AndyTA

As some of y'all know, I recently completed a 427 swap in my 99 Fbody. I need a daily driver friendly blower cam recommendations. You might be thinking why I don't just get one specced from Pat G - I did (Current cam). I'm just looking for other opinions.

Blower going on:
F1X - aiming for an impeller speed of around 66,000 (keeping it below the 72k rating, because I'm the better safe than sorry type of guy)
^I don't know what that would translate to in terms of lbs of pressure.

Induction:
5.75" runners - Fab Aluminum
102mm TB
Speed Density

Block:
LS 427 - Gen 4 5.3 Sleeved to a 427
4.125" bore
4.00" Stroke
-20cc dishes

Heads:
PRC 247cc with 68cc chambers
.040" MLS Head Gasket
Stock ratio Rockers (Stock + Trunion kit)
.660 PRC Springs Titanium retainers

SCR = 9.8:1 (could be 10:1 at most)
DCR = no idea

Cam currently spec'd by Pat G -
235/244 .629/.615 112+4 - 7.5 degress of overlap

Cam mentioned by Lonnie -
241/250 .629/.615 113+4 - 11.5 degrees of overlap

What kind of Cam do the members here have in mind for my build? D4rth? ;-)

Thanks,
Andy

Edit:

I'm not too knowledgeable on blower cam grinds - from what i understand though, lower overlap is preferred - as boost can leak through the valves when both are open, decreasing overall pressure.

bortous

After reading your post I would not go with the Pat G spec for a 427.
The one from Lonnie is better but you need less overlap.
The IVC is too early and EVO is too late.
You need an EVO point of at least 60 and an IVC of around 52 for that engine size.
The supercharged LS9 has an EVO point of 60 on a 6.2 litre and you certainly do not want to open the exhaust any later especially on a larger engine.
The specification below will work great for your engine with minimal boost loss.

234/250 118 LSA +3

This gives you an IVC of 52 and an EVO of 66 with only 6 degrees of overlap.

This will drive well with no bucking whatsoever and will pull really hard in the mid range and top end.
The supercharger will take care of the low end for you.

AndyTA

Bortous,

Thank you for taking the time to read, and replying with informative detail.

Do you feel that the cam specs given to me by either Pat G or Lonnie were because of cathedral heads? (My PRC 247's)

If I was for example to go with the cam you just spec'd (234/250) - and given the engine information up above in my OP, would you say I would be safe from any PTV issues? (Obviously I would check, but curious)

Thanks again for your response,
Andy

Darth_V8r

iTrader: (4)

That is a really good cam spec bortous! Nice job. You should not have PTV at all with that cam.

AndyTA

Thanks Bortous and Darth.

I assume this is using the same lift? .629/.615?

thanks,
Andy

G Atsma

Looks like one could assume(look out! lol!) so.

bortous

Hi Andy,

I thought they were square port heads for a second. Haha.

Regardless, because you are running a blower the specs are identical anyway and I still stand behind what I suggested.

Since you are running cathedral port heads also, you could run a camshaft with an earlier exhaust opening due to the more efficient exhaust port (this is what Pat G and Lonnie specified), however you will lose power and rpm capability on a 427. The IVC point is too early for a 427 on both camshafts as stated earlier.

Because you have a 427 the torque will still be plentiful down low with cathedral port heads so it makes even more sense to run the spec I suggested.

If your car is an auto you may not even need a stall converter. ( maybe a small one)

PTV should not be an issue at all. The installer must check this to make sure.

Darth agrees too and he is one of the most knowledgeable guys on here.

Lift is perfectly fine too.

bortous

That's good.
Someone in these forums taught me a thing or two!

AndyTA

Ordering this cam today. Thanks again Bort/Darth for your invaluable input! I'm excited to see what it can do once I get my engine all back together.

bortous

Fantastic.
Who are you going to get to grind it for you?
Please PM me once you install and tune the camshaft because I really want to know how it drives and how high it revs in your engine.

AndyTA

Heck yes, it's the least I can do! What's on the list as of right now:

1) Take engine to machine shop to re-clearance all the things (I have another thread going on this) - no idea when I'll have the time to take it in
2) Retrieve engine once done at the machine shop, install new cam, new everything again
3) Finally, schedule time at a reputable dyno

So it might be a while... I'll estimate about 1.5 months - but I will let you know.

bortous

I see the supercharger you are using is a centrifugal type.
Damn, this camshaft is going to pull forever in the mid-top end.
The engine size and head type will take care of the low end torque.
You should hit 7000rpm+ with ease.
Just make sure you got good lifers and springs.
I would use high rpm lifters from Isky or Morel and pac 1209x springs to ensure valvetrain stability.
The other two cam specifications were given to you to take care of the low-mid range power band as the centrifugal type supercharger does not add any power in this rpm range.
I can see the sacrifices Lonny and Pat G made.
However, in a 427 with cathedral port heads, not needed.
The cam I specified will be mental from 4000rpm+ so its a mid- top end type with a stockish idle.
Who are you going to get to grind this camshaft for you?

rkupon1

iTrader: (3)

I know who it was...it rhymes with Hokey C,...lol

AndyTA

Your explanation really helps understand, thanks for taking the time to do so!
I'm loving the description you provided of what the 234/250 will be capable of!

1) I am currently running LS7 Lifters, and PRC .660 Springs - will these suffice for up to 7000rpm?
2) I enjoy the choppy idle that I have now, and I understand the limitations to "choppiness" when spec'ing a cam for a blown application. What are my options to perhaps have a cam like the one you spec'd, but to retain at least some of the lope/chop? If possible :-)
3) TSP Will be grinding this camshaft

Thanks again,
Andy

bortous

No problem Andy.
If you want something with a bit more note this cam specification will also work as the IVC and EVO are the same, It's just the overlap that is more and because of it you will make more peak torque and hp.
Although it will bleed off some boost you will make it up with the added power.
238/254 116 LSA +3
This has 14 degrees of overlap versus 6 for the previous cam spec.
This will certainly have a notable idle but will still drive well. 90 % stock like in the low end once it gets a good tune.
I certainly would not go with any more overlap.
Another spec that will work well is a 236/252 117 LSA +3.
This has 10 degrees of overlap so it right in the middle of the other 2. So you have 6, 10 and 14 degrees. Good choices.
Which ever cam you choose it will perform well.
If you are revving to 7000 rpm the ls7 lifters will be ok although i would not go any higher.
If you ever plan on spinning higher than 7000rpm get some high rpm lifters.
Those springs should be ok.
If you don't already have them I would get the pac 1207X kit at a minimum.
Hope you got good rockers too.

bortous

TSP are really good since they upgraded their machinery.
They have some of the best grinds out there now.

bortous

Haha.
No. He helped me with understand head cylinder measurements such as CSA etc through PM.
Darth is the one who helped me with the camshaft specifications.

AndyTA

Holy smokes, you basically spec'd out all the options I'd want! Thanks Bortous!!

I'm really leaning towards the one with 14 degrees of overlap - I understand that I'd want no more overlap than this, noted. I'm glad I waited to order, I'll be ordering this cam (238/254 .629/.615 116+3 LSA) today! :-)

And regarding rockers - I'm actually using the stock ones with the "Trunion Upgrade" kit that I installed. <-- Any concerns with this?

Thanks,
Andy

bortous

Haha. It's good to have options.
The option you have chosen will bleed off the most boost but will make the most power obviously because of the extra duration.
I remember you stated at the beginning of your post that you wanted something that drove well and did not bleed off boost. That's how I came up with the first spec.
10 degrees of overlap in a 427 would drive like stock too.
This is probably the one I would choose but it's personal preference really.
Best compromise of the 3


Best bet it to use yella terra roller rockers. These will also free up a bit of HP too
Not a fan of these trunion upgrades.

Depending on spring pressures either go the ultra lite pros or the pro street version.

AndyTA

It's true - you gave me specs based upon my request :-) Which I truly appreciate.
You're obviously far more knowledgeable than myself. so I have to ask:

1) What is it about the trunion upgrade you don't like
2) How would something like the YT's free up some hp? Do they just roll better?
3) Given the spring pressures below, would I be better suited with the UL Pros, or Pro Street?

Genuine questions to learn here.

Thanks,
Andy

I feel I owe you some beer at this point.

nstall Height: 1.810"
Closed Spring Pressure: 160 lb. @ 1.810" Installed Height
Open Spring Pressure: 415 lb. @ .660" lift
Maximum Spring Lift: .660"
Coil Bind 1.015"