[footjoy]

I was reviewing some things on my 400 x.040 build I have come to the conclusion I might have made some mistakes. Not sure

pontac 406 block
flat top pistons with 4 reliefs
Crower 40240 cam straight up
pontiac #15 heads small valve 90cc
performer intake
Quickfuel carb 735 cfm
stock exhaust manifolds
HEI
2004r with 3.73:1 = 2.55 final gear

Looking at the cam information it is recomended to have 9.5:1 compression.
I don't think I have that much compression probably more like 8.75.

according to Wallaces charts the block and heads are rated for 290 horse engine that does not take into consideration cam and carb.

Questions
1. do the heads and cam work well together?
2. what would it take to get 350 horse power from this block?

The car runs OK but gas mileage is 10 mpg. If I am going to get that kind of mpg I think I'll look at more horse power.

Any constructive thoughts?

Thanks greg

[pastry_chef]

Originally Posted by footjoy

Crower 40240 cam straight up

This cam?

https://www.summitracing.com/int/par...0240/overview/

[steve25]

Your heads flow 182 Intake cfm @ .450" lift, that's enough for 360 hp in a well tuned motor with the needed compression for the Cam its running, that being said I have not run the numbers , but I do not think your even at 9 to one comp with your set up now.

To save your combo if it lacks snap with your rear gears you might concider running a Vari duration lifter , or advancing the Cam 4 degrees.

[tooski]

I couldn't find a 40240 cam. Maybe 60240. I have a similar cam, only on a 110 lsa. I had a thread on CR for that cam. Smaller cam, good cylinder filling. Was told to use not much more than 9:1 for it. I think others will say the performer intake is not ideal. A stock intake would be better but the QF will need an adapter and still not be ideal. Mine is an RPM with 750 VS. I like the power but I couldn't say if it is 350. My mpg is likely in the high teens as a guess ( my RA4 , 10:1, 4.11 gears engine got 11 mpg city driving - calculated. This one is much better.)

[ponyakr]

Assume you mean 60240. That cam might do OK, especially in the lower rpm range. . But, a Voodoo 262 cam should get you closer to that 350hp number.

https://www.lunatipower.com/voodoo-h...8-262-268.html

A '71 400 with 96cc #96 heads was rated at 300hp, with only an 067 cam.

A '70 400 with 72cc #13 heads was rated at 350hp, with that same 067 cam. So, the CR does make a difference. A '69 RA3 400 with a 744 cam was rated at 366hp.

Therefore, I'd guess that your 90cc heads, with a 262 Voodoo cam, should make somewhere near 350hp.

Obviously, the exact specs of the build, as well as state of ignition & carb tune will help determine max hp number.

Len Williams estimates aprox 385hp for this 9.25 CR 400.

http://lenwilliamsautomachine.com/400_Long_Block.html

Cam specs are not listed. But Rhoads lifters are on the list. Rhoads lifters can allow you to run a larger cam, but still have a decent idle, good vac, and good low rpm torque. This might help you reach that 350hp number you mentioned, but still have a very streetable cam. Some love Rhoads lifters. Some hate 'em, & badmouth 'em every chance they get. A Voodoo cam does not need Rhoads lifters.

It has been posted here many times that there have been lots of guys very disappointed with an 041 clone cam, in a street 400. So, I think it is safe to say that less than 230° intake duration @ .050 lift will be better suited for a street 400.

If trying to get anywhere near 350hp, I don't see any reason to use a cam smaller than an 068 clone. The 2801 Summit is similar, with more lift.

Besides the 262 Voodoo I mentioned, here are a few more that might work.

Howards 410021-12

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

Lunati 10510312

https://www.lunatipower.com/street-m...8-276-286.html

Howards 410141-12

https://www.summitracing.com/parts/hrs-410141-12

Crane 283951. This cam, with Rhoads lifters, should have a broad power range, getting you to, or very near that 350hp range, but maintaining decent low rpm manners.

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

[footjoy]

What compression is what we shoot for Static or Dynamic


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[Steve C.]

From the Crower 60240 cam card.....

"4 degrees of advance have been ground into this Camshaft"


.

[Steve C.]

2004R Gear Ratios:

First- 2.74:1
Second- 1.57:1
Third- 1:1
Fourth- .67:1

3.73 rear gear x .67 = 2.499 final gear


.

[77 TRASHCAN]

Are you going to, or can you zero deck the block? IT would help with any type of a build.

I assume stock type .039 head gaskets?

I get 8.6:1 with pistons .020 in hole, 8.92:1 with zero deck

[STEELCITYFIREBIRD]

Originally Posted by Steve C.

2004R Gear Ratios:

First- 2.74:1
Second- 1.57:1
Third- 1:1
Fourth- .67:1

3.73 rear gear x .67 = 2.499 final gear


.

I believe first gear calculation is where you want to look for adequate torque multiplication for a given cam/displacement/CR.

You got a pretty deep first gear!

[Steve C.]

Correcting the first post...

2004r with 3.73:1 = 2.55 final gear


.

[footjoy]

Would I get any help from these heads if I put bigger valves in?

Would it be worth it to Mill these heads?

What would be a good set of heads to get me to 350 hp but still have street manners?

Thanks

[STEELCITYFIREBIRD]

Is this a fresh bore, ball and ring job, etc?
What pistons?
Dual exhaust?
What year make and model is it in?

Holley carbs are notorious for heavy fuel consumption if not tuned well or in a good state of tune.

You may gain some performance and fuel economy by tweeking your dizzy and carb.
Vacuum advance operational?

A heavy FOOT will kill MPG in any vehicle.

I'd look at the tune, cranking compression before changing out any major components.

[PunchT37]

It might not be the best cam for your app but, it will work fine. I ran one of those in a stock W72 400. No problems.

[steve25]

In terms of your # 15 heads I know that installing a larger Exh valve will pick you up flow nicely, but I am not sure about the Intake valve.

The thing you can count on by installing larger valves is a increase in compression .

For instance a easy .030" mill on the Deck ( no need to mill the Intake flange at .030" ) knocks you off 5 CCs of chamber volume and the bigger valves like 4 CCs , so right there your down to near a 80 CC chamber

Every .006" milled off gets rid of 1 CC of chamber volume.
If you where to mill .045" of the head I would want to see you mill that same amount off of the Intake so that all bolts back together nice & happy!


If you can hold off on making a decision until the weekend, I have a # 15 casting and I will stuff in a 2.11" valve and then flow test it to see what gives for you if you like?

Also since we are taking about maybe pulling your heads for a workover, I would like to know what valve springs are on them because if they can take up to .500" lift ( stock ones can't) you can add higher ratio rockers now or down the road to that Cam and pick up more over the nose duration ( will not effect idle really) and close to .040" in lift which in itself is worth atleast 10 hp .

[Cliff R]

If you are in just under 9 to 1 compression you have the right cam. I'd make sure to modify the heads so you can add high ratio rockers. The 60240 is an awesome cam for a lower compression 400 build. Plenty of vacuum for power brakes, strong power down low and excellent street manners. If you want to add some "spice" later on it will do very well with your set-up topped with a set of 1.65 ratio rockers.......Cliff

[gtofreek]

Originally Posted by footjoy

What compression is what we shoot for Static or Dynamic


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Always, ALWAYS, base cam choices off of static compression, NOT dynamic. Dynamic compression can be deceiving. Two cams with the same intake closing point will show the same dynamic compression, but one may be better at cylinder filling than the other[say a roller cam compared to a flat tappet cam] thus raising the dynamic compression of the engine even though the valve is still closing at the same point. Plus I have cured detonation problems in engines by advancing the cam, NOT retarding it. So the dynamic compression thing can be real deceiving, and shouldn't be used for cam determination, IMO.

[Cliff R]

Correct.

Cam choice can certainly make or break an engine build. Case in point. Last Saturday a customer trailers his 1970 Chevelle SS 454 4 speed car here for me to custom tune. It's a very well done restoration and I restored the carb for it. The engine was "built" for it pretty much to "stock" specs from what I was told, about 10.5 to 1 compression and custom ground flat cam close to stock specs just a little "better".

So from day one the engine runs poorly, and of course everyone is blaming the carb guy, so efforts via phone calls and emails are unsuccessful so I have the car brought here.

It just doesn't run for chit! "Quirky" idle, doesn't like, want or need much timing, lackluster throttle response and pings unless you pull a lot of timing out of it.

So I adjusted the carb some, and difficult getting the idle speed low enough, a little control with the mixture screws but it just didn't act right anyplace. So I pull the carb and all is fine and it is set up for a pretty close to stock 454 LS5 engine.

So I ask the owner if he has the cam card, and he looks around some and finds it on his phone. It's a custom grind 220/224 @ .050". Well that isn't going to make the grade in this big high compression 454 and not anywhere even close to the specs of the factory cam with it's 260 something advertised seat timing. Probably more suited for a 350 build around 9 to 1 compression....IMHO.

So I remove all the idle bypass air, lean up the idle system, put it back in place and it's better for idle quality and now we can slow it down to spec, but the engine is still a turd and it even pings when you crank it with only 8 degrees initial timing in it!

Moral of the story, don't put 350 size cams in big 454's, or 455's if you are building a Pontiac engine. Nothing ever goes right with that deal, especially if you are trying to manage pump gas with pretty high compression on this new fuel.......Cliff

[Lee]

Stock exhaust manifolds are going to choke off your power a bit after 4,000rpm.

No need for high compression or a big cam to operate at that rpm.

[footjoy]

I have written 3 or 4 responses and they get lost.

The motor is already built and has 1500 miles on it. I looked up the headwork reciept and it looks like they might of shimmed the springs to find the pressure for the cam. There is no mention of new springs on the reciept.
So if that is the case can I check spring pressure while on the motor?

Do I need special springs to run roades lifters? And I guess there needs to b work done to put 1.65 rockers on.

2 choices
1 be happy with 10 mpg and leave alone
2 Put another set of Heads on and enjoy the horse power and 10 mpg.

As Always Thanks for the constructive thoughts.

Greg