C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

fuel pump and injector question with modified engine.

Old Jan 14, 2013 | 04:32 PM
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Default fuel pump and injector question with modified engine.

Back in fall I did a head cam and super ram on my 86. Got the car running. Runs better than I expected with the stock chip. I called a dyno tuner in my area to ask if they did tuning on older obd 1 cars and if they could burn a new chip. The guy said yes said I would be looking at around 550 bucks. I told him what I did to the car 180 afr heads mild flat tappet cam and the intake. He started to tell me that I will probly need to change the fuel pump and the fuel injectors. My guess is with what I did I added 100 to 125 more hp wouldent 24 pound injectors and the stock fuel pump be just fine? If so should I not evin waste my time with this shop and just get a mail order tune? Whad do you guys recomend I do? Thanks
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Old Jan 14, 2013 | 05:03 PM
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I ran a Super Ram with mild flat tappet cam and AFR 195 heads with 24# injectors and a stock pump. Did you do anything with the exhaust? If not, you might not need a new tune.
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Old Jan 14, 2013 | 05:09 PM
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Originally Posted by red86silver78
Back in fall I did a head cam and super ram on my 86. Got the car running. Runs better than I expected with the stock chip. I called a dyno tuner in my area to ask if they did tuning on older obd 1 cars and if they could burn a new chip. The guy said yes said I would be looking at around 550 bucks. I told him what I did to the car 180 afr heads mild flat tappet cam and the intake. He started to tell me that I will probly need to change the fuel pump and the fuel injectors. My guess is with what I did I added 100 to 125 more hp wouldent 24 pound injectors and the stock fuel pump be just fine? If so should I not evin waste my time with this shop and just get a mail order tune? Whad do you guys recomend I do? Thanks
He may be correct, my 1986 ran out of fuel pump at 270 RWHP and I switched to 24lb injectors when I hit 300 plus because I was out of injector.
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Old Jan 14, 2013 | 05:54 PM
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Just heads and Super Ram are not going to get that engine to 300 RWHP. Add headers and it gets closer. We need to know the rest of the build. Even if his mods added 100HP, the 24# injectors with tuning will suffice.
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Old Jan 14, 2013 | 06:12 PM
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I do also have long tube headers. I guess technically my injectors are not stock. I have 24# injectors I replaced years ago I think the stock ones were 22#. I just never remember hearing on the forum any one saying bigger injectors or a bigger fuel pump are needed for what I have done to the engine. I do think it needs a chip made to help it run better. I no longer have the cold start injector on the car. The car wont idle all that great until it's fully warmed up. Once warmed up it's not too bad. When cold if you stab the throttle it will some times die. I am just wondering every ones thoughts on here.
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Old Jan 14, 2013 | 07:22 PM
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I would contact PCM4Less about a tune. See what they think about the injectors. My guess is they're OK. The headers really do make a difference. I ran my setup with stock manifolds and with headers and there is no comparison. You're probably running lean.
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Old Jan 14, 2013 | 08:10 PM
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I agree , you should get a tune done. When I had my 383 built a few years ago I talked to Jon at FIC about injectors and he said with 370 hp I would need 24 lb injectors, if anyone would know about injectors, it would be Jon Banner at FIC....The guy that did my tuning said with this hp I should step up to a higher output fuel pump, I went with the Walbro 255 fuel pump kit.. If you have the original fuel pump in your car its probably a good idea to change it out anyway..WW
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Old Jan 14, 2013 | 08:19 PM
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Your stock pump should be good up to about 400 HP. The injectors should not be a problem either, especially if you went from 22 to 24 lb.

Go for the tune.

Your set up is similar to mine and my tune is great without a problem.
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Old Jan 14, 2013 | 08:35 PM
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Originally Posted by bjankuski
He may be correct, my 1986 ran out of fuel pump at 270 RWHP and I switched to 24lb injectors when I hit 300 plus because I was out of injector.
My 87, stock pump did not keep up with a ZZ4/180 motor. Watching a FP gauge and the wide band while on a dyno showed it.
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Old Jan 14, 2013 | 11:39 PM
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Thanks for the help guys. The fuel pump in the car is about 3 years old. Due to the old one crapping out on the side of the road. I was able to change it out on the side of the road just had to call a friend to bring me some tools and a trip to the parts store. Anyway I think I will just call pcm for less. I am just not sure if I trust this shop. They are located in a town about 45 min away from ware I live. I grew up in the town they are located and just recently heard about this place. So I know they have not been around too long. I know that doesn't mean they don't know what they are doing either. They do have a nice web site with examples of cars they have done but they are all either newer modern computer controlled cars or cars with carbs. I was just suprised how the guy I talked to almost insisted the fuel pump and injectors needed up grading. He actually asked me to if my car a 86 had the tuned port engine. I said yes a l98. So just that makes me think he has no experience with these older computer controlled cars. My gut feeling is I would be better off calling pcm for less.

Last edited by red86silver78; Jan 15, 2013 at 12:03 AM.
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Old Jan 15, 2013 | 04:36 AM
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After i did all my mods the engine wouldnt rev past 4500, I could feel the knock sensor activating so i knew it was leaning out,
the last mod i did was a 255 LPH fuel pump, and guess what, 5500 rpm !
this was with the Fastchip already in.
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Old Jan 15, 2013 | 06:31 PM
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Well I talked with a guy from pcmforless today. Told him pretty much everything that has boon done to the engine. He said I should be fine with the stock pump and 24# injectors. Like I said I have driven the car since doing everything. I can't believe how hard the car continues to go above 4500 rpm. I have taken it up to just under 6000 rpm and it pully hard the whole way. I am just thinking I will data log it and have pcmfor less burn a new chip.
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