347 Street Cam

[Tom1500]

Looking at a cam change to bring more street-ability to the weekend car. Classic big cam stuff - runs great on power, fine on flowing roads, but is tedious in traffic. It was built to see the track but never does, and it would be nice to be able to throw the keys to a family member once in awhile.

Current combo:
347 SBF
Twisted wedge 205
Shaft rockers, LSX valve train
Super victor EFI
1 5/8, 1 3/4 step try y headers
236/248 @ 50, .608/.600, 106 ICL, 109 LSA Hydraulic roller grind - running solid roller lifters. Intake closes (@50) 44* ABDC. I only have the 50 specs unfortunately.
10.5:1
8" vac at 850 rpm, 14" vac at 1500 rpm, no load
3.89 gears, 4 speed manual

I'd like to to keep the existing liters - bam bushing solids. Bad experience with the original hydraulics and don't want to remove the heads again. I'm not racing, so not concerned with loosing some HP. I do enjoy the moderate (7k) rpm capability of the current combo.

To keep things simple, I'm considering one of comps smallest street roller cams:
XR268R 268/274, 230/230, .589/.602, 110 LSA
XR274R 247/280, 236/242, .602/.608, 110 LSA

As I understand, being solid roller grinds with appropriate lash ramps, both of these should be significantly smaller than the current hydraulic roller cam, and sensible on the valve train. I would consider getting one ground on a billet core.

Would they both be steps in the right direction? Too big/ too small? Interested to get some thoughts.

[Tom68]

Did you see how GRT got happy with his too much overlap cam for the street ?

Fully divided dual plane. He does have a couple of extra cubes for some low speed power though.

viewtopic.php?f=1&t=58475

You will of course drop some power at 7000, but it'll still go there.

[Tom1500]

I did see that. Its port EFI though.

[Tom68]

I did see that. Its port EFI though.

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

[frnkeore]

So, if yours is a TBI, EFI, why not go to the Edel Air Gap? It should help, a lot. Victors and S Victors, are not noted for their street manors.

If not enough, then the street 230 cam but, I would add, at least 4° to the Ex duration.

[F-BIRD'88]

I assume with solid rollers on a hyd roller cam you are running the valve lash very tight.(.002" to .006").
As a short test what happens if when you re- adjust the valve lash bigger to reduce running duration and overlap?
Short term "drivability test"
What valve lash setting does it likw best?
This can help you determine if its really the cam ans or what new smaller cam might be better.
The EFI and spark timing curve may need work.
What happens if you install a intake manifold divider plate to split the plenum? Reduces exhaust dilution at idle and low speed. Increases runner flow velocity at low speed.

Thats a lot if exhaust duration.. Bigger valve lash will reduce both duration and overlap tame the cam down.
From there you can see if thats practical for you.
Note: All those Comp street rollers that you see in the catalog can be custom grind ordered on wider LSA and or single pattern versions and also on steel cam cores if you like.. All you got to do is call Comp.

A 230/236 on 112 or a 236/236 on 112 LSA
Will be a lot more drivable.
But I think your XR cam choices are in the ball park.
Wider LSA tames the overlap and broadens the power curve...
I found on these Comp XR solid street rollers you can play with the valve lash to effect within a range.

In the same way you can try different +/- valve lash on your current cam to evaluate the effect

[F-BIRD'88]

Note: on some TBI EFI setups they cannot tolorate a fully split isolated divided plenum wether single plane or dual plane.
It depends where the MAP sensor is mounted on the T body. If its on one side of the plenum there needs to be at least partical plenum sharing (a hole or slot in the plenum divider so the MAP sensor can read correctly.
Or a lil cheater pipe on the MAP sensor fitting that runs to the other side of the split plenum to correct MAP sensor signal.

[F-BIRD'88]

The more I look at this the more I like the milder Comp 230/236 XR cam but ground on 112° LSA. 107/117 or 108/116 installed phasing.

You can "adjust" the running duration on these. for effect.
If you want "more cam" make the valve lash smaller EG:
.008" to .012" set cold. This makes the lil XR cam act a bit bigger in the running engine.

[Tom1500]

I did see that. Its port EFI though.

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.

[Tom1500]

So, if yours is a TBI, EFI, why not go to the Edel Air Gap? It should help, a lot. Victors and S Victors, are not noted for their street manors.

If not enough, then the street 230 cam but, I would add, at least 4° to the Ex duration.

Its not TBI, its direct port EFI on a supervictor EFI manifold.

[Tom1500]

I assume with solid rollers on a hyd roller cam you are running the valve lash very tight.(.002" to .006").
As a short test what happens if when you re- adjust the valve lash bigger to reduce running duration and overlap?
Short term "drivability test"
What valve lash setting does it likw best?
This can help you determine if its really the cam ans or what new smaller cam might be better.
The EFI and spark timing curve may need work.
What happens if you install a intake manifold divider plate to split the plenum? Reduces exhaust dilution at idle and low speed. Increases runner flow velocity at low speed.

Thats a lot if exhaust duration.. Bigger valve lash will reduce both duration and overlap tame the cam down.
From there you can see if thats practical for you.
Note: All those Comp street rollers that you see in the catalog can be custom grind ordered on wider LSA and or single pattern versions and also on steel cam cores if you like.. All you got to do is call Comp.

A 230/236 on 112 or a 236/236 on 112 LSA
Will be a lot more drivable.
But I think your XR cam choices are in the ball park.
Wider LSA tames the overlap and broadens the power curve...
I found on these Comp XR solid street rollers you can play with the valve lash to effect within a range.

In the same way you can try different +/- valve lash on your current cam to evaluate the effect

Running the lash quite tight, close to zero cold at the valve. It grows to about 0.010 hot at the valve, so there isn't much opportunity to play with it without ending up off the lash ramp. Could test it short term, but makes me nervous. I will also see if I can come up with an intake divider to test.

I have gotten it running alot better with the tune and timing. Its not a pig or anything, buts its reasonably hot as shown by the idle vac.

Thanks for the detailed responses F-Bird, appreciated. Gives me the confidence to try one of these small comp rollers, perhaps on a custom LSA.

Other option is an individual runner manifold I have sitting on the shelf. Either EFI or carbs.

[bob460]

Go to Jones cam site an see what he sends you.

[ClassicComp]

4FB528F8-375D-4080-9AAF-4DBE8DDBB85F.png

Runs well for me and I use the factory efi and a tuned chip

[F-BIRD'88]

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.

[Tom68]

I did see that. Its port EFI though.

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.