yes OFFYS still around

grumpyvette

Administrator
Staff member
http://www.exeterautosupply.com/Docs/Of ... atalog.pdf

THE OFFY base IS STILL CURRENTLY MADE, and can be adapted

ofy-5893_w.jpg


http://store.summitracing.com/partdetail.asp?autofilter=1&part=OFY-5893&N=700+115&autoview=sku

ofy-5903_w.jpg

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

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

the basic crossfire manifold is a HUGE restriction EVEN if ported to the max, the XRAM is nothing but a single plane carb intake with a mickey-mouse adapter to allow the TBI injection to be bolted on.

read thru this

http://www.swko.net/~lionsden/crossfire.htm

either the OFFY or the SY1 intake base, with a custom top plate will be a HUGE improvement, easily able to support 500hp or more on a correctly configured engine with decent heads like the AFR 210cc or AFR 195cc

http://www.airflowresearch.com/210sbc_rh.php

and a decent cam like this crower

http://www.crower.com/misc/cam_spec/cam_finder.php?part_num=00404&x=25&y=17

installed in a 10.5-11.0:1 cpr 383

but keep in mind youll need a 3000rpm stall converter and 3.73:1 rear gear to run those
keep in mind INTAKE HEADS AND CAM and COMPRESSION ALL must be upgraded to get full flow into the heads , so that the power levels your looking for can be achieved,and the stall and rear gear must be changed to use the significantly higher rpm power band effectively, but theres no comparing the results after the mods are correctly made, youll have well over 140 plus MORE hp,(plus) if you do things correctly

if you want to build something responsive for street/strip use, these smaller 4 barrel carbs below ,make tuning easier on a car used mostly on the street

http://www.holley.com/0-8007.asp
 

grumpyvette

Administrator
Staff member
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 operational 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 you'll 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 you've 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 HYDRAULIC cam as most hydraulic cams enter valve control issues in the 6000rpm range,area, where the intakes pull very effectively, so you'll 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 difference 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 different types of intakes even thou their design looks similar.
if you use a basic 383 engine size they produce even better power.
Ive found the cam that works best for street/strip use in a hot street car combo 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/

http://www.exeterautosupply.com/Docs/Of ... atalog.pdf

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/partdetail.asp?autofilter=1&part=OFY-5893&N=700+115&autoview=sku

http://coloradohotrodparts.com/Offenhau ... Y-5901.htm

BRAND NEW LOWER WITH GASKET $344

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

dual quad lid $150 NEW

BRAND NEW LINKAGE $117


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

this link gives you good info

http://jobyteknik.homeip.net/corvette/2002-11_offy_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 tuned 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

IF you want to maximize the results, you can produce using a cross ram intake, youll need to have a set of heads and a cam ETC. that match the full flow potential of a mildly ported cross ram intake and its designed power band, which is in the 4500 rpm 7000 range with a 377-406 sbc which most guys will run if theres no limits on displacement, it will result in a combo you can,t run on street octane fuel, (PUMP GAS)
but it will produce a good deal more hp.
the changes will require you to swap to heads like
the 210cc AFR,
http://www.airflowresearch.com/index.php?cPath=24_33
or 210cc profiler heads
http://www.profilerperformance.com/sbc-heads-176.html
two 600cfm holleys
a solid roller cam similar to this
http://www.cranecams.com/?show=browsePa ... e=camshaft
and about 11.5:1-12:1 compression
Id strongly suggest a FORGED internally balanced rotating assembly with 7/16" ARP ROD BOLTS
a manual transmission and a 3.90-4.11:1 rear gear range is the absolutely lowest numerical ratio, range Id consider ,on short tracks, with 4.56_4.88:1 being a better match on short tracks
keep in mind youll want to keep that combo spinning in the 4500rpm-7000rpm band, and that requires roller rockers, a rocker stud girdle or shaft rockers and a well designed 7-8 quart oil pan and windage screen to maintain oil pressure

full length headers designed to match the cam profile selected, and open headers with a tuned collector


http://www.scatcrankshafts.com/ (310-370-5501)

CHEVY 400 SMALL-BLOCK 2-PC REAR SEAL 400 MAIN, 4340 FORGED CRANK, I-BEAM OR H-BEAM RODS WITH 7/16" CAP SCREWS
CI Crank Rod Piston Boresize Type 58cc 64cc 70cc Inclcrp Inclcrprb Compl
377 4-400-3500-6000 2-350-6000-2100 PREMIUM FORGED 4.155 FLAT 11.6 10.8 10.1 1-41010-1 1-41010 1-41010BI
377 4-400-3500-6000 2-350-6000-2100 PREMIUM FORGED 4.155 DOME 14.2 13.0 12.0 1-41210-1 1-41210 1-41210BI
407 4-400-3750-5700 2-ICR5700-7/16 HYPEREUTECTIC 4.155 FLAT 12.5 11.6 10.8 1-41250-1 1-41250 1-41250BI
407 4-400-3750-5700 2-ICR5700-7/16 FORGED 4.155 FLAT 12.5 11.6 10.8 1-41255-1 1-41255 1-41255BI
407 4-400-3750-5700 2-350-5700-2100 PREMIUM FORGED 4.155 FLAT 12.5 11.6 10.8 1-41260-1 1-41260 1-41260BI
407 4-400-3750-5700 2-ICR5700-7/16 FORGED 4.155 DISH 10.4 9.8 9.2 1-41305-1 1-41305 1-41305BI
407 4-400-3750-5700 2-350-5700-2100 PREMIUM FORGED 4.155 DISH 10.4 9.8 9.2 1-41310-1 1-41310 1-41310BI
407 4-400-3750-5700 2-ICR5700-7/16 FORGED 4.155 DOME 14.0 12.9 11.9 1-41355-1 1-41355 1-41355BI
407 4-400-3750-5700 2-350-5700-2100 PREMIUM FORGED 4.155 DOME 14.0 12.9 11.9 1-41360-1 1-41360 1-41360BI
407 4-400-3750-6000 2-ICR6000-7/16 HYPEREUTECTIC 4.155 FLAT 12.4 11.6 10.8 1-41400-1 1-41400 1-41400BI
407 4-400-3750-6000 2-ICR6000-7/16 FORGED 4.155 FLAT 12.4 11.6 10.8 1-41405-1 1-41405 1-41405BI
407 4-400-3750-6000 2-350-6000-2100 PREMIUM FORGED 4.155 FLAT 12.4 11.6 10.8 1-41410-1 1-41410 1-41410BI
407 4-400-3750-6000 2-ICR6000-7/16 HYPEREUTECTIC 4.155 DISH 11.1 10.3 9.7 1-41450-1 1-41450 1-41450BI
407 4-400-3750-6000 2-ICR6000-7/16 FORGED 4.155 DISH 11.1 10.3 9.7 1-41455-1 1-41455 1-41455BI
407 4-400-3750-6000 2-350-6000-2100 PREMIUM FORGED 4.155 DISH 11.1 10.3 9.7 1-41460-1 1-41460 1-41460BI
407 4-400-3750-6000 2-ICR6000-7/16 HYPEREUTECTIC 4.155 DOME 14.2 13.0 12.0 1-41500-1 1-41500 1-41500BI
407 4-400-3750-6000 2-ICR6000-7/16 FORGED 4.155 DOME 14.2 13.0 12.0 1-41505-1 1-41505 1-41505BI
407 4-400-3750-6000 2-350-6000-2100 PREMIUM FORGED 4.155 DOME 14.2 13.0 12.0 1-41560-1 1-41560 1-41560BI
434 4-400-4000-6000 2-350-6000-2100S PREMIUM FORGED 4.155 FLAT 13.1 12.2 12.2 1-41565-1 1-41565 1-41565BI
434 4-400-4000-6000 2-350-6000-2100S PREMIUM FORGED 4.155 DOME 14.6 13.5 11.6 1-41566-1 1-41566 1-41566BI
 

grumpyvette

Administrator
Staff member
this is the type of challange/upgrade I work on for the guys all the time, AND IM CERTAINLY NOT SUGGESTING YOU CAN,T REACH YOUR GOAL,THRU OTHER ROUTES, BUT THAT APPROCHING THE PROBLEM LOGICALLY ITS FAIRLY EASY TO PLAN YOUR GOALS AND COURSE TO ACHEIVE THEM,
the first thing youll need to get strait in your mind is the realistic budget youll be willing to work with and that performance is basically the result of the power to weight ratio and HOW effectively you can get the power to the ground. keep in mind that for a street car your NOT building the engine for max peak power, your looking to build for the best average power/tq curve over the rpm range youll use most

AND THAT HAVING SLIGHTLY MORE HP THAN THE MINIMUM REQUIRED IS SMART, simply because you won,t always have the ideal tune or traction available,its silly to shoot for minimum levels yet its a waste of money to over build the engine, to levels youll seldom use or even want, as theres always compromizes in driveability

ok first Id point out that its silly to build anything smaller than a 383 displacement simply because youll make significantly greater total power from a larger engine than a smaller one,COSTS for a 383 are just not that much higher than a 350, and its TOTAL POWER not horsepower per cubic inch your interested in!

next,CORRECTLY MATCHING the cylinder heads, cam and compression ratio , to the rpm range where youll get the best results is where youll make most of your power potential.

think it thru before buying parts, and only sellect those components that match your goal,by far the most comon mistake is randomly sellecting mis-matched parts because you "GOT A DEAL"

ok lets look at your options, to keep costs reasonable we want to use what we can from your current engine but its insane to limit yourself to parts that restrict your potential power levels severly like the current heads,intake and rear gear ratio.



the formula for hp is (tq x rpm/5252=hp
example
450 ft lbs of torque at 3000rpm=257hp
450 ft lbs of torque at 6000rpm=514hp
because the torque is available at that higher RPM RATE and at the higher rpm useing gearing the rotational force the engine supplied can be applied faster or slower to the rear tires

[color:"red"] here read these ALL CAREFULLY [/color]
http://www.69mustang.com/hp_torque.htm

http://www.ubermensch.org/Cars/Technical/hp-tq/

http://vette.ohioracing.com/hp.html

http://auto.howstuffworks.com/engine1.htm

http://auto.howstuffworks.com/horsepower.htm

http://auto.howstuffworks.com/question622.htm
where most guys go wrong is in not correctly matching the cars stall speed and gearing to the cars tq curve, if you mod the engine for increased high rpm performance but fail to also match the stall speed and gearing to that higher rpm tq curve much of the potential improvement is wasted.


calculate, your minimum hp levels needed

http://www.runeb.org/www_docs/Jexoticasite/frames/horsepowercalc.htm

http://www.stealth316.com/2-calc-hp-et-mph.htm

http://www.gordon-glasgow.org/hpcalc.html


a few calculations will quickly point out that your realy looking to have between 350-400 rear wheel hp, that basically translates into an engine making about 18% higher power at the flywheel, so lets assume or goal is a 420-450 hp engine, now your basic 383 will be correctly designed and matched to a rear gear ratio in the 3.73-4.11 rear gear so youll maximize the area in the torque curve that can give the best results, the 2500-6000rpm band. so thats where we NEED TOO concentrate our efforts. this should point out the stall speed of about 2500-2800rpm is ideal in this application to match your needs

30228b.gif

look at this chart, it shows the ideal durration for best results at differant rpm bands, well want the MINIMUM DURRATION that will supply our needs thats going to be in the 220-230 range for street use,while the 230-235 range would be about ideal for power.
we quickly find that durration will match to a 10:1-10.5:1 cpr if we want to use pump gas.

ok,now the CYLINDER HEADS and intake NEED to supply that RPM RANGE and DISPLACEMENT, youll want a set of heads that flow about 230cfm AT .500 lift at the least,to easily match that requirement.

currently this is a good choice in performance per dollar in heads

heads

http://www.jegs.com/webapp/wcs/stor...goryId=78237&parentCategoryId=10187&langId=-1

cam

(READ THIS)
http://www.idavette.net/hib/camcon.htm


(minimum cost flat tappet hydrolic)



http://www.cranecams.com/?show=brow...-400 C.I.&partNumber=114201&partType=camshaft

upgraded ROLLER CAM
(what IM useing in my similar engine)

http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=119661&lvl=2&prt=5

(what ID use if I was to build it again)

http://www.crower.com/misc/cam_spec/cam_finder.php?part_num=00471&x=20&y=9


stroker kits

http://www.speedomotive.com/383 Mighty Mouse.htm

http://www.speedomotive.com/383Forged.htm

oil pan
http://www.midwestmotorsportsinc.com/order_part.php?item=CP100LT&line=MWM

now your intake really will be a huge restriction, ID strongly suggest finding a SY1 base and installing a custom top

these guys can help there

http://www.crossfire.homeip.net/
 

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grumpyvette

Administrator
Staff member
I constantly see these intakes for sale at flea markets, and theres a good reason, people try them and then they can,t wait to get the money or at least part of the money back by passing it off on the next guy that wants to experiment
offy1.JPG

offy2.jpg

offy3.jpg

let me tell you from my experience Ive had mostly less than impressive and some times out right dismal performance results using most offenhauser intake designs, look thru the pictures, most have large divided plenums very short runners and as a result any place in the rpm band lower than about 5000rpm torque is significantly less than either a dual or single plane design like most edelbrock or holley or wieand designs
offy5.jpg

offy6.JPG

offy7.JPG

offy8.jpg

offy9.JPG

offy10.JPG

offy11.JPG


the port-o-sonic dual runner design makes good torque but not much high rpm power
offy12.jpg

offenhauser%20dual%20port%201.jpg

THE CROSS RAM IS THE ONE DESIGN THAT SEEMS TO WORK FAIRLY WELL IF YOU CAN TUNE
offy13.jpg
 
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