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Discussion Starter #1
Hey guys,

I need to know at approximately what RPM the Thumper heads will stop making usable power. 5,000? 5,500? Higher? Lower?

Reason being, I am getting these heads installed and bought a cam that isn't very suitable for the power range of the heads. I know the ported E7's will make killer low end and midrange power, but the cam I bought likes higher RPM's and will want to scream up to 6k or higher.

It was suggested to me that either the Comp Cams XE264HR or XE270HR would work very well for my setup, because those cams will make great low-end and midrange power which will compliment the Thumper heads nicely.

Here are the specs:

XE264HR: 212/218 dur., 512/512 lift, 114 LSA

XE270HR: 218/224 dur., 512/512 lift, 114 LSA

The XE264HR is described as being a "good H.O. replacement cam" and its power range is rated from 1,500-5,500. The XE270HR is better used with higher-flowing intake and exhaust, and steeper gears (all of which I will have in less than 2 weeks). It's rated power range is 1,800-5,800.

I'm thinking I should go with the XE270HR simply because with my 4.10 gears and the Thumper heads, I'll have plenty of low end already. Plus with the 4.10's, my car rarely sees RPM's as low as 1,500 so it would almost seem like a waste to run the XE264HR since that's when the power starts coming on. Also, when racing, midrange and upper RPM power is very important since you only see low RPM's once and that is when you launch...the rest of the time you are usually above 3,000 RPM.

But, the XE270HR will make power up until 5,800 and I want to make sure that is fine for Thumper heads. If it is the nature of ported E7's to die off around 5,500 or so, maybe it would be in my best interests to go with the XE264HR. Although a guy on 50tech.com ran the Thumper/Tmoss/XE264HR combo in his heavy convertible and complained of too much tire spin!! Hence my reasoning for wanting the XE270HR since it'll soften up the low end a bit.

Thoughts/opinions very much appreciated!!

Thanks guys.
 

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I would run the cam you got, the 270H. I run a TFS #1 cam-221* @ .050, .499 lift intake and 225* @ .050, .510 lift on a 112* sep. with a set of PowerHeads (sold) and then a set of stock '93-95 Cobra style GT40 iron heads.

Using the specs you listed,the 270HR seems to be smaller the the TFS #1 and should work good in your combo.
 

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Actually, the biggest difference between the TFS and the CompCam mentioned is lobe design. The Comp has much more aggressive ramp rates than the TFS - area under the curve is greater. This is a great example -- even though the TFS has slightly more listed duration, the Comp is 'more' cam and will likely provide better power down low, in the midrange and on top. Duration by itself doesn't really tell you much.
 

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Micheal, that is why I stated..Using the specs you listed,the 270HR seems to be smaller the the TFS #1 ...

I know Comp has some killer lobes, I've got the Mustang 'R' Cheater series lobes on my custom. The most agressive hydro profiles they have :evil:
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I think any of the three cams mentioned would be a good choice. They should make around the same power. Use the one ya got and take it from there.

Just make sure the valvesprings can handle the cam.
 

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84LTD - I understand now; actually what I was getting at was that we re-define what "smaller" means, or better yet how we describe cams in general.
 

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Discussion Starter #10
'84 LTD LX said:
I think any of the three cams mentioned would be a good choice. They should make around the same power. Use the one ya got and take it from there.

Just make sure the valvesprings can handle the cam.
Well, the one I have is the Steeda #19. I bought it simply because it works well with the 94-95's and didn't really pay attention to how it would match up with my combo. D'oh! Now that I know the Comp Cams grinds will work far better, I'm gonna sell the Steeda and get one of those. Looks like I'll be getting the XE270HR since it's similar to the Crower 15511 which I've heard GREAT things about.

And I did get the upgraded valvesprings with the heads so I'm good there. :joy:
 

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How come you don't want to run the Steeda #19 cam ?


I'm thinking with some 1.7 Cobra rockers, the cam will work fine. A wider lobe sep usually gives a flatter torque band, the #19 has a 115* sep.

IMO...it should perform similar to the other cams listed, ( I thought you had the 270HR already )

I'd run the TFS #1 cam with that combo, makes good vacuum and idles around 800. Mine stops pulling around 5500 rpms and for $140 you can't beat the price. J-dawg runs a combo similar to yours. You should make about 20 or so more rwhp with your T5 verse his AOD 89 LX -PA manual valve body w. TB-FMS 4.10s -KYBs
-FMS upper control arms -Lakewood Traction Bars -FMS AC delete -K&N filter -C&L 73 mm MAF -FMS 65 mm TB -Edelbrock Performer Intake -GT 40 Cast Iron Heads
-FMS 1.6 RRs -TF Stage 1 cam -BBK Chromed shorties -March pullies -B&M Tranny cooler -Ramcharger Fan-3 Core Radiator -Edge Racing 9.5 inch converter 3200 stall with lock up -FMS 30# injectors -155 lph fuel pump -MAC subframes -paxton adj. fuel regulator - Crane Hi6s ignition -Hypertech chip
- 276 rwhp, 285 rw ft lb torque
 

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Discussion Starter #13
'84 LTD LX said:
How come you don't want to run the Steeda #19 cam ?


I'm thinking with some 1.7 Cobra rockers, the cam will work fine. A wider lobe sep usually gives a flatter torque band, the #19 has a 115* sep.
Because I already have 1.6 Scorpion rockers and don't want to go to 1.7's. And if I was going to go with 1.7's, I'd probably run the Crower 15511 because I've heard only good things about it and guys are running impressive times with it.

I'd run the TFS #1 cam with that combo, makes good vacuum and idles around 800. Mine stops pulling around 5500 rpms and for $140 you can't beat the price.
I agree that the cam is hard to beat for the price, and if I had a Fox Stang or a TwEECer I'd probably run it. But, and I'll say this ONCE AGAIN, I want to stick with a cam that has a 114-115* LSA because the 94-95 computers are much more friendly with those cams. Cams with a 112* or lower LSA tend to cause problems and headaches that I'm not ready or willing to deal with on my daily driver. I could always get it tuned, but the XE270HR should work great out of the box and work VERY well for my purposes.
 

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I want to stick with a cam that has a 114-115* LSA because the 94-95 computers are much more friendly with those cams.
I did not know about the computers in those cars, all I've ever run is carbs. I am going to run EFI on my 347, but will be an eec4 based mass air EFI with a Crane Interceptor 2 controling it, collecting parts now. My cam is a PureStreet grind 230*/236* @ .050 with a .500 lift on a 110* sep, using Comps most aggressive hydro profiles

What kind of trouble happens with a tight cam?
 

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As the LSA gets tighter/overlap increases, the low speed drivability and ability to get a stable idle speed starts to get kind of whack; but it's not a universal. Some seem to have more problems than others -- it doesn't seem to be too predictable. And.....displacement will solve some of the problem. Your cam LSA and durations won't have near the effect on a 347 that they would in a 302. It'll probably be just fine.
 
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