[pontiacmark]

OK, this might be a long post but I will try to post as many details as possible. Finally, after 20 years of wanting to improve the power in my 70 GTO, I am getting around to doing something instead of talking about it. Time is available due to COVID and money has been saved.
Goal: Nice sounding street cruiser that could theoretically run in the 13's with a good driver. May never be taken to the strip however. Idle quality is not very important as long as I have decent vacuum for power brakes and eventually operating A/C. Stock bottom end and budget precludes high rpm.
What I have:

70 GTO
Keisler RS 600 5 speed (ratios 2.80 1.99 1.33 1.00 .67)
3.23 Safe-T-Track rear

Stock 69 YD 400 short block (2 bolt mains) that has been running in the car with great compression and oil pressure. Likely had stock #254 2 barrel cam to go along with the #46 high compression, small valve heads. When I pulled intake and heads intake valley was clean as a whistle and cylinders showed very little wear with the stock bore cast pistons. It ran fine but was done by 4000 rpm and just was slow as molasses in winter.

My original #12 heads completely reworked but not ported by Butler Performance with 7/16" studs and Crower 68404 springs. CC'd at 72 cc.

Original cast iron intake with correct Q-jet

Ram Air III exhaust manifolds
Stock points distributor

What I need:
Camshaft
Lifters
Polylocks
Rocker arms
Timing Chain
Pushrods
Gasket set
Oil pump

What I am asking:
1. Yep, which cam. I know if I ask 5 people I will get 5 answers. Has to be flat tappet for budget. Considering either the Summit 2802 for budget route or Lunati 10510702. They are fairly similar in specifications.
Part Number, Advertised Duration, Duration @ .050, Lift With 1.5 Rocker Arms, Lobe Separation Angle, Intake Centerline
Lunati 10510702 265/268 219/227 .468/.489 112 108
Summit K2802 282/292 224/234 .465/.488 114 -

Yes, I know the heads will not take advantage of the lift that these cams offer, but the additional duration should be worth some power over smaller cams.

I have heard of a few recent quality issues with the Summit cams but not sure if Lunati is worth double the price. I would gladly pay it if the quality is there though.
2. Lifters, this seems to be another ever changing subject as to what is the true Pontiac lifter with the right quality. So, what is the best source at this current time?
3. Rocker arms, which to choose. I don't need a $400 set for this application. Even though stamped plain types are known for not having accurate ratios, they seem to be better than PRW or other low end roller types that seize up.
4. Pushrods, this will need to wait until geometry is established and then order the correct length. Not so much a question as a statement.
5. Timing chain, assuming that I will not likely advance or retard, what about a simple Cloyes stock type such as C-3007K from Summit? Or are there better budget choices?

Ultimately, I don't see really having the budget to do a decent bottom end with forged rods and pistons in the next 5 years, so I am would like to take my chances with what I have. For this head and cam swap along with resealing the engine, I have budgeted $800-1000 in parts.

Thanks all.

[steve25]

Your thinking on valve lift in regards to the lift that the heads attain there peak flow at is a little flawed.

Peak Intake air flow demand made by a cylinder takes place by about 74 Crank rotating degrees after TDC, thus the higher your total amount of valve lift is the greater the greater the valve will be for a given amount of Crank rotation.

In short assuming the same duration between 2 Cams the one with more lift will sooner fill a cylinder and in turn make more power at a lower rpm.

Another way of looking at it is that your averaging more air flow in a given time frame.

One thing that concerns me is that your not putting in better Rods.

Besides the added safety factor of the stronger Rods they are also far lighter then the factor Rods which allow the motor to rev up noticeably faster, and this alone adds a good chunk of performance gain to the car!

[jamaca85]

summit also has a cam it has a 480 lift, 230 duration at .50. about same price as the other cams they have. its almost the same as the comp 280h cam. guys dont like this type of cam on this forum, but i have run it with great results in my old 400 street car. but of course its up to you. do some research and just go with what you think is right for YOUR build. good luck...

[Cliff R]

#12 heads make for pretty high compression on a 400 build with flat top pistons. My cam of choice for those is the Crower 60243, 228/234/112. It will make around 425HP with stock #12 heads and closer to 450-470hp with 240-260cfm head flow. It will also help with dynamic compression and you can tune it for pump gas.

I use and prefer the stock Morse timing sets but haven't bought any in at least 4 years. I was getting the Melling sets from NAPA and perfect success with them but with all the outsourcing going on I'm not sure if what you are buying today is still USA made and top quality. I would avoid any of the double roller type "low end" sets, they are NOT an upgrade over a stock timing set and will stretch out considerably and pretty quickly in one of these engines.

The stock Melling oil pump w/screen is fine, but make sure that you make a strap or drill and pin or screw the pick-up to the pump or it will end up in the oil pan. They material they are making them from is "soft" and once driven in place it will be easy to turn and fall out if you don't do something to retain it.

Nothing wrong with stamped steel rocker arms and they fit easily under the stock covers. They are still available in 1.65 ratio last time I looked.

Buy good pushrods, Comp Cams as excellent and available in .050" increments to get the geometry spot-on.

The Crower 68404 springs will have enough room for any of the cams mentioned, but you need to check retainer to seal clearance if PC seals were installed and stock retainers as they are longer due to having to seal the factory "O" rings. I would imagine Butler wouldn't have used them and went with shorter heavier retainers instead, but still check them........Cliff

[Jay S]

Cliff mentioned it in his post. Lunati 702 compared to the summit 2802 or the Crower 60243 the intake closing and profile in general is much more aggressive on the Lunati voodoo cams. Apples to apples to run a Lunati cam with higher compression it takes a bigger cam than the 702. The 702 is probably 2 sizes to small to match up with a Crower 60243 for running the same octane. You would need to step up to a 704 Lunati or a custom 703 with the LSA spread out to 112 for what your wanting to do.

I like the Crower 60243 better than the summit 2802. But in a stock bottom end cam swap the 2802 is probably the better choice. The wider lsa makes the power smooth and broad. It would be friendlier to your stock rotating assemble. Then just run the stock pushrods.

QC does’t seem to be great anywhere in the cam industry for major corporate cam companies. Imho, Your odds of getting a dud cam are about the same between the summit, Crower or lunati. I ordered a jegs 224/234 cam (Same mfg as the summit cam) a few weeks ago and they were back ordered.

The cheap double roller timing sets stretch a lot in about 10k miles. If your going to drive it more than that step up and buy a better quality billet link timing chain.

[Formulajones]

13's should be an easy goal with that setup, you'll be pleasantly surprised.

Here's mine, which is basically stock, 400, #12 heads, 068 cam, 3.31 gear, RA manifolds, 3890 race weight. It would run 12's if I could ever get some decent air in Phoenix.

https://youtu.be/er1z7PpqsnY

I agree with the others, I'd prefer to go with more cam than what I'm currently using, making tuning with that compression a bit less finicky, and since you have a stick, converter choice isn't a concern. I like both the Lunati and the Crower choices others suggested. It will make a really nice running little 400 on the street.

[steve25]

The op needs to keep in mind that with the factory 400 cid RA4 motor that made only 370 hp that they saw the need to build the motor with forged Pistons. If you build the motor to the 420 hp level then over the course of 5 years your taking a pretty good chance of cracking the ring lands out of a few of the Pistons and even cracking rings.

Broken rings the unfortunate side effect of scoring the cylinder's badly enough to have to sleeve some of them!

[Navy Horn 16]

Call Butler Performance back since they did your head work. Ask them what cam to run to meet your goals. You trusted them once, trust them again.

[Jay S]

Butlers are going to suggest a XE274 on a 112 lsa.

XE hydraulics flat tappet cams are usually very noisy and hard on parts because if the jerk on and off the profile. They tend to bounce the valves off the seat if the spring pressure is marginal and cause reversion. End result is hp noses over early, 45* intake valve work better than the 30* with a XE.

I think Pontiac went to forged pistons on the RA4 because of piston speed more than HP. A lot of references say stay under 3500 fps for cast pistons. That would be around 5500 in the build. We have mainly broke skirts when we pushed cast pistons. Not to say it a broken ring land won’t happen, it certainly can happen. I have ran some pretty high hp combos with cast pistons, higher than this build. Broken lands we have seen mostly happened when preignition was ignored or it overheated and they kept driving. Lol.. To much starting fluid or to tight of ring gap for the application kills ring lands on any piston.

[pontiacmark]

Thank you for all the replies so far. To address a few of the comments.
1. Yes, Butler recommended the XE274.
2. I figured static comrpession would be in the high 9s (~9.6-9.8:1)
3. I get the idea behind the larger cams to bleed off the higher dynamic compression ratio,
4. The concern with the larger cams is obviously the stock bottom end. Some of these should pull over 5500 rpm and the temptation could be there.
5. Cast pistons-Yes, if destonaton is an issue they could be a problem.
6. Cast rods/stock bolts-rpm limitation of course.

"To play you gotta pay" or something like that.
So, to make this relatively bullet proof then I would need forged pistons and forged rods to go with one of the larger cam selections. This would also likely mean an overbore and turning the crank. So that would add up to about another $1500-2000. At that point why not just buy a Butler rotating assembly and call it about $2500 over the $800-1000 budget I had.

The #46 small valve heads have an advertised compresison over 10:1. Even with the tiny cam in the car, I never once heard detonation running 93 octane with these heads. Not saying it didn't have it, but I didn't see it. The cast pistons still look good with only minimal carbon buildup.

Maybe just take the cast pistons out and mill a dish in them with my friend's CNC mill. Just kidding. Not going to happen.

So, maybe just put the bigger cam in and limit the rpm until I can get the bottom end to support it? What's a good setup to replace the stock points ignition that has a rev limiter?

Thanks,
Mark

[Jay S]

Steve25 can probably answer this better than me. I was thinking 46s hover close to 80cc, and paired up with a stock piston 400 it is low 9’s scr.

It isn’t a numbers matching deal. For budget builds if the engine was out I would replace the rod bolts and rod bearings, add a 60 psi oil pump, put the cam and heads on it and have fun with it. If it is in the car, bolt the heads on and swap to that summit cam. Peak power will be around 5500. Set the rev limited and roll. The bigger cam and higher compression will still make more power than the smaller cams even if you back the rpms down to 5000.

I use to run Malory tach that has a built in rev limiter. Worked great. Points or electronic ignition triggered MSD 6AL is other way we did rev limiters.

I know of 455s over the years that turned 6k with stock rods and arp bolts. The engine internals depend some on the engines past life. Back when about the only choice for rods was SD’s and early rods we scavaged the cast rods from 2 bbl engines for circle track racing. One engine we did even had cast pistons. We took them out of service before they broke. We always replace the rod bolts with arps. At the end of the straight on a dry track the engine turned a little past 6000. On some nights the car had to go thru the heats and both A and B features, that was some serious abuse. The only engine we lost used the early 60s style forged rods.

It is nice to do forged on this stuff. If you use your head and don’t overly abuse it the econo build’s can go along time.

[Formulajones]

Originally Posted by pontiacmark

Thank you for all the replies so far. To address a few of the comments.
1. Yes, Butler recommended the XE274.
2. I figured static comrpession would be in the high 9s (~9.6-9.8:1)
3. I get the idea behind the larger cams to bleed off the higher dynamic compression ratio,
4. The concern with the larger cams is obviously the stock bottom end. Some of these should pull over 5500 rpm and the temptation could be there.
5. Cast pistons-Yes, if destonaton is an issue they could be a problem.
6. Cast rods/stock bolts-rpm limitation of course.

"To play you gotta pay" or something like that.
So, to make this relatively bullet proof then I would need forged pistons and forged rods to go with one of the larger cam selections. This would also likely mean an overbore and turning the crank. So that would add up to about another $1500-2000. At that point why not just buy a Butler rotating assembly and call it about $2500 over the $800-1000 budget I had.

The #46 small valve heads have an advertised compresison over 10:1. Even with the tiny cam in the car, I never once heard detonation running 93 octane with these heads. Not saying it didn't have it, but I didn't see it. The cast pistons still look good with only minimal carbon buildup.

Maybe just take the cast pistons out and mill a dish in them with my friend's CNC mill. Just kidding. Not going to happen.

So, maybe just put the bigger cam in and limit the rpm until I can get the bottom end to support it? What's a good setup to replace the stock points ignition that has a rev limiter?

Thanks,
Mark

Mark, for what you want to do, for the time being I probably wouldn't worry about the pistons and rods. Just run it with the 12 heads, with one of the cams suggested, keep it cheap and simple within your budget and enjoy it for a while. In the mean time you could plan another budget for later in case the short block needs attention. Keep rpm to 5500 and timing conservative and it'll probably treat you fine for a while.

On the rev limiter, I prefer to keep the points distributor and run an MSD box off of that. It's simple to wire up, gives you capacitive discharge and a rev limiter, and the points trigger it. So if the box ever fails you can simply swap the coil wires around and drive away on the points.
I've been running a couple of them this way for quite a while now and find it's probably the most rock solid system you can do that won't leave you stuck looking for parts if it quits, and it's still an OEM distributor and not some of this China stuff. It'll also save you some time if you've already dialed in a timing curve with it that works. So if it's in good working order, I'd stick with it.

[pontiacmark]

Lots of good input.

A few more follow ups:
1. Lifter source recommendation?
2. Before I declare the short block 100% good as is, what would be acceptable bore wear in thousandths of an inch? As stated before, compression is good in all cylinders and it does not smoke. Thinking out loud if I can swing ICON forged pistons and 5140 rods without having to bore 0.030 over. Doubtful I can do it,, but a thought.

[Formulajones]

You would need a dial bore gauge and pull rods and pistons out to check cylinder wall taper to determine if there is excess wear.

Putting new pistons and rods in a short block without boring, or at least a good torque plate hone is not something I'll recommend, especially since it would all need rebalanced anyway, may as well go the rest of the way and have the block work done.

If you're worried about ring seal and don't want to go that far with it, you could get away cheap with a quick ball hone and slapping a new set of rings on your old pistons and run with it. Maybe put a fresh set of bearings in while your at it. Not what I'd prefer to do but I understand budget constraints.

[77 TRASHCAN]

A quick ball hone can be deceiving...LOL All the grit that is expended when using a ball hone...makes for a tedious clean up job...BUT the ball hone can make a difference in ring seal!!!

[pontiacmark]

Thanks for confirming my thoughts. I had done a quick check with piston down in bore with a borrowed dial bore gage and didn't see any taper over that length. I will stick with the short block as is and take my chances.

[Formulajones]

I don't think you'll have any issues. When we were kids and had no money we threw engines together like that all the time. Heads and cam swaps on zillion mile unknown stock short blocks, and then beat the snot out of them. Never scattered one like that, but they did get tired after a while and start smoking. We'd just start over and do it again, lol. It was hotrodding on a budget back then.

[BLANK1]

I used to have a stock bottom end 400 in my 68 GTO. I put stock unported #13 heads on it, a Performer intake and a Lazer hyd flat tappet cam 230/230 @ .050 .490 lift and 108 LSA. It ran a best 13.08 in the quarter in my GTO at over 3800 lbs. Fun little motor. Still have the motor. Could sell you the cam if interested.

[pontiacmark]

Reviving this thread of mine from exactly one year ago. I have not pulled the trigger due to various circumstances but the good news is my budget has increased to this whole deal with more reliability and somewhat more power in mind. I unexpectedly ran across a great deal on a 3.00" main, 4.25" stroke Eagle cast crank brand new in the box. This will of course require new rods and pistons. So I am looking at the budget 4340 Eagle rods and Icon -30cc pistons to get close to 9.5:1 compression with the 72cc #12 heads. i would go with 0.035 over on the bore to take advantage of the Icon pistons being in stock. Complete block machining would be done. That leaves the only other major component as the cam. I liked the previous suggestion of the Crower 60243 in the 400 cubic version to kill dynamic compression if I didn't change pistons originally. Now I am thinking that would still be a good midrange cam for the stroker engine. I know the unported but reworked #12 heads are a chokepoint in generating power but porting is not feasible at this time. The problem is I have not found the 60243 in stock anywhere at this time due to the core shortage. Butler does have the Lunati 703 in stock but as previously mentioned it has more aggressive ramps that may cause more jerk in the valvetrain. So, back to cam availability what other HFT would you consider? Also, good lifter availability?

[Formulajones]

Well now you're talking about a 4.250 crank and 4.155" bore. That's a 461 and a complete game changer when it comes to cam selection. You aren't going to want to look at the 60243 Crower anymore. You'll have to step it up a bit.