I have a 73 350 block with 69 heads (3946813) I believe has 1.72/1.50 valves. I do not know what piston or cam that is in the engine at this time. It runs strong, no smoke, etc.

Without changing the pistons out or removing the engine from the car what would you suggest to increase the hp by 10% - 15%?

The engine appears to be very stock:

Carb Qjet 7029207
Dist Delco Remy 1112021
Intake Stock 3927184
Exhaust Stock
Heads Stock 3946813

 

The cheapest way out would be to buy a set of the Vortec heads right form GM as we pay around 480 for a set and you can bolt them on and you can buy the self alinging rockers from GM as a kit and you will need to change the intake and go to a different set of valve covers.

 

Can you pull the cam with the engine in the car? I was thinking of buying and edelbrock performer intake, changing the cam, NEED RECOMMENDATIONS, and putting some modern cast iron heads on. Thought If I pulled my heads I could identify the pistons and then match the head trying to get a 10:1 cr.

 

I've been thinking about a top end swap on my 350 too, although I heard 300hp is well within reach with the vortec kits. The cam can be changed in the car with the radiator out of the way, but what I'd like to know is if the ac condenser has to come out too. air conditioning is one of the few things I don't like messing with on cars.

 

i would go with a set of heads.the summit house brand alum heads are hard to beat.get the smaller(64cc)chambers to get compression up.a cam and intake would be nice.however,the biggest restriction you have is the heads.replacing them will give you more power everywhere.
the vortec heads are a great deal.you have to decide whether you want to buy heads or an intake and heads.if you go with the summit alum heads(or any other)don't go any larger than 180cc on the intake runner.for a mild/street motor 170cc might even be better.

 

Mortec.com shows those heads as being from a 69-79 350 truck motor, but I couldn't find any info on valve size, combustion chamber size, etc.

I personally wouldn't buy anything until I knew my existing combustion chamber size, piston type (dish or flat top), and more about the camshaft. Any heads you buy must be matched to the cam you plan to use to ensure decent cylinder pressure.

Also, what kind of exhaust manifolds do you have? Anything other than 2.5" Corvette ram's horns are gonna cost you some power.

A few things about aftermarket heads to consider:

-- Some have angled spark plug holes. These can cause the plugs to interfere with some headers and manifolds.

-- Some are wider (as measured from passenger side to drivers side exhaust gasket surfaces), and may have the exhaust ports raised by 1/4" to 1/2". These dimentional changes could cause exhaust manifold and head pipe clearance issues.

-- The valve cover rails are often taller to move the gasket up out of the oil. This might create valve cover clearance problems if they're already close to the firewall, A/C compressor, brake booster, etc.

I know this is getting long, but before you do anything else, check the timing to make sure your mechical advance is optimal for performance. And if you have restrictive exhaust, get some headers, performance mufflers, and 2-1/4" or 2-1/2" pipes. Sometimes simply upgrading an exhaust system will add 20hp or more.

 

once you loosen those head bolts you are committed. Like the guys said above, your existing engine needs to breathe and have correct timing and spark. If that is still not doing it for you, you can put on a kit. But, as I've been told, you might be putting good money to bad if your bottom end is not new. Carbon buildup on pistons, seals, gaskets all of the lower end might make you wish you had done an overhaul or rebuild....

just my .02

 

Use a Victor Junior intake and heads for max flow... on a 350 you should have a 750 Holley as well. I have a 302 with the Victor Junior intake and a 790 Holley with long tube headers and aluminum heads and it is pretty doggone quick. Edelbrock does most of the engineering for the aftermarket, everybody else copies his stuff , get the best, you won't be disappointed. Check for hood clearance issues though......

 

I wouldnt do anything until you know exactly what CR, cam, etc is in that motor.
Best bang for the buck would be some 1-5/8 primary tube headers and a dual 2.5" exhaust.

 

Not to hijack the thread, but I am also thinking about doing the same thing. I think it will be hard to sell a $6000 crate motor to my wife so I think the top end is all I am going to do.

I also have a random '73 350 2-bolt in my '65, and God knows whats in it. It seems pretty peppy, but I want at least 400hp. I want to make the motor look like a stock 327/300 so I will most likely pull it to paint and clean up the engine compartment. I will put on 2.5" manifolds but will this be enough for 400hp if I use a edelbrock RPM top end kit?

Next question I had is using a retro fit hyd roller cam. How exactly do these retro fit cams fit and what needs to be done?

And last, if I pull the engine, part of me says rebuild the whole thing and replace all gaskets and go through it. Is this really required? If I do this I know I am going to want to stroke it to either a 383 or 391 and then at that point my "budget" build is out the window.

I figure a top end kit runs about $1800 with a roller cam, $300 for a carb, and $400 for ignition. If I get a rotating assembly that will be another $1000. And what about machine work? When do I know I need machine work, and what does it usually cost?

 

I've lurked these forums for years. Engine upgrades seem to have 2 results.
1. The owner does their homework, spends more money than planned, wastes more time than previously thought, finds other things that need to be upgraded w/engine and gets solid results.

2. The owner tries to save money by mix & match parts they have/find for cheap. Parts are put together that were not made to do so. Other problems are left behind due to a lack of time/money.
The owner starts posting "My engine is not putting out like it should"?

Bolting together a solid sb is not rocket science. Decide what your needs/goals are, then find the combo that fits for you. There are some very knowledgable on this forum.

Ricisan

 

Guys if you want to make power... it's not tricky to do.. you must
become familiar with the Head Flow Data of the heads you are considering.

The Vortec suggestion was a good one... another one would be the Bowtie Vortecs (Small 185cc Port).. they outflow the
stock Vortecs and only cost about $150.00 more... they are a great
bargain... just like the Std. Vortecs.

For your cam choice... you want to choose a cam that lifts the
valves into the head's flow sweet spot... within reason...i don't think
most guys are going to want to lift .700 on a street motor...

Don't make the mistake of using a cam that was designed for other
heads.... look at the flow data... you will see where the head if flowing
the most cfm.... get your lift into that area within reason... if you need
a little bette valvetrain or a roller cam to get there... buy them and
drop them in... drop in roller lifters(with the cross bars) are available
from Isky, Crane, Comp Cams, etc... (the bars keep the lifters from
twisting so the rollers roll properly on the cam... blocks that come
with factory rollers have the rollers kept in proper direction by the
block.)

The most important flow numbers are the flow at your peak lift
and the flow numbers within .100 under it...
ex: your cam has a peak lift of .525... look at flow at .500 and .400

here are the flow numbers on the small and large port Bowtie Vortecs

http://www.superchevy.com/technical/...ec/index1.html

The small port Bowtie Vortecs...flowing 251cfm @ .500... the HP potential is 500hp if properly cammed and tuned..

I'd probably look at a cam that lifted .510 to .550... with the
duration and LSA that matched my desired performance level and RPM
range.

A well designed motor will make 2hp for every 1cfm of flow...

The Bowtie Vortecs are drilled to accept either a Vortec or 1st gen
SBC manifold.... they have holes for both... regular Votec L31 heads
will require a Vortec manifold.

 

That's why I am looking at a top end kit from possibly edelbrock that comes with cam/heads/intake. Assuming my SCR isn't 7:1 these are the main things people screw up when you mix and match. Other things to worry about are the 2 bolt block which really isn't anything to worrk about, and the condition of the rods/pistons/crank. Like I said I would like 400-450hp. No shooting for anything more than that. I don't need all the polished BS that crate engines generally come with either.

The edelbrock Performer RPM package should be fine with a SCR of 9:1 and be a decent power builder assuming I upgrade the ignition a bit and make sure the CR suits the package. What else is there consider if the bottom end is in good working order?

 

Go with headers .. and a Dr. Gas X pipe.. regular balance tubes or H pipes do very little on a dyno-bottom line.....when it comes to your mufflers... look at the cfm numbers just like you do the heads.. don't just guess.. look at the hard cfm numbers... I like the look of a stock looking motor... but not when that motor is following a ricer Honda with a turbo..Take a look at this Big Block



It still retains it's stock look... but it has an Edelbrock intake and headers looks cool and runs great.... bolt ons that can easily be changed..

Running indadequate exhaust is just like stuffing a rag down the
carb... you're blocking airflow.. you're going to loose 15 to 40 hp and
waste the improvements you've made... the only guys who say otherwise are guys who haven't spent dyno time.... go to the local
dragstrip and see how many guys are running stock exahaust manifolds
..... if it wasn't that big a deal you'd see alot of stock mani's... but
you won't find any.... very few places you can get 15 horses for $100
... but you can with headers.
Here's the Dr. Gas website...there's alot of good info on there and
most NASCAR teams are using his products.

http://www.drgas.com/store/home.php

once the hard parts are bought.. the rest is tuning.... carb, cam,
manifold, exhaust... but these make the difference between a
350hp 355ci and a 500hp 355ci.

 

Assuming you have about 300 horse in stock form, you're looking for a 30hp increase. You can do that through a good tuning setup:

Pull the distributor. Shim out the endplay. Set up the curve to produce 18 to 20 degrees of centrifugal advance, and make the full curve come in at 2500-2800 rpm. Use a VC1765 vacuum advance control unit. Use NAPA points CS786. Set total timing to 36 degrees.

Pull the carb. Do a detailed rebuild on the Q-Jet with a new Echlin 2-440 float. Set float level to .375". Change your stock carb jet/rod combo from 66/36 to 74/45 and set secondary spring windup to 3/4 turn. Verify you're getting full throttle opening when you push the pedal to the floor.

These tuning mods will get you 30 hp over stock every time.

 

These tuning mods will get you 30 hp over stock every time.
TRUE .... did it ... works good - last a long time!

 

A bigger cam won't do much good with those heads. In fact, good heads with a small cam is much better than poor heads with a big cam.