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Discussion Starter · #1 ·
I recently started a new project.
1968 mustang. I have a 8.8 rear axle with 3.73 gears, TKO 600 5spd, and a 1995 lightning motor (roller cam 351 with GT40 heads, crane 1.7 roller rockers)
My question is about both cam and intake manifold. I have two intakes a Victor Jr. and a Performer RPM, I also have two cams a F303 and a E303.
This will be carbureted, I have a 650 mechanical secondary Holley. Which intake and which cam do we think would be best, I'm totally open to buying a new cam but just really want whatever cam I go with to work with my steel distributor gear I already have setup on the distributor. Thanks in advance for everyone that replies!
 

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I recently started a new project.
1968 mustang. I have a 8.8 rear axle with 3.73 gears, TKO 600 5spd, and a 1995 lightning motor (roller cam 351 with GT40 heads, crane 1.7 roller rockers)
My question is about both cam and intake manifold. I have two intakes a Victor Jr. and a Performer RPM, I also have two cams a F303 and a E303.
This will be carbureted, I have a 650 mechanical secondary Holley. Which intake and which cam do we think would be best, I'm totally open to buying a new cam but just really want whatever cam I go with to work with my steel distributor gear I already have setup on the distributor. Thanks in advance for everyone that replies!
I would spend money on better heads. Your limited to 300-320 hp with gt40 heads.
 

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Discussion Starter · #3 ·
I would spend money on better heads. Your limited to 300-320 hp with gt40 heads.
I appreciate your opinion on the heads and I agree with you, but my question is about the cam and intake choices on this particular engine. I actually have another motor I'm currently building with better everything, this is just a temporary motor while I wait for parts to come back in stock for my higher end build.
 

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then it doesn't matter what cam you use if its temporary. ive installed an e303 into a stock 5.8 roller with nothing but valve springs. It sounded good but performance wise was about equal to stock. i used a duel plane manifold. i think it was a weiland
 

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Discussion Starter · #5 ·
then it doesn't matter what cam you use if its temporary. ive installed an e303 into a stock 5.8 roller with nothing but valve springs. It sounded good but performance wise was about equal to stock. i used a duel plane manifold. i think it was a weiland
It matters to me! Due to the time it is taking to get certain parts I might have this motor in the car longer than I really want. (some of my parts I have been waiting on for 6 months)
I'm just trying to get feedback on what others have seen with this combo of parts, and if anybody has experience with a similar combo.
Which it sounds like you do. And thank you for sharing that insight with me.
 

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No one can give you an answer Bubba, as you never gave a goal or how the car will be used.
 

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Discussion Starter · #7 ·
No one can give you an answer Bubba, as you never gave a goal or how the car will be used.
Very true, That is some well needed information. (My Fault)
It will be used for Auto Cross mainly with limited street driving.
I'm not at all worried about street manners or daily drivability!
The car will be ran up and down through the RPM rang from corner to corner, basically drag racing from apex to apex.
I have a good deal of experience with smaller 302 based engines and combos, not as much with the larger displacement 351.
 

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You're going to see greater RPM variances in autocross as opposed to drag racing. The Performer RPM will give you a better torque curve that you can use throughout the RPM range as you take sharp turns and decelerate. It is a dual plane intake. The thing with the Victor Jr. is that its useable RPM range is something like 3500-8000 rpm. Your 5.8 GT40 headed motor will only use like 2000rpm worth of intake. Victor Jr. is a single plane intake. On the other hand, the Performer RPM's operating range is 1500-6500, a much more useable intake for your combination. As far as camshafts both will give you what you're looking for. They're older cams that have "antiquated" valve events. Since you're building a hotter motor already, I'd just pick your poison and run with whatever cam is in best shape.
 

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65 fastback pump gas .060 289 (297) solid roller, T5 all motor. 11.12 122 mph
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Rear gear and tire height? The advertised RPM range for the intake manifolds is a joke.
 

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Rear gear and tire height? The advertised RPM range for the intake manifolds is a joke.
How so? Curious because I genuinely don't know. Maybe the manufacturer want to cover a broad range of builds so they could shill out more intakes? How far off are they in real world applications?
 

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You will probably run the entire autocross course in second gear, probably 3.55 rear gears will keep the engine in the powerband throughout. You're aiming for the greatest area under the curve, from recovery on tight corners, to trying to not having to shift on the longest straights on the course. Shifting on an autocross course is equal to slow lap times.

The dual plane manifold will give you more area under the power curve for the engine speeds that will be used on the average course. I would guess that the alphabet cams were originally designed for 5.0 liter engines so they would be relatively mild for a 351. I'd go with the larger of the two cams, more duration would be a plus for feeding a larger engine with restrictive heads. Timing events will not be ideal for the shorter runners of the carb intakes, again, I'm thinking they were originally designed for long runner EFI intakes.

Jay
 

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65 fastback pump gas .060 289 (297) solid roller, T5 all motor. 11.12 122 mph
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How so? Curious because I genuinely don't know. Maybe the manufacturer want to cover a broad range of builds so they could shill out more intakes? How far off are they in real world applications?
Those rpm ranges advertised were before good heads, overdrive transmissions, and modern cam design. not to mention modern fuel injection. 👍

If you look back in the day single intakes won the old engine masters competition with average power under 6,500 rpm.
I tend to nerd out on this stuff and am pretty picky how I spend my money on the fastback. It worked out and never looked back and moving forward with something a little more radical.

The ‘64 falcon convertible will be a cruiser. The Wieand Stealth dual plane will be happy on that beach cruiser.
 

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65 fastback pump gas .060 289 (297) solid roller, T5 all motor. 11.12 122 mph
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That’s the friendly version. Low end torque and going fast discussion… biting my tongue. Lol
 

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That’s the friendly version. Low end torque and going fast discussion… biting my tongue. Lol
I have a track day '95 with a well built 363 Dart block, AFR heads, FTI cam, Pro-M engine management, TFS EFI single plane intake (similar to Super Victor). It's soggy on the bottom end compared to the previous Holley SM2 configuration, but has an awesome mid/top end. It doesn't really pull hard until well past 3K. I have to shift it to keep the engine speed up, on a road course this isn't a lap time killer like it would be on an autocross course. I can only assume that you're not suggesting that intake runner length isn't an important consideration relating to an engine power band. If so, don't bite your poor tongue, that hurts, let it all hang out.

Jay
 

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65 fastback pump gas .060 289 (297) solid roller, T5 all motor. 11.12 122 mph
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Runner length is very important! If you’re racing in any form below 3,000rpm you are doing it wrong. Even in truck pulling. Just me.
 

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I'm currently working on a second '95 that will be used for street cruising/autocross, it's going to be wearing aforementioned SM2. The very wide powerband necessitated by autocross racing is a given, sounds like something you've not done. To be honest neither have I, but something I'm really interested in, have studied quite a bit, and intend on participating in shortly.

Jay
 

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65 fastback pump gas .060 289 (297) solid roller, T5 all motor. 11.12 122 mph
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So absolutely no higher rpm combos race auto cross? One engine makes peak hp at 7000 rpm and the other 6,000 rpm. You will not gear each the same. They will shift at the SAME mph just operate at a different rpm. Now think about what the difference in rear gear does to toque at the tire which is what counts. Vintage racing is not full of 6,000 rpm combos in spite of twisty tracks. They operate well above that and gear accordingly. One of those high dollar builds could tear up an autocross track in spite of the small displacement.

A broad power band does not have to include 3,000 rpm and below.
 

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65 fastback pump gas .060 289 (297) solid roller, T5 all motor. 11.12 122 mph
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my tongue feels much better now. Lol
 

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So absolutely no higher rpm combos race auto cross? One engine makes peak hp at 7000 rpm and the other 6,000 rpm. You will not gear each the same. They will shift at the SAME mph just operate at a different rpm. Now think about what the difference in rear gear does to toque at the tire which is what counts. Vintage racing is not full of 6,000 rpm combos in spite of twisty tracks. They operate well above that and gear accordingly. One of those high dollar builds could tear up an autocross track in spite of the small displacement.

A broad power band does not have to include 3,000 rpm and below.
It's pointless for yourself and myself to argue about a discipline neither has competed in. I'm going to trust the high level competitors whom regularly post in the road race/autocross threads on this site.

If you scale a power band between 2500 RPM to 6500 RPM, that equates to 3500 to 9100 RPM, even if you make enough torque at 3K to accelerate well out of a tight 180, that scales to a top end of 7800 RPM. I would suggest that is unreasonable for the average competitor, serious valvetrain componentry, and high maintenance. But I'm glad you got your opinion out there, not good to stifle one's very own self! (y)

Jay
 

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Discussion Starter · #20 ·
Just to let you know I have won 3 SCCA season championships in SOLO 2 (Autocross) So I have a pretty good idea of what works and what does not.
This motor that I asked about is only a place holder as I accumulate the rest of the parts for my long term engine.
All of my experience has been with 302-306 ci engines, so I was just seeing if anyone had more experience than I do when it comes to a 351w mild combo.
My gut feeling is the Performer RPM, intake with the E303 cam, however if someone here has tried that combo and had feed back it would be great.
And yes, if a car is set up properly you will run most tracks in a single gear, depending on engine operating range and transmission it is normally between a 3.25 and 3.75 ratio.
 
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