347 Street Cam

[Tom1500]

The 180 degree separation still helps even with the port EFI. Not as much improvement as with a carb.

My question would be do you want more power at say 1500 ? or dose it just need to be more drivable ?

180 degree separation will reduce (not eliminate) exhaust dilution at low RPM which will reduce misfires.

180 degree separation (dual Plane) will make more power at 1500.

But if you can't get a dual plane EFI I guess it's a cam change.

We have a few expensive options for our local V8s.


EFI Dual Plane.jpg

I would just like it to be more drivable/ friendly. I dont have a 180 EFI manifold available. I do have a weber IDA and an IDF manifold though. Individual throttle bodies or individual carbs may be even better than a 180 manifold, but more work.

Getting enough runner length and a tidy air filter would be the hard part with them. You won't get the shared pulse advantage of a dual plane but you will get less exhaust gas dilution, so it should of course run nicer down low.

What is the shared pulse advantage of a dual plane manifold over IR? Nice holden btw.

[Tom68]

Not my Holden.

The dual plane 1500 to 5500 power range is not runner length as much as it is shared reversion pulses. The closing of one intake bounces back to the next opening valve as it can't easily reverse through the already flowing carby. With an IR that reversion pulse become stand off.

[Tom1500]

If you do change the cam to a lil solid roller cam be sure your valve springs are uo to that .
Comp will recomend compatable seat and open spring force. Think 155-200 seat. 380 420 open for those XR cams.

The individual runner intake is interesting if it has longer length high velocity runners. (Maybe with a custom EFI plenum top)
I was thinking about a tunnel ram intake for you to convert to EFI.. EG old Weiand Hi- Ram 289-302W with a custom EFI top Like the Chevy Stealth Ram EFI.
Lingers runners = big street torque. Lots of power
if you can fit it under hood.

Installed height is 1.8" currently with a 1.3" OD spring. Comp recommend at least a 953 - I will aim for at least 160 seat, 430 open, which is achievable. I was also looking at the smallest lunati voodoo solid rollers, but they want 200 seat, 500+ open for the entire line of cams. Difficult to achieve without a bit of rework.

IR runner length would be limited to a typical IDA carb and stack.

I'm not chasing more power everyone - car has more than I can use. Am I right in my thinking that even the bigger Comp XR 236 / 242 / 110 LSA would be a significant drivability improvement over the current 236 / 248 / 109 LSA hydraulic roller due to the proper lash ramps making it quite a bit smaller? Ie I should be comparing 040 vs 050 duration numbers (if I had them)?

If you compare the 050 overlap - 19* vs 24*, and the seat durations are likely 57* vs 77*. Understand these numbers may be useless as we are comparing cams with different lash ramps.

[F-BIRD'88]

I like the PSI ct 1225 springs for thia job.
I'm betting on the milder choice 230/236 XR cam on 112 LSA. I think overall you'll like this one best.
Modding the Edelbrock Performer RPM for EFI injectors for your EFI system is interesting.
Lots of toeque plenty powerfull well over 6000+ rpm
on your 347. You have lots of possibilities for induction now.

[F-BIRD'88]

I am not well versed on EFI.
Where is the MAP sensor located on your EFI throttle body?
I do know that the MAP sensor has to be able to see all the intake pulses (all 8 cylinders) wether the plenum is open style or divided style.
The Dual plane RPM manifold will pull well over 6000 rpm even with the smaller cam choice on your 347 W.
Its not going to lack for rpm range.
You can still buzz it 7K with the lil XR solid cam
If you want.. The low mid range torque and part thottle
driving impression will be much better.
Just splitting the plenum on your current intake may get you there. Make the divider thick and strong. EG 5/15" aluminum plate. Anchor it to a carb spacer between the throttle body and intake flange.
It has to be strong and anchored well in the plenum.
There is a whole lot of hell going on in the manifold plenum @WOT.

[Tom1500]

I am not well versed on EFI.
Where is the MAP sensor located on your EFI throttle body?

Has a port to the plenum, below the throttle blades.

[F-BIRD'88]

I am not well versed on EFI.
Where is the MAP sensor located on your EFI throttle body?

Has a port to the plenum, below the throttle blades.

That "port" has to see BOTH sides of the split plenum.
Puting the MAP sensor on a carb spacer /plenum divider combo with 2 ports (1 to each plenum ½) will allow running the split plenum on either intake style.

[F-BIRD'88]

My Dual plane intake choice for you to consider modding for EFI injectors and a MAP sensor/ divided carb spacer for this
Is Weiand Street Warrior # 8124WND. These are Weiand's latest design Mid Rise High perf Dual Plane intakes.
@ $228.00 retail its hard to go wrong.

[Tom1500]

Honestly I'd rather swap cams than modify a dual plane manifold for EFI - you are looking at a decent amount of work, fabrication effort and cost to do so. The runners aren't the same height/ angle etc. Plus some porting to make it somewhat match the heads.

[Tom68]

Honestly I'd rather swap cams than modify a dual plane manifold for EFI - you are looking at a decent amount of work, fabrication effort and cost to do so. The runners aren't the same height/ angle etc. Plus some porting to make it somewhat match the heads.

Even then the short runners to a common plenum mean you have to go pretty small with the cam with your current manifold, are there any longish runner EFI manifold options ?

[F-BIRD'88]

There are tons of variations on long runner EFI intakes for a Ford small Block. All are versions of a folded over tunnel Ram. Like the OEM factory EFI on the 5.0 L Mustangs.
A Cross Ram manifold is a tunnel Ram where the runners are layed down. The runners can be various tuned resonance length.
All these induction system manifold designs that can be a challenge with a carb or carbs. Become much more Street friendly with Port Fuel Injectors. And EFI.

[F-BIRD'88]

Question: What is the rated air flow cfm of your throttle body on your EFI system?

[F-BIRD'88]

Honestly I'd rather swap cams than modify a dual plane manifold for EFI - you are looking at a decent amount of work, fabrication effort and cost to do so. The runners aren't the same height/ angle etc. Plus some porting to make it somewhat match the heads.

No pain no gain.

You could test evaluate the Weiand Dual Plane intake manifold for driving impression with (wait for it) a carburetor. Then decide.

[russxr67]

Was the engine ever dynoed?

I’ve done a bunch of 347’s and almost always use airgap style intakes . One I did with an OTS hydraulic roller went 462 hp recently. That one had a larger cam than I would typically use ( low 240’s @50)

[F-BIRD'88]

https://i.ebayimg.com/images/g/Xt8AAOSw ... -l1600.jpg

https://i.ebayimg.com/images/g/dBEAAOSw ... -l1600.jpg

Least amount of injector firing angle difference required.
This also equates to the least compromise in injector firing angle when a common injector firing angle and height is decided on. Allows you to re-use your injectors and fuel rails.
The lower height of the carb flange allows the underhood room for a generous spacer/MAP sensor mount
A high rise. like the taller RPM (air gap) intake will need
2 distinct injector firing angles.
These new Weiand Mid rise intakes test very close to the high rise RPM intakes.
The spacer itself adds height and volume to the (Divided) plenum. IMHO this mid rise is a better choice.