Thoughts on switch to 3:55's & Dual Plane Intake

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80fbody

80fbody

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So I've got this nice f-body I barely drive. New motor. Probably 500 miles over several years.

360 w/ 10.17 to 1 comp
Heavily ported factory heads with 2.02 intakes (63cc)
Comp .507/.510 cam
Victor intake port matched
4 Speed
4:10 Posi Rear
Superstocks & Drag shocks in rear
2 1/2" exhaust

I have a real nice rebuilt 3:55 posi rear w/ stock springs & a Performer RPM Air Gap sitting on the shelf. Got a drag car so I have no interest in spinning the tires at the track in this car.

See any issues with swapping to a dual plane & 3:55s to try and enjoy driving the car around more? Maybe some longer drives to cruise nites, etc.
 
With the combo you have the Victor is way out in left field anyway, I would switch to the RPM air gap first. and save the gear swap until afterwards. My feeling is that with the RPM that a 3.55 is all you will need. Victors are great with lots of compression, lots of cam, and lots of gear, which don't look like what your running. The RPM will outperform the Victor with your combo.
 
What is the cams duration @ .050?
Your compression is a bit high as well.

I had a similar set up. A 10-1, 360, 750 single plane, Purple 292/.509, super comp headers, 4spd & 4.10's. This was the fun cars engine. When the daily driver took cap and ed over dead, I NEEDED a car for work. Well the hot rod got the nod and I swapped parts.

I went to a LD-340, AFB 625, 3.23's. The cam stayed in. The change of parts helped low end torque a bit but the cam was a bit large for daily driving. I later swapped cams around. Went real mello. I used a split wide Crane. 216/228-,454/.480-112. I also used a very thick gasket to drop the comp ratio down a good bit. Molars .060 head gasket space was used so I could run 89 octane.
 
Id go for it. I had a strip dominator and 3:91s in my swinger. 10.2:1 340 w .484 cam. Hated the combo. Who wants to be turning 3500 @ 45 mph? Not me. Swapped to LD340 and 3:55s much better to cruise in. Now turns 2800 @ 55
 
Here's the cam info.

Street/strip, needs 3000+ stall, headers, gears, rough idle.

RPM RANGE 2300-6500

ADV. DURATION 284/296

DURATION @ .050 240/246

VALVE LIFT .507/.510

LOBE CENTER 110
 
I'm looking forward to cruising the car more thus I think the gear change is a good idea. I'm not opposed to a cam swap if it becomes tough to keep the tune "clean".
 
swinger340 said:
Id go for it. I had a strip dominator and 3:91s in my swinger. 10.2:1 340 w .484 cam. Hated the combo. Who wants to be turning 3500 @ 45 mph? Not me. Swapped to LD340 and 3:55s much better to cruise in. Now turns 2800 @ 55
Click to expand...

Wow, I had identical combo in my 65. 68 big valve 340, 284/484 mopar cam, Strip Dominator-3.91 SG full length headers, axle dumps didn't help. Didn't do a lot if freeway driving, that's for sure. Had 205/70R14 tires so no low profile for me. Wasn't ideal but it sang on the highway for sure. 3.55 is a great all around gear.
 
80fbody said:
Here's the cam info.

Street/strip, needs 3000+ stall, headers, gears, rough idle.

RPM RANGE 2300-6500

ADV. DURATION 284/296

DURATION @ .050 240/246

VALVE LIFT .507/.510

LOBE CENTER 110
Click to expand...

I think I'd try a set of lifters by Rhoads first before a cam swap. I'd also shoot for as little depression on the lifter as possible. This would give it the max amount of duration reduction. About 8-10*'s. That would be awesome and fit right into the program.

Do you have an adjustable valve train?
 
Yes. Cruise rpm has a lot to do with the cam as well as the rest off the combo.
This is why I suggest the Rhoads lifters. Go to Rhoads .com and read up on how there lifters help in this. They are a variable duration lifter.
 
I would change the intake and gears.
I think the cam will be fine. Its a 4 speed so no converter miss match issues.
 
Mo-Par said:
I would change the intake and gears.
I think the cam will be fine. Its a 4 speed so no converter miss match issues.
Click to expand...

Agreed..... I have run The MP .509 w 3:55s and Duel plane air gap. Will be much more cruiser friendly, better on gas, and less wear and tear on your engine. Id leave the cam alone. I think you will be quite happy w a gear and intake swap.
 
Nice to bounce this off you guys before I start swapping items. Intake is already cut some so I may get lucky & just have to do a quick port match. It does have a set of isky adjustables on it.
 
If you so decide to try the Rhoads lifters, readjust them for as little lifter preload as possible. This will make the engine think it is a smaller cam until theifter pumps up around 3000 rpm's. I think you may cruise at a lower rpm.
 
Sounds like the Comp XE284H. That cam is a beast but not great for street. You'll be glad you changed that cam out. regardless if you re going to use Rhoads lifters or not, that cam is way to big for a just a street cruiser. Remember, by lowering gear ratio and going to a dual plane your going to be loading that 360 up and it won't be pleasant to drive at all. Try a XE268H. The engine will be happier with the 3.55's and dual plane running the XE268H and you'll enjoy driver her more often rather than fighting to keep her from loading up all the time.
 
The cam is the best bet to change. The Rhodes lifters are a cheaper way to alter cam timing without changing the cam.
 
put the 355 and dual plane in it and see how you like it since its not really going to cost you anything and not much work.The 355 is the perfect street gear with 26 to 28 inch tires
and the dual plane is better for the street There is charts on the internet that will tell you exactly how many rpms you will turn with different gear ratios and tire height
 
I wouldn't even mess with the cam. It should work great with the RPM and 3.55's. If you were running an automatic it might have some degree of effect on that seat of the pants feel but with a 4 speed it should be a great combo. Intake and gear swaps are a bunny, cam swaps are not quite as easy.
 
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