yes the combo matters and yeah thinking it through helps

Grumpy · Jan 21, 2019

I recently ran across a thread on a different web site,
where some guy was really disappointed in the rear wheel, DYNO test results, he had from a 454 chevy engine.
near 300 rear wheel hp.
this is not all that un-common, but surely its going to disappoint many guys,
who have dumped several thousand dollars into performance parts,
who failed to think critically , and do research, required,
during the parts acquisition and planing process.
even small mis-matches in components and a lack of tuning skills can have a very significant effect on the engines power potential.
if your dyno gets much lower than expected results...
you could easily be dealing with a tuning issue such as a carb throttle bores not fully opening,
the valves poorly adjusted, the cam not indexed or it might not be correctly,installed.
the wrong ignition advance curve, or carb jetting, or a restrictive exhaust or,
clogged catalytic converter, etc.
so obviously a the basics need too be verified a compression check needs to be done,
check the fuel pressure and firing order, and the timing verified and have a tune-up done.
I've had simple issues like a distributor clamp being loose ,
causing timing issues or a clogged fuel filter , marginal fuel pump,or partly restrictive exhaust,
kill power.
like with most performance parts and applications the critical part of the build,
is generally in selecting the correct components for that particular application,
and in assembling those components correctly with the correct clearances.
its always a multi layered process,
you can,t expect sub-par or weak parts to withstand the shock and torque and rpm/impact loads.
you can,t also expect improperly installed or clearanced or insufficiently lubricated or cooled parts to last very long under loads.
obviously the process REQUIRES the person doing the work, or assembly to do some in depth research,
and have any tools or measuring devices that will be needed.

he had gotten, a dyno test, on a car that he had installed a freshly rebuilt 454 into.
keep in mind its not at all unusual for there to be 15%-18% drive line power loss,
and if you run accessories like power steering and clutch fans and an air conditioner etc,
those add considerable drag reducing the dyno result noticeably from what might be expected on an engine dyno.
the ignition timing curve was not listed so that may have been way off also.
but in this case it was both a rather obvious mis-match in components and lack of proper tuning,
that also was a major contributing factor in the lower than expected power curve.
he had built the engine using a basically stock short block,
and replaced the heads and intake and cam, without thinking through the potential parts compatibility issues.
first he used a basically stock 454 short block with flat top pistons,
this was matched to 320 cc port rectangular port heads,
a rather more radical cam than the combo might have justified in that he had a car with an automatic transmission and a 3.36:1 rear gear.
and the A/F ratio was set at 14:1 rather than at about 12.8:1-13:1 to maximize power and the dyno only went to 5800 rpm,
certainly hurting the combo results in that the cam used was designed to run in the 2600 rpm-6500 rpm range,
and larger port cylinder heads were designed for the 4500 rpm-6500 rpm power band.
both the cam selected and cylinder heads were designed to operate best in the 4500 rpm-6500 rpm range,
and a dual plane intake , a 750 cfm Holley carburetor on a 40 year old dual plane intake design
,and use of a restrictive exhaust and shorty headers further reduced the potential.
INSTALLING AN (X) PIPE IN THE EXHAUST ON A DUAL EXHAUST CAR

keep in mind that a properly designed exhaust system and headers goes a very long way towards increasing the efficiency of the intake manifold and head flow , and remember that the better the heads and the more effective the exhaust scavenging the less duration the cam used will require!
what goes in, needs to flow out with near zero flow restriction
the low compression and less than ideal, drive train gearing,
were badly mis-matched to the cam duration and rectangle port cylinder heads, designed for upper rpm power,
where the car was geared for.
not low and mid rpm torque, and restrictive exhaust.
if you do the math the static compression was near 7.8:1.
none of the parts are defective,individually,
but you can,t mis-match components designed for different operational rpm,
and compression ranges and requiring or limited by different air flow rates.

https://www.rbracing-rsr.com/compstaticcalc.html

https://www.rbracing-rsr.com/runnertorquecalc.html

https://www.summitracing.com/parts/hrs-cl120265-10/overview/make/chevrolet

https://www.summitracing.com/parts/pmx-2211/overview/make/chevrolet
you may find this video interesting

Maniacmechanic1 · Jan 21, 2019

Guys are on tight budgets.
Many do not want to rebuild with new forged pistons.
Comes from the LS World thinking since they all have cast Hyperuentic pistons except the crate LSX 376 B8 & B15.

Not working.

What is needed is a cross reference chart made.
What every engine has for pistons stock by application and model year.

Maniacmechanic1 · Jan 21, 2019

Just about every needs a rebuild.
That's a fact.
Olds V8 powered seem to last the longest or best shape when found.

Grumpy · Feb 4, 2020

its probably not going to gain you much,
going to full roller rockers is generally a 15-20 hp gain

yes the combo matters and yeah thinking it through helps

Grumpy

The Grumpy Grease Monkey mechanical engineer.

Maniacmechanic1

solid fixture here in the forum

Maniacmechanic1

solid fixture here in the forum

Grumpy

The Grumpy Grease Monkey mechanical engineer.