Budget Pontiac Engines comparisons: Mild to Wild

Phil400
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Joined: July 10th, 2020, 8:14 am

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by Phil400 »

Ok thanks for all the info really appreciated, Sorry for hi-jacking your thread. Learning alot here.
78 T/A 4 Speed, mine since '99, Third and final owner as long as I'm alive.

JayS.
Yellow Horse
Posts: 82
Joined: June 23rd, 2020, 2:44 pm

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

More than happy to take this thread where ever it needs to go. I anticipate each of these different engines covering broad topics.

For less than 5000 rpm on a 4.21” stroke a cast piston will work ok, cast pistons rpm limits are largely dependent on piston speed (most suggest staying under 3500 fpm).

http://www.wallaceracing.com/calc-pistonspeed.php

This econo 455 is pushing the envelope on the piston speed with the cast pistons, but only very intermittently, it is a street engine. Aluminum has a fatigue life. The higher the stress, and the more frequent the cycles, the quicker the failure do to the fatigue life will occur. I have turned some cast piston 3.75” strokes engine to 6000 pretty frequently with no issues on the street, but since it is very intermittent the fatigue life has not been an issue. Sometimes you can find cheap forged STD bore Speedpro pistons to use that are cheap insurance. Even a used forged piston is better than a new cast piston most of the time.

Breaking a piston skirt is the most common failure. Breaking a ring land usually from a combination of preignition and overheating the engine is the other issue that happens with cast pistons. I think a casting flaw in the piston is fairly common. Lastly improper ring gap can cause failures on cast pistons easier than a forged ( forged will fail from this to though). To tight of a ring gap and the rings ends touch and when the pistons gets hot, the rings expand and break the ring land.

You can press the pins out and switch pistons and rods back and forth. I have not had an issue on pressed rods having the pins move. I know it can happen, more common to have that occur on an aftermarket press rod that had improper tolerances. Many shops have a special torch set up that heat the small end of the rod so that the pin does not score the small end of the rod. The pins do not generally press out that hard with the right equipment. I have pressed them out without heat, then thrown the pin in a freezer before I put them back in to make them go in a little easier. I built one press on a work bench the uses a bottle jack to press the pins out, it worked very nice. Using our powered hydrualic press is faster, but requires some caution. If your not comfortable switching pressed pin rods have a competent shop do it.

Phil400
Two Feathers
Posts: 25
Joined: July 10th, 2020, 8:14 am

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by Phil400 »

Great post Thanks, I'd have to have a shop do it, but I've just heard conflicting info. So thanks!
78 T/A 4 Speed, mine since '99, Third and final owner as long as I'm alive.

Phil400
Two Feathers
Posts: 25
Joined: July 10th, 2020, 8:14 am

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by Phil400 »

If setting up 6x-4 heads with new valves, would it be better idea to just get 5.1" length valves right away for 1.7 IH and open up spring choice? Or should it depend on the cam your gonna run?
78 T/A 4 Speed, mine since '99, Third and final owner as long as I'm alive.

JayS.
Yellow Horse
Posts: 82
Joined: June 23rd, 2020, 2:44 pm

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

If the stock pushrods will work for the cam/spring combo, and your planning on running 1.5 rockers, I would go with the stock length valves.

This Ultradyne 280/288 247/255 solid cam in this 455 will work with stock pushrods and a Crower 68404 valve spring and a 1.52 roller tip rocker. I wanted the option of running a 1.6-1.65 rocker on this engine, so I went with the longer valves. With 1.65s this cam is .577”/.594” lift, taking out the lash down to the min setting it is .560/.576”. Which is close to coil bind on the exhuast. Lashing this UD cam on the tight side of the lash results in .51”/.53” lift at the valve with a 1.52 rocker. We haven’t bent push rods with that combo, but I think that lift is about the limit (310-320 lbs psi at max lift). We bent a bunch of pushrods on a .54” lift cam and spring combo that had 330-340 lbs of pressure at max lift. It seems like once the stock pushrods start to have some deflection they fail/bend pretty quickly.

On any D port cast iron head, if using 1.65 rockers and/or the total lift is past .520”, I prefer to run the longer valves and the 1.7 install ht springs, plus the heavier pushrods. The melling ra4 push rods are the cheapest push rod upgrade, and make the geometry line back up using the longer valves. But the guide plates have to be bent out slightly for the 11/32 push rods. Comp hi tech 5/16” work good and just drop in using the same ra4 length.

There are some advantages to the longer valves. With 1.65s and the longer valves you do not need to grind quite as much to make the intake pushrod clear the pushrod passage on the head. There is also more room to clear the valve stem boss and it does not need to be cut down as far, and retains more support.

The stock length valves and the Crower 68404s springs max out at .540” lift when the seat pressure is set to 130 lbs, at .54” that would be about 310 psi max. When pushing the max lift on the 68404s the stem boss on the heads usually needs to be cut down on most heads or the retainer can hit the boss for the stems.
Last edited by JayS. on July 31st, 2020, 6:24 pm, edited 4 times in total.

Phil400
Two Feathers
Posts: 25
Joined: July 10th, 2020, 8:14 am

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by Phil400 »

Ok thanks
78 T/A 4 Speed, mine since '99, Third and final owner as long as I'm alive.

JayS.
Yellow Horse
Posts: 82
Joined: June 23rd, 2020, 2:44 pm

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

Some progress is being made on the engines. I haven’t made much progress on the econo 455, but RA4 stoker is getting assembled. My T/A engine is on deck, as soon as I get a stand free. The main girdle for it will be here next week. I have 10 main girdles ordered.

I was fooling around with my dyno program tonight using the econo 455. We flowed the 62s in stock form. I am going to shoot for 240 cfm on the intake and 180 cfm on the exh. About a 15% increase over stock.

I have 4 cams on hand I could use right now in the econo 455. So I ran some sims, it wouldn’t cost me anything if one appeared to be a better fit. The Isky solid roller is an old cam, this might be a good place for it since it does not have much lift, where as the Ultradyne can use 1.65s and utilize some better flow heads. The Ultradyne looks to have pretty good number trends though. Theses 62 will likely go turbulent after .5” lift. The comp cams on the bottom of the list kind of surprised me with it’s tq numbers. It is the worst street cam though, it isn’t designed to last very long. I think the Isky solid would out last it. The old stand by ra4 cam did ok, but I am going to go for the extra 30 hp the other cams show. You can tell they are bigger than the 041 by looking at the hp nose over at 6000 rpm. Plus the Ultradyne and the Compcams are asymmetrical grinds, the Isky and the melling are symmetrical. In real life against a symmetrical profile the same size the comp and Ultradyne will out run the simulator on the top end rpm numbers.

Ultradyne 280/288 solid 247/255, 112 lsa w 1.5 rockers installed on 108, .020”/.020” lash. Range for the lash is .018”-.030” for this cam.
3000 301Hp 527 tq
3500 346Hp 519 tq
4000 395Hp 518 tq
4500 436Hp 509 tq
5000 469 Hp 492 tq
5500 476 HP 454 tq
6000 433 HP 379 tq
Melling RA 4 292/303, 231/240, .516/.526 with 1.65 roller tip prw rockers 113.5 lsa installed on 109
3000 292 hp 511 tq
3500 336 hp 504 tq
4000 385 hp 505 tq
4500 427 hp 498 tq
5000 452 hp 497 tq
5500 457 hp 436 tq
6000 403 hp 352 tq

Isky 505 solid roller 285/285 252/252, .521/.521, 1.65 Crane roller rockers .022/.022 lash, 112 lsa, 110 installed icl
3000 293 hp 514 tq
3500 340 hp 510 tq
4000 391 hp 514 tq
4500 435 hp 508 tq
5000 470 hp 493 tq
5500 481 hp 459 tq
6000 443 hp 438 tq

Compcams max area solid 283/291 256/264 112 lsa, 1.65 Crane rockers, installed 108, .561”/.561” lift, .020” lash. This cam has extreme lash ramp. The lash range IRC is .018-.024”

3000 302 hp 530 tq
3500 349 hp 523 tq
4000 400 hp 525 tq
4500 444 hp 518 tq
5000 472 hp 496 tq
5500 480 hp 458 tq
6000 426 hp 373 tq
Last edited by JayS. on August 14th, 2020, 2:11 pm, edited 1 time in total.

JayS.
Yellow Horse
Posts: 82
Joined: June 23rd, 2020, 2:44 pm

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

Deciphering Sim numbers for these 4 very different cams. I am mostly looking for trends in the numbers. I was shooting for 480 hp @5500 with the combo, the numbers are fairly close to that.

The trends I am looking at are in average power, peak power and tq, power and tq at both ends of the range, and past the range. Also looking at net gains on HP versus tq. I will try to combine that stuff with valve events and head flow to pick the best cam.

Right off I am seeing one mistake I made. I was going to use 45* intake valves. If the cams max lift is lower .5”s and the heads are going to go turbulent at .5” lift, it will run better with the 30* valve seat angle, making the most of flow in the cam lift range, and the most average power. So I think I will move the 45*s over to another engine project and use 30*s.

The overall winner on average power, and likely peak power was the compcam Max area 283/291. It is the only exception I would make for running 45* valves, it really needs more port work on the heads to be worth using it. Comps Max area solids SLAM the valve open and shut. It takes a bunch of spring pressure to turn rpms with 45*s, 30* valves takes another 20 lbs on the seat for that cam. With 45* it would take at least 140 lbs on the seat with 1.65s, with the 30* valve closer to 160-170 lbs. That adds up to over 400 lbs over the nose of the cam. It would need hardened seats or it would quickly grind the valve into the seat too. There is nothing budget about that cam other than it is a flat tappet. It just does not fit this build. Notice how the shorter seat timing knocked the hp down at 6000 rpm up against the Ultradyne. Even though on paper the Comp looks a fair amount bigger, the Ultradyne has more seat timing than that comp MA solid, the extra area under the curve of the comp cam caused some of that hp loss at 6000 too. The comp max area grind is wanting more head flow.

The Ultradyne and the Isky roller are in kind of a dead heat for performance. The Isky might have a little better idle, it has similar overlap but a little more area under the curve, less dilution on the intake charge, the exhaust opening event is later also. That will help evac the exhaust some at idle, providing a stronger pressure wave at low rpms. But the symmetrical aspects of the cam cancel some of that out against the UD cam. It make things a little hard to compare. Past the power band at 6000 the UD cam was up 30 hp over the RA4, and the Isky was up 40hp. Most of that is from the increase in duration at .2” lift of the roller cam. I have two sit down and look at the numbers closer. My brother is thinking Nostalgia, dual quads should be the Isky and I am thinking more Ultradyne. :lol:

Overall dependability using edm solid lifters on the Ultradyne, overall power, to me the Ultradyne is the best choice.
Last edited by JayS. on August 14th, 2020, 8:34 pm, edited 7 times in total.

JayS.
Yellow Horse
Posts: 82
Joined: June 23rd, 2020, 2:44 pm

Re: Budget Pontiac Engines comparisons: Mild to Wild

Post by JayS. »

A quick view of the cams. Since I didn’t have plans for the 041(I paid $113 for it from a link DDrag posted on one of the other forums. I traded the 041 cam with the Ultradyne in the photo with a friend. The Ultradyne was used for a short spell, it does not show any wear. He doesn’t have plans for the 041 either. I will add it’s photo next time I am through his shop. The area over the nose noticeably less.

Here is the Compcam Max area solid flat tappet. If you look closely you can see the asymmetric grind of the cam. The opening side (right side of the lobe, is steeper than the closing side. Not many cams can you actually see this. Look at the ramp at 2 o’clock and at the 10 o’clock side of the lobe. This cam is a exception in that the symmetric’s really show.
778D5263-4B0D-48F2-9935-30717E84DCA1.jpeg
Here is the Ultradyne. The asymmetric’s are not as visible.
1AAA2A4E-9BFF-4519-9686-E4CD254E2CE5.jpeg
The Isky has short fat lobes. Totally symmetrical
606C012F-CBE5-4D16-A821-3AF3FB19F571.jpeg

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