[pontiacman63383]

I'm new to building performance engine but not new to cars. Been turning wrenches professional for 10+ years now. The motor for my 69 lemans is at the machine shop as we speak getting rebuilt. So I need to figure out what cam and valve train I'm going to put in it. The motor is a 400 that is going 30 over and getting a strokes kit put in it. Heads are a 73 4x heads. (98 cc). Flats top Pistons, my engine guys says should be 9:1 compression. Cars transmission is a 69 m22 and rear is 3.73. I'm looking for good power and would like a rough idle but not to where it's not fun on the street. I'm open to ideas, what do you guys think I should go with cam wise and what size rockers? Thanks for the help

[unclescratch]

Pontiac's 744 cam w/1.65 rockers

[68WarDog]

With 98cc heads with a "stroke" 400 and 9:1 c/R , I'm guessing about 455 ci. The 744 IMO is too small, I would try something like a 041 and a little more if you spend for porting. Good luck

[rexs73gto]

If you look at any of my posts you'll see I'm a fan of the RA IV cam. I use the Crane blue print RA IV cam in a lot of my builds. It will give you good power & a good sound & a bit of rough idle, but not bad. Also use the 1:65 rockers as it give the full lift out of the cam which it is designed for. With the 3:73 rear end it will put the best use of that cam too.

[pontiacman63383]

Originally Posted by 68WarDog

With 98cc heads with a "stroke" 400 and 9:1 c/R , I'm guessing about 455 ci. The 744 IMO is too small, I would try something like a 041 and a little more if you spend for porting. Good luck

Strokes kit is by eagle. 4.25 stroke. Again going off my engine guy he says it should be 461 ci. (Don't know if that will make a diff in your choice) You guys are recommend factory grind cams, is there a place I can look up the pics for these cams to get in idea as to what they are? And why factory grinds? Do aftermarket ones not work as well or would they just be better with my setup?

[68WarDog]

Sorry, wasn't trying to be literal about an 041 hft. Just making reference to cam size only. Whichever you choose, think roller.

[ponyakr]

All this talk about running a roller instead of a flat tappet, brings up a question, in my mind, which I'm quite sure many on this forum will consider absolutely ridiculous. But, I'm use to that by now.

I don't think there is anyone who does not agree that roller cams can make a lot more power than flat tappets. A flat tappet lifter simply will not work on the aggressive shape of a roller cam lobe.

And, most everybody agrees that when using the best roller cam components, in good condition, the roller cam set-up SHOULD last longer, with less wear and less chance of failure. I assume this is the reason that most car makers switched to roller cams years ago.

But, since NOT EVERYBODY who is building a street engine, is looking to make absolute max horsepower, or to build an engine that will produce the quickest ET possible, why do most who post, seem to recommend cams that will do exactly that ? Having done quite a bit of racing, I understand wanting to make more power and go quicker.

But, what about the guys who never plan to take their car to a track at all ? What about those who just want a mild street engine, which has a smooth idle, and plenty of vac and low end torque, but at the same time want the reliability, longevity, and other advantages of a roller cam--similar to what most folks want from any new vehicle's engine ?

Has anybody ever ordered a roller cam with specs similar to the popular flat tappet grinds ? Some might say--what advantage would there be in doing that ? Well, the 1st thing that comes to mind is that the reduction in lift and effective duration, from what most roller cams have, would eliminate the need for the high spring pressures, and all the possible negatives and problems associated with higher spring pressures.

One of the problems with the hyd roller seems to be the longevity of the lifters. So, wouldn't less spring pressure, put less stress on the lifters, thus preventing premature failure, in most cases. Less spring pressure would also put less pressure on the cam lobes, which should also decrease wear and increase longevity. There would also be less pressure exerted on the valves, rockers, pushrods, and most every part of the valve train. There are lots of vehicles nowadays that get 200,000 + miles, with their factory roller cam engines--right ?

So, could this be a POSSIBLE solution, for the guys who just want a mild street engine, with a reliable, long lasting valve train ? Could you just order a roller cam with the exact lobe specs of one of the flat tappet cams mentioned in this thread, and use the same springs and associated parts ? If so, what would be different ? Cam core material, lifters, dist gear, pushrod length ? OR ???

Any positive ideas along this line ? Or, does everybody think you should go for max streetable power & lowest ET your budget will allow ?

[Karck]

Originally Posted by ponyakr

But, what about the guys who never plan to take their car to a track at all ? What about those who just want a mild street engine, which has a smooth idle, and plenty of vac and low end torque, but at the same time want the reliability, longevity, and other advantages of a roller cam--similar to what most folks want from any new vehicle's engine ?

This is what im considering for my engine alot. I want my engine turn effortlessly whit minimum friction to have it last long! But the price and rumors about lifter problems keep me at bay. Also already mentioned that it needs more spring pressure means that other valve train parts are gonna wear faster, is it worth trade off after all? Could i use same springs as in flat tapped if i just used flat tapped specs ?

[Will]

The factory grinds are amazingly effective, the PMD engineers really knew what they were doing.

Will your budget allow a roller cam? If so, that's the way to go.

In an engine that size you can easily go to mid 230s @ .050" on the intake side with a 112 lobe separation to get a nice wide powerband out of that big engine.

[mnfatcat]

Really like the comp cams XE284, the Dude recomended it, same motor as yours with a different head combo. Sounds awesome thru 3'' pipes w/o a crossover, oval Dyno Max Ultra Flows.

[rexs73gto]

I have/had a 462 in my 73 GTO with 3:73 rear gears , the engine consists of a 455 at 30 over, with SRP forged pistons, E-heads Performer RPM intake, Crane Blue Print RA IV Cam, 1:65 roller tip rockers, M22 4 spd, Pertronix ign, (unit # 1) Eagle forged H-beam rods, a new Eagle cast crank, RA IV cast iron exhaust , topped off with an 800 cfm Q-jet. The car before I had some concerns with it (blew a head gasket) & caused some other concerns to. But it ran 11:72 @ 122 mph in my 73 GTO . Thats the 1/4 mile. I like the RA IV cam as mentioned before Pontiac knew what they were doing when they designed that cam. There are some that I will same are as good but I stay with what works. As far as roller cams , they are good but they do cost a lot of money extra to use. If you were to go with the RA IV flat tappet cam , & then if you go to a roller cam with the same grind or any other, you'll add about $ 1500.00 to your build as the cam is more then you need the lifters, different push rods, different rockers & the possible machine work to use the roller cam & lifters, it all adds up very quickly for a roller set up. If you use the break in oil & do the proper break in of the flat tappet cam you won't have to go roller. Thats why most go roller because their afraid the cam will go flat during break in. But if you do it right you won't have any problems at all. Just use the break in oil & you'll be fine with a flat tappet cam. I have the RA IV cam in my 400 60 over thats in the car right now & it runs & sounds great. Same car, with the 400 60 over the car went 12:48 @ 114. I used all the parts from the 455 in the 400. So the cam works.

[krisr]

I ran an XR288HR in my 400 with #16 heads and tomahawk intake. Fuel injected though, it ran awesome! The heads were the limiting factor as I couldn't put anymore than 28deg timing into it otherwise it'll rattle all the way down the road. Have switched to a e-heads and a cam with 6deg more duration at 0.050 and it runs pretty good so far for a half dialled in combo. You have cubic inches on your side aswell as good rear gear ratio, don't be scared to cam it.

[mnfatcat]

Is there a Pontiac Kool Aid that I'm not aware of ? Love my Poncho, but I don't genuflect at the altar of 50 year old cam technology.

[lust4speed]

I do a lot of engine builds for our car club members. Some of the builds are to replace flat cams, but most are to step up performance. Most of these engines are just a few years old and pretty low mileage. Some were put together by the owner and some by professional shops. The punch line here is that in the last two years I haven't pulled out a flat tappet cam that I would have put back in - all were showing signs of failure. Some might have lasted another 10,000 miles, but there were a few where I don't know why they were not making noise yet. Everyone swears that they stuck to recommended break-in procedures, and were running a ZDDP additive.

You've spent good money on the stroker kit and the build sounds great, and I would suggest spending the money for the roller cam and not have to worry about when (not if) the flat tappet was going to fail.

I would follow Dave at SD Performance's suggestion and go with the Stump Puller for a mild iron head. He generally recommends the Old Faithful for better breathing aluminum heads, but the Stump Puller for iron heads. Another reason that the stump puller will work out good is the close ratio trans and 3.73 rear isn't a lot of gear in first and the Stump Puller roller cam is going to help drivability.

Here's a photo of some of the failed flat tappet cams waiting to go to scrap - no rollers in the group.

[Cliff R]

Another vote for a roller cam upgrade. Below are back to back dyno sheets same engine with only a cam change.

It was first assembled/dyno'd with a the Comp XR276HR cam, pinged on the dyno, idled "****ty" and didn't make much power.

The second cam is one I recommended for the shop to replace it with. It's a custom grind from Comp, basically the Old Faithful on a 114LSA.

The 455 used 250cfm iron heads flowing 250cfm, nothing else "exotic" going on with it, Eagle stroker kit and tight quench........Cliff

[GRX]

Feel compelled to state the obvious and mention a good set of valve springs. Ones that will handle the new cam & added lift of the 1.65 rockers.

[jonmachota78]

Originally Posted by GRX

Feel compelled to state the obvious and mention a good set of valve springs. Ones that will handle the new cam & added lift of the 1.65 rockers.

X2 and be prepared if you go Old Faithful with 1.65 rockers, you're looking at .660" lift. Have your heads been clearanced for 1.65 rockers?

[Lee]

I agree with Mick and Cliff, go roller cam.

[ponyakr]

"...HFT cams have lobes grinded on angle to turn the lifter..."


I knew the lifters were not flat, and that the bores were offset, so that the lifters would spin in the bores. But, I never read or heard that the cam lobes were actually ground at an angle. So, thanks for that info. It was there online, all the time. But I just never saw it.

http://www.crankshaftcoalition.com/wiki/Lifters

[ponyakr]

Don't know why I haven't thought about it sooner. But, Bullet Cams has a master list of HR lobes, which includes some VERY small spec lobes.

http://www.bulletcams.com/Masters/HRlobes.htm

So, even if they can not grind a HFT spec lobe(less the bevel) on a HR core, you can get a very mild roller cam, ground with your choice of any of the lobes on the list.

"... Roller lobes need rounded noses so the lifter will stay in contact with the cam..."

I never heard this either. I thought the roller lobes were round so that they would have more effective duration, above .050 lift. I assumed that with the high spring pressures, the lifters would stay on the lobes, regardless of their shape(within reason, of course).

I assume that there is a lobe shape, beyond which the roller lifter will not stay on the lobe, passed a certain rpm, with a given spring pressure. I also assume that you could increase the spring pressure to keep the roller in contact with the lobe, at a higher rpm. But at some point, the spring pressure necessary would be too high to be practical.

So, I reckin cam lobes are a compromise. You need the best compromise of lobe shape and necessary spring pressure, to provide the performance and/or longevity, fuel mileage, etc, you desire from your cam. Obviously, all out race engines, HP 500+hp street engines, and daily driver 400hp street engines, will require 3 completely different cam lobe grinds. But, the good news is, almost any grind you could need is available.

But, you may need a custom ground cam to get exactly what you need. I assume that many of the cam grinders charge quite a bit extra, for custom grinds. But, there are probably some who don't charge extra for custom grinds. So, will some of you guys who know, please post a list of all the cam grinders you know of, that will grind a Pontiac HR cam for a reasonable price. Please post info about those companies with whom you have had a good experience, ordering a custom grind. Please include contact info. This may help a lot of guys who read this thread. Thanks !