Small Block Intake

-
its a flat tappet cam, all matched,, cam lifters, springs... Ignition it set up.. 38 degrees total on premium, orange box, it runs strong up to around 4800 and seems to lose its pull after that...
PRH said:
I’m going to call “foul” here.
First off...... it’s a BBC, not a SBM.

Secondly, that test is an RPM vs an RPM A/G.

The OP is asking about going from a std Performer to a Performer RPM.

On the right build, the difference in power between those two on a SBM could be pretty sizable.
The question is....... how much different will it be with the OP’s combo?

I wouldn’t expect too much.

We had a low CR 360 on the dyno here last year(not built by us).
SM heads that were checked out, rpm intake, headers, 750 Ede carb, XE268 cam, PRW 1.5 rockers.
Peak hp of 331@5200.

It was surprisingly low.
The intake and 750 didn’t work any magic with that one.
Click to expand...
i would like to be at around 300-350 Hp.. I'm just asking if my performer which is suppose to be a small port intake will hold up or would it be worth the money and effort to go with the bigger port( i assume) RPM or RPM Air gap?

cam specs are
Duration @ 50 213/226
Lift .480/.516
lobe separation 109 degrees
 
Many years ago I built a 340 that got put into a lil red express truck.
I used a std Performer on it.
It had no problems pulling to well over 6k.
It was slightly over cammed for the rest of the combo.

A few years back I freshened it up.
I put a little smaller cam in it when I did....... a Comp 268H.
That improved the seat of the pants low/mid feel in the truck, but it didn’t have as strong of a top end rush........ but it was a better overall package.
It still goes to 6k without any protest though.

You say you bought everything matched for the cam......

The question I have is....... did you buy springs for the aluminum heads, or springs for stock heads?
The installed height between the two is quite a bit different, and springs for stock heads, installed on aftermarket aluminum heads, would have low pressures, unless someone specifically addressed it.
 
PRH said:
Many years ago I built a 340 that got put into a lil red express truck.
I used a std Performer on it.
It had no problems pulling to well over 6k.
It was slightly over cammed for the rest of the combo.

A few years back I freshened it up.
I put a little smaller cam in it when I did....... a Comp 268H.
That improved the seat of the pants low/mid feel in the truck, but it didn’t have as strong of a top end rush........ but it was a better overall package.
It still goes to 6k without any protest though.

You say you bought everything matched for the cam......

The question I have is....... did you buy springs for the aluminum heads, or springs for stock heads?
The installed height between the two is quite a bit different, and springs for stock heads, installed on aftermarket aluminum heads, would have low pressures, unless someone specifically addressed it.
Click to expand...

i sent the springs, retainers and locks to Todd Marsh @ Marsh performance where i bought the heads and told him what my cam specs were and engine specs and he set the heads up for me
 
If you reach a point where you’re not getting the results you’re looking for with induction system changes, you may want to pull a couple of springs and have them tested.

Do you have the part number for the springs you sent him?
The Ede and Ede copy heads have a nominal 1.800” installed height.
 
PRH said:
If you reach a point where you’re not getting the results you’re looking for with induction system changes, you may want to pull a couple of springs and have them tested.

Do you have the part number for the springs you sent him?
The Ede and Ede copy heads have a nominal 1.800” installed height.
Click to expand...

Hughes 1110p

  • Installed Height/Pressure: 1.660"--120#
  • Pressure @ .450" lift: 280#
  • Pressure @ .500" lift: 303#
  • Pressure @ .550" lift: 327#
  • Coil Bind: @ .600" lift
  • Outer Spring ID/OD: 1.033"/1.440"
  • Type of Spring: Single w/Damper
 
So, it’s not the “correct” spring for the aluminum heads with 1.800” installed height.

-Are the springs shimmed up to get to 1.660?

-Are the springs installed at a height enough taller than 1.660 to have a lower enough spring load to affect performance?

-Did they just swap the springs for something that’s a better fit on those heads?

This is actually a fairly common occurrence.
Several engine platforms use fairly short spring installed heights....... and their aftermarket counterparts often have taller heights.

Someone orders the springs in the catalog to go with their cam....... but the catalog parts are assuming you’re using stock heads with stock installed heights.
It’s best not to order springs until you know what installed height you’re working with.

I just went through this on some aftermarket SBF heads.
Customer had a healthy solid roller cam, and ordered the “matching” springs.
The problem was...... the springs were designed for a 1.700 installed height(for stock heads), but the new heads set up at 1.900.
No one checked....... so the 1.700 springs were in at 1.900, with the result being 130lbs on the seat instead of the 220lbs the cam wanted.

Needless to say....... the motor didn’t rpm very well.

Might be worth you verifying what you have.
Installed height, spring load at that height, load at open height, etc.
Using the numbers you provided, those springs would be-
[email protected]
[email protected]
[email protected]
 
Last edited:
PRH said:
So, it’s not the “correct” spring for the aluminum heads with 1.800” installed height.

-Are the springs shimmed up to get to 1.660?

-Are the springs installed at a height enough taller than 1.660 to have a lower enough spring load to affect performance?

-Did they just swap the springs for something that’s a better fit on those heads?

This is actually a fairly common occurrence.
Several engine platforms use fairly short spring installed heights....... and their aftermarket counterparts often have taller heights.

Someone orders the springs in the catalog to go with their cam....... but the catalog parts are assuming you’re using stock heads with stock installed heights.
It’s best not to order springs until you know what installed height you’re working with.

I just went through this on some aftermarket SBF heads.
Customer had a healthy solid roller cam, and ordered the “matching” springs.
The problem was...... the springs were designed for a 1.700 installed height(for stock heads), but the new heads set up at 1.900.
No one checked....... so the 1.700 springs were in at 1.900, with the result being 130lbs on the seat instead of the 220lbs the cam wanted.

Needless to say....... the motor didn’t rpm very well.

Might be worth you verifying what you have.
Installed height, spring load at that height, load at open height, etc.
Using the numbers you provided, those springs would be-
[email protected]
[email protected]
[email protected]
Click to expand...
these heads were all set up by Marsh Performance.. he said he set them up correctly as needed.. i sent him the same numbers from Hughes website and he set them up... it rpm's fine... no float, no rattle or anything.. it will rev to 6200 no problem
 
If it revs fine to 6200, then maybe you’re just expecting “more” out of it than there is.

The cam isn’t very big.
I wouldn’t expect to have to go higher than 54-5500 to use it all up.

Going back to the beginning of the thread....... I’d say if you can borrow a known good 750 from someone to try....... that would be a good test.
 
Last edited:
PRH said:
If it revs fine to 6200, then maybe you’re just expecting “more” out of it than there is.

The cam isn’t very big.
I wouldn’t expect to have to go higher than 54-5500 to use it all up.

Going back to the beginning of the thread....... I’d say if you can borrow a known good 750 from someone to try....... that would be a good test.
Click to expand...
yeah i would like to see if i cam find a bigger can to run later, but i dont want to have to go through changing springs and all that right now. i dont know if there is another cam i can run with those springs other than the next step up whiplash cam that has same spring rates, but its 226/236 duration @ 50 and .539/.539 with lobe sep @ 107
 
I ran those springs (sold as a kit with their retainers) on new EQ heads w/stock length magnum valves in my 410 stroker. Cam was a 280 advertised, [email protected]” with a calculated .517” lift (w/1.6 rocker ratio but actual lift due to geometry was less, I never measured it though) Those springs should be good for about a measured .540” lift. You could definitely go with a bigger optimized cam: with more duration @.050” etc, and maybe on a better LSA? and depending on geometry losses even bigger “lobe” lift.
 
You must log in or register to reply here.
-

Back
Top