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how can i get more power from my 454?

the_blaze

the_blaze

Nightmare / Plan B
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Hey guys!
I figured there wasn't a better place to go with my chevy related questions than here.

I have a 454 with very very low mileage on it. Since I installed it i haven't felt like i was getting all the power i wanted or should get out of this engine. when my engine was built the company said they put a " mild RV cam" in it. I don't have any other specs on it.
My thought was I wanted to put a different cam in it to see if it would wake this up. a couple guys from summit racing suggested this kit http://www.summitracing.com/parts/cca-k11-231-3/ . Another guy told me to put in a higher RPM stall converter in my trans and go to an even bigger cam....
another "Tech" told me to put on a carb spacer...

I am really lost! I am pulling the engine and trans out of my jimmy to do various repairs and mods and i figure while its all out I want to do everything I can to gain every ounce of power out of this setup.
suggestions would be amazing!:bow:

let me give you the specs of my jimmy-
I use it as a "Sunday driver" I won't lie I love to mash the gas and beat up little ricers. I also like to go off-roading in places such as Moab which as you know is usually slower paced stuff that I will need a lot of bottom end power for. in my state I don't need to pass emissions (because of the age of my truck) so really i can do anything i want to get the power i need.

1978 GMC Jimmy
454 fairly fresh rebuild
Holley Truck Avenger 770CFM Carb
Edlebrock performer 2.0 intake
flowtech long headers
MSD HEI

Transmission:
700r4 built and upgraded just about as much as it can be.

axles
rear: 14bolt full float
front Dana 60
Gears: 456
tires 37"
 
Try to find out what that cam is....rv covers a lot of ground!
what valves, what heads (casting #'s) what springs, etc.
is it stock bore/stock pistons, or bored and new pistons?

Alot of people build engines that don't have matching parts...this may be part of the problem. It may have been built for a different application as well.
find out what your ignition curve is, what rpm it starts to advance and how much mechanical advance its getting and at what rpm it is all in...start about 12*BTDC and advance it up from there and see where the happy spot is...if the carb is working decent you should feel the difference when the engine is happy (not spark knocking under load). A heavy truck will want a somewhat slow advance starting about 1200 rpm and advancing about 18-20* by 3500 rpm, for a total of 34* max for an iron head BBC.
 
Well I know they did new valve springs and lifters with the new cam. (I'm hoping it came as a matching set) I have the old cast heads I believe it was bored .30 with new Pistons and rods. As far as ignition curve... I'm clueless how to test that. I know it idles at 16 BTDC. Once I pull the engine I can look for all the numbers and see what I can come up with.
 
Currently it runs and drives well I just want more power. The only issue I have had is sometimes when under a load (like trying to climb up on something or towing something heavy) it feels like it bogs down and it has actually stalled a few times.
 
Did the builder / shop give you an itemized receipt? If not, is there any kind of description at all? I'd say any good shop would give a receipt with part numbers.

I agree with Dave, you need to know what's in there before you can buy new parts - you don't want to take a chance on buying he same or less cam, right?
 
Bogging down under a load and stalling could mean weak spark--might need a coil or plug wires..maybe the fuel pump is not delivering enough volume and pressure..things like that need to be examined and a good tune up done and timing has to be right for the thing to put out its full potential..playing with timing and advance curve might wake it right up too..if your at high elevation you will lose power too,sometimes the carb needs to be jetted differently to make more HP..

Carb spacers can make a big difference too,I tried a few different ones on a stock 454 I had,and one with a divider down the center made the engine feel a lot more peppy on take offs than one with 4 separate holes did...every engine is different,you might find the opposite is true on yours..

Usually the RV /towing cams are great for better low end power,which is what you want off road and around town..so many people put a too much camshaft and high stall speed torque converters in trucks ,then find out too late its got a drivetrain better suited for a rail dragster,that cant be driven slowly without loping and surging,fouling spark plugs,etc--on top of being a gas hog.....you dont rev an engine up on the street or trails over 4500 rpm too often,and that cam will make good power up to at least that rpm..I\
 
They sent hardly any information back on the engine. And the kicker is they aren't around anymore so I don't have a way of getting any specific information on it.
 
Is there any way to determine what camshaft it has? Like markings or anything?
 
Another thing it has felt the same way since the day it was all put together. All the parts were brand new EVERYTHING
 
The cam has a part number marked on the end but you'd need to pull the timing gear off to see it (that means disassembling the entire front of the motor).
 
Ok cool :) it will be out on an engine stand so should be easy to do.
 
In that case, pull the valve covers and get the head casting number (it'll be a raised number between the valve springs) and the block casting number (might as well).

You might try to find someone or place that will lend or rent a bore-o-scope and look down the spark plug holes at the pistons to see if they are a dish, flat or dome type.
 
Ok. I have to take off the intake manifold anyways so I was going to do the valve covers and all that since I was there
 
Anyone have advice on a freeze plug that leaks a tiny bit from time to time? This motor has two that have done this since the rebuild.
 
I'm not sure if this helps at all but these are the only real docs I got with the motor
0


0
 
I use Permatex gasket maker #1 or gasket shellac on freeze plugs,have not had any I installed leak or come out after using that "bear tar"..

One thing to check if your tearing it down,before you take the timing chain off,see how much slack it had,also I read if you use timing gears from a earlier 454 (pre 72) they are different,I guess later ones were set up to retard the timing some to improve emissions ,at the cost of some performance..so the book reccomended getting ones for an earlier engine...

Its unlikely anyone degreed the camshaft properly during the install also,most likely it was just put in and the timing marks aligned and called "good",,usually it is,but some gains can be had by making it "spot on"..not everyone bothers or knows how to do it properly..

I had three 454s and none of them were real powerhouses,they were 1973 and 74 engines from smog era chevelle and an impala,and one came in a 74 C-10 factory..they had ample low end power,but were nothing like the 1970 one my brother had,or ones like the SS chevelles had in the early 70;s that had the higher compression,the timing set up for power,not emissions,and heads with bigger valves...

In a truck though,the small port heads from smog era engines are actually better ,along with a RV/towing cam -they make more low end torque...but do limit the top end a bit..but how often does a truck need to see over 5000 rpms anyway?..454's have a long stroke and high revs and longs strokes usually result in thrown connecting rods...
 
Yeah good call, the timing chain and gears were brand new with the build. But I agree I don't think the company that built this cared at all. I Don't think I have ever taken the motor over 5k so having a low power range like idle to 4500 to 5000 would be ideal. Once I yank it out and get numbers off everything I'll have a better idea of what's going on inside.
 
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