I need engine advice. Please Help.

[davidbroberts]

I have a 69 coupe with a 302. The short block is only 50,000 miles on it but I want a few mor ponies at the rear tires. How can I achieve this on a budget of only $1500 minus the cost of rebuilding the cylinder heads. What about a cam, what will I need to make it work with factory heads. I would appreciate any and all advice anyone might have.
Thanks

[mean81GT]

If you are going to redo the cylinder heads anyway, something you might look into is 289 hi-po heads. these will give you a slightly higher CR (more power). You can also go with an edelbrock power package. They have all sorts of parts that they match together and test. They advertise the package with how much power it will make when it's done. This way there is no more guessing game. If you don't want to get that far into the motor, and being that the motor has such low mileage, i would go with Nitrous. You can do that, rear gears, k&n filter (the one that the lid is also filter). There are some other things you can do too.

There are numerous possibilities, ranging anywhere from 50 horsepower, all the way to 150 or so.

Hope this helps.

[davidbroberts]

thanks for the advice

[hobgoblin351]

Hey Mean 81 has it right. Just a few things, make sure you've got forged pistons, or dont go over 150 HP shot with the Nitro. I might be wrong but I dont think most cast pistons can handle much more without burning through.

[1968FastbackN20]

Most cast pistons cannot handle more then 100hp shot of N20 without ending up in your oil pan. For $1500 I would look at a intake, carb and head porting. Make sure these all match each other. You may want to consult your local machine shop as to recomendations. Magazines have decent info but it always seems the company paying the most for advertising or giving free parts gets the most press. Not necessarily the best parts. Just my .02 worth.

[davidbroberts]

thanks for the advice guys, but I want to stay away from nitrous and all, but what kind of carb and intake and cam and all could give me the kind of street power im lokking for.

[Clark Rodgers]

David,
If it was me I would get one of those edelbrock packages with a new cam & manifold ($300). Don't know what kind of carb you have but might be a good time to change. A different set of heads would be nice but they are kind of pricey. What kind of rear end and exhaust do you have? These areas need to be looked at as well.

[davidbroberts]

The exhaust is stock, and the rear end is stock, i believe a stock nine inch. But the exhaust is definitely soon to change.

[1968FastbackN20]

A good dual 2.5 exhuast is a great place to start along with some good gears and a posi. As for the cam and intake I would get a performer RPM along with a matching cam. For a carb I would get a Holley avenger series, vacuum secondary.

[jim_howard_pdx]

Wow, I love your question. How do I get the most smiles for 1500 bucks.

This is what I would do. Disassemble the engine. Everything. Check the main bearing surfaces. Are they all copper? Hopefully yes. New main bearings are lead on the outside, copper on the inside, and have a steel support base. If you see a bunch of steel, the crank may need to be turned. If the bearings are all copper just chamfer the oil holes and you should be good to go.

Disassemble the heads, everything and have them hot soaked. If this is an engine you do not know about have the heads checked by a shop for cracks. Now buy a head porting kit. Should run about 50-150 dollars. You can use an electric drill to run the cutters and sand rolls. I use air and a dye grinder.

Buy a set of World Product Cast Iron Victor JR Heads. Purchase a used high rise dual plane intake and the biggest exhaust headers you can find that work with your ground clearance. Keep the primary tubes around 1 5/8 for a street engine and 1.75 or larger for a bracket racer.

Buy ported sized gaskets that work with the intake and exhaust manifold you are using. Mark the opening you need to reach. Cut the ports and blend them back about 1 inch. THAT IS ALL. It will get you at least 15 horsepower and as much as 35. We call this gasket porting.

Use the sand rolls and smooth off any casting flash from the valve pockets and runners. I like to sand the combustion chamber completely smooth and round off any edges in the combustion chamber to eliminate hot spots when running pump gas. DO THIS IT HELPS.

Buy a matching cam kit with springs. I would shoot for about 275 advertised duration and about .480 lift. I like to use a short duration high lift cam. I like 260 to 270 duration at 540 lift. This makes the engine think it is running 11.5 compression and this is why my engines are so much fun to drive. They rev like a rice burner and power up like a 428 cobra jet. You can have your cake and eat it too. If you run over 500 lift PLEASE CHECK HEAD TO VALVE CLEARANCE or you may detonate the engine. You must have at least .08 clearance, and I like to have .10 to .12 for a street engine.

By the way PAW and some other shops can sell you a rebuild kit that has reconditioned cranks, rods, pistons, and everything you need to go, including the heads and cam kits. This may be the least expensive way for you to build.

I like dual plane intakes. Buy one off e-bay. Try to find a high rise if possible. Email me at jim_howard_pdx@yahoo.com and I will explain how to modify it if you are interested. I gasket port the intake as well and smooth it back as far as my porting tools allow me. I do not polish any part of the intake, in fact I like to leave them rough so they will not pool liquid fuel which will sheet away at higher RPM and leave some cylinders lean and others rich.

Go for a good ignition. Use a distributor from a 79 or newer 302. This will have the magnetic trigger. Use an MSD 6A or Crane HI-6 box and appropriate coil. Use NGK plugs, I like their racing plugs if available for your application. YOU MUST USE A spiral type ignition wire with the multiple spark ignitions. I use the durospark cap, rotor and base. This is 50 bucks well spent.

I spend alot of time modifying carbs. Email me for some tips. I do not like any stock carb. They are useless gas and power wasters. I do like Barry Grant stuff, but you have to be running over 350 hp to need one. I buy Holley 750's on the ebay for 20-50 dollars and modify them. I end up spending about 100 to 150 dollars to set one up, but they will get great mileage, atomize fuel efficiently, and give you AWESOME power. You can do this yourself. I can tell you how.

I like people's advice for using a 2.5 inch exhaust system. A 2.25 would be better under 350 hp. I run a 2.5 at 400 hp. I would need a 3" at about 500 HP. A 2.5 might kill your low end torque. Force the shop to do a crossover tube behind your transmission crossmember. This is good for a free 6 HP and it helps reduce noise.

If running a manual transmission go for a 3.5 or 3.7 gear ratio. If an automatic you will be happy with a 3.25 like mine. You can run 3.5 but the RPMS are high at 80-90 mph on the freeway. The 3.25 is a good balance.

On a strip car run 4.30 to 4.57 gears and a good posi. You need a corresponding clutch or torque converter.

Put some money into good brake pads or shoes. I like Praise Dyno stage one pads. I pay 220.00 for all 4 pads. They are carbon kevlar with brass. Very little rotor wear and they do not fade. I quarter mile at over 100 MPH and have no problem stopping.

Hope this helps.

[davidbroberts]

thanks for the advice this is the info i was looking for. thanks for taking the time to write it all out. this is alomost everything i wanted to know and i just bought a new msd distributer with dual vacuum.

[1968FastbackN20]

Jimmy gave some good advice, but look at it this way. Never do something twice. If you plan on having 400hp like jimmy get 2.25 exhuast. If you plan on having 400hp like me get 2.5" exhuast.


Arron Spitzer
Best ET 13.2@109
(2.3sec. sixty foot)
Mini tubs coming soon!

[Rev]

I completely agree with everything recommended except for one thing. I don't believe that back pressure in the exhaust is ever a positive factor. Now, velocity in the headers will help evacuation of the combustion chamber and can improve power even if more restritive than larger headers in some cases. Restriction (to any degree) in the pipes and mufflers after that never helps anything. That in a nut shell is my unvarnished opinion. I run 2 1/2" pipes with 3 chamber FlowMasters for that reason with a mild 306 street engine.

Rev

[jim_howard_pdx]

Man you guys are a tough crowd!

First, you might be best served by having a shop line hone your main caps and turn your crank. That way you will not be prone to spinning a rod bearing like I did Saturday night. Beat up a bunch of Chevys on the way. The car ran acceptable oil pressure so we drove it home. Guys FORD is built TOUGH!. I did the same thing with a 500 HP Cleveland engine. Drove it for two weeks with a spun bearing, and it still did no extra damage.

Second, I really don't care at all if you guys are using 2" pipes, 2 1/4" pipes, 2.5" pipes, 3" pipes or 4" pipes. Hell why not run the engine without pipes at all?

Because back pressure is needed for the engine to develop torque.

When we dyno an engine, we specifically pull out a header with a minimum of 4 to 6 inches of straight shot off the head. WHY? Because any bend adds back pressure and back pressure reduces horsepower reading. Everyone is looking for the HP figures on a dyno run. It is only guys like me that pour over the torque readings. WHY? Because I like to win, and HP is calculated. TORQUE is measured. It takes torque to move your beast down the street or down the quarter mile.

Back to headers, small blocks usually like 1 5/8 primary tubes and 2.5 or 3 inch collectors. A stroker engine will like 1 3/4 to 1 7/8 primary tubes and 3-4 inch collectors. So will most big blocks. A 641 HP engine I saw was running 2" primaries and 4" collectors. They were after 7 second quarter mile times. Eight seconds will be the gas only times.

If back pressure doesn't matter, then why not run 2 1/2 inch primaries and 4 inch pipes all the way????

Come on guys! You need to know the fundamentals, then you race and learn what works, then you use engineering to improve the margin of victory.

We tune the headers and the pipes to get the backpressure right for where we aim the peak torque point of the engine, and to get the broadest torque curve possible over the usable RPM range.

I have seen some great engines run really slow times and they could never figure it out. They saw a dyno report that showed they picked up 10 horse power by going to 3" tubes. Well they did pick up 10 horsepower at 6,000 RPM. But they lost 20 foot pounds of torque from 2,500 to 4,500 RPM and lost 36 foot pounds or torque from 4,500 to 6,500 RPM. So they ended up with an engine that sings at 6k but has to go from 600 RPM to 6,000 RPM just to enjoy the magic. Hope they use a 5,500 RPM Stall converter and 5.67 gears to get them there really really fast.

An internal combustion engine is basically just a big air pump. The more air it pumps the more HP it is able to make. So WHY does intake runner shape, diameter, and length make a difference on a fuel injected car?

Why did TFS go to a 90mm MAS on their improved intake system? Because they had big *** ports but could not pull enough air through the MAS. Now they are kickin butt.

Remember guys, the intake runners, the heads, the swirl, the quench, the compression, the air fuel mixture, the ignition timing, the exhaust ports, the primary tubes, the collectors, and the exhaust tube size all work together, or they slow you down. It is the total system approach that goes into making a great engine. Remember that as you spend your money.

It all fits into a total package that equals performance. God I am beginning to sound like Vic Edelbrock!!!!

[Rev]

I agree with everything said except that a restriction in the exhaust system after the collectors cannot produce more torque under any circumstances. It just increases the pumping work and saps power (torque or horse power) from the engine.

I know this goes against some popular opinion, but it is well supported. Never do I see any professional drag racers, NASCAR, or other circle track racers use an exhaust system after the headers more restrictive than the rules require.


Rev