[footjoy]

Originally Posted by Murf

Why the fixation on 9.4 comp if it’s just a fun driver?


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I would like to put a bigger cam and get as close to 340 hp as I can. Mid 300 hp will give me close to 275 rear wheel hp. I already figured out 220 to the rear wheels is no fun.




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[Murf]

I guess I’m with ponyakr. Why not get what compression you can easily, then cam for that compression ratio? If you have to sink a bunch of money in your 15’s maybe trying the Speedmaster aluminum heads would be an alternative. It doesn’t take long to get some money wrapped up in a set of old heads. Good luck whatever you do!

Murf


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[ponyakr]

[QUOTE=footjoy;6084425]I would like to put a bigger cam and get as close to 340 hp as I can. Mid 300 hp will give me close to 275 rear wheel hp. I already figured out 220 to the rear wheels is no fun./QUOTE]

So, you're after a certain hp number and NOT low rpm torque ?

At what rpm do you want your peak "Mid 300 hp" ?

Assuming this is a stock stroke 400 ?

Took a quick look back over the thread. All shortblock specs may have been mentioned. If so, I missed it.

Piston specs ? Deck height ?

According to the Wallace Engine ID look-up, 350 hp 400 engines had from 10:1 to 10.75:1 CR, and either an 066, 067, or 068 cam. And they all had a 750 cfm Q-jet.

http://www.wallaceracing.com/enginesearch4.htm

Those are pretty small cams. I assume that a larger cam would have increased peak hp, & moved the peak up the rpm scale. An example might be the early '69 366 hp manual trans RA3 engine, which used a 744 cam. But, that same 366 hp number was used with the 068 cam, with #48 & #12 heads. But, I don't know how accurate those adv hp numbers were.

Anyhow, as you reduce the CR, the hp will be lower, if you use the same cam. So, common sense would say that if you lower the CR, but wanna maintain the same hp, you'll have to make up the lower CR, with the cam choice.

As many have mentioned, the steep ramp cams, such as the Voodoo series, makes up for some loss of CR, by increasing cyl pressure. Paul Carter seems to be the biggest promoter of the Voodoo cams, here. His engine builds have posted some very impressive numbers, using Voodoo cams.

Now, if you don't care about having a smooth idle, lots of vac, & lots of low rpm torque, there are lots of larger cams that will make at least 350 hp in a correctly built 400, with at least 9:1 CR.

Assuming an 068 cam actually did make 350 hp, in the '69-'70 D-port engines, I assume a small cam, such as a Lunati 10510312 should make real close to 350, in a 9.4 CR engine like you're proposing. A Summit 2801 might even do it. Should be some guys here who can post what a 2801 made in a similar 400 engine. Either of these 2 cams should work with fairly low pressure valve springs.

A 2802 would make a little more & move peak up the rpm scale. Rhodes lifters might make this a real nice 400 street engine. But, it seems that most Pontiac forum & FB page dwellers now hate even the mention of Rhoads lifters.

I ASSUME that a small Voodoo would make max below 5000 rpm hp. But, Paul Carter has mentioned that because of the steep ramps, the Voodoo cams require lots of spring pressure. I would not wanna have to run that much pressure, on an engine I was gonna drive a lot, on the street. But, lots of Pontiac guys brag about running huge roller cams with high spring pressures, on the street, for many years, with absolutely no problems at at. So, everybody has to decide what they wanna run.

[footjoy]

[QUOTE=ponyakr;6084479]

Originally Posted by footjoy

I would like to put a bigger cam and get as close to 340 hp as I can. Mid 300 hp will give me close to 275 rear wheel hp. I already figured out 220 to the rear wheels is no fun./QUOTE]

So, you're after a certain hp number and NOT low rpm torque ?

At what rpm do you want your peak "Mid 300 hp" ?

Assuming this is a stock stroke 400 ?

Took a quick look back over the thread. All shortblock specs may have been mentioned. If so, I missed it.

Piston specs ? Deck height ?

According to the Wallace Engine ID look-up, 350 hp 400 engines had from 10:1 to 10.75:1 CR, and either an 066, 067, or 068 cam. And they all had a 750 cfm Q-jet.

http://www.wallaceracing.com/enginesearch4.htm

Those are pretty small cams. I assume that a larger cam would have increased peak hp, & moved the peak up the rpm scale. An example might be the early '69 366 hp manual trans RA3 engine, which used a 744 cam. But, that same 366 hp number was used with the 068 cam, with #48 & #12 heads. But, I don't know how accurate those adv hp numbers were.

Anyhow, as you reduce the CR, the hp will be lower, if you use the same cam. So, common sense would say that if you lower the CR, but wanna maintain the same hp, you'll have to make up the lower CR, with the cam choice.

As many have mentioned, the steep ramp cams, such as the Voodoo series, makes up for some loss of CR, by increasing cyl pressure. Paul Carter seems to be the biggest promoter of the Voodoo cams, here. His engine builds have posted some very impressive numbers, using Voodoo cams.

Now, if you don't care about having a smooth idle, lots of vac, & lots of low rpm torque, there are lots of larger cams that will make at least 350 hp in a correctly built 400, with at least 9:1 CR.

Assuming an 068 cam actually did make 350 hp, in the '69-'70 D-port engines, I assume a small cam, such as a Lunati 10510312 should make real close to 350, in a 9.4 CR engine like you're proposing. A Summit 2801 might even do it. Should be some guys here who can post what a 2801 made in a similar 400 engine. Either of these 2 cams should work with fairly low pressure valve springs.

A 2802 would make a little more & move peak up the rpm scale. Rhodes lifters might make this a real nice 400 street engine. But, it seems that most Pontiac forum & FB page dwellers now hate even the mention of Rhoads lifters.

I ASSUME that a small Voodoo would make max below 5000 rpm hp. But, Paul Carter has mentioned that because of the steep ramps, the Voodoo cams require lots of spring pressure. I would not wanna have to run that much pressure, on an engine I was gonna drive a lot, on the street. But, lots of Pontiac guys brag about running huge roller cams with high spring pressures, on the street, for many years, with absolutely no problems at at. So, everybody has to decide what they wanna run.

That was written so I can understand and I appreciate that. Thank you

This is everything I know about this engine.
Short block is a 71 400 bored .040
It has forged pistons with 4 reliefs 6.7 ccs. I do not know the distance to the first ring from top of piston.
The deck height measured .018

I have 2 sets of heads both are fresh .
1 set #15 small valve that ccd at 90cc and I added screw in studs and .550 springs
1 set #16 heads large valve that ccd at 75cc .550 springs and roller rockers.

I own a brand new 2801 summit cam but if that is not right for this build I will not use it.

I have a 2004R over drive and 3.73 gears maybe 2000 stall.

The engine with 15 heads and crower 60240 cam put out 217 hp to the rear wheels maximum torque 276 8.5 compression and was a dog with only 12 mpg.

Both sets of heads have less than 2000 miles

I will be running a tri power because I want to.

Now you know everything I know.
I want the best streetable engine on pump gas without changing my stall.

I understand torque gets me off the line and hp keeps me going

I won't be starting any new threads I have worn a lot of people out who taught me quite a bit so thanks to all of those people. I can't list them all.

Greg

[Dragncar]

Originally Posted by footjoy

I need to mill .050 off of these #15 heads to get what I want 9.4:1. At what point do you know if you have to mill intake after assembly or after milling the head you take some kind of measurement. I saw The formula but I have read where guys say they didn't have to do anything.

Greg

If you can mill them .020 and get 9.2 CR you will not notice the minuscule increase on power the .2 difference gets you. Its not worth milling off the extra. A plain ol 9-1 engine will do fine.
And you will not have to mill the intake, at .040 either.

[Scott Roberts]

Do you just want to do a head change or are you willing to pull the engine and make other changes? Is this a budget deal or lets just get it right and make some power with pump gas with iron parts? If it's the latter, I would say change pistons and run the 16's with some port work and change the cam.... you can make some good h.p. with the little 400...

[footjoy]

Originally Posted by Scott Roberts

Do you just want to do a head change or are you willing to pull the engine and make other changes? Is this a budget deal or lets just get it right and make some power with pump gas with iron parts? If it's the latter, I would say change pistons and run the 16's with some port work and change the cam.... you can make some good h.p. with the little 400...

Its a budget deal.

[Scott Roberts]

Originally Posted by footjoy

Its a budget deal.

I understand where your coming from.... just an idea..
Have you considered dealing with what you have and saving money over the next year or so and doing it differently? You can make a 500h.p 400 for a fair price... just an idea, I just don't want you to be unhappy and spending money twice...
Just my 2 cents...

[footjoy]

Originally Posted by Scott Roberts

I understand where your coming from.... just an idea..
Have you considered dealing with what you have and saving money over the next year or so and doing it differently? You can make a 500h.p 400 for a fair price... just an idea, I just don't want you to be unhappy and spending money twice...
Just my 2 cents...

I appreciate your idea but I am going to stay with my shortblock and build a low 9 compression engine.

Thanks

Greg

[ponyakr]

When I plugged some numbers into the Wallace CR Calculator, it looks like you'll need 83cc heads to make 9:1 CR, if using the cheap FP 8518PT head gaskets, assuming they crush to .045.

http://www.wallaceracing.com/cr_test2.php

Those .045 gaskets will give you an .063 quench distance, which some say is not great.

Some Cometic .027 gaskets would provide a good .045 quench, and a little more CR. But, they are not budget friendly. And, I've read that they require a certain smooth head & block surface, to seal.

The .039 thick #1016 gaskets will help a little. They're higher than the cheap ones, but much cheaper than the Cometics. With 84cc heads, they'll give you 9.03 CR.

[Murf]

Quick ? I see people recommending Cometic gaskets due to the various thicknesses available.

Am I mistaken, I thought the Cometic gaskets required a specific surface finish on the heads & block?

Thanks
Murf


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[Stan Weiss]

If the spec I have are correct. Pontiac in '70 offered a 400 ci engine that they rated @ 330 HP @ 4800 RPM. Only problem with the specs I have is I have 2 different CRs. Lemans 10:1 and Firebird 10.25:1

Stan

[Stan Weiss]

This is the output from an old somewhat simple engine simulation program. Using their numbers for 6X heads and me entering the specs that I have for an 067 cam.

Stan

[steve25]

The base line 400 4 bbl in the A and body cars for 1970 was rated at 350 gross hp, the 330 gross hp motor was for the F body car and the only difference between the two was the Carb with a limiter to not allow full throttle.

[ponyakr]

Originally Posted by Murf

...I see people recommending Cometic gaskets due to the various thicknesses available.

Am I mistaken, I thought the Cometic gaskets required a specific surface finish on the heads & block?

They're probably not in his budget, for this engine. But here is what I found, on the cometic.com site.

" WHAT SURFACE FINISH IS REQUIRED TO US AN MLS HEAD GASKET?
A surface finish of 50 RA (roughness average) or finer, is recommended for a proper gasket seal. Anything rougher may conflict with the gasket design."

I'm just curious. What RA do most shops use for the finish on blocks & heads ? Is a 50 RA a super fine finish that can only be accomplished with the very latest state of the art equipment. Or does it just require some sort of finer grit stones or whatever, for older surfacing equipment ?

Sorry for the dumb questions. I'm just not familiar with engine machine shop equipment. Didn't know 'til recently there were different smoothness of surfaces, or that the Cometics required a smoother surface than the Fel Pros Pontiac guys have been using for years.

When I 1st saw all the different thicknesses & bore sizes available with Cometic gaskets, I thought they would provide an easy way to increase CR & provide a better quench distance. Wasn't 'til later I found out that most of the older builds couldn't use Cometics, because the surface finish of their heads & block was too ruff.

Just curious. Anybody here ever try Cometics, not knowing about the smooth surface requirement, & had the gaskets fail to seal ?

Anybody use 'em & they DID seal, even with a rougher than 50 RA surface ?

[SD455DJ]

Sorry about the long read, but I posted this recently of the ’70 small valve 400 I recently rebuilt and dyno’d a few weeks ago over in the 70-72 GTO Tempest & LeMans forum…

This motor is built for the pure stock drags and is based on the XV code small valve 400 4-bbl available on both A & B bodies (non-GTO and Big car) that has 10.0 to 1 advertised compression, rated at 330 hp and 430 lbft torque. The stock factory cam is the 066 cam rated at 273/282 (200/210 @ .050” lift) and .413” lift.

The block is a late ’70 400 block (F240) that is .030 over (406 cu. in.) with Icon forged pistons (1/16”, 1/16”, 3/16” rings), RPM 4340 I-beam forged rods, stock N-crank, balanced with careful rebuild (not blueprinted). The pistons are off-the-self 400 + .030 pistons with the 1.720” pin (compression) height, 4.5 cc valve reliefs and .0015” in the hole. The head gaskets are Flepro 1016’s with .039” crush thickness for a quench of .041”.

The stock factory small valve # 16 heads (date castings D160 & E200) measured in at 78 cc’s after a slight clean-up cut (80 cc’s factory) with a calculated static compression ratio at 9.94 to 1. The stock pressed-in rocker studs were pinned (like in the good ol’ days) with stock 1.5 stamped rocker arms and factory pushrods. The valve springs are basic CC-990 with 120 lbs seat and 240 lbs @ .400” open pressure (5600 rpm max. shift points). The valves are 1-pc SS 1.96”/1.66” Ferrea’s with 45 degree faces/seats (no back-cutting of the valve heads). The heads weren’t flow benched, but other small valve heads flowed around 190-195 cfm intake/150-155 cfm exhaust stock.

The Q-jet carb we used on the dyno is a 7041264 (’71 400 auto application with 73/43 primaries and CC secondary rods to start out with) on an untouched ’70 cast iron intake manifold. The distributor is from a ’69 400 manual trans application with a Crane XRi electronic replacement ignition. The exhaust manifolds are the std. A-body log style with 2-1/8” openings flowing into Pypes mandrel bent 2.5” head pipes 4’ long.

The cam originally selected was going to be the Summit 2800, but we decided to go with the 2801 instead because of the higher compression to bleed off a bit more cylinder pressure since this is a street driven car 95% of the time. As discussed earlier, the Pure Stock Drags now base cam limitations on the engines ability to maintain 16 in. vacuum at 1200 rpm in neutral. The 2801 does that easily and (actually closer to 20 in.) and is very mild with minimal lope. It is essentially a high lift version of the factory 068 cam (214/224/112 @ .444”/.466” lift). Interestingly, the Desk-Top Dyno predicted 341 hp/445 lbft for the 2800 and 359 hp/429 lbft for the 2801, so very little difference and a trade-off of torque for horsepower. The 2801 was installed straight up as the DTD predicted the highest hp/tq and averages at -2 degrees with the 2801 valve timing specs anticipating timing chain stretch.

The ’70 small valve YH code 455 (462) I dyno’d a few years ago with the same compression and exhaust logs made 391 hp/512 lbft torque with the 2802 cam.

Corrected (Uncorrected): 383.9 hp (357.5 hp) @ 5300 rpm and 454.1 lbft (425.4 lbft) @ 3600 rpm (pull #11 with the highest torque). Pull #12 (no changes – back up for pull #11) netted the highest corrected hp at 384.7 with max torque a tad lower at 452.5 lbft. The highest average power was pull #12 at 343.8 hp and 423.7 lbft torque through the 2500 rpm range. We were surprised how the power hung on to 5500 rpm (the TH400 trans governor is set up to shift at 5600 rpm automatically).

The timing was set and left at 36 degrees for all 14 pulls. The exhaust system off the manifolds was Pypes 2.5” mandrel headpipes tied into another 8’ of 2.5” flex and straight pipe (12’ total length). The 7041264 Q-jet started with 73 jets/43 rods on the primary side and CC .030” M tip secondary rods on a ‘K’ hanger. The secondary rods were changed 4 times more getting leaner with every change…to CE - .0410” M tip; then DR - .0570” M tip; then CL - .0667” M tip; and finally CG - .0774” M tip, which were the leanest we had and still a tad rich. We then swapped in a ‘T’ hanger which leaned it out enough for decent BSFC’s (0.467 avg.).

The max corrected hp/tq with the 2.5” exhaust pipes was 380.7 hp/451.1 lbft. The most power (pulls #11 & #12) were made with the Pypes headpipes dumping into big 6” diameter straight pipe and swapping back in the ‘K’ hanger on the carb. It didn’t like the baseplate on the carb and lost a 4-5 hp and tq.

Oh, we used a 50/50 blend of 93 octane and 110 octane gas just to make sure we didn’t have any detonation as the knock sensor wasn't working. The motor ran beautifully without a hiccup or any blow-by. The rings are definitely seated now.
I believe good believable power numbers for the XV 400 with these cams are:

•Pontiac 066 Cam – 330 hp at 445 lbft torque
•Summit 2800 cam – 340 hp at 440 lbft torque
•Summit 2801 cam – 360 hp at 430 lbft torque (actual uncorrected dyno values)

…with 10.0 to 1 compression and a careful rebuild with torque plates and quality components (pistons, rings, bearings, etc.).
Regarding Cometics gaskets and deck finish, we always spray the gaskets with cooper coat (block deck side) and let cure before installation of the heads regardless of the surface finish cut, but it needs to be clean and flat.

Dennis

[PAUL K]

Great info Dennis. Thanks for posting!

[ponyakr]

"...small valve # 16 heads...measured in at 78 cc’s after a slight clean-up cut (80 cc’s factory) with a calculated static compression ratio at 9.94 to 1..."


So, for you guys who know how to estimate stuff. Can you use the numbers from this build to estimate the power, of a .030 over 400 build with small valve heads, producing only 9:1 CR. Also, consider that this shortblock will have heavier pistons & heavier cast rods, thicker rings, and more quench distance.

Assume a 256 Voodoo, a Howard's 410021-12, and a 262 Voodoo, or some other shelf HFT cam you think would be better, for a 400 pump gas 9:1 CR street cruiser.

https://www.lunatipower.com/voodoo-h...8-256-262.html

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

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

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

I love cam comparisons in the same engine.

[Stan Weiss]

This is simple program and does not has parts weights or quench distance.
Using 9:1 CR, Flow numbers for Stock #15 Head, Stock manifolds and mufflers
NOTE: No adjustments made to ICL

Summit 2800 - 277 HP @ 4500 - 378 Torque @ 3500
Summit 2801 - 281 HP @ 4500 - 370 Torque @ 3500
Summit 2802 - 278 HP @ 4500 - 356 Torque @ 3500
Howard 267 - 276 HP @ 4500 - 385 Torque @ 3000
Lunati 256 - 250 HP @ 3500 - 406 Torque @ 2000
Lunati 262 - 263 HP @ 4000 - 398 Torque @ 2000
Lunati 278 - 262 HP @ 4000 - 369 Torque @ 3000 and 3500
Pontiac 066 259 HP @ 4000 - 372 Toque @ 3000
Pontiac 067 268 HP @ 4500 - 365 Torque @ 3500
Pontiac 068 251 HP @ 4500 - 333 Torque @ 3500 -- I have not had good results with the 068 on any simulation I have done. Not sure why.
SD Stumper Puller 284 HP @ 4500 - 370 Torque @ 3500 -- Hydraulic Roller

Stan

[Stan Weiss]

Had a few minutes and create a couple more cam files / simulations. So the question is do you want low end torque or more HP at a higher RPM?

Lunati 268 / 703 Voodoo - 280 HP @ 4000 and 4500 - 396 Torque @ 3000
Lunati 276 / 704 Voodoo - 289 HP @ 4500 - 387 Torque @ 3500

Stan