1970 351C Dyno Numbers (you should all be interested in this)

The vacuum in your motor is going to drop from say 12" to 1 or 2" when you open the throttle blades.Since the power valve opens when the vacuum is less than what it is rated,your motor sees 8.5" before it will see 3.5" when the vacuum drops off so the 8.5" power valve opens sooner.Think of it this way, you have two coil springs with the same amount of weight on them so both are fully compressed.You start removing weights until one starts to rise.The one that rises first is the stronger one, not the lighter one.Vacuum doesn't open the power valve, the spring opens the power valve.Vacuum is trying to compress the spring just like the weights do.So a stronger spring means it will rise earlier as the amout of vacuum is reduced.
 
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351LX said:
The vacuum in your motor is going to drop from say 12" to 1 or 2" when you open the throttle blades.Since the power valve opens when the vacuum is less than what it is rated,your motor sees 8.5" before it will see 3.5" when the vacuum drops off so the 8.5" power valve opens sooner.Think of it this way, you have two coil springs with the same amount of weight on them so both are fully compressed.You start removing weights until one starts to rise.The one that rises first is the stronger one, not the lighter one.Vacuum doesn't open the power valve, the spring opens the power valve.Vacuum is trying to compress the spring just like the weights do.So a stronger spring means it will rise earlier as the amout of vacuum is reduced.
Hehe thanks dude. Most people do think of the power valve backwards. I do the PV the same way 351lx does it. That is the most accurate way. There are just way to many variables at idle that can cause vacuum to be different at idle.
 
New Jets In Place ! ! Huge difference

I put in the 72's in place of the 69's on the primary and 75's in place of 68's in the secondary. This was recommened to me by the dyno tuner from last week.

Holy sh@#$#@$. This car is wicked fast now. It feels like 25 to 35 more horses on the ground. The dyno should read about 260 now. And that is with the king of power robbers (An FMX).

Anyway I will post my new dyno numbers after this Saturday's run. Till then, keep up the posts yall.

70Mach1...Ryno...
 
Are you doing the Round up this year? I did it last year and it was sweet. Send a pic of your ride if you can. Here is mine with Craig tuning it. See attachment.
 
Well,

1st off those heads are going to need a bigger cam, if you want low end power get the 2v heads, you need to match the set up better. Along side with the cam you'll need a bigger carb, at leats a 750, but i hear that 4v 351c owners say they run better with even bigger carbs than that. Also you need a 2 1/2- 3" exaust system. If you carb is new get the other things first, then carb last, you dont want the fuel to puddle in and make the motor rich cause the exaust cant dump it all out.

Those 4v heads ARE HUGE, they need a big cam, try 280's- 300's adv. dur. depending how high you want it.
 
351LX - That stands to reason with the smaller carbs. Unless it's a magic engine, basic carburetor theory applies. If one does the calculations on a 351 street engine, you probably won't need more than 600 CFM. With a 650 CFM vacuum secondary carb, you'll never see 650 CFM.

As far as the exhaust is concerned, unless you're making 500 HP, a 2.5" exhaust is just what the doctor ordered.

Ryno, as we've discussed, you're choking point now is the out-of-date manifold. I ran in to the same problem on my old Ventura and an obsolete P4B manifold. It just would not let the engine breathe. By moving up to a Torker II, the beast was released. :nice:

When I get in to the swap meet early, I'll find the one that you want and make you a great deal on it. :D
 
I was going to build a 351c 2v but after speaking to some people I decided on a 4v, Someone told me if your going to build a Cleveland you minds well use the heads that made the Cleveland a legend. I heard low ends not that bad if you run a high stall and big gears. Im planning on a all out street/strip/weekend cruiser 70' 351c 4v, solid cam, adjustable valve train/450ish HP, 3:90 outback, built c4 with 3k stall. Should run a pretty good quarter mile time. On the other hand the one kid here with a 1973 mach 1 with a 351c 2v ran some pretty impressive times.

Jim
 
Thanks for asking cfauvel. The latest numbers were 245 hp @ 4800 and 310 lb ft @ 3600. This is only 10 Hp peak higher than before the re-jet but it was 10 hp almost everywhere in the curve. And from 4800 to 5100 I had gains as high as 25 at the wheels.

The 10 Hp I gained from 1500 to 3500 is huge becuase as a percentage of total Hp is it bigger than at the peak. At 2500 I am making 155 vs 145 for example instead of 245 vs 235. So as a percentage the power is higher.

So now the limiting factor is my intake. I have an old F-351 Edelbrock. They are obsolete and only flow air to 5,000 rpm where my engine wants to make poewr up to 6000 theoretically. So my tuner says there is still alot more there. Probably another 15 to 35 Hp if RPM can be raised. I will do that next year unless I come across a steal on a nice intake.

I am going to try to replace my 4-hole 1 inch spacer below my carburator with a open 1 inch spacer. This should allow the engine to flow more air / fuel on the top end. And it is easy and cheap to do. But other than that, I will wait till next winter. 245 at the wheels seems really fast now compared to 202 when I started.

Any opinions on good intakes? 351-4v? Or open vs 4-hole spacers? Please post
 
Thanks for the update on latest numbers

I can't really help you with 351c, since I haven't reasearched them, cuz I don't have one.

I believe the 351c is better in the higher RPM range, which from what I read, you would want to go with a single plane intake.

From what I understand the single planes produce more HP in the higher rpm range than lower and the dual planes do the opposite.

Me, being the PU$$y that I am and nearly 40 years old, have stopped high speeds over 80mph in any of my cars.

I am more interested in 0-60 get up and go....so I want my peak HP and torque at lower RPMs.

I've heard conflicting things about the open bore spacer compared to 4 bore spacer...some say the 4 bore directs the air/fuel mixture better down the runners, but that doesn't make sense to me since right below the space in the intake is just one big open chamber (or two big open chamber for dual planes)....so I'd say go with the open bore spacer.

Please keep us abreast of the progress. Your posts are very detailed along with other people's replies and are very helpful.

Chris
 
a torker would probably be the best all around intake for you or the Weiand X-Celerator

the 4 hole helps the carb get a better signal when you run alot of overlap in the cam.. good for TQ, the 4 hole will increase the plenum area and give you more top end..

if that F-351 is a dual plane, you might try milling down the center divider some... it'll give it more top end..

cfauvel, I'm older than you and I'm aiming for 150MPH in the 1/4 mile.. heheh
 
maybe this will help with the head discussion, http://users.erols.com/srweiss/tablehdc.htm

At .400 lift, the 4V heads flow 220/146cfm, 2V heads 203/145, and Aussie heads 178/130. At .500 lift, the big 4V's flow a whopping 256/159 cfm, no data for the 2V, and Aussie heads bring in 187/153. At .600 lift, the 4V's flow 269/165, 2V's flow 230/172, and no data for the Aussies. As far as average numbers go, the 4V does 224/142, 2V does 216/158, and the disappointing aussies muster 138/103. For comparisons sake, a late model E7TE 302 head averages 115/84 cfm. PowerHeads ported 2V aussies move 182/144 on avg.
 
HUGE News about the 351C, Dyno info coming soon.

Dudes !
Bottom line:

I removed the MPG port plates and Edelbrock intake and replaced with a Blue Thunder intake.
MASSIVE power change. Probably 75 Hp on the ground. No sheeeet. I will get dyno data soon.


A little history:
Remember back when this thread was started in 2004? Well, the car has not changed a bit except for a T-5 in place of the FMX. Power wise the car did not seem different in 4th gear (T5) versus 3rd gear in the FMX. I say this because both are 1:1. I also changed to a 3.89 gear from the 3.00.

Regardless………

MASSIVE news.
I finally bought one of those Blue Thunder Intake Manifolds that are now being reproduced (www.mustangsunlimited.com). When I took the old Edelbrock off and compared it to the Blue thunder and the stock steel one, it was a huge difference dimensionally. The dyno guy thought my intake was limiting the poiwer above 4500. Sure enough I think he was right. The thing absolutely screams now. And it pulls past 6000 now. Before it seemed to run out at 4800 which is what the dyno said too.

Can’t wait to post the new numbers.

Bottomline, buy a Blue Thunder !
:lol:
 
Dudes !
Bottom line:

I removed the MPG port plates and Edelbrock intake and replaced with a Blue Thunder intake.
MASSIVE power change. Probably 75 Hp on the ground. No sheeeet. I will get dyno data soon.


A little history:
Remember back when this thread was started in 2004? Well, the car has not changed a bit except for a T-5 in place of the FMX. Power wise the car did not seem different in 4th gear (T5) versus 3rd gear in the FMX. I say this because both are 1:1. I also changed to a 3.89 gear from the 3.00.

Regardless………

MASSIVE news.
I finally bought one of those Blue Thunder Intake Manifolds that are now being reproduced (www.mustangsunlimited.com). When I took the old Edelbrock off and compared it to the Blue thunder and the stock steel one, it was a huge difference dimensionally. The dyno guy thought my intake was limiting the poiwer above 4500. Sure enough I think he was right. The thing absolutely screams now. And it pulls past 6000 now. Before it seemed to run out at 4800 which is what the dyno said too.

Can’t wait to post the new numbers.

Bottomline, buy a Blue Thunder !
:lol:

I just bought a Blue Thunder as well and am in the process of getting it installed along with a lot of other upgrades.
I also have the old Performer with a 670 Avenger and a mild cam. The best thing that I did for that combo was to put a 1" spacer and a 700dp.
My car also has Hooker long tubes with a 2.5" exhaust and an X-pipe. I also have a Tremec TKO so I can't wait to get it on a dyno when all is said and done to see what it does.
Great thread!!!
 
Pushrod power, will spacer fit with Blue Thunder Intake?

The BT intake is about 3/4 of an inch taller than the edelbrock. I had to take my 1" spacer off. Can you get the spacer to fit on the BT intake and get your hood shut? If so, you have have any cut outs in the hood?

DUDE, your car set up sounds really close to mine. I agree on the 750 DP carb. The secondaries I have are vacuum and they are OK, but I think the Machanicals would "hit" harder off the line.

Do you have any DYNO sheets??

Also, I thought the TKO was too tight to fit in the 70? I have a World Class T-5. I am worried it might blow up if I get over 300hp on the ground and would like a TKO.

Also, what is your rev limiter set at? With the new intake I raised it from 5500 to 6000 conservitively. My comp cam says it makes power to 6250RPM but the old intake wouldn't go past 5000 so 5500 was generous. But now with the BT, sheeeeeeeeeett, I hit it so fast I decided to up it to 6000 .
 
The BT intake is about 3/4 of an inch taller than the edelbrock. I had to take my 1" spacer off. Can you get the spacer to fit on the BT intake and get your hood shut? If so, you have have any cut outs in the hood?

DUDE, your car set up sounds really close to mine. I agree on the 750 DP carb. The secondaries I have are vacuum and they are OK, but I think the Machanicals would "hit" harder off the line.

Do you have any DYNO sheets??

Also, I thought the TKO was too tight to fit in the 70? I have a World Class T-5. I am worried it might blow up if I get over 300hp on the ground and would like a TKO.

Also, what is your rev limiter set at? With the new intake I raised it from 5500 to 6000 conservitively. My comp cam says it makes power to 6250RPM but the old intake wouldn't go past 5000 so 5500 was generous. But now with the BT, sheeeeeeeeeett, I hit it so fast I decided to up it to 6000 .


I'm not using the spacer with the BT because of the additional height.

I switched to the 700dp because the 670 couldn't pull enought vaccuum to open the secondaries even with the white spring. The change was night and day.

My car is a '73 and the TKO bolted right in with no problems at all.

The only rev limiter I had currently is my right foot. Seriously the car isn't quite done yet so I haven't had a chance to run it with the BT. I haven't dynoed it yet but I plan to once I get it done and back on the road. When I do I'll post the dyno sheet.
 
The BT intake is about 3/4 of an inch taller than the edelbrock. I had to take my 1" spacer off. Can you get the spacer to fit on the BT intake and get your hood shut? If so, you have have any cut outs in the hood?

DUDE, your car set up sounds really close to mine. I agree on the 750 DP carb. The secondaries I have are vacuum and they are OK, but I think the Machanicals would "hit" harder off the line.

Do you have any DYNO sheets??

Also, I thought the TKO was too tight to fit in the 70? I have a World Class T-5. I am worried it might blow up if I get over 300hp on the ground and would like a TKO.

Also, what is your rev limiter set at? With the new intake I raised it from 5500 to 6000 conservitively. My comp cam says it makes power to 6250RPM but the old intake wouldn't go past 5000 so 5500 was generous. But now with the BT, sheeeeeeeeeett, I hit it so fast I decided to up it to 6000 .


Get her dynoed and document the increase... i'm sure the old guys will appreciate #'s proving they know what they're talking about.. :)