I'm gonna be watching this thread very closely as well. There are a lot of people who at the moment are in the process/wanting to be in the process/will be in the process, of upgrading to EFI and i am one of them. There are at least 8 or 9 guys on the forum with TPI systems on their cars and to them I ask, Does it really decrease your cars performance like the C4 guys say?

 

WOW! must be a hot topic. I appreciate the posts. Let me get this straight TexasShark. The Holley Commander needs more clearance? That is the system that gave me this EFI bug. I saw a spot on it on Trucks!

What does TPI stand for? And how does it work?

 

There are some guys who just flat beleive in carbs, and for ultimate power on a dragstrip, maybe just maybe they are correct, even today...but I think those power differances are pretty much closed up these days....

the TPI systems were designed for max ram effect on a 305 engine, apparently, to give max street torque, they rean really well on the 350 engines in early C4 vettes, F bodys....
I think the overall driveability and fuel economy more than justify the outlay in cost/effort for any conversion....even using a TPI, now the TPI system is not all dead above 4500 rpm's as most guys claim, I think it's more the cam limitations, and for sure like my car the runners, and manifolds can be increased in size...giving the 350 engine more power yet....

now the runners were modified plenty shortened, maybe even enlarged for later versions, but that is all LT1-4 engines....and are not a bolt on directly for an older engine like ours in C3's.....

there are plenty of aftermarket systems, but hood clearance issues seem to raise their ugly heads for some reasons.....but that's nothing unusual, seems most manifolds have troubles under a vette hood anyway....

GENE

 

My measurements so far show that the injector base and butterflies are about 1.5" lower than the existing carb installed height so that looks good to go,i aleady had a fuel ret line with the rear mounted holley blue so that looks good,and as far as i can see the only simple place i can put the computer controller is under the paasenger seat.....under the dash....well that's a joke,i can barely get my hand in there.....obviously not smart to put it under the hood and the only other place is under the guard somewhere but that could expose it to weather/road debris.....any ideas gratefully recd...john :chevy ;)

 

Wish I could help you, but I deal with only the stockish type computers....specifically GM 1227730 I can't help about aftermarket mounting as the units are differant...730 mounts flat against backside of map pocket on that fiberglass panel....i expoxied mounting clips to the glass.....another good spot was forward of the a/c/lighter/shifter plate under the radio.....may not work with stock radio....

GENE

 

C3Daddy -
TPI stands for Tuned Port Injection. This is actually a GM term (as I recently learned) for EFI. With EFI (vs a carb) a computer constantly monitors and adjusts your fuel/oxygen mixture. A carb simply maintains a "range" for this mixture. The EFI allows for a more efficient "burn". TBI is Throttle Body Injection as is an older system. I don't know enough about these to comment one way or the other. As mentioned elsewhere, the GM TPI was actually designed for a 305 but should perform fine on any small block (don't know about big blocks).
I narrowed my EFI choices to the Holley Stealth Ram and the 950 Commander. The Ram is 10 1/4" tall, and the 950 is 8 1/2". Although the 950 is shorter, you have to consider the filter which will add 3" or 4". The Ram will probably fit with a stock SB hood but I was worried that in order to get a good flow of air the throttle body/filter element would extend to far forward and interfere with the hood opening (plus, I like the L-88 hood anyway). I know of at least one person on this forum who installed the TPI and modified his radiator support to grab air from the front grills. Unfortantely, this interferes with the hood and won't open all the way (maybe just a minor inconvenience).
I'm still pretty new to this conversion. I'll try and relay my expereiences as they come, but there are many people in here with more extensive experience. They were a big help for me and I'm sure will be happy to lend their expertise :smash:
BTW - My other toy is a '71 K5 Blazer - "Trucks!" Rocks!!!

 

jdunne - can't tell which Shark you have but my Holley Pro-Jection CPU lives behind the pass seat in the storage comparment on my 81. Wire harness plenty long enough to reach.

YOU DON'T WANT IT OUTSIDE PASS COMPARTMENT--NOT WEATHER/HEAT SEALED.

 

Don't think the Stealth Ram fits under the stock hood, the tb sits further forward right where the hoods arches down, don't think it fits under any C3 hood just because of where the tb is but could be wrong.

 

The throttle body should be in the exact same location as the L98 TPI, it is the lingenfelter designed upgrade for the chevy TPI and you can buy just the runner/plenum that is a direct replacement. It should fit just fine under a slock hood unless it is too wide. I am thinking about the stealth ram for mine and it is almost a full inch lower than the stock setup on my vette.

 

I measured 10-3/4" from the base of the manifold to the center of the stock '81 air cleaner. Don't quote me, but I believe on the Holley website says the Stealth is also 10-3/4". The only problem is that our hoods slope, and the stock manifold has this slope built it. I don't know if the Holley Stealth slopes toward the front. Now with all that said you could have the Holley Stealth shortened to fit if you wanted to stay with the stock hood. I believe grumpyvette over at the ChevyTalk.com website was modifying them at one time. I may even have a website with pictures and info.

Mark



[Modified by 81vette, 9:40 PM 8/28/2003]

 

I put a RamJet 350 in my 68. As far as the fuel system; I ended up using a 1990 Ford Bronco fuel pump since it comes with it's own reservoir system and the fuel return line dumps into this reservoir....so far no starvation; and I ran it so low that I ran out of fuel in the driveway(lucky). Since the fuel lines of the Bronco fuel pump come out the top I used the former supply line as the return path and then I ran a braided steel hose all the way to the front as the new supply, placed the fuel filter in the engine compartment, and plumbed it together. The reason I used a Bronco fuel pump is because I also own a Bronco and had helped a friend replace his(so I knew what it was like). I had to slightly enlarge the already big hole in the gas tank and drop it in. I did this all with the tank in the car. Works like a dream so far...didn't really want to deal with sumps so I thought I'd try this since I already had the "emergency" pump for my Bronco.
I used to have a Holley Pro-jection with an external fuel pump and it would stumble when going around corners if the tank was about 1/8 full or less.

 

Same positon but sits higher, know this because the stock tpi fits under a stock c4 hood but the Stealth Ram does not, go over to the c4 board and ask. Grumpyvette is selling shaved Stealth Ram intakes to fit under the c4 hood.


[Modified by Fevre, 8:46 AM 8/29/2003]

 

Well here in CA. you can't use an aftermarket EFI setup that is adjustable. No smog station will pass it for emission purposes. Even if it's cleaner.

I'm looking into a TPI '92 vintage to install this winter. I'm tired of the electronic carburator hassels every other year. I know it will give me better response and driveablility plus keep me "smog legal".

I will be documenting this project and will post findings and pictures as I go. Plan to start around December or January.

 

weendoggy youll be happier in the end,that tpi will work mucb etter then that electronic carb.

 

I'll throw in my $.02. I have a SuperRam TPI system from Accel stuffed under the hood of my 82'. I had to cut out the cold air duct from the hood to get it to fit, but it works nicely. I'm using 36# injectors, Accel Dual Sync distributor (sequential injection), Accel 300+ ignition box, and an Accel coil. The Accel computer is in the glove box and is programed using Calmap. Ultimately I've been pretty happy with the system. In the two trips I made to the track I manged a 13.03 1/4 on street tires with quite a bit of spin. I took it to get it dynoed and the guy at the shop managed to pick up 20 HP and 80 ft. lb. of torque bringing the car to 290 HP and 390 ft. lb. of torque at the rear wheels. Never made it back to the track. The car is torn apart now after a wreck, but I plan on running mid 12's when I get it back together. 20+ mpg on the highway and it cranked everytime I turned the key. Expensive but worth it IMO.

 

carrilijc - what hood did you use to clear that Ramjet? I've been looking at that setup. Too bad they dont sell it without the motor.
At least they could have installed it on a ZZ4.
:lurk:

 

I already had an L88 hood from when I had installed a Performer RPM with the Holley Pro-jection. It fit under that. Right now I'm trying to figure out a way to use the cowl induction to feed the intake. If you wish I can send you a picture of how it fits underneath.....I don't know how to attach a pic here.

 

Cool - send me the pic and I will post it for you
jetspecialist@hotmail.com

 

You can buy the ram jet system from Summit for about $2800

 

Hmmm, does the Ramjet fit under a stock 68 - 72 small block hood?

Thanks...

Doug