my built 4v 351c is a dog

DarkoStoj · Mar 21, 2006

I got this 66 mustang and the whole car is decently built

open chamber 4v heads
edelbrock performer 4v dual plane intake
edelbrock 600 cfm carb
pop up pistons, not sure of the CR but I detonate with anything under 93 octane
solid flat tappet cam that has quite a decent lope & 1.7 rockers
lakewood bellhousing
toploader 4 speed
Long tube 1.75" headers
3" flowmaster exaust
hurst comp shifter
mallory ignition
ford 9" rear
3.89 gears
Detroit locker
Anti lift traction bars.

it feels like it doesn't have any bottom end power, and doesn't start pulling hard until 3-4k rpm, then runs out of breath a 6000rpm. It's probably a 14 second car the way it sits right now.

I'm basically assuming that the intake and carb are a complete mismatch for this motor. I was thinking of looking around for some type of used single plane and a holley 750vacum secondary carb (3310). I wish I knew the cam specs!!!! I'm probably going to pull the valve covers this weekend and see how much total lift I'm getting with a dial indicator to give me an idea.

any ideas?

mustangdave · Mar 21, 2006

Definitely need a 750 carb., not sure about what intake would work best. Those heads are known for lack of bottom end and a big cam doesn't help. Consider getting port plates for the heads.

brianj5600 · Mar 21, 2006

Performer+solid cam=? The intake and carb are both too small for the rest of the package.

XXBULLETSXX · Mar 21, 2006

I have to agree with everyone else. The carb seems way to small and the intake maybe incorrect for the heads. You do want a dual plane intake for a street car to help get the bottom end. If you want bottom end you don't want a single plane manifold, those are great for high RPM applications.

What kind of heads are they and who did the work on them? Do you know if they ever spent any time on on the flow bench? I know a guy from a race shop out here in NC who can build a killer set of heads for you and likes Ford stuff so he's not going to tell you to get a 350 like the typical chevy guys.

But before I'd pull the heads to get work done I'd replace the carb and if that doesn't do it talk to someone who will be honest about your setup and how it should perform.

ttoney · Mar 21, 2006

You definately need a 750, and a better intake. Hands down. My car has wicked power and I don't have the new 3.70 gears in yet.

Here is a Cleveland Intake performance article.

http://www.mustangsandmore.com/ubb/DanJones351CIntakes.html

Your cam matters a lot but I would bet that if you swap the Carb & Intake you will see a world of difference in that super light car.

10secgoal · Mar 21, 2006

I second the port plates. I've heard them cure that problem first hand from a buddy with the same symptons. In a pig of a car at that, too.

pabear89 · Mar 21, 2006

I was running a 600 Holley on my stock 351.
And it fell flat at about 52-5300.

Replaced it with a 750 and it woke the engine up and will turn 6500 easy.
and pull a 8% grade in 3rd at just above an idle with good throttle responce.
Still waiting on the missing speed goodies to build it.

PB

pabear89 · Mar 21, 2006

10secgoal said:
I second the port plates. I've heard them cure that problem first hand from a buddy with the same symptons. In a pig of a car at that, too.

I'd grind out the exhaust port bumps before putting plates in.
open up the exh will help the flow.

PB

4MuscleMachines · Mar 22, 2006

Let me save you some money, time, and headaches. I am no expert, far from it, but I have had my share of Clevelands and matching performance parts. The Clevelands love two intakes that I have come to experience, the two best ones for it are the strip dominator (no longer made) and the Blue Thunder dual plane. Here is an interesting link...read up on it. I have purchased/tried most of the intakes on this page http://www.panteraplace.com/page35.htm
and what they say is true. Look in eBay, they were cheap about 2yrs ago, they are now going for more. I even tried that cool Bud Moore tunnel ram box, it was so cool.

Here is the Blue Thunder I have on mine. None will make the low end torque of a Windsor, but is will pull like hell upwards of 4k rpm. Mine does, all the way to 7K easily. They love revs...

IMO, the Weiand Excellerator (sp?) comes in a not so close third.

4MuscleMachines · Mar 22, 2006

Ooops, I was wrong about the strip dominator being cheap, it was years ago.

http://cgi.ebay.com/ebaymotors/Holl...ryZ36474QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

But thats ePay, you can get it for about $250 thru some forums.

jes72mustang · Mar 22, 2006

I wanted to chime in here as well. I am no Cleveland expert, but I have one in my 72 and I have been doing a lot of research in planning my future build. Everything I have read and been told is that the v4 heads are designed for better top end. The v2 heads are more of a low end head. My understanding is that is has to do with the port sizes.

Another suggestion would be to go over to the Cleveland board at: http://www.network54.com/Forum/119419/ and get some opinions there.

Hack · Mar 22, 2006

Possibly these will be stupid questions, but bear with me. Rather than assuming anything:

-do you know when the engine was put together? Any chance it could be tired?
-have you done a compression test?
-are the plugs, wires etc in good condition and gapped properly, etc?
-is the engine in a good state of tune(timing, carb settings, etc)?

Yes I agree that there's probably a mismatch going on, but with a manual tranny that engine should be pretty quick in that car, regardless. Also, running out of breath at 6,000 rpms isn't bad for a street engine. Does this engine have the original two-piece valves? Are you sure it's going to be a good idea to spin it faster than 6,000 rpm?

How much power doesn't the engine have? I mean, you should be able to spin the tires in first and second gear, I would think. 14 second quarters are pretty fast, much faster than most cars on the road.

302 coupe · Mar 22, 2006

351C 4V's lacking low end power is myth perpetuated by the magazines, then spread by unknowing readers that think it is gospel. You are suffering from mismatched components, not the big heads. Personally, I'd go with the BT intake, 750 dp w/ manual secondaries, and a cam with around 540 lift, 230-ish duration. It will run like a hot rod and pull strong up top, while still making good low end torque, especially in such a light car with a 4 speed and 3.89 gears. Chances are, since it has had a solid lifter cam installed, you'd likely be suffering from a cam thats too large rather than too small, it would be a good idea to measure it though. If you measure lift at the valve tip, remember to divide by the rocker ratio, 1.73 for clevelands.

DarkoStoj · Mar 22, 2006

Hack said:
Possibly these will be stupid questions, but bear with me. Rather than assuming anything:

-do you know when the engine was put together? Any chance it could be tired?
-have you done a compression test?
-are the plugs, wires etc in good condition and gapped properly, etc?
-is the engine in a good state of tune(timing, carb settings, etc)?

no idea when the engine was put together, but I went through and replaced all the gaskets on the motor, and it looked real clean inside. It could be tired, I have ~20psi oil pressure at idle when warm and the car does smoke sometimes. I'm not sure if thats due to it not being tuned though.

-I have not done a compression test.

has new ngk plugs, 8mm wires, head gaskets, intake gaskets

I think the previous owners had the car setup at one point with a better intake/carb, and when they sold it maybe switched them off for some reason. It just doesn't make sense for this motor to have a edelbrock performer intake and a 600cfm edelbrock.

I've been looking around for intakes, and I think the blue thunder would probably be the best bet for me, they are just so damn expensive!! How would I be with hood clearance and that intake?

Would it be beneficial to go with a vac secondary 750 or a mech secondary 750? I'm already getting 9mpg right now, premium is almost $3/gallon here. How much worse would the setup be with a 750 and a different intake?

302 coupe · Mar 22, 2006

I'd never go with vaccum secondaries on a double pumper, but then again I don't build performance engines for fuel economy. In that car, with those gears, and a manual trans....perfect car for mechanical secondaries. With a proper tune, I don't see any reason for it not to get 13-14 mpg, assuming you drive like a mature adult most of the time.

DarkoStoj · Mar 22, 2006

302 coupe said:
I'd never go with vaccum secondaries on a double pumper, but then again I don't build performance engines for fuel economy. In that car, with those gears, and a manual trans....perfect car for mechanical secondaries. With a proper tune, I don't see any reason for it not to get 13-14 mpg, assuming you drive like a mature adult most of the time.

I do have a speed demon 750cfm double pumper in my garage. The only problem is I don't have choke and its my DD. If I tune the carb correctly could I have it run smooth on cold startup? Right now I wouldn't be able to live without having a choke on the edelbrock.

milner351 · Mar 22, 2006

if you want fuel economy, you don't want a cleveland,
pull it out and go get an efi 302 with all the wiring and stock computer and drop that in there, you'll probably get 18mpg or better.
I drove a 70 mach1 with a 4v cleveland and a four speed for years. I built the engine for the street, mild hydraulic cam, dual plane intake. It ran best with a 650DP with the 4spd.

I agree with most of the previous statements, it's a mismatch, but I'd say the cam is the biggest problem, not the heads. Port plates would be nice for sure... but I'm not so convinced you need to dump the intake and carb, I think you'd be much better off dumping the cam and putting in a more streetable grind.

the cam I ran was a crane as I recall, 292 298 adv dur, 506 519 lift.
I think a comp 280 would be a good choice, or even a step down from that, and I think with one of those cams or similar it would run quite well with the performer intake and carb.
For a daily driver, you can't beat an edelbrock carb for being trouble free and dependable.

DarkoStoj · Mar 22, 2006

milner351 said:
if you want fuel economy, you don't want a cleveland,
pull it out and go get an efi 302 with all the wiring and stock computer and drop that in there, you'll probably get 18mpg or better.
I drove a 70 mach1 with a 4v cleveland and a four speed for years. I built the engine for the street, mild hydraulic cam, dual plane intake. It ran best with a 650DP with the 4spd.

I agree with most of the previous statements, it's a mismatch, but I'd say the cam is the biggest problem, not the heads. Port plates would be nice for sure... but I'm not so convinced you need to dump the intake and carb, I think you'd be much better off dumping the cam and putting in a more streetable grind.

the cam I ran was a crane as I recall, 292 298 adv dur, 506 519 lift.
I think a comp 280 would be a good choice, or even a step down from that, and I think with one of those cams or similar it would run quite well with the performer intake and carb.
For a daily driver, you can't beat an edelbrock carb for being trouble free and dependable.

I will never run a hyd cam in any v8 ever again. I love the solid. I love high rpm screamers and ****ty lumpy idles. I'm sacrificing fuel economy for performance, but I don't want to get stupid with it and end up at 6mph.

Hack · Mar 22, 2006

If the engine has a big cam right now and you have some detonation issues, I would recommend against swapping to a small cam. Big cam overlap helps to bleed off some of the cylinder pressure at lower rpms, which helps reduce detonation when running a higher c.r.

4MuscleMachines · Mar 22, 2006

I agree with Hack. Also 302Coupe is leading you the right way, IMO. You need a healthy cam in there and the mech secondaries is A MUST. I recently had a stroker Cleveland built with a solid lifters .605lift 300dur, and mech secondaries and it runs very well and very streetable. Most anything can be made streetable with a properly tuned carb. Since Clevelands love big lift and big carbs, that is why they lose some low end TQ, just like any other engine would. BTW, the Blue Thunder is probably an inch taller. It made no difference in my car but it's a 71 Mustang.

my built 4v 351c is a dog

DarkoStoj

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