a 302 crank is a 283 crank, not very rare at all. Chevy 302's are 283 cranks stuck into a small journal 327 block. SBC's generally don't like anything over 6,500 RPM max, normally 5,500-6k RPM b4 they give a fit and toss everything on the pavement. get a 4 bolt block, have it stiffened with the valley girdles ( I think that is what there called ), and hope that it holds togther, I don't think that any SBC will live to 8k RPM. ain:

 

I disagree, a smallblock built right with good parts can be shifted at 9500 no problem, a guy here in town runs a 377 that twists to 9500shifts all summer long at the dragstrip.

Use a 400 block with main bearing spacers and a forged large journal 327 crank, the 3.25" stroke will help it live and it'll be 350ish cubic inches. I think JE makes a compatible piston. You'll want 11-1 compression or better and a long solid roller cam with good springs and rockers, good rods and 200cc heads, the airgap intake will fall off at 7K so a single plane intake would be the better choice. I have no idea if the fuel injection will work.

 

im pretty sure you can stick a 283 crank right in the motor you got but would probably expect it to blow up being unbalanced i always thought that a 377 was a 400 block with a 350 crank a 327 is a lot shorter stroke :evil:

 

You are kind of pulling your motor in two different directions. You say that you want it to be streetable, and start making power at 3500 RPM so I assume that you are going to run pump gas. You also want it to make power to 7500-8000 RPM which will require a large set of heads and a big cam, and alot more compression than will be acceptable on pump gas. If you dont mind running 13:1 compression, you can do it, but it will not be making a lot power by 3500 RPM. I have a 358 (destroked 400) with 14.5:1 compression, 230cc runner brodix 11-x heads with porting and a cam with 274 @.050 ~.660 lift. That motor made 608 hp at 7800 RPM on an engine dyno. I had a 5000 stall in it and it was still not extreemly snappy off the line. The car previously had a 6000 stall and a turbo 400 with a transbrake. That was just about right on motor, but with nitrous, it was too much stall so we dropped it back to 5000 and a glide. I would focus on a ~6500-6800 max RPM if you are planning on running pump gas.

Adam

 

Keep that up and that squealing will give way to "I wanna drive! I wanna drive!"
A 283 might be easier on the CV joints, and will make power if you rev it high enough. Or, you might look into bearing spacers & try a 283 crank in the 350 block (302cid).

 

i would have to agree w/firestone.my 283(.60 over), looking to SHIFT at 6200,and redline(my build)would be around 65-6800,93 oct.3-600 rpm safety zone so i dont waste my money or ruin anything.just my opinion(and machinest).

 

Ok, Lets assume I run it at 91 on the street (premium here), and at the track I run 100 octane, can I advance the timing a bit, and it will give me more top end?

I dont understand were the difference between 6800 streetable and 8000(or like posted 9200) race is...

There must be a way to compromise between the two...

Im not looking for a 600hp motor right now. If I did, it would be turbocharged.

Im looking at about 400hp, 350tq and alot of rpm's to work with.

I understand my goals are lofty, but I can always work down

Yes, the engine needs to be fully streetable.. but I dont see what is preventing this engine from reving as high as the other sbc's out there with bigger displacement..

I thought rod bearing spacers were bad? Anyone running them?
Would you trust them for 8k rpm's?


Andrew

 

I would like to keep this a low budget build, and will probably buy just about everything on ebay or summit on the cheep. Im thining about 3k would be a good budjet for the build. Considering that 600 would be needed in machineing for the engine rebuild and balancing, and the rest would be parts.

Thanks guys!
Andrew

I see the problem right away. I don't see a reliable 8000 rpm SBC being built for 3K. $600 in machining costs seems way under priced for a quality build.

 

Ditto.... last time I looked at machine costs local..... it was right at 1000-1200 bucks for a well prepped short block.(thats just machine work). A reliable 7500 rpm engine is not going to be cheap.

Talk to Keith Star on this board!! He is an Engine builder.....and a GOOD one.

 

my $.02...
autocross is all about being instantly "quick"

autocross is 75% handling and the right tranny gears and the right rear gears

very probably the "other" sbc's are winding higher due to lower rear gears...not a 8000 rpm motor build....ask what gears they are using

if your post, 3300rpm=75mph is true, that's probably 3.25 or 3.55 rear gears, definitely not "quick" for how fast the motor CAN wind up under load...lower gears (4.56?) for much quicker will drive you nuts on the hwy

a 600lb 400hp 350 motor in a Porshe can be fast.....as in road racing....not easy to be quick in a slalom course with 3.55 gears

 

Why not use a 911 motor with a turbo?

 

This car is a mid engine and uses a Porsche transaxle. Andyrew's was probably from a 4 cyl. 914 and was geared for a 4 cyl., meaning about 4.6 or so. You can't call Summit or JEGS and order a new gear for these cars. Remember, his car only weighs 2,200 lbs. with this gear. He doesn't need, and the transaxle can't take, much torque. I used to have a 914 with a Ford V6 (before it was flooded with salt water by Hurricane Ivan) and they are a blast to drive (pic below). A 2,000 lb. car with 200 h.p. and a 4.6 gear will scoot. I can't imagine the same car with 400 h.p.

I'm pushing 60 years old and can remember 283, 302, and 327 Chevy's consistently running to 8,000 rpm back in my youth. You older guys need to jump in here and help Andyrew out. I think he should build a 302 with a 283 crank and a small journal 327 block, or go with a 4 bolt 350 block using the 3" crank and 5.94" rods from the L99, 4.3 Liter V8, late model Caprice. Those were PM rods. He should be able to find a 4.3 Caprice in a salvage yard. I think there are threads on this board discussing the L99 to 302 build.

Andyrew’s biggest problem will be his budget. Building a high revving engine is not cheap. You will need some serious valve train parts and a well built bottom end Andyrew

 

my $.02...
autocross is all about being instantly "quick"

autocross is 75% handling and the right tranny gears and the right rear gears

very probably the "other" sbc's are winding higher due to lower rear gears...not a 8000 rpm motor build....ask what gears they are using

if your post, 3300rpm=75mph is true, that's probably 3.25 or 3.55 rear gears, definitely not "quick" for how fast the motor CAN wind up under load...lower gears (4.56?) for much quicker will drive you nuts on the hwy

a 600lb 400hp 350 motor in a Porshe can be fast.....as in road racing....not easy to be quick in a slalom course with 3.55 gears

Unfortunately, this is not your normal transmision.. this is a transaxle. I dont have much options on them.. Sure theres a couple gears I could swap out. but the " rear gears" are not avalible in different gearings without serious bucks, read fabbing up a new one...
In autox, generally you are in 2 gears, first and second, and on a fast course, 2nd and third.. In my transaxle I dont use first whatsoever due to the strength of 1st..

different transaxle options are out there, I wont discuss those because thats not the topic... lets just say there not cheep.

Haulin.. have you priced a rebuild on a 911 motor, let alone a turbo? 10-20k isnt out of the question for a simular motor as a sbc.

On machining. I just laid out a price.. I understand I need a lot of money in balancing and blueprinting everything... and thats were I'll pick up the top rpms and good reliablility..

jhs, The caprice engine is interesting, I think I might go with the 283 crank and 327 block though... hmm.


Heres a little about my car...
And I have somewhere near 10k into my car (including car), Coil overs on the rear, 275lb springs, koni yellows rear, reds front, 911 front struts, A calipers, Racing pads, vented rotors front and rear, 19mm m/c, Nascar front sway bar, v8 conversion (I wont even go into the engine... lol),flares front and rear, fiberglass front and rear bumpers, harness bar, 5 point harnesses, momo steering wheel, engman long kit, Rennshifter, seam welded rear suspension, couple of tubes for reinforcement, racing seats, and also, hoosier or kumho 710 tires. 255 40 17's front, and 285 35 18's for the rear street tires..

I understand most of that you wont understand... but I wrote that a while ago.. Car is in dissasembly, and the suspension is being seam welded and reinforced.

 

Andyrew,

I haven't been hanging out on the 914 Forum much since I got rid of my flooded 914, but I followed the construction of your car there when you were building it.

Just before the hurricane hit I was about to build a SBC to put in mine. I found a rebuilt 327 that I was going to use as a starting point. I couldn't find a L99 locally. You can get the rebuilt L99 cranks easily, but the rods are hard to find by themselves and are expensive new. GM still sells them, but not in sets. Out in Kali-Fornia finding a used L99 Caprice shouldn't be difficult. Think taxi cab.

If you use a small journal 327 and 283 crank you will have to use early 302 Z28 pistons and small journal 283 rods. With the L99 set up you can use standard 350 pistons, if I recall.

Race Engineering makes a 4340 steel, large journal, 3.00" crank that would drop in your 350 block. Last time I looked, it was about $900. Part #CO-LS30003A.

A 327 will be cheaper and easier to build than a 302. You could get a large journal 327 crank (used in the last 327's made in 1967 or 1968) and use your 350 block or find a 4 bolt 350 block.

A 302 uses a 3" stroke crank (283-small journal or L99/after market-large journal) and 4" bore (327 and 350 blocks are 4" bores. Early 327 blocks are are small journals, later 327 blocks & 350 blocks are large journal).

A 327 uses a 3.25" crank & 4" bore.

A 283 uses a 3" crank & 3.875" bore. Because of the small bore, large valve heads will have clearance problems with the block, according to what I have heard. A 283 will rev like a 302, but can't breath as well at high rpm's because of the smaller valves.

 

Back in the day,ive run both little high revvers and mid rpm longer stroke engines.IE: 277 cu in=11,000 rpms,331= 8500 rpms,the little engine didnt have any power till 8 to 9000 as it takes a huge head to get the power where you need it and needs all the tricks to stay together.*** valves,aluminum rods,light pistons,and it was always killing exh springs every pass. That destroked 283 was $7200 in 1981,so today would be crazy for a little engine. The 331 was in a 1950 lb anglia,and was very dependable at 8500 rpms and never hurt itself,but again it took light wt parts to make it live and rev dependably.

 

Back in the day,ive run both little high revvers and mid rpm longer stroke engines.IE: 277 cu in=11,000 rpms,331= 8500 rpms,the little engine didnt have any power till 8 to 9000 as it takes a huge head to get the power where you need it and needs all the tricks to stay together.*** valves,aluminum rods,light pistons,and it was always killing exh springs every pass. That destroked 283 was $7200 in 1981,so today would be crazy for a little engine. The 331 was in a 1950 lb anglia,and was very dependable at 8500 rpms and never hurt itself,but again it took light wt parts to make it live and rev dependably.

Would you be willing to tell me what was in the 331? What block, what crank, what size cam?

Thanks!

Andrew

 

Now this was in 1972 so I might not remember everything.
It was a .030 over 327 with a Hank the Crank crank,Howards rods and Venolia .043 ring with for at the time was high 13.2 c/r gas ported pistons.I had Either the 492 or the 292 head castings ported by Valley Head service with titanium valves and Smith Bros pushrods and Crane rockers with a Gk roller that was .654/.630 somewhere around 280@.050 i believe on a 109 seperation with a TR-1Y tunnel with 6224 carbs with 850 baseplates and a Mallory YC-465HP dist.This was current Pro-Stock tech then.

 

Now this was in 1972 so I might not remember everything.

Sounds like you didn't forget much.

 

Thanks, Useful information!

Andrew

 

I will try to answer your question about a high RPM motor not being a good choice for a street car. First off, a high PRM motor by design will not have very good low end power. On the street, it is fun to have something that is snappy, and will break the tires loose at half throttle. If you have a high RPM motor, you have to wind it way up to get into the power to have any fun. Also, a motor with a large cam and a manual transmission can tend to "chug" at lower RPM's which is not very fun in stop and go traffic. My motor does not come togather and run smoothly until around 3000-3500 RPM. I dont think it would not be very fun to have to cruise up and down the street at 3500 RPM. The previous examples are matters of perference. If you dont mind those things, then it doesent matter. The following are more technical. First off, a high RPM motor means expensive parts. In my motor, I have a $2500 LAE billet steel crank, GRP aluminum rods and forged pistons along with a dart little M block. All this may not be necessery, but it is good insurance when you are spinning a motor to 8500 RPM. Also, a high PRM motor will probably not last as long. The faster stuff spins, the shorter the life will usually be. The last thing is compression. I dont understand this completely, but as cam size increases, more compression is needed to properly match the cam. If you run lower than recommended compression with a large cam, the motor will feel mushy. It will loose most of its pop. That on top of the fact that most of the bottom end has been taken out of the motor in the first place doenst make for a great performing motor especially on the street. As far as the reason for compression and cams, I would like some more info, so if anyone can give a physical reason for it I would be interested. According to the comp catalog, with 10.5:1 compression you are good to around ~250 @.050 duration. This will vary with the size of the motor, but it is a conservative place to start.

Adam

 

I will try to answer your question about a high RPM motor not being a good choice for a street car. First off, a high PRM motor by design will not have very good low end power. On the street, it is fun to have something that is snappy, and will break the tires loose at half throttle. If you have a high RPM motor, you have to wind it way up to get into the power to have any fun.
Adam

Guys,

Read his post, and watch his autocross video. HE DOESN'T NEED OR WANT BOTTOM END TORQUE! He is racing a 2,200 lb. Porsche with a 4.6 gear, using a transmission designed for 100 h.p. four cylinder. A high torque motor will rip the transmission and/or CV's out of this thing. You can't use 1st gear in these V8 914's because it will snap the output shaft in the tranny. If you watch his autocross video at the end he breaks a CV using his 350 smog motor.

If you are driving a 3,500 lb Chevy with an auto trans on the street, fine, run a 383. He is autocrossing this 2,200 lb. car and wants to wind the motor up so he doesn't loose time shifting (and this car demands careful shifts).

Now I will agree with your point (see my earlier post) that building a reliable 8,000 rpm motor will take big bucks. Andyrew is a young man who has built this car himself using mostly used parts and working around problems as he goes. What he is doing is an updated version of high school kids in the '40s and '50s dropping Olds and Caddy V8's in clapped out Model A's.

I've had the same car he has with a V6 and have done tons of research and talked to people who have built and driven these cars with V8's. Andyrew has the right idea for a motor for THIS CAR and THE WAY HE PLANS ON USING IT! Just because this motor is not right for you and your situation, don't throw cold water on his idea.

There, I feel much better now. :sweat:

 

A 302 or 327 sounds like what he needs then. A 327 with flattop pistons and a 50 or 55cc head would make enough compression for a 250 @ .050 cam. A 302 would require domed pistons. A 400 block with a 3 inch stroke crank would be really interesting...

 

Guys,

Read his post, and watch his autocross video. HE DOESN'T NEED OR WANT BOTTOM END TORQUE! He is racing a 2,200 lb. Porsche with a 4.6 gear, using a transmission designed for 100 h.p. four cylinder. A high torque motor will rip the transmission and/or CV's out of this thing. You can't use 1st gear in these V8 914's because it will snap the output shaft in the tranny. If you watch his autocross video at the end he breaks a CV using his 350 smog motor.

Torque is torque, no matter if it's at 3000 rpm or 6000 rpm. If you build a high rpm, high horsepower motor, it will make as much torque as any stump puller.

 

Torque is torque, no matter if it's at 3000 rpm or 6000 rpm. If you build a high rpm, high horsepower motor, it will make as much torque as any stump puller.

Not as far as the drivetrain is concerned, for two reasons.

A hypothetical example:

One motor makes 400 ft. lbs. of torque @ 3000 rpms and 290 ft. lbs. @ 6000 rpms.
A second motor makes 290 ft. lbs. @ 3000 rpms and 400 ft. lbs of torque @ 6000 rpms.

(Reason #1) Now, dump the clutch at the starting line at 3000 rpms (shock load the drive train). Motor one is transferring 400 ft. lbs. to the drivetrain to accelerate the car from a standing start. Motor two is transferring 290 ft. lbs. Which one do you think is more likely to break something in the drive train?

Now shift into second at 6000 rpms (another shock load to the drive train). Motor one's rpms drop back to 3000 rpm (hypothetically). Now you are shock loading 400 ft. lbs. again. Motor two is shock loading 290 lbs. Same question. Same answer.

(Reason #2) The transfer of 400 ft. lbs. of torque with the higher rpm motor takes more rpms from the motor but this also means the transmission/differential turns more rpms. This spreads the load. Think of the strain put on each tooth on the tranny gear. The same amount of torque applied at 6000 rpms vs. 3000 rpms is spread out over twice the number of gear meshings (if that is a word) at 6000 rpms. This means the loading on the gear teeth is half as much at 6000 rpms @ 400 ft. lbs. vs. 3000 rpms @ 400 fl. lbs.

Another way to think of it is striking a nail with a hammer. Swing a 10 lb. hammer at nail once every two seconds and you have applied 10 lbs of force to the nail every two seconds. Now swing a 5 lb. hammer at the same nail once a second and you have still applied 10 lbs. of force to the nail every two seconds. BUT, this time the nail never receives more than 5 lbs. of stress at a time. Which hammer is most likely to bend the nail? It's the same principle with the transmission/differential gears.

 

JH, if I'm reading what your saying correctly I think 99% of what you wrote is a bit off base. I'm trying to figure out where to start, as it made my head hurt.

Torque is torque. HP is torque over time. two taps of 5 ft/lbs of torque for 2 seconds is 5 ft/bs of torque. one tap of 10 ft/lbs of torque for 1 second is 10 ft/lbs of torque. Not that tapping has ANYTHING at ALL to do with what torque actually is. Just do a google on torque and you see the twist I"m geting at versus the hit deal.

Here is a head scratcher. When does a motor make the most torque? When it's stopped at locked rotor current. No time at all is being recorded as it's not rotating. No hitting, punching screaming just sitting there making torque.

If 400 ft/lbs of torque will break an axle at 3000 RPM 400 ft/lbs of torque will break the axle at 4000 RPM as well.

What is confusing you or you forgot is the torque multiplication in first gear versus a higher gear. That's the only variable in your reason two.

Reason one, I don't think anyone was arguing that issue at all. Of course on a low torque motor your going to rev it higher to take off so..............mute point in a competition application in most cases.

Torque is torque. Twist twist twist not hit hit hit.