a dog off the line. You really need a higher compression ratio than stock to take advantage of that porting.

 

[longarm]

My 2 cents.
You wouldn't gain enough to add the bigger valves,
infact you might disrupt the flow by doing it.

If you feel the guality of work is not as it should be,
buy better castings and start over.
Trying to better a port job rarely works.

It the valve job was done correctly, the valves sunk
into the head wouldn't matter as the valve hieght would
have been corrected so as to not disrupt the valvetrain geometry,
spring hieght and pressure would have been addressed at that
time also.

My advice, if you change the cam do the springs also and
have the spring pressures set correctly.
Upgrade to headers and better exhaust system.

Another possible way is to improve your manifolds or cam
choice, heres an article that might help.
http://victorylibrary.com/mopar/ci-man-tech-c.htm

 

[longarm]

I would go with the 1.88 valves and mill the heads to get 9-1 comp while its apart. It will be worth it in the end.

You might mill the heads more but it will effect the fit of
intake manifold and set the distibutor deeper into the
block, possibbly changing the cam gear alignment/timing and
valve geometry.

You have to take everything into consideration as
you stack tolerances.

 

[69 Cuda 440]

Whoa Fella's

The Compression Ratio is approximately 10.3 to 1.

This is a 273 engine, bored .040 with a set of Arias (10.5 - 1) Lightweight Pistons.

The cylinder heads were milled to 57.8 CC.

(Note a 57.3 CC Chamber would be 10.5 to 1.)

We are performing a 'step-by-step' upgrade, to see what the true results are.

The car is a 1967 Barracuda Fastback, 4-speed - (Weight #2965 lbs. without Driver)

 

[longarm]

Were not talking about your build in this thread,
we're trying to help TheCraigMachine maximize
his already ported heads and engine.

I agree in your case, the lessons learned will
benefit all that are building a new engine.
This is excellent info.
Maybe you could share this info in a thread
of your own so it will not get buried and lost
trying to help someone that won't be able to use it.

 

[69 Cuda 440]

OUCH,,,,,,,,,,,,,Longarm.

I thought I was adding some information, but maybe I should start a new thread with
the build we are performing, using Econo-Racer 'old school budget ideas'.

 

[longarm]

I'm sorry I didn't mean it to sound rough.
You have added.

I do a lot of research on the web and find
most good ideas and info buried in threads
and chat rooms like this, never to be seen again.
You've put a lot of time, effort and
money into your heads/engine to find that extra edge.
I would not want to see your research lost, as
you've expanded the total knowledge base by sharing,
its a wonderful thing you've done.
Thank you for sharing!

 

[66fs]

I agree! Please start a new thread, Nice to hear upgrades with results.
Thanks

I'm sorry I didn't mean it to sound rough.
You have added.

I do a lot of research on the web and find
most good ideas and info buried in threads
and chat rooms like this, never to be seen again.
You've put a lot of time, effort and
money into your heads/engine to find that extra edge.
I would not want to see your research lost, as
you've expanded the total knowledge base by sharing,
its a wonderful thing you've done.
Thank you for sharing!

 

[clifftt]

Nice!

 

[Abodybomber]

69 Cuda,great info! My ex employer did similar,in the early 70's. Similar combo,4.88's,4 speed.Ran a best of 13.0 's @102,103 on the West coast .Still has the heads,on the shelf.

 

[bad440]

You might mill the heads more but it will effect the fit of
intake manifold and set the distibutor deeper into the
block, possibbly changing the cam gear alignment/timing and
valve geometry.

You have to take everything into consideration as
you stack tolerances.

it won't set the dist no different, it's not a chevy

 

[longarm]

Heres a site with help on milling.

http://victorylibrary.com/mopar/intake-mill-c.htm

You're right bad440 :banghead: mixing my motors again.

I think if you had this conversation or shared this thread
with a cam grinder, you might be suprised how much could
be gained by adjusting cam timing or a different cam profile.
Might be worth considering.

 

[longarm]

double post.

 

[69 Cuda 440]

Thanks, A-Body-Bomber -

I think I'll start a thread with 'true performance results' on the track with
each improvement.

Thread Title

"1967 Barracuda 273 Commando" (Upgrades with Track Results)

 

[69 Cuda 440]

Test-and-Tune Completed.

Performance Results, lowered E.T. (-.16)

We went from a best of........12.92 @ 105.72 MPH
To best of..........................12.76 @ 106.13 MPH

yes

 

[moturbopar]

Well in the next couple weeks, Ill be doing this. Small port 318 heads. I will do a fresh 3 angle valve job on the 1.78 and see what it flows, then go with the 1.88 intake and measure the difference. If I can find my velocity probe I will check the fps and see what happens between the two sizes. If I feel motivated maybe I will measure the exhaust port also. I will be using stock valves. I plan on doing a mild port job also, be kinda interesting to see the differences!