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Old 03-28-2006, 06:13 PM
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Building a SBC to rev to 8k, and have power

Dont think you guys remember me... I have a 73 914 porsche with a 350 sbc.

Im doing some research and Im trying to figure out how to build an engine for it...

My purpose for the car will be a track and autox car (if you dont know what an autox is.. Heres a video of my last autox in the car
http://www.teamgracer.com/cars/videos/scca91605.wmv

For this purpose, autox especially, shifting gets in the way, and for track purpose, high rpm hp is king.

I would like to build my engine to rev up to 8k rpm's, be streetable, and probably make max power at 7.5k and cam profile starting it at 3500.
Under the cam I will still make a lot of tq for a 2200 lb car to move.. so im not worried.. Im concerned that a sbc engine will not like it up at that high an rpm.

My current engine is a 350, 4 bolt main, with smog heads (my limiting factor..) and a 3k-7k rpm cam, headers, FI, HEI, all that jaz.. It ran 240rwhp and 275 rwt. It makes max power around 5800. because of the valves, and valve float, and I havent seen it go over 6300 (except when reving it).

I was considering looking for a 302 crank, but those are extremely rare. Then I started thinking maybe a 327 crank, then IM now thinking of a 283 and boring it as much as possible. My uncle has about 2 dozzen cranks, and about 6 blocks and a "camaro" engine We can probably find a 283 in there, and probably a 327 large journal crank... usable is the question.

Rods and pistons dont matter, some H rods shot peened and cleaned I would assume would handle it. Compression under 11 would be good.

I love turbo's, and some day it will have a turbo... If this helps in giving it enough air to hold a rev that high while having a smaller cam lobe would be cool. Im a turbo guy.. but thats way down the road.

Camshaft is questionable. The transaxle choices make it interesting as far as were I will be cruizing at 75mph.. current transaxle (can only hold 300lbs tq) is around 3300rpms. but Im looking for advice on that.

Rocker arms Im considering full roller, and as light weight as I can get. maybe aluminum? Suggestions please.

Lifters Im also considering full rollers, but I dont know much about them..

Then there is the solid vs hydraulic.. Is it possible to go with a hydraulic at that rpm's? Good idea? Bad idea? I dont mind adjusting valves... previous engine in the car was a porsche 4.. and require valve adjusting, in a much more cramped position.

Intake manifold. I have a performer RPM currently, Will that be good enough for that high rpm's? I have very limited hood clearance, but can modify hood if I need another inch.. Tunnel ram is out of the question.

I also have Holley Pro Jection 4DI laptop programable fuel injection, and I can change anything on that, RPM's, Fuel curve (obviously) Fuel comp, idle, Electronic ignition curve, and some other good stuff. Impressed with it.

Distributor and electronics. Dont know. but would like to go electronic. HEI would be nice too...

Heads, I have double humper heads, would like to go aluminum.. but I am on a budjet.


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

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Old 03-28-2006, 06:34 PM
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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.
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Old 03-28-2006, 07:46 PM
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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.
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Old 03-28-2006, 08:13 PM
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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
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Old 03-28-2006, 08:23 PM
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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
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Old 03-28-2006, 09:19 PM
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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).
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Old 03-28-2006, 10:44 PM
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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).
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Old 03-29-2006, 01:10 AM
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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
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Old 03-29-2006, 02:56 AM
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Quote:
Originally Posted by Andyrew

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.
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Old 03-29-2006, 06:59 AM
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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.
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Old 03-29-2006, 07:19 AM
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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

Last edited by red65mustang; 03-29-2006 at 07:31 AM.
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Old 03-29-2006, 07:44 AM
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Why not use a 911 motor with a turbo?
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Old 03-29-2006, 12:25 PM
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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
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Old 03-29-2006, 01:48 PM
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Quote:
Originally Posted by red65mustang
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.
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Old 03-29-2006, 03:15 PM
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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.
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