matt_82transam

I have an 82 crossfire 305 with the following mods done;
-heddman standard 1 1/2 shorty headers
-full 3'' single straight exhaust with dynomax muffler
-dual k&n open element
-8.8 m accel performance plug wires
-high torque starter
-advanced timing to 8*
-no smog pump
-made stock cowl induction open full time
-always have 92 octane gas

what kind of ET would be possible with these mods, I know it should be low 16's but do you think its possible to get a 15.8.

If not will bumping fuel pressure up couple psi over stock do the trick? if so, how the hell do I regulate it

IROCaholic

I really dont know man , I havent really ever seen a crossfire camaro or firebird run before. I hear in good condition they run 16.0 flat stock so with what you have, your probably capable of mid 15's. Change your ring gear to like a 3.42 or 3.73 and you should be able to pump out low 15's.Good Luck

Tom 400 CFI

Waaaay back when, I had a similar combo to you:
305 CFI
160 T-stat
advanced timing -don't remember the degree
no smog pump
raised fuel pressure
Edelbrock headers and Y
3" SLP cat back
'86 and newer cat
Also, it had 3.23 gears, and a T-5 trans

In that configuraton, it ran a 14.5 @ 95mph. So running in the 15's should be a piece of cake, even with the gear and three speed you have, you should be able to run 15's easy.

One suggestion, Get rid of the open element and put the stock air cleaner lid back on. The cold air is more important, and that housing won't impede air flow to a 305.

You can adjust the FP by removing the FPR, pop off the plug at the bottom, and then you will be able to turn the adjusting screw.

matt_82transam

HOLY ****

you ran 14.5@95 mph....that is soo pro, thats faster than most carburated 350's.

ya iI still have the lit so I just have to take off wingnuts and put cover over the open element. Ill try to take it to the track and run it with cover and without.

and for the fuel pressure part Ill try to do , however I dont want to set my timing more than 10* advanced so Im keeping it at 8* for now.

THanks alot, you may just talk me out of the 368+ hp camaro engine i might drop in next year

kdrolt

Look here:

http://www.crossfire.homeip.net:81/c...e+and+Upgrades

You can also do a search for the name "chevyhacker" to find his other posts, so you can see the performance of the car before he started modding it. And his isn't the only post that would be useful to look at; there's a lot of Crossfire + TBI specific info at the Crossfire (CF) vault.

FWIW at the CF vault (the name for the CF website) there are flow bench data on not only the intake manifolds but also on the TBI's themselves if you search for them. The TBIs (with single bores) were used on the LU5 (Fcar 305, in 82-83) and L83 engines (Ycar 350 in 82 & 84) and they have the same bore size as those used on the 305/350 conventional manifold TBI engines like LO3 and LO5. So the flow data on the single bore TBI can reasonably be multiplied by 2 to get a very good idea of what the 305/350 TBIs can flow. This comment wasn't addressed to you; rather it was addressed at 3rdgen readers who complain about the lack of real flowbench data on the TBI.

One of the main CF contributor's has his own flowbench and that's where the data comes from. Maybe he'd even flow a 305/350 and 454 TBs just for comparison sake (hint), because some Crossfire owners have remove the stock dual (single bore) TBIs and replaced them with a new top manifold plate and either a 2 bore TBI from a 305/350 or the one from the 454 (or the big Holley). It would be useful data for CF people to have, as well as non-CF 3rdgen owners. HTH.

chevyhacker

My current time is 15.4 in almost 90 degree heat

I have done lots of mods in the past 6 months, but here's the rough summary with times

Stock & way out of tune - 16.8
Added headers, accel coil, wires, general tune up stuff - 15.75
Added torque converter (2100 stall) and ported manifold - 15.4

Within the next 2 weeks, I'm adding world torquer 305 heads (FYI, summit has these VERY cheap right now - $552 for a set to your door) All the data I can find points to 1.72 valves in our stock heads - they choked these motors from the factory, yes, a restrictive intake (port it) and very restrictive exhaust (you already knew that!)

I'm also adding a more aggressive cam (stock one is VERY mild), and a new timing set & roller tip rockers. I will post results by mid August hopefully.

Here's some links:

Dyno (after headers) - http://www.chevyhackers.com/x-fire_z... - 168_258.jpg

Dyno (after manifold) - http://www.chevyhackers.com/x-fire_z...2003_SMALL.jpg

Caveat emptor on the dyno results - they are from two different dynojets - the numbers don't seem to match the .35 sec gain after porting the manifold. But dynos are like statistics - "lies, damn lies, and dyno results!"

How to port & polish the manifold - http://www.chevyhackers.com/tech_art...rt_polish.html


You've already got a link to the crossfire injection vault - spend some time reading

matt_82transam

by the way the stock air cleaner lid is the most restrictive junk ive ever seen. It may not seem like it is because it lets some cold air in. However when I took it off and just had the 2 dish filter covers like and open element, when you stomp on it you just get a constant charge forward for a long rpm range. Try it.

mrr23

on the airlid thingy. we took chevyhacker's off at the track and gained nothing. did 2 runs w/o it. he has k/n filters in it now. also on his 15.75 run he forgot to mention the 3" cat and the floqmaster 3" catback in addition to the headers and tune up stuff.

90RS305

I have never seen a cross-fire 305 in person, but I do know what you are talking about. As for getting it in the 15's, I sure hope so. I more than likely am wrong, but our cars shouldn't be that much different performance wise. I have a 90' RS with the 305 tbi engine, andwhen I ran it it was BONE STOCK with nothing more than a flowmaster muffler, i got a 15.3 out of it. Don't ask how, but I pulled it off. I guess driving ability does say quite a bit....

25THRSS

Correct me if I'm wrong, but doesn't offenhouser make a crossfire intake manifold that flows a lot better than stock?

kdrolt

Offy made one for carb use, yes. There are others as well, incl the original 68-69 cross ram manifold made by GM, and available as a dealer-installed option on the 302 Camaro. The Cross fire website has all of these manifolds shown, if you seqarch on the Alternative Induction segment.

Warning: all the aftermarket manifolds breath well, but they were built for dual 4v carbs, so they were intended for high-flow high-rpm use. A near stock sbc for steet use wouldn't be the best choice. Can they be made to work? Yes, but not without some tuning effort.

Tom 400 CFI

Like Mrr23 said, removal of the air cleaner lid will gain you NOTHING, unless you have dirty/clogged air filters. ESSPECIALLY on a stockish 305. The air cleaner assy is SO not a restrictionat that level.

After I put the sbc 400 in my car, I bought a spare air cleaner lid, chopped out the "hats" and ran the empty housing w/no filters at the track only. I DID see a gain with this; ~.10, but I was at the 320+ hp level. Again, that housing isn't even remotely a restriction at the power levels we are discussing on this thread.

Notice that mrr23 and I have run our cars MANY times at the track, Trying both configurations, so we actually have HARD data on this. Matt_82, though well intentioned, has squat. SOTP doesn't count for chit.

"...you just get a constant charge forward for a long rpm range" There's some scientific results for ya. lol.

mrr23

actually it's not my car. it's chevyhacker. but i have been there with him throughout this whole ordeal. i saw an '84 corvette gain .3 after taking his off. so we took his off. after 3 runs squat difference. different design between the 2.

matt_82transam

well i may not take my car to the track after every single mod but im smart enough to know the difference between when my car accelerates like **** compared to it booking like it never did before.
Maybe your other cfi 305's had different set timing than mine, or other mods that might change the situation. So take it easy tom and try to be open to other possibilities than only the ones based on your own experiences..

matt_82transam

hey tom, how much does that offenhauser crossram intake manifold cost? and is it easy to buy or did they stop making it.
I heard about it from that crossram website that has a lot of corvette pics.

Tom 400 CFI

It's right around $250 - $270.

They still make it, and it's available through PAW. You need to -or get someone to- fabricate a top plate for the intake, as it was designed for two 4 bbls, so your TBI's won't bolt directly on. The plate is very simple though, and could be made at home w/some basic tools, and careful measuring.

Sorry for coming off like I was angery, but kids that read stuff on here that don't know any better, will read a post like yours, and go remove their air cleaner. That would be a mistake, as my (and MANY other's) HARD data will show. No way is the stock aircleaner housing a restriction on a 305 CFI. Myself and many others have the numbers to prove it. This is F-bod BTW -I can't speak for the Vette, and it's magnesium aircleaner housing.