[pmd400]

Engine is getting close to completion. Just got heads back from machine shop. Heads had exhaust valve opened up to 1.77 and had previous bowl modifications. I already purchased a crower raiv cam but I'm thinking it's not a good selection for my compression and exhaust to intake flow ratio. Specs are

Pontiac 461 - bore 4.18, stroke 4.21
Rods length 6.625
9.4:1 compression
Edelbrock p65 dual quad/dual plane intake
2 edelbrock 600 carbs
1 5/8 diameter/unequal length primary headers
2.5 x pipe exhaust. Mufflers to be used but not yet purchased
6x heads. Flow as follows
Lift Intake Exhaust E/I ratio
.100 76 54 72%
.200 134 117 88%
.300 181 154 85%
.400 219 178 81%
.500 229 194 85%
.600 229 202 88%

Car is a '72 firebird, 3500lbs
Rear is 2.41 or 2.73(have both)
Trans is a Richmond 5 speed, ratios are
1st - 3.28
2nd - 2.13
3rd - 1.57
4th - 1.24
5th - 1.00

Car is a street car. Power brakes are a must. Engine will never go above 5500rpm. Hyd flat cam a must.
Any recommendations will be much appreciated.
Thanks

[ponyakr]

I've always liked those 041 clones with Rhoads lifters.

But, with reg lifters, you might like the Howards version. It has less adv duration.

https://www.summitracing.com/parts/h...w/make/pontiac

But, if you really don't plan to go over 5500, then the Crower 60243 should be plenty of cam.

https://www.crower.com/pontiac-287-4...m-284-hdp.html

Even a Summit 2802 should go 5500.

https://www.summitracing.com/parts/s...AagaAqTx8P8HAQ

But, with your exhaust flow, a single pattern might work well. There are lots of single patterns. I'm thinking there's no need to go over 230 degrees dur @ .050 lift, for a 5500 rpm redline. And, most say a 112 or more LSA will give more vac and a better idle. But, I'd say go at least 110 LSA. CC & Lunati make single patterns with 230 @ .050, & 110 LSA. Either of these should do what you want.

https://www.summitracing.com/parts/c...WoYaAjJC8P8HAQ

https://www.summitracing.com/parts/lun-10510471

The Crane 10508 has 228 @ .050, with a 112 LSA.

https://www.summitracing.com/parts/crn-10508

http://www.jegs.com/i/Crane+Cams/271...pGUaAuIo8P8HAQ

http://www.jegs.com/i/Crane-Cams/271/105082/10002/-1

I'm assuming that you realize one good 800 Q-jet, will probably be a better choice, as would 1 3/4" tube headers. But I also assume you have a reason for using those you listed. So, that's all I'll say about that.

[pmd400]

I'm thinking with the intake/exhaust ratio that longer exhaust won't be needed.
Reason for 1 5/8 headers was cost. Bought them locally cheap. Exchange rate plus shippinging makes decent headers expensive. Iv got a couple of quadrajet carbs that will need to be modified and a couple of factory intakes plus a torker 2. Reason for p65 and eddys is for aesthetic reasons and the challenge.

[ponyakr]

Just happened to remember that Summit has a single pattern. It looks identical to the Crane, but cheaper. Crane probably made 'em.

https://www.summitracing.com/parts/s...w/make/pontiac

[steve25]

Isky 901271 with 1.65 rockers and a spring package to handle .550" lift even though the lift will only be some .510".

[ponyakr]

If 108 LSA will produce enuff vac for power brakes, here's a Lunati that might work, also. It's 275/225/.477/108 LSA.

https://www.summitracing.com/parts/lun-10510301

And the next bigger Isky is 280/224/.465/108.

http://iskycams.com/cart/index.php?m...oducts_id=1019

[Lee]

Member Stickboy had a very similar combo in his '65 GTO (except the intake/carbs). Doug Nash (Richmond) underdrive 5spd with 2.73 gears, even.

He ran an UltraDyne 280/288 (223/231 @ .050) on a 112lsa. You can get that grind from Bullet Cams. I believe he ran 12.2's with iron heads, and drove it on the street often.

Stickboy (Obeid) stills posts here at times I believe, maybe send him a PM for details.

[ponyakr]

That UD cam is real close to the Crower 60242 & 60916. And I assume the Crower would be cheaper than a custom UD grind from Bullet.

http://www.bulletcams.com/Masters/ultradynemasters.html

But, I've never bought a custom. So, maybe some of you guys can tell us the price of a Bullet custom HFT UD grind.

[pastry_chef]

Originally Posted by ponyakr

But, I've never bought a custom. So, maybe some of you guys can tell us the price of a Bullet custom HFT UD grind.

300000UD CUSTOM GRIND FLAT TAPPET (ULTRA DYNE) 183.08

From
http://bulletcams.com/pl.html

[tom s]

Guys,he is looking for a good street driving cam for a 461 CI engine.From my experiance a 108 is a crappy street manner cam.Also the CI of the engine eats up duration.If me it would be a 232-240 ish at 50 on a 112.Also stick shift cars tend to buck more and required to pull back a lower gear at lower street RPMs.This type of engine has been gone over tons of time and 230-240 ish cams on a wide lobe always get the nod.NOT for peak HP or racing but good street manners.Also too small of cams tend to be more detonation prone.FWIW,Tom

[61-63]

What Tom said. A Crower 60919 with Rhoads lifters.

[ponyakr]

"...230-240 ish cams on a wide lobe always get the nod..."

Yeah, some guys don't like it, but the old 041 grind is hard to beat.

But, if a single pattern would be better, there are some that are in this neighborhood.

And, if you include customs, such as the Bullet cams, you can zoom in to EXACTLY what you want. If you don't like the UD lobes, Bullet has a long list of lobes to choose from. I didn't count 'em, but there appear to be well over 100 lobes shown, from 230 thru 240 @ .050. Bound to be some combo of these lobes and a 112-114 LSA that will work.

http://www.bulletcams.com/Masters/Hlobes.htm

[ponyakr]

"...A Crower 60919 with Rhoads lifters..."


This brings up the subject of Rhoads lifters again. So, has anybody heard any more about whether Rhoads quit using Hylift Johnson cores or not ?

Also, I asked this before and got no answer that I remember. Butler advertises the CCA-852B-16 Comp Cams lifters as being Hylift Johnson. Is this correct ? If so, I assume that these are just the base lifters and NOT the Hylift Johnson 951R lifters that most say are better ?

http://butlerperformance.com/i-24453...tegory:1234799

Are these CCA-852B-16 lifters the exact same lifters that everybody else sells, which are called High Energy lifters, with a part # 852-16 ?

http://www.ebay.com/itm/Comp-Cams-85...25.m3641.l6368


Just an observation: For those on a very low budget, which seems to be a fairly large percentage of Pontiac street guys, one of the Summit cams is over $100 cheaper than a Bullet custom.

[pastry_chef]

Comment from Chris Straub.
I've known him to get results for years!

---------------------------------------
Math does not discriminate, it doesn't care if it a Poncho or a Mopar. The numbers have been listed. Based on the demand set by the piston speed, the potential fill and evac of the heads, the math will not lie to you. It will provide a "smart brain" for the engine....the camshaft is the brain of the engine.

Years ago when I was in my 20's, I would hesitate when the math was totally opposite to what was considered the norm. The first time I got the balls to hold my ground was a Super Stock Hemi guy. The math's result was met with, "Hemi's only run on XXX LSA". I can't remember exactly what I said but it was to the tune of "Doing what everyone else does is following." That didn't work but what did was if the cam didn't work it was free. If it did he paid for it. She made more power and she was quicker at the track. From that point I followed the math. Even with a local guy here in TN when his BBC 540 needed a 26 degree split favoring the exhaust I stood with the math. That engine had an I/E ratio in the low 50's. Power gain on the dyno was 146HP with cam change.

My experience is follow the math, its does not mix words. This engine and any other NA engine with that kind of I/E ratio needs a reverse split camshaft. Hell the Japanese figured this out 3 decades ago.
Chris Straub

-----------------------------

Another thread worth a read.
http://www.chevelles.com/forums/showthread.php?t=374438

[72LuxuryLeMansLa.]

Originally Posted by pastry_chef

Comment from Chris Straub.
I've known him to get results for years!

---------------------------------------
Math does not discriminate, it doesn't care if it a Poncho or a Mopar. The numbers have been listed. Based on the demand set by the piston speed, the potential fill and evac of the heads, the math will not lie to you. It will provide a "smart brain" for the engine....the camshaft is the brain of the engine.

Years ago when I was in my 20's, I would hesitate when the math was totally opposite to what was considered the norm. The first time I got the balls to hold my ground was a Super Stock Hemi guy. The math's result was met with, "Hemi's only run on XXX LSA". I can't remember exactly what I said but it was to the tune of "Doing what everyone else does is following." That didn't work but what did was if the cam didn't work it was free. If it did he paid for it. She made more power and she was quicker at the track. From that point I followed the math. Even with a local guy here in TN when his BBC 540 needed a 26 degree split favoring the exhaust I stood with the math. That engine had an I/E ratio in the low 50's. Power gain on the dyno was 146HP with cam change.

My experience is follow the math, its does not mix words. This engine and any other NA engine with that kind of I/E ratio needs a reverse split camshaft. Hell the Japanese figured this out 3 decades ago.
Chris Straub

-----------------------------

Another thread worth a read.
http://www.chevelles.com/forums/showthread.php?t=374438

I have a friend that is a member on this board. He is a very experienced and knowledgeable mechanic, not a "technician". He always tells me 350 cubic inches is 350 cubic inches! The cam doesn't care who made the engine! I guess that's another way of saying the math doesn't lie!

[Steve C.]

UltraDyne has been brought up here. And Skip Fix once made this comment before...

"Harold was also a big proponent of matching the intake/exhaust duration split to the head flow"

Harold Brookshire was UltraDyne. And to further Skip's comment of matching the intake/exhaust duration split to the head flow here was a comment I made that is related:

Years ago I asked Harold at Ultradyne when he was posting here on PY about the subject of a single pattern vs. a dual pattern cam. Here was his reply:

There are two different items at work here.
1.---On most cylinder heads, whenever I have around a 75% exhaust-to-intake ratio, I use an 8 degree bigger exhaust cam. If the ratio is under 70%, I use 12 degrees, and around 80%, only 4. Whenever the ratio gets around 85%, single pattern cams seem to work as good as anything. Rarely do reverse-pattern (intake bigger than exhaust) cams work. The two times they do, blown alcohol and turbo-charged, are both for putting heat into the engine or the exhaust.

2.---At the same time, it depends upon what you want the engine to do. Single pattern cams have better bottom-end, dual pattern cams have better top-end. At low RPM, the longer power stroke of a single pattern cam puts more torque into the crank. At high RPM, the most important thing is getting exhaust gas out of the engine. You can't get more charge in if old exhaust gas is still in the chamber. This is why the torque curve makes a sudden down-turn at peak horsepower. The exhaust cam has suddenly become inefficient about getting the old exhaust out, and some gas is retained and trapped, and the intake cannot fill completely because of this extra exhaust gas hanging around.

So, for the best overall power curve, on the average you want a dual-pattern cam, and around 8 to 10 degrees more exhaust. However, if a lot of bottom-end is your goal, or you have heads with a high exhaust/intake ratio, a single-pattern cam will work better.
Was this confusing enough? This is based on 30 years(1972-2002) of cam design and application.
UDHarold

( side note: There have been interesting conversations, and opinions, here with skip and others regarding reverse pattern cams. Remember the above was Harold's opinion )

Also related. If you call Bullet Racing Cams about a custom cam with UltraDyne lobes or their own lobes do not be surprised if they bring up the topic of a narrow lobe separation. As often Harold Brookshire did at UlltraDyne.




.

[Lee]

Things to note in the opening post:

9.4:1 CR
Power brakes are a must
Street Car
Dual Edelbrock carbs (which are NOT friendly to tune)
2.41 or 2.73 gears

He does NOT need a cam with 230 or more duration at .050".

He needs a cam that provides excellent low-mid range characteristics.

The Crower 242 would be good. The UD 280/288 is PROVEN in a very similar car. If he were closer to 10.0, then I'd say that is too small of a cam (detonation risk), but at 9.4 he should be good.

[pastry_chef]

More about reverse split (Dave Crower).

Originally Posted by Singleton

Filled out the online cam recommendation sheet on Crower's site the other day. Looking for a healthy solid flat tappet for street/strip.

Here's the basic info given to them:

66 GTO ~ 3600lbs
Manual trans
3.90 gear
Tire height-28"
No power accessories (steering,brakes etc)
428 + .065 (440) 4.185X4.0
6.8 connecting rods
9.5 CR
Tomahawk intake
800-850 cfm carb
SDperf ported 6X heads (90cc)
261/214 cfm @ .600
Int/Exh ratio 84% average
1.65 rockers
RPM range desired- 3500-6000

Got a call from Dave Crower, (nice guy btw), the next day.

262*/252* @.050, .585/.570 w/1.65, 110LSA

Reverse Split. I was surprised considering that almost every Pontiac cam that I have seen has about 8 degrees more on the exh side. Dave explained that my intake ports are deficient compared to the exhaust ports, (84%avg).

[tom s]

FYI,the worst 455 street engine I ever built was a 9.5 455 with a 2801 summit cam.Pumped 200 lb and had to ad race gas to every tank of gas.Tom

[72LuxuryLeMansLa.]

Originally Posted by Steve C.

UltraDyne has been brought up here. And Skip Fix once made this comment before...

"Harold was also a big proponent of matching the intake/exhaust duration split to the head flow"

Harold Brookshire was UltraDyne. And to further Skip's comment of matching the intake/exhaust duration split to the head flow here was a comment I made that is related:

Years ago I asked Harold at Ultradyne when he was posting here on PY about the subject of a single pattern vs. a dual pattern cam. Here was his reply:

There are two different items at work here.
1.---On most cylinder heads, whenever I have around a 75% exhaust-to-intake ratio, I use an 8 degree bigger exhaust cam. If the ratio is under 70%, I use 12 degrees, and around 80%, only 4. Whenever the ratio gets around 85%, single pattern cams seem to work as good as anything. Rarely do reverse-pattern (intake bigger than exhaust) cams work. The two times they do, blown alcohol and turbo-charged, are both for putting heat into the engine or the exhaust.

2.---At the same time, it depends upon what you want the engine to do. Single pattern cams have better bottom-end, dual pattern cams have better top-end. At low RPM, the longer power stroke of a single pattern cam puts more torque into the crank. At high RPM, the most important thing is getting exhaust gas out of the engine. You can't get more charge in if old exhaust gas is still in the chamber. This is why the torque curve makes a sudden down-turn at peak horsepower. The exhaust cam has suddenly become inefficient about getting the old exhaust out, and some gas is retained and trapped, and the intake cannot fill completely because of this extra exhaust gas hanging around.

So, for the best overall power curve, on the average you want a dual-pattern cam, and around 8 to 10 degrees more exhaust. However, if a lot of bottom-end is your goal, or you have heads with a high exhaust/intake ratio, a single-pattern cam will work better.
Was this confusing enough? This is based on 30 years(1972-2002) of cam design and application.
UDHarold

( side note: There have been interesting conversations, and opinions, here with skip and others regarding reverse pattern cams. Remember the above was Harold's opinion )

Also related. If you call Bullet Racing Cams about a custom cam with UltraDyne lobes or their own lobes do not be surprised if they bring up the topic of a narrow lobe separation. As often Harold Brookshire did at UlltraDyne.




.

Steve,

I am FAR from an expert! My question is this. Shouldn't the exhaust system come in to play here? Say you have an 80% exhaust to intake ratio on the head flow but instead of headers you run ram air exhaust manifolds..... Does this negate some of the exhaust to intake ratio of the heads?