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Camshaft questions for 434 with small heads

General engine tech -- Drag Racing to Circle Track

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Monza355
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Camshaft questions for 434 with small heads

Post by Monza355 »

Hello guys. I’m going to build a 434 street engine and have many of the parts already available. It will be a 10:1 compression and it must drive on 91 octane pump gas. It will go in a tall geared tight converter driver with TH350 transmission and Aprox. 2500-3000 stall.

I want to use a set of Dart sportsman iron heads that i was going to use for another project. But since i have them i want to use them for now. I might upgrade them later on when funds allow. But they are in very good shape. They have been pocked ported and did work well on a 406 they were on.

For intake manifold i have both a regular performer rpm, victor jr or super victor 2925. I also have a 80496 950cfm holley hp carburetor that will be used.

I want to run some kind of street solid roller that’s easy on parts, like comp cams xe lobes. Going by the 128 David Vizard formula i calculate the need for 103.5 LSA for a 2.02” intake valve in a 434 cid engine. So we round that up to a 104 LSA.

What duration should i be looking at for an application like this.
I was thinking a redline of about 6200 rpm should work good for this application.

Is there anyone specific i should talk who can help me out with camshaft for an under headed engine like this ?
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Re: Camshaft questions for 434 with small heads

Post by Walter R. Malik »

Monza355 wrote: Mon Jan 06, 2020 3:23 pm Hello guys. I’m going to build a 434 street engine and have many of the parts already available. It will be a 10:1 compression and it must drive on 91 octane pump gas. It will go in a tall geared tight converter driver with TH350 transmission and Aprox. 2500-3000 stall.

I want to use a set of Dart sportsman iron heads that i was going to use for another project. But since i have them i want to use them for now. I might upgrade them later on when funds allow. But they are in very good shape. They have been pocked ported and did work well on a 406 they were on.

For intake manifold i have both a regular performer rpm, victor jr or super victor 2925. I also have a 80496 950cfm holley hp carburetor that will be used.

I want to run some kind of street solid roller that’s easy on parts, like comp cams xe lobes. Going by the 128 David Vizard formula i calculate the need for 103.5 LSA for a 2.02” intake valve in a 434 cid engine. So we round that up to a 104 LSA.

What duration should i be looking at for an application like this.
I was thinking a redline of about 6200 rpm should work good for this application.

Is there anyone specific i should talk who can help me out with camshaft for an under headed engine like this ?
You are considering camming that engine for maximum power at Wide Open Throttle for a certain redline but, your application will not be at wide open throttle most of the time.

So, make a consideration for this in your camshaft choice.
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Re: Camshaft questions for 434 with small heads

Post by Monza355 »

Walter R. Malik wrote: Mon Jan 06, 2020 3:27 pm
You are considering camming that engine for maximum power at Wide Open Throttle for a certain redline but, your application will not be at wide open throttle most of the time.

So, make a consideration for this in your camshaft choice.
I understand. I mentioned the redline because i want to go to the drag strip on occasion, but since this is primarily a street car good manners, reliability and the fact itmust be able to run on 91 octane pump gas are very important factors of this build. Much more important than maximum horsepower.
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Re: Camshaft questions for 434 with small heads

Post by PRH »

Aaaahh yes...... the “what camshaft” question.

They usually result in as many different general types of recommendations(and some specific recommendations) as there are responses.

But, in general...... I agree with where Walter is coming from in this application.

For a street car running with closed exhaust........ a cam with a 104lsa wouldn’t be where I ended up...... even if that meant I was leaving power on the table.
As I’ve gotten older, I’ve gained an appreciation for “wider” lsa cams for cars that see a lot of street use.

If it’s really going to get tall gears and have less than 3000 stall....... I’d say something along the lines of a Comp xr280r would work.

I’d consider the next step up from that to be the xr286r intake lobe as a single pattern on a 110. Might be a tad big for the low stall, but could be okay with the RPM intake.
Somewhat handy with a die grinder.
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Re: Camshaft questions for 434 with small heads

Post by Monza355 »

I get the point about the lsa and wasn’t sure about it. It was just calculated from the 128 formula and a lot of reading. Maybe DV point is the 128 formula is best suited for wot applications.

The car is 3600 lbs with 3.50 gears and 275/60 (28”) drag radials. However the converter hasn’t been decided yet but i was thinking about a nice 10” with around 2800 stall. This size engine should be able to make decent amount of torque at that rpm. Of course camshaft depending…
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Re: Camshaft questions for 434 with small heads

Post by lefty o »

just off the cuff, but id be looking in the 230-235 degr ballpark with 108-110lsa. would be different for something you plan to race a lot and putter around a little.
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Re: Camshaft questions for 434 with small heads

Post by F-BIRD'88 »

Howards cam #110183-08S

Use the Rpm intake.. I would not use a 104lsa cam on this street motor with intent to run on mild gasoline nore
with the dual plane...
It will make a ton of torque with the off the shelf cam.
This is the small base circle version.
This is not the cam that makes the most horsepower but meets your intended use.
Any 10" converter will show more than 2800 stall at the track on sticky tires when behind a 434 cid big torque sbc.
Thats a +. (hard launch)
IMHO a full street exhaust system will throw a wrench in
the real success of a 128 formula speced 104 lsa cam for this one.

The installed intake C/L of this 108Lsa cam can be played with.
it will be very enjoyable to drive around in street duty mode.
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Re: Camshaft questions for 434 with small heads

Post by Walter R. Malik »

Monza355 wrote: Mon Jan 06, 2020 3:49 pm
Walter R. Malik wrote: Mon Jan 06, 2020 3:27 pm
You are considering camming that engine for maximum power at Wide Open Throttle for a certain redline but, your application will not be at wide open throttle most of the time.

So, make a consideration for this in your camshaft choice.
I understand. I mentioned the redline because i want to go to the drag strip on occasion, but since this is primarily a street car good manners, reliability and the fact itmust be able to run on 91 octane pump gas are very important factors of this build. Much more important than maximum horsepower.
Personally ... I would simply get a Lunati "Voo-Doo" hydraulic flat tappet, 227/233 grind with the Victor Jr. intake.
#10120703 ... 268/276 off the seat, .489"/.504" valve lift, 110 separation; 106 intake C/L.
A 1.6/1 intake rocker for a little more lift.

EDIT: There must be plenty of others within the same realm.
Last edited by Walter R. Malik on Mon Jan 06, 2020 8:30 pm, edited 3 times in total.
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Re: Camshaft questions for 434 with small heads

Post by cab0154 »

i would run the comp 12-771-8 with the biggest single plane possible. the dual plane tq theory only works if it doesnt choke off the engine. with a small head, with a lot of cylinder under it a big single plane is the way to go.
"Anyone who thinks the low RPM engine will be faster just does not have as much experience as the rest of us" -The late, great Joe Sherman.
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Re: Camshaft questions for 434 with small heads

Post by GARY C »

Monza355 wrote: Mon Jan 06, 2020 3:23 pm Hello guys. I’m going to build a 434 street engine and have many of the parts already available. It will be a 10:1 compression and it must drive on 91 octane pump gas. It will go in a tall geared tight converter driver with TH350 transmission and Aprox. 2500-3000 stall.

I want to use a set of Dart sportsman iron heads that i was going to use for another project. But since i have them i want to use them for now. I might upgrade them later on when funds allow. But they are in very good shape. They have been pocked ported and did work well on a 406 they were on.

For intake manifold i have both a regular performer rpm, victor jr or super victor 2925. I also have a 80496 950cfm holley hp carburetor that will be used.

I want to run some kind of street solid roller that’s easy on parts, like comp cams xe lobes. Going by the 128 David Vizard formula i calculate the need for 103.5 LSA for a 2.02” intake valve in a 434 cid engine. So we round that up to a 104 LSA.

What duration should i be looking at for an application like this.
I was thinking a redline of about 6200 rpm should work good for this application.

Is there anyone specific i should talk who can help me out with camshaft for an under headed engine like this ?
I don't know how easy getting a cam for a 104 would be, if it was me I would probably run something like the Comp XE 288 on a 106 and this converter as to not complicate things, if your exhaust is done correct it should reduce sound and not power, at least that has been experience.
https://www.jegs.com/i/COMP-Cams/249/12-433-8/10002/-1
https://www.jegs.com/i/JEGS/555/60429/10002/-1
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Re: Camshaft questions for 434 with small heads

Post by BrazilianZ28Camaro »

The dual plane intake will choke that engine.

I'd get a HR cam around 234-238@.050 0n 109 LCA/ 105ICL with all the lift possible.

Should make plenty of torque to launch your car well.
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Re: Camshaft questions for 434 with small heads

Post by RevTheory »

On an under-headed engine, about all you can do is give it more duration but that comes with the obvious drawbacks.

I did a 10:1 383 years ago using a single-pattern Comp XSR 280, 242 @ .050 on a 106 and the torque curve hit like a truck but it was out of steam by 6,000 rpm using AFR pre-Eliminator 195s and a Performer RPM. It had a pretty aggressive idle but I'm sure your additional 60 cubes would tame quite a bit of that out. Enough to run tall gears and a tight convertor, though? I doubt it.
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Re: Camshaft questions for 434 with small heads

Post by CGT »

A 2500-3000 converter is too tight for a stock cam technically, if fastest ET was the only goal but that's not the main goal so.....If it was mine I'd probably choose the vic jr or super vic, whichever one fits the head better if your not wanting to do much work.
BrazilianZ28Camaro wrote: Mon Jan 06, 2020 10:49 pm I'd get a HR cam around 234-238@.050 0n 109 LCA/ 105ICL with all the lift possible.
lefty o wrote: Mon Jan 06, 2020 6:22 pm just off the cuff, but id be looking in the 230-235 degr ballpark with 108-110lsa.
I think both these suggestions are a good basic area to be at. I think that combo could be made to be a pretty mean street combo if some time was spent on it.
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Re: Camshaft questions for 434 with small heads

Post by raynorshine »

CGT wrote: Tue Jan 07, 2020 10:06 am A 2500-3000 converter is too tight for a stock cam technically, if fastest ET was the only goal but that's not the main goal so.....If it was mine I'd probably choose the vic jr or super vic, whichever one fits the head better if your not wanting to do much work.
BrazilianZ28Camaro wrote: Mon Jan 06, 2020 10:49 pm I'd get a HR cam around 234-238@.050 0n 109 LCA/ 105ICL with all the lift possible.
lefty o wrote: Mon Jan 06, 2020 6:22 pm just off the cuff, but id be looking in the 230-235 degr ballpark with 108-110lsa.
I think both these suggestions are a good basic area to be at. I think that combo could be made to be a pretty mean street combo if some time was spent on it.
X 3!! really solid advice =D>
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Re: Camshaft questions for 434 with small heads

Post by Monza355 »

Walter R. Malik wrote: Mon Jan 06, 2020 8:23 pm
Monza355 wrote: Mon Jan 06, 2020 3:49 pm
Walter R. Malik wrote: Mon Jan 06, 2020 3:27 pm
You are considering camming that engine for maximum power at Wide Open Throttle for a certain redline but, your application will not be at wide open throttle most of the time.

So, make a consideration for this in your camshaft choice.
I understand. I mentioned the redline because i want to go to the drag strip on occasion, but since this is primarily a street car good manners, reliability and the fact itmust be able to run on 91 octane pump gas are very important factors of this build. Much more important than maximum horsepower.
Personally ... I would simply get a Lunati "Voo-Doo" hydraulic flat tappet, 227/233 grind with the Victor Jr. intake.
#10120703 ... 268/276 off the seat, .489"/.504" valve lift, 110 separation; 106 intake C/L.
A 1.6/1 intake rocker for a little more lift.

EDIT: There must be plenty of others within the same realm.

I did think about going with a simple flat tappet camshaft. But i’ Not sure that it fits because of the long stroke because of the base circle.
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