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Old 02-22-2008, 11:00 PM   #1
redmen031
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Grumpy - Offenhauser intake/SY1 Edelbrock

I was reading all the threads I could find about 84' intakes and edelbrock SY1 intakes with custom lids. Then I came across the thread where the Offenhauser intake is mentioned and some problems seem to encompass it. Would the the Offenhauser be the best bet or the Edelbrock SY1 with custom lid? Some pros and cons of each unit?

Link to the Offenhauser - CLICK HERE

Link to the previous discussion - CLICK HERE

All replies are greatly appreciated
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Old 02-23-2008, 09:03 AM   #2
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I ran the Smokey Ram on my '65 small block. It was underwhelming under 2500, but anywhere above that and it ran great.

I was running 10.5:1 compression, stock 2.02 intake heads, stock '30-30' cam, and a 750 double pumper.

It was scads of fun!

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They've gone up in price recently ...

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Old 02-23-2008, 02:41 PM   #3
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BOTH the OFFY and the SY1 were DESIGNED for producing max power in the 3500rpm -7000rpm plus band in the 302 displacement SBC, used in the ORIGINAL TRANS AM RACE CARS, they work great on the larger SBC PROVIDED the cam, compression ratio, and CYLINDER HEAD FLOW RATES and gearing keep the engine in its effective opperational band which stays at or about 3000rpm- 7000rpm due to the design of the runners length,and cross sectional area.
since they are basically max effort race intake designs no effort was made to make the under 3000rpm performance work very well, and youll notice that if you install either intake, yet above about 3000-3500rpm with a 383, with 10.5:1-11:1 cpr and the cams listed below they come alive once the rpms build...if youve got the manual trans and correct rear gearing to keep the rpm band in the 3000rpm-7000rpm band.
BTW its kind of a waste to install a HYDROLIC cam as most hydrolic cams enter valve controll issues in the 6000rpm range,area, where the intakes pull very effectively, so youll want a solid lifter design that can reach 6500rpm plus to 7000rpm, too maximize the intakes potential, OR too install these intakes on heads that flow less than about 250 cfm at .500 lift as that would restrict the intakes flow potential.
both can support 450-500HP as they flow 270 cfm plus (UN PORTED)while the stock cross fire flows less than 190cfm,the differance in power is simply amazing IF you match the components correctly so ALL the components maximize that 3500rpm-7000rpm power band.
NOTICE the stock cross fire restricts power badly above about 4000rpm with its 190cfm flow,so they are totally differant types of intakes even thou thier design looks similar.
if you use a basic 383 engine size they produce even better power.
Ive found the cam that works best is usually the 114681 or 110921 CRANE solid lifter cams and a 4.11-4.56 rear gear ratio and a manual trans.
now Id point out that they both can be a P.I.T.A. to tune if your not good with carbs and the offy is designed for two small four barrel carbs, in the 450cfm-600cfm range, the SY1 for a single 780-850 cfm
YOU can ADAPT the bases to use the STOCK or modified TBI injection off the cross fire, but it requires an adapter plate to match the base,
theres a guy on this site than makes the correct adapter plates.

http://www.crossfire.homeip.net/

BTW the SY1 doesn,t hit the windshield wiper motor while the OFFY does, and both will require a small dia. distrib. the OFFY is still easy to buy off summit racing, the SY1 is only available USED

http://store.summitracing.com/partde...5&autoview=sku



BRAND NEW LOWER WITH GASKET $344

http://store.summitracing.com/partde...?part=OFY-5903

dual quad lid $150 NEW

BRAND NEW LINKAGE $117


http://store.summitracing.com/partde...?part=OFY-5902

this link gives you good info

http://jobyteknik.homeip.net/corvett..._installation/

BTW Ive used BOTH intakes with CARBS several times ,on my cars and would not hesitate to do so again,and they look and run great once tunned correctly, with a conversion to TBI it easily something you can do, but it takes more work and while Ive worked on a couple cars that were modified that way, its not as easy as carbs, too use and tune, so while its a huge potential increase over the crossfire, the TBI, will require a bit more effort
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Old 02-23-2008, 03:47 PM   #4
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Excellent info OldVetteFan and Grumpy, Thanks for clearing everything up!!
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Mods: Ceasefire is no more...LS1 clone on the way! | 3.73 gears | Cross drilled-Slotted rotors | 18x10 out back & 17x9 up front | Headers | highflow CAT | 2.5" custom exhaust no mufflers

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Old 02-23-2008, 04:28 PM   #5
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you might want to keep in mind that hp is a result of both torque and where in the rpm band that torque can be accessed and, used with access thruu gearing, and what moving the peak hp from about 3500rpm to about 5500-6500rpm with those part swaps and better flow can do for your effective power levels.

the formula for hp is found bye the following method, torque times rpm divided by 5252=hp

220ft lbs at 3500 rpm results in alot lower power than about 430ft lbs at 5000rpm plus that you could easily do with the listed combo.

you gain about 4% in tq for every point in compression, you gain about 45 ft lbs thru a displacemment increase from 350 to 383, so a stock cross fire that makes about 210hp at 3500rpm with those changes has a very noticably increase in useable hp.

http://www.stingray.nu/tips/tech84.htm

lets say the 1984 tq peaked at about 2500rpm and held steady to about 3500rpm, add the increased displacement, better heads , better intake and increased displacement and you could easily MORE than double the orriginal engine power curve, its no trick to hit the 450-500 hp range with the correct parts and assemby with careful use of clearances and tunning with the right parts

a rought guide to hp potential,from air flow thru the ports is the formula .257 x port flow x number of cylinders
the stock intake and heads barely flow 190 cfm, the correctly sellected parts can exceed 250-275 cfm, easily doubling the power potential when the other factors are taken into the formula

SY1





OFFY



offy

Part numbers are 5893 base,
http://store.summitracing.com/partde...5&autoview=sku

5903 for the dual-four top,
http://store.summitracing.com/partde...?part=OFY-5903

5902 for the linkage.

http://store.summitracing.com/partde...?part=OFY-5902
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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
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Old 02-23-2008, 04:40 PM   #6
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Yeah Im still tossing around the idea of building an entire engine or just modding the 84 crossfire. But if I go the modding route I will most likely do the SY1 with custom lid, long tubes to true dual exhaust with 3:51 gears out back. As far as upgrading heads, cam, lifters and rockers, I'll decide that after I see how the vette feels after the above mods. Maybe gears, intake and exhaust will be enough to hold me over for a few months

Do you think 3.51's are too low or too high to go with?

Thanks
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Mods: Ceasefire is no more...LS1 clone on the way! | 3.73 gears | Cross drilled-Slotted rotors | 18x10 out back & 17x9 up front | Headers | highflow CAT | 2.5" custom exhaust no mufflers

Check out my LS1 engine build thread HERE

SAVE THE WAVE
Pictures ------ More Pictures
Lots of donuts in the SNOW!!
Old 02-23-2008, 04:53 PM   #7
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Quote:
Originally Posted by redmen031 View Post
Yeah Im still tossing around the idea of building an entire engine or just modding the 84 crossfire. But if I go the modding route I will most likely do the SY1 with custom lid, long tubes to true dual exhaust with 3:51 gears out back. As far as upgrading heads, cam, lifters and rockers, I'll decide that after I see how the vette feels after the above mods. Maybe gears, intake and exhaust will be enough to hold me over for a few months

Do you think 3.51's are too low or too high to go with?

Thanks
THE MORE GEAR, IE 3.73:1 the better the combo will run simply because youll spend a greater percentage of your time in the effective power band of the engine, any time you spend under about 3000rpm with those mods will be producing noticably lower power than when your "IN THE ZONE" 3000-7000rpm plus

read this also

http://www.digitalcorvettes.com/foru...ight=crossfire
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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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