351w Efi Intake In A 67-68

brianj5600 · Jun 21, 2013

Anyone know what will fit under a stock hood? I don't want to rev it much over 6000 rpm. I am looking at a RPM2 or trick flow.

65ShelbyClone · Jun 22, 2013

I'd like to know too. A 351W might be in my future and I really don't want to go back to a carb after I put EFI on my 302. That, and I prefer the long runners and big plenum for a street engine.

Are you set on a long-runner intake like the ones you mentioned, or would a carb-style be in the cards?

brianj5600 · Jun 22, 2013

I have not seen any carb style intakes for below 6500. Even the Vic jr is out of my rpm range. I have been running a TorkerII and making good power but I am pretty sure it doesn't flow enough to feed my AFR185s. I would like something that would be efficient. I plan on running e85 and would like to get decent fuel mileage.

clement · Jun 23, 2013

the vic jr out of the box is very small. so if you are concerned about lack of low end on a Windsor with an unported vic jr, don't be. ill be fine unless you have a pretty large cam in it.

brianj5600 · Jun 23, 2013

The Vic jr is designed to operate between 3500-7500 while flowing wet. Removing fuel will raise it almost 10% from what I have read. My converter will only flash to 3200 now with a TorkerII and it needs to be tighter. I would like an intake that is designed for what I want it to do. I drive my car a lot and many trips over 100 miles round trip. I don't believe a Vic jr is a good fit for a motor that never sees more than 6200 and spends more than 99% of the time under 300 rpm. I can turn up boost to make about any horse power I want, but I need enough torque to get it making boost.

clement · Jun 23, 2013

with a small cam a 2.1" min cross sectional area (which is what both the 302 and 351 vic jr measure at the head) will reach target port velocity for peak hp at 5400 rpm on a 44 ci cylinder. the larger the cam or the larger the cross section the higher you raise that rpm. it will hold way past peak to around 7k because of its design. boost will elevate the airspeed, which will cause the powerband to shift lower. I had a 302 xcellerator and it averaged about 1.88 min cross section. so the 302 xcellerator and 351 with the vic jr will have similar powerbands.

brianj5600 · Jun 23, 2013

How do you know? What effect will runner length have on rpm range? Are you saying i will not lose any bottom end with a Vic jr? I am way more worried below 3000 than over 3000. Boost increasing airspeed will not help in the 99% of the time running under vacuum.

clement · Jun 23, 2013

with a Windsor it will have more driveability than the 302, even when not under boost. I just told you the minimum cross section of the intakes. the powerband of the vic jr on the Windsor is going to act like the 302 with the xcellerator because the relationship of cross section to cylinder displacement remains constant. not to mention that you are going to have an extra 1/2" of stroke over the 302. if we were talking about a super victor, than yes it would be softer on the bottom. but you are not going to notice a difference with the jr, especially if its cammed correctly.

runner length doesn't effect peak hp rpm, runner length effects how far it holds on after peak. in this case you wont notice a difference and its not like you are running an 18" runner.

65ShelbyClone · Jun 24, 2013

An 18" runner or longer would be more inline with what's being asked of the engine. However, now we have several conflicting goals. Do you want something that fits under the hood, something that makes power, or something with a slab of off-idle torque? "Decent" economy with E85 going a through a boosted engine built for pump gas just isn't going to happen IMO.

I mean, the impression I'm getting is that even a stock Lightning intake would be suitable.

clement said:
Have you done it? I have.....

clement said:
ask me how I know

brianj5600 said:
How do you know?

clement said:
I have done what you are doing.

Why not use "because I said so" as an argument instead?

clement said:
boost will elevate the airspeed, which will cause the powerband to shift lower.

Airspeed where?

What effect will runner length have on rpm range?

Long runners are more conducive to making torque at lower RPMs. Ideally port tuned length would be chosen in order to bolster a desired area of the curve while sacrificing a less important part.

clement said:
runner length doesn't effect peak hp rpm, runner length effects how far it holds on after peak.

That's going to depend at least partly on the target harmonics...

brianj5600 · Jun 24, 2013

I don't need off idle torque. I want it to work between 2500-6000. That is cruise rpm and shift point. I know I will take a hit in milage. I don't think I have conflicting goals at all. I realize i could go up some in compression. It has 9.2 compression ratio now. It already makes over 650rwhp with the converter slipping 17%. E85 will let me up timing and boost about 5 each from that level. I am not worried about making power.

clement · Jun 24, 2013

65ShelbyClone said:
An 18" runner or longer would be more inline with what's being asked of the engine. However, now we have several conflicting goals. Do you want something that fits under the hood, something that makes power, or something with a slab of off-idle torque? "Decent" economy with E85 going a through a boosted engine built for pump gas just isn't going to happen IMO.

I mean, the impression I'm getting is that even a stock Lightning intake would be suitable.

a gt40 will go into port stall.

Airspeed where?

everywhere. it advances the whole curve.

Long runners are more conducive to making torque at lower RPMs. Ideally port tuned length would be chosen in order to bolster a desired area of the curve while sacrificing a less important part.

with a 3.5" stroke itll be more than fine with an ootb vic jr. the problem with runner length under boost is that the longer runners create more friction. friction creates turbulence and you get enough turbulence you get port stall.

That's going to depend at least partly on the target harmonics...

min cross section over a given cylinder diameter and piston speed, coupled with your cam lobe area creates target port velocity for your hp peak. the longer the runner it is true that it makes more under peak. but it also will drop off quickly after peak. that is because of the port stall mentioned above. the short runner intake will keep pulling until the port goes sonic. back in '98 I did a turbo technology kit on my 93. it already had gt40 heads and intake. at 12lbs of boost it made peak hp at 5200 and power dropped off a cliff immediately after that. I put a efi vic jr 302 on it, the peak hp still happened at 5200 but it dragged power all the way to the 6200 rpm limiter. and it still made 500lbs of tq at 2700 where the turbo spooled up. not under boost it still drove around like a stock motor even with a short runner. when you start adding boost to stuff it doesn't act like the packages the head, intake and cam manufactures advertise for all motor.

brianj5600 · Jun 24, 2013

This is what has me thinking an RPM2 is a good choice. http://www.dragzine.com/features/in...zy-story-behind-4000-miles-in-an-8-sec-stang/ He tried a Victor 5.0 and it hurt bottom end enough he would have restall the converter. He said it would probably go faster, but he didn't want to up drivability.

clement · Jun 24, 2013

he is running 2 61mm turbos, which is a lot of compressor for a 3.4" stroke. with a 3.25 gear. exactly what is your combination and goals? because I was running a t64 and making well over 500rwhp and running 10.60s@131 mph and the short runner didn't hurt a thing. are you building an 8 second car? because you are going to need more than an AFR 185 to get there.

we have been working with my buddies big bore dart 347 with a nice set of 240cc high ports. it wouldn't spool up with the 104mm, so we have been running a 88mm to get it to spool. we are running an efi super victor on top of it. it maxes out our dynojet at 1200hp and runs 5.0s at over 140 mph in the 1/8 mile in x275 trim.

brianj5600 · Jun 24, 2013

Who owns the car? I know some people in DFW. I grew up there and moved back 2 summers ago for 7 months.

I am not trying to go 8s, but several people have gone 8s with 185s on the turbo forums. I am shooting for 9.20-9.30. I have made some suspension changes that should be good for .3 or more in the quarter. It has been 6.38@110 and 9.99@135 on 14psi and a 1.48 60' on E47.5.

clement · Jun 24, 2013

ok, I thought we were talking about a less serious combo. id put a super victor on it since you are going to push it hard. if you want an efi intake put a TFS R on it, its got runner length and cross section. I don't think the rpm 2 will run as well, especially with the longer stroke. out of curiousity, how much cam are the guys using that are running 8s with AFR 185s?

blown65 · Jun 24, 2013

Those AFR 185's should run low 9's. My ported victor Jr's are a little better than them and I've ran 9.10@152 and there is more left in it. Thats supercharged, not turbo so you should have an adv with the turbo for power right off the get go.

Right cam and what not should run much faster I'd think.

brianj5600 · Jun 25, 2013

clement said:
ok, I thought we were talking about a less serious combo.

It isn't serious other than the turbo and drivetrain.

clement · Jun 25, 2013

14lbs on a little set of heads running 9s is pretty serious. from what im told, the min cross section of that head is 2.1".

brianj5600 · Jun 25, 2013

It ran 8.50s before the turbo, which is a low 13. It hardly has any chop at idle even in gear at 600rpm.

brianj5600 · Jun 29, 2013

I found a TFS-R used locally i am buying. We will see if it fits.

351w Efi Intake In A 67-68

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