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engine selection

4K views 44 replies 15 participants last post by  454C10 
#1 ·
i have a 67 camaro rs and i think the engine that is in my car is on it's last leg
so i want to build an engine myself for the car. But the problem i am having is i am not sure what i want to put back in it. The car currently has a small block 305. So my question is what should i build a big block or a small block? I am not looking to go the strip i just want a street car that has plenty of power. I would say that the most important thing that i am looking for is if i am at a red light and a new mustang or corvette pules up next to me and wants to play i will have something for them. Basically i don't want any of the new cars to leave me in the dust. So please give me some options.

thanks
 
#3 ·
There are plenty of high power crate engines from GM that will bolt right in with minimum hassle. They also come with a warrenty, and after what you`ll pay to build it yourself, you`ll likely come close to breaking even. If you`ve never built one yourself, you`ll be doing yourself a favor by taking the crate engine route.
 
#4 ·
rphillips said:
i have a 67 camaro rs and i think the engine that is in my car is on it's last leg
so i want to build an engine myself for the car. But the problem i am having is i am not sure what i want to put back in it. The car currently has a small block 305. So my question is what should i build a big block or a small block? I am not looking to go the strip i just want a street car that has plenty of power. I would say that the most important thing that i am looking for is if i am at a red light and a new mustang or corvette pules up next to me and wants to play i will have something for them. Basically i don't want any of the new cars to leave me in the dust. So please give me some options.

thanks
Playing with a full house new Corvette or Mustang will take a lot of expense and work for either a small or big block.

Before we get to the engine what is the transmission? Old automatics don't take kindly to fresh engines, so if you have one, better include its replacement in your cost estimates.

If you want a drag car that's sudden but can't be made to give sports car handling a big block is the way to go. You can recover considerable handling with a BBC by going to aluminum heads, which you'll need to run with modern Vettes and Stangs. These days it takes a lot of Chevy just to run with an Audi or Beemer.

If you want competent handling and reasonably sudden to very sudden a small block is the way to go. The advantage of today's technology is that you can get a very large displacement in a small block giving that tremendous torque advantage that comes with large displacement and long strokes while minimizing weight over the front axle and reducing the forward biased polar moment of inertia which limits cornering and weight transfer ability. Plus building a small block, even a big small block is a lot less expensive. More bang for your buck kinda deal.

Bogie
 
#5 ·
i am planning on buying a new trany or at least going through the existing one i think it is a 350 or a 400 turbo i also plan on a new rearead for the car and yes i would much rather have sports car handling so it sounds like the way to go would be the small block. If i need to get a new trany to get up to the power that i want then that is what i will do. What is the approx hp that i would need to look for in order to meet my requirements?
 
#6 ·
i also would like to use unleaded gas or should i say pump gas.
So if i am going to go with a small block which one would be the best.
I have been looking for a 400 small block, some people believe that the 2 bolt is stronger than the 4 bolt. If i was looking for a 400 is there anything that i should look for?
 
#8 ·
rphillips said:
i also would like to use unleaded gas or should i say pump gas.
So if i am going to go with a small block which one would be the best.
I have been looking for a 400 small block, some people believe that the 2 bolt is stronger than the 4 bolt. If i was looking for a 400 is there anything that i should look for?
400s are getting pretty scarce on the used market, but if you can find one pick it up. The 2 bolt is reputed to be stronger in the bearing webs because the same webs with 4 bolt mains cause the outboard bolts to fasten into an area not beefed up for them. Which is a way of saying that 4 bolts on a typical 400 case isn't buying any additional stiffness in the bearing cap. Generally a 2 bolt SBC case is good for about 500 hp which is more than you can use continuously on the street. So the concept of Duty Cycle gives you some safety as 500 hp as continuous out put has a different meaning than going there now and then. The 400's crankcase can be helped a lot with internally balancing the engine. This will require the balancer put Mallory Metal in the counter weights, this is a bit pricey but a lot less expensive than replacing a blown engine. I make it a habit never to build an externally balanced engine. Balancing the engine main bay by main bay greatly reduces out of plane stress and resulting strain on the mains, for bulkheads, caps and bolts this greatly improves engine life.

But given the lack of 400 engines you may want to consider a 350 block with a stroker crank to 383. It's mighty easy these days to get 400-450 hp from a 350 and certainly from a 383. The difference being the RPM range where the power peaks. For a 350 it will take about 6200 to 6500 RPM, for a 383 that will come in around 5600 to 5800. The 383 set up like this is very automatic trans friendly. A 350 can be run with an auto but you've got to give some on stall, a manual is a better solution as the power peak gets up over 6000 revs as this usually indicates a loss of bottom end torque which an auto really likes. This drives you toward high stall converters and all the heat related problems that can create when driven in traffic.

If your looking at an automatic a beefed up TH350, 700R4/4L60 will work well behind the 350. Getting into a 383, 400 or bigger you need to look to the TH400. Unfortunately in an OD gearbox you should hold out for a 4L80E, but that takes a computer, available from GM or the aftermarket to operate. Otherwise you need to look toward a beefed up 700R4/4L60. The 200R4 with a beef up is popular having better gear ratios than the 700R4/4L60, but it's a touchy box to set up and regardless of the beef, it's really working over the cases design limits with a big engine and heavy car so it gets to be a problem if you get in the engine much. While racers may pull this stuff down once a week or so for maintenance and repair the average guy doesn't want to spend that much time under his car, so thinking about something stronger under the seat is a good way not to see the underside of the floor boards so often.

Bogie
 
#9 · (Edited)
Engine Selection

Adding torque is a good way to go faster but don't forget to shed as much weight from the car as possible. All the torque in the world will not do you any good if you can't get it to the pavement. Think about some frame connectors and suspension mods and maybe a 4 point roll bar. Back to your question. If you can afford it look at the LS7 427 crate motor with carb. The heads for the LS7 are hard to beat for flat torque curve. Meaning you have a higher torque number at a lower rpm. I wish I would have made this decision when I started my build. See my journal.

Bob
 
#10 ·
As Oldboogie said playing with a new Vette or Mustang will require some horsepower. A few months ago I took a ride in an old friends new new Z06 427 Vette, absolutely the fastest car I've ever been in.......scary. I don't think anyone asked you how much money you have to spend. A new LS7 crate motor is $13,900 or so, too rich for me, so I would look for a 400 small block and build a 406. With the right part combination you could build a very healthy streetable engine, probably smoke a standard Mustang but I doubt an LS7.
 
#11 · (Edited)
thanks for all the great help!

ok so now i have decided to go with the small block, so the only question that still remains is what size some say the LS7 427, some say the 400 and some say the 350 or should i say the 383 stroker. So i guess my question would be which motor would be the best for an constant driver 2 or 3 days a week?

I aslo wanted to ask should i look for a cast iron block or should i purchase one of the aluminum blocks from motown?

what are the pos and cons of an aluminum block?
 
#13 ·
If you want the baddest ride around, that has excellant street manners, and ridiculous tire frying torque throughout the curve spend 6500 to 9000 bucks and build yourself a nasty BBC. My makes 250 horse at 3000, 500 at 5200, and 600 at 6500. Torque starts out at 350 at 3000 and peaks at like 650 at 5000 rpm and I only spent about 7000 for the whole thing from pan to air cleaner including exhaust. Oh and it runs on 91 octane
 
#14 ·
so now i have decided to go with the small block, so the only question that still remains is what size some say the LS7 427, some say the 400 and some say the 350 or should i say the 383 stroker. So i guess my question would be which motor would be the best for an constant driver 2 or 3 days a week?
So does any one have any comments on the above
 
#17 ·
That's right..the proper engine formula for me looks like this. You have to determine what is right for you and shoot for that.

How much horsepower do you want x $10 for a small block

How much horsepower do you want x $17.5 for a big block

(there are exceptions)

But with a big block you get increased reliability at higher numbers and the ability to make big numbers at low compression (aka "on pump gas") a flatter power curve also means you don't have to wind the heck out of it to get peak numbers.

All of the engines you listed can make awesome power it all boils down to:
1. Price 2. Need 3. personal preferance
 
#18 ·
383 with edlebrock 170cc heads. They come in 3 different combustion chamber sizes. Pick the size to match the cam and pick the cam to match the gear. Try using a flat top piston if possible. If you must use a dished piston then use a D-shaped dish.

3.08 gear with th350, use a compcam 252H, 2000 stall, 9.25:1 cr

3.42 gear with th350, use a compcam 260H , 2200 stall, 9.5:1 cr

3.55 gear with th350, use a compcam 268H, 2400 stall, 9.75:1 cr

3.73 gear with th350, use a compcam 270H, 2600 stall, 10:1 cr

3.73 to 4.11 gear with th350, use a compcam 280H, 2800 stall, 10.25:1 cr

4.11 gear with th350, use a compcam 292H, 3000 stall, 10.5:1 cr
 
#19 ·
so this may sound like a stupid question but if i am going to build the motor my self how do i find out what the correct parts are to go with my block selection for the hp and torque that i am going for?

Are the parts sold by the hp you are going for?

what is the difference between high compression or low compression 9.25:1 or 11.0:1?

If i want to use pump gas what compression should i go for?
 
#20 ·
There are lots of kits available anbd you can't really beat the engineers at the major companies like trick flow, dart, or even edelbrock for top end stuff. The bottom end also comes in kits from Eagle, Scat, and a few others. If you want to try to save money you can shop on ebay and find the parts that are in the kits usually you can get some scraemin deals Ishopped smart and got:

Eagle 4.25 forged crank- $600
Eagle H-Beam Rods- $350
Je forged pistons -$450
Federal main and rod bearings $110
Total Seal chromoly file fit rings $105

And for around 1600 bucks I got a rock solid bottom end that is good to 900 horse and about 8000 rpm even though it will never see those kind of stresses. Better to overbuild in case I want to add a blower or a bunch of nitrous later.

The one thing you absolutely shouldn't skimp on is the Cam. Get the right setup by calling a company that custom grinds camshafts. The cam and lifters won't cost you any more than some of the name brand companies and it will be custom made to your application. I called ultradyne who makes Bullet Racing Cams and for 1300 bucks I got:

Solid roller Cam with a everwear cam gear
Roller lifters
double valve springs
titanium retainers and 10 deg locks

It was worth every penny and they got it to me in three days.

They asked me every single detail about my vehicle and it's intended purpose and I learned more about roller cams in 30 minutes of talking to one of their tech guys than I could in three years of reading forums
 
#21 ·
All of the combo I listed above will run on pump gas.

longer duration cams require more compression because the intake valve is open longer during the beginning of the compression stroke which reduces the amount of air trapped in the cylinder.

There is an ideal compression ratio for each cam duration. All the engine combo's listed above will all have about 175psi of cranking cylinder pressure and will easily run on pump gas. A 11:1 cr engine with a small cam like a 252H will detonate badly on pump gas but it would run fine with a 292H.

Pistons are listed in application and volume. For example, you would look for a 383 piston for 5.7 inch rods and a flat top (typically -5cc). They should also list the CR when used with a standard head gasket and 64cc heads. But it is easy to figure out cr knowing the engine cid, head volume, gasket volume, piston volume, and how deep the piston in under the deck (typically 0.020).

cr is the total volume (piston at bottom of the stroke) divided by the smallest volume (piston at top of the stroke).

So a 383 with flat tops (-5cc) and 0.020" under the top of the deck will have cr of.......with 64cc heads
cylinder volume=785cc (383/8 then times by 16.387 to make cc)
head volume= 64cc
gasket volume= 9cc (4.15 bore and 0.040 thick)
piston volume= 5cc (extra volume due to side clearance and valve reliefs)
piston in the hole 0.020= 4cc (need to measure this)

so add it up
785 + 64 + 9 + 5 + 4 / 64 + 9 + 5 + 4 = (785 + 82)/82 = 867/82 = 10.6 cr

70cc head would make
785 + 70 + 9 + 5 + 4 / 70 + 9 + 5 + 4 = (785 + 88)/88 = 873/88 = 9.9 cr

So to make 9:1 you will need more of a dish in the piston

Keith Black makes a 12cc and 18cc D-dish piston for a 383 with a 5.7 rod and costs about 250.00 for the set.

so 64 cc head and 18cc dish would make
785 + 64 + 9 + 18 + 4 / 64 + 9 + 18 + 4 = (785 + 95)/95 = 880/95 = 9.26 cr

and a 70 cc head and 18cc dish would make
785 + 70 + 9 + 18 + 4 / 70 + 9 + 18 + 4 = (785 + 101)/101 = 886/101 = 8.77 cr


understand???
 
#22 ·
The difference in compression ratios is basically how far you squeeze the atmosphere inside the combustion chamber, the higher the number the more the squeeze. The more you squeeze fuel and air the easier it is to get it to ignite and burn creating a more violent explosion which makes more horsepower (torque actually). However with todays fuels anything over 9.5 to 1 and the fuel will explode before it even gets a spark, which is called detonation. So your fuel explodes before the piston is at the top of it's stroke which causes a lot of stress on parts and can damage pistons and rods. Octane is basically the rating for the fuels' resistance to detonation. This is kind of an estimate and there are a lot of variables but with 9:1 you should use 91, 9.5:1 use 93, 10.0:1 use 96, 11:1 use 99, 12:1 use 104, and so on. It is kind of an exponential thing. For every point of compression ratio you have to have more and more octane to resist detonation. Now you will notice that at some point the octane rating goes higher than what you can purchase at the gas station (pump gas) so running a vehicle on "pump gas" simply refers to having a low enough compression ratio in your motor to be able to use gasoline that you can buy at a gas station.
 
#24 ·
And another thing. You are building a mild/moderate street engine so you don't need or want forged pistons. They are loud when cool, wear out much quicker, make the oil dirty quicker, and cost twice as much. Also a simple hyd flat tappet cam is all you need. This is you first engine build so keep it simple. And use diesel engine oil with your flat tappet cam.

Furthermore, a cast crank is all you need. Don't build a race engine for the street, doesn't work well.

What gear ratio do you have and is that what you plan on using?
 
#25 ·
that is a very good example so just to review in english
basically higher compression gives more torque and requires higher octane gas?

about the cam selection, why is the cam selection so important for performance?

i have heard some people's engines and they say "i have a really bid cam in it or it has a really hoped up cam" why does the car at idle sounds like the car is going to shut off rather than a smooth continues idle?

this is one thing that i don't want my car to do.
 
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