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I currently have a 400 with 14 heads and the original tri power setup. I have a set of 16 heads from a 68 Firebird - big valves, screw in studs, and small chamber ~72 cc (need to get exact). I also have a set of 62 heads, but have been told the 16s flow better. I would also like to add a camshaft if swapping the heads. (My goal is to get the motor to 350+ hp with a nice broad power curve.) My concern is the compression ratio and 91 octane here in socal.

My questions are:
(1) Can I effectively lower the CR enough with a thick head gasket?

(2) Is there a popular camshaft that would not only make more power but also lower the CR? Any specific recommendations would be great!

(3) If options 1 & 2 won't be sufficient in lowering CR enough (to ~9.25:1), I guess I need to build the bottom end with dished pistons ?

Thanks
 

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I currently have a 400 with 14 heads and the original tri power setup. I have a set of 16 heads from a 68 Firebird - big valves, screw in studs, and small chamber ~72 cc (need to get exact). I also have a set of 62 heads, but have been told the 16s flow better. I would also like to add a camshaft if swapping the heads. (My goal is to get the motor to 350+ hp with a nice broad power curve.) My concern is the compression ratio and 91 octane here in socal.

My questions are:
(1) Can I effectively lower the CR enough with a thick head gasket?

(2) Is there a popular camshaft that would not only make more power but also lower the CR? Any specific recommendations would be great!

(3) If options 1 & 2 won't be sufficient in lowering CR enough (to ~9.25:1), I guess I need to build the bottom end with dished pistons ?

Thanks
All D-port heads with the big valves basically flow the same, so its your choice. Best improvements would be gasket match the intakes & 3-angle valve job. Add ARP 7/16" BB screw-in rocker arm studs and poly-locks.

Do not go with thicker head gaskets -band aide fix. Get the correct dished pistons to give you 9.0-9.3 compression.

Cams with a nice broad power curve will be those like factory - 114 LSA. Narrower LSA will typically narrow the power curve, boost cylinder pressure, and are more "explosive" but run out of steam early.
 

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Discussion Starter #3
All D-port heads with the big valves basically flow the same, so its your choice. Best improvements would be gasket match the intakes & 3-angle valve job. Add ARP 7/16" BB screw-in rocker arm studs and poly-locks.

Do not go with thicker head gaskets -band aide fix. Get the correct dished pistons to give you 9.0-9.3 compression.

Cams with a nice broad power curve will be those like factory - 114 LSA. Narrower LSA will typically narrow the power curve, boost cylinder pressure, and are more "explosive" but run out of steam early.
Jim, I am coming back to this as I have the car pretty much done now and running well. Fundamentally what I am struggling with is what to do with the motor. Currently the motor runs fine - no smoke on acceleration or engine braking, but just is not a monster. The motor appears to be out of a 1968 Catalina (400 with #14 heads) and according to Wallace Racing's site should have a ~8.6:1 CR. I don't have any pinging (that I can hear) using 91 octane and when I did a compression test on the motor the numbers were all low but consistent, so I suspect it is a low compression motor. From what I have read the Catalina had a small cam, although I haven't found details other than what apparent stock replacement cams advertise. Is there really a huge difference between 8.6:1 and 9:1 ?

Given that all D-port heads flow close to the same, why not just replace the HFT cam with a better suited cam for the tri power and displacement and see if I am happy with the power results? It sure seems better (financially), than buying a built motor and heads. Worst case scenario I blow the motor and have to buy the built motor anyway..... I am sure I am missing something....Thanks in advance
 

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"... why not just replace the HFT cam with a better suited cam for the tri power and displacement and see if I am happy with the power results?..."


If the heads have press-in studs, you are limited on cam choice. Anything bigger than an 068 clone, such as a Melling SPC-7, is a gamble. And, if the springs are original, you'd need new springs.

https://www.autozone.com/internal-engine/camshaft/melling-camshaft-spc-7/107135_705947_0

https://www.ebay.com/itm/Pontiac-V8-stock-valve-springs-400-455-389-350-428-GTO-Firebird/283583622848?hash=item4206e6aec0:g:LYAAAOSwmrlU0mJ9

From a performance standpoint, a 262 Voodoo would probably be best for your low CR 400, to meet your goal. But, with it's steeper ramps, more lift, & stronger springs needed, it would very likely pull some studs.

https://www.lunatipower.com/voodoo-hydraulic-flat-tappet-cam-pontiac-v8-262-268.html

https://www.summitracing.com/parts/cro-68404-16?seid=srese1&gclid=Cj0KCQjwzozsBRCNARIsAEM9kBM9peTKUEIF45lweSgh95DB9Chp31rr367fUkNe7-urGydO03YcQRoaAgLIEALw_wcB

Some have been lucky, using larger cams, with press-in studs. If I was gonna try to get by with a cam larger than the 068, I might try something like a Lunati 10510312. It has only .454 lift, and the ramps are not as steep as on a Voodoo. And I'd use the stock springs from Ebay, linked above.

Cams like a 744 clone adds more duration, without adding lift more than the 068. But the 744 was designed for high CR engines. Actually the 068 was also used mostly in high CR engines. The only low CR engine the 068 came in was the 455HO, & the only low CR engine the 744 specs were used in was the SD455.

https://www.ebay.com/itm/Engine-Camshaft-Stock-Melling-SPC-3-/292730769560

The Lunati version of the 744 has less duration @ .050 lift, but has more total lift, at .424, and a lower LSA of 110°.

https://www.lunatipower.com/factory-performance-hydraulic-flat-tappet-cam-pontiac-v8-301-313.html

If you wanna try .450 lift, here's a possibility. Should make more power in a low CR engine than the 068. But, the ramps don't appear to be quite as steep as the Voodoo ramps.

https://www.summitracing.com/parts/hrs-410021-12/overview/make/pontiac
 

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Discussion Starter #5
BigD - Thanks a ton for all the help. How would I know if I had press in studs. If I recall correctly they appeared to have nuts on the end. (Sorry for the noob question. I really know almost nothing about camshaft design or selection, rocker arms, and/or lifters.)
 

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"...How would I know if I had press in studs. If I recall correctly they appeared to have nuts on the end..."

Screw-in studs have a hex that holds the pushrod guide plate down. Press-in studs do not have a hex. The bottoms are smooth all the way into the head. The guide plates are held down by bolts.

Here's a pic of #11 heads with press-in studs. You can see the head of the bolts that hold the guide plates down. The 2nd pic shows how the screw-in stud hex holds the guide plate down.
 

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Discussion Starter #7
OK, why not put my big valve #16 heads on with a nice HFT cam and run 50/50 e85/91 octane for an effective octane of ~98 octane ? From what I have read, e85 loves timing and runs cooler too.
 

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OK, why not put my big valve #16 heads on with a nice HFT cam and run 50/50 e85/91 octane for an effective octane of ~98 octane ? From what I have read, e85 loves timing and runs cooler too.
The carb must be modified to run E85. So, getting it calibrated correctly for running some mixture of E85 & pump gas might be difficult. If you want more octane, you can either mix in some race gas, or add Torco Accelerator octane booster.

https://www.summitracing.com/parts/tic-f500010t?rrec=true
 

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Jim, I am coming back to this as I have the car pretty much done now and running well. Fundamentally what I am struggling with is what to do with the motor. Currently the motor runs fine - no smoke on acceleration or engine braking, but just is not a monster. The motor appears to be out of a 1968 Catalina (400 with [URL=https://www.gtoforum.com/usertag.php?do=list&action=hash&hash=14]#14 [/URL] heads) and according to Wallace Racing's site should have a ~8.6:1 CR. I don't have any pinging (that I can hear) using 91 octane and when I did a compression test on the motor the numbers were all low but consistent, so I suspect it is a low compression motor. From what I have read the Catalina had a small cam, although I haven't found details other than what apparent stock replacement cams advertise. Is there really a huge difference between 8.6:1 and 9:1 ?

Given that all D-port heads flow close to the same, why not just replace the HFT cam with a better suited cam for the tri power and displacement and see if I am happy with the power results? It sure seems better (financially), than buying a built motor and heads. Worst case scenario I blow the motor and have to buy the built motor anyway..... I am sure I am missing something....Thanks in advance

The #14 heads are press-in studs & small valves. 8.6 compression can be worked with. The draw back will be the press-in studs which will limit your lift. You probably don't want to go more than .440" lift to be safe. Factory lift is .406" and the H-O blueprint manual says that coil bind can occur at .446". Obviously larger lift cams can be used, but changes are in order and you want to use your stock heads "as is."

To take advantage of the 8.6 compression ratio, you want to build up Dynamic Compression. This adds more cylinder pressure in loosely the same way a higher compression ratio does. The factory cam in your engine now is very mild - and 7.6 seconds for the 0-60MPH most likely reflects that. The valve overlap is at 47 degrees - not a very "hot" cam.

You can use the Wallace Dynamic Compression Calculator to get an idea of what it will take to raise the Dynamic Compression. However, this may require a custom ground cam. I did play around with a couple cams offered on line, but nothing really fit the bill with the limits of the stock heads.

I went with a Comp Cams XE cam on my previous 1972 400CI build with its stock 8.2 compression, maybe less with the aftermarket 8-eyebrow cast pistons I used. The heads were the 7K3 which had the big intakes and screw-in studs so I could use a high lift cam. The cam really made that engine perform - I was impressed. Ran on regular octane gas all day long.

The Comp Cams use a tighter 110 LSA vs the factory 113-116LSA. The tighter LSA can build more cylinder pressure. These cams have "explosive" power, but peak early as opposed to a factory grind that has a broader and more even power range for longer.

The XE series has steep ramps that throw the valve open faster, so be advised that heavier springs may be needed to keep the lifter on the cam lobe - depending on type of cam grind/series some companies offer.

That said, and in my opinion in keeping the stock heads and wanting to do just the cam/lifter swap, I would inquire about a custom ground cam that will build cylinder pressure (Dynamic Compression) to work with the 8.6 ratio you presently have.


So using the Dynamic Compression Calculator, and as an example, you see how the Intake closing point affects Dynamic (cylinder) pressure.

67 degrees - 6.75 ratio (yours now)
64 degrees - 6.90 ratio
60 degrees - 7.10 ratio

So this is why I say you may need a custom ground cam to maximize your combination using the stock #14 heads. I think I might give it a try and then start saving for the "new" engine. You may even like the new installed cam in your present engine and just go with that. :thumbsup:
 

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Discussion Starter #10
The carb must be modified to run E85. So, getting it calibrated correctly for running some mixture of E85 & pump gas might be difficult. If you want more octane, you can either mix in some race gas, or add Torco Accelerator octane booster.

https://www.summitracing.com/parts/tic-f500010t?rrec=true
I am struggling with what would need to be modified as the accelerator pump uses ethanol friendly rubber and all of the other bits are metal....Maybe you mean jetting needs to be increased?

I have read that some pumps and fuel lines need to be changed, but I suspect this is more internet myth. I have new fuel line which I believe to be ethanol friendly as well. The seals in the fuel pump (mechanical), I am not sure of.....Other than that, what am I missing??
 

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Discussion Starter #11
The [URL=https://www.gtoforum.com/usertag.php?do=list&action=hash&hash=14]#14 [/URL] heads are press-in studs & small valves. 8.6 compression can be worked with. The draw back will be the press-in studs which will limit your lift. You probably don't want to go more than .440" lift to be safe. Factory lift is .406" and the H-O blueprint manual says that coil bind can occur at .446". Obviously larger lift cams can be used, but changes are in order and you want to use your stock heads "as is."

To take advantage of the 8.6 compression ratio, you want to build up Dynamic Compression. This adds more cylinder pressure in loosely the same way a higher compression ratio does. The factory cam in your engine now is very mild - and 7.6 seconds for the 0-60MPH most likely reflects that. The valve overlap is at 47 degrees - not a very "hot" cam.

You can use the Wallace Dynamic Compression Calculator to get an idea of what it will take to raise the Dynamic Compression. However, this may require a custom ground cam. I did play around with a couple cams offered on line, but nothing really fit the bill with the limits of the stock heads.

I went with a Comp Cams XE cam on my previous 1972 400CI build with its stock 8.2 compression, maybe less with the aftermarket 8-eyebrow cast pistons I used. The heads were the 7K3 which had the big intakes and screw-in studs so I could use a high lift cam. The cam really made that engine perform - I was impressed. Ran on regular octane gas all day long.

The Comp Cams use a tighter 110 LSA vs the factory 113-116LSA. The tighter LSA can build more cylinder pressure. These cams have "explosive" power, but peak early as opposed to a factory grind that has a broader and more even power range for longer.

The XE series has steep ramps that throw the valve open faster, so be advised that heavier springs may be needed to keep the lifter on the cam lobe - depending on type of cam grind/series some companies offer.

That said, and in my opinion in keeping the stock heads and wanting to do just the cam/lifter swap, I would inquire about a custom ground cam that will build cylinder pressure (Dynamic Compression) to work with the 8.6 ratio you presently have.


So using the Dynamic Compression Calculator, and as an example, you see how the Intake closing point affects Dynamic (cylinder) pressure.

67 degrees - 6.75 ratio (yours now)
64 degrees - 6.90 ratio
60 degrees - 7.10 ratio

So this is why I say you may need a custom ground cam to maximize your combination using the stock [URL=https://www.gtoforum.com/usertag.php?do=list&action=hash&hash=14]#14 [/URL] heads. I think I might give it a try and then start saving for the "new" engine. You may even like the new installed cam in your present engine and just go with that. :thumbsup:
Jim, thanks a ton. Very informative. Rather than work the #14 heads and low compression, why not use my #16 heads + cam + a blend of 91 / e85 (race fuel combo)? Seems like the #16 head route would certainly get me past the 350 hp level and I would be happy with that (for now)....
 

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Cj Lunatics will grind you a custom cam for $50 more than an off the shelf cam......call them they are near Memphis.

Jim and BigD can advise you and Lunati can cut it for you.....
 

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I am struggling with what would need to be modified as the accelerator pump uses ethanol friendly rubber and all of the other bits are metal....Maybe you mean jetting needs to be increased?

I have read that some pumps and fuel lines need to be changed, but I suspect this is more internet myth. I have new fuel line which I believe to be ethanol friendly as well. The seals in the fuel pump (mechanical), I am not sure of.....Other than that, what am I missing??
You can read all about E85 & E85 carbs, online.

https://www.hotrod.com/articles/ccrp-1211-e85-carburetor-conversions-tech-questions-ask-anything/

https://www.hotrod.com/articles/converting-from-gasoline-to-e85-for-the-street/

https://www.e85carbs.com/
 

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Cj Lunatics will grind you a custom cam for $50 more than an off the shelf cam......call them they are near Memphis.

Jim and BigD can advise you and Lunati can cut it for you.....
Yeah, I think most custom HFT cams will probably cost at least $200 or more shipped.

Most of the NHRA Stocker cams come from either Comp Cams or Bullet. Therefore, they have lots of experience grinding cams with low lift, but more duration than most shelf cams, with that same lift, will have. We ran a Lunati "Stocker" cam, back in '75. They were big into Stocker racing back then. But, somewhere along the way, they sorta backed out of Stocker racing.

http://classracer.com/classforum/showpost.php?p=334595&postcount=2

Bullet Cams Master List

Now will a custom cam be worth the extra price, to you ? Nobody can possibly know the answer to that. My answer would probably be: Only if I knew for a fact that the custom cam was much better than any shelf cam I could have bought. In street apps, there are probably lots of similar cams that will provide very similar performance, with the difference only detectable by dyno or drag strip testing. For street driving, you probably can't tell much(if any) performance difference between similar cams.
 

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Jim, thanks a ton. Very informative. Rather than work the #14 heads and low compression, why not use my #16 heads + cam + a blend of 91 / e85 (race fuel combo)? Seems like the #16 head route would certainly get me past the 350 hp level and I would be happy with that (for now)....
Sure, the #16 heads would be better, but if I were to go to all the trouble of tearing down the top end, then I would have them gone through and completely rebuilt. They will most likey cc out at 75 CC's.

Always have a machine shop disassemble them and magnaflux for cracks. I recall you mentioned these in the past. The cost to rebuild the heads can get high if you go through them with all new parts. I posted my heads before on the forum and they ran about $1200 complete.

Obviously they can be done much cheaper as long as the valves can be reground and the tip at the stem are not too badly worn. I would do a 3-angle valve job which will help performance - but this may require new valves with the "meat" on them to do it.

Springs can be re-used as long as each is checked with a spring pressure gauge and they meet the requirements of what ever cam you select.

Your stock valve retainers, oil shields, and split locks can be reused.

I would go new valve guides. Don't knurl them. If anything, the shop can use a steel liner and them make sure they are toleranced per Pontiac specs - too tight and they can seize.

The next option is bronze guides along with the Viton valve seals, but this will mean some machining of the valve guides so they will work.

Use the ARP Big Block 7/16" rocker arm studs along with matching polylocks. I would not use the bottleneck screw-in studs from the #16 heads.

Gasket match the intake ports and clean them up with sanding rolls if you feel confident enough to do it. I use a high speed die grinder and carbide cutter to get most, and then follow up with a course grit sanding roll to finish and blend. You want a little rough versus smooth/mirror finish.

Buy new 1.5 stamped rocker arms. If you feel rich, you can go roller tip. The new stamped will work just fine and have a true 1.5 ratio vs the factory that seem to fall a little short of this.

You want to talk with your machine shop and give him an idea of the cam lift you want to use.

If you go high on the lift, you may want to install new RA IV valves as they are longer, and matching springs/retainers. This is what I went with - Ferrea stainless steel, bronze valve guides, Viton seals, and new springs & valve retainers.

With those heads, you will be back up around 10.25 or so compression. Could be a problem unless you go with an additive or perhaps straight E-85. I would not blend - and how you going to know how much to blend?

I would not use thicker head gaskets, this is a bandaide that still might give you problems.

Cam choice will be the opposite of the #14 heads - you may want to lower Dynamic Compression. bigD pointed out a few cams. Wider LSA and long durations can help, but then bottom end may suffer and power won't be really pulling hard until mid and upper mid-range RPM's. I have read that the Summit 2802 cam is a better choice for this. There is a YouTube Video with a GTO having this cam and no detonation on a 1967 GTO engine and 93 octane
But, you will need new springs.

Also, read the last post on this forum. https://forums.maxperformanceinc.com/forums/showthread.php?t=831437
 

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Well said bigD,..as you and PJ both said in essence,....

the bottom line is tailoring it for what cj wants to get ,.....smart of him to get it all thought out and explored,....that way he will get it right.
 

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Discussion Starter #17
BigD / Jim / Lemans Guy - Thanks so much for the information. I am learning a ton from you!! Thank you thank you thank you. I am trying to find a great Pontiac machine shop out here in SoCal. I was told to find Jerry Goodale, but I can't find him - he probably has retired. If you know of anyone out here in SoCal, please pass me their contact info.

I've been playing with ethanol gas (e85) blends for a while now and absolutely love the fuel for high compression and forced induction motors. As long as your are not running on the ragged edge, it is easy to run ~ 5 gallons of e85 and 12 gallons of 91 octane and effectively get ~e30 with a ~95 octane rating. This blend is very knock resistant, runs cool, and is not % wise ethanol that you generally need larger injectors and my guess is the jetting on my GTO would be fine (as my AFRs are in the mid 12's on the GTO).

Again thanks for the help!
 

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Discussion Starter #18
OK I read more on the Torco additive and was skeptical. I will try to find the MSDS on it and see what it really has in it. That said, according to their literature 64 oz (2 bottles) should bring my ~ 20 gallons of 91 octane to ~102 octane :). Seems like an easy (and not too expensive) solution to the high compression issue.
 
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