I suppose this I one for the engine builders really. I have a small journal 327 that will be built for a race only Model A roadster and I'm buying parts and want to make sure I head in the right direction. I'm building a screamer motor just because it will be fun with a manual trans behind it and want it to be comfortable to rev up to 8,000 rpm in case we get carried away, and everyone should do it at least once. I've got a forged GM crank, after market H beam 6.125" rods and will be using light forged pistons. Whilst the heads are iron I'll be using light weight valve train and solid lifter etc to cope up top which I'm all happy about. My main concern is main cap walk using on the 2 bolt setup. Ultimately I can't see the motor really producing more than 460hp / 400ft.lb (tops) so not really sure if its an issue. It will run good studs to mount a windage tray on as well so will have as good a clamping force as it can. I've read about main cap girdles but can't really see how they would prevent walk (or if they are even designed to) and would like to avoid spending £500 or more on fitting splayed 4 bolt caps as its a budget build for fun So what's the professionals thought or experiences? It will be a 2 or 3 run what you brung event car and not a serious competition can but I suppose the engine won't know the difference. Thanks in advance Stephen
I use to spin mine up to a little over 6k on a regular basis. It was built to factory 350hp specs. The valves would start to float right about there.
I'd have no problem with a 2 bolt sbc at those power levels. IMO, The bottom end will take more rpm than the valvetrain you are describing.
Large journal or small journal? When I raced my Anglia (small journal 327), I ran 5.38 gears, wound it to 7000 and then shifted (4 speed) with a basically stock bottom end. If I were worried about it, I think I'd check how tight the main caps indexed into the block and run main studs instead of bolts. Yea, a 2 bolt main engine could blow the bottom end out on the first pass,..........................................but so could a splayed 4 bolt engine.
If you're gonna buzz that motor, the machining needs to be spot on. Rebuilder quality won't cut it. Align hone the mains at least and ditto on the main cap fit with studs.
We ran one at 7200 in a dirt modified. What will blow are your valve springs. We just staked the caps from walking and chamfered the edges of the bearings. Of course you will need to run a forged crank.
As for the 2 bolt mains withstanding 8000 RPM, yes they can and they will support even more if done properly. However, there are a lot of things that need to be done in order for it to survive. There is no doubt that a 4 bolt is stronger, and that a splayed 4 bolt is even stronger, but a 2 bolt can take a lot more than what most may think. I have personaly taken a 2 bolt 272ci (destroked 283) to 10k several times. To do this right, you will need extensive balance work, exceptional machine work and block prep, along with a very high quality rotating assembly. The best advice I can give you for building a high strung SJ327 is to buy Grumpy Jenkins engine building book and read it, and start saving your pennies. There is no doubt it can be done, but will it last? and for how long? Just some food for thought.
main studs and the rest of your planed mods, but make sure the valve springs are enough to keep the valve float away, good plan. ive got one now that been to 7500 ALOT, and never missed a beat, the bottom end shows nothing bad.......
My friend Lamar Walden had a 2-bolt small-journal 327 in his Pro Stock Vegas back in the early '70s, and he never had a problem. The small journal blocks have thicker caps than the large-journal blocks, so you don't get cap-walk or other issues. Also, if it's a small journal block, I don't think you have the meat there to put in 4-bolt caps--at least I didn't on my sj 283 with a 327 crank build. For RPM, well, he was running Pro Stock with it, and beat Sox n Martin's Hemi cars. I don't remember what he said they twisted, but it was way the hell up there, and he told me that on the launch, he'd put his foot on the floor and the valve train float acted as his rev limiter until he side-stepped the clutch (Lenco). You won't have a problem, so long as you use good rods, forged pistons, and studs to hold the crank in. -Brad
In the olden days, only the Z28 was typically run up to 8k. I'd probably set up with a mid to upper end cam profile, with duration emphasized over lift, and shift at ~7.4-7.5k. There were a couple of 'best' oil pump strategies that helped too.
Happy with piecing together the valve train, question is about the 2 bolt mains only with intended rpm and power level.
x2 with George. The launch w/sticky tires and max load conditions are the failure mode, yes guys? If you spin up, just make the valve train as robust as you can. The BBC's would shuck a stem 'keeper' off a valve, then it was over.
Now that you mention Z-28's, I believe the 67 models were 2 bolt main blocks. And I will guarantee you, drag cars were turning over 8,000 before Z-28's ever hit the showroom.
Since you said you are using iron heads, your first issue will probably show up in the castings. When the rocker stud bosses are cut for screw in studs and guide plates, they become weak, and love to crack do to gross lift, and spring pressure flexing the rocker studs. Titanium retainers, good lightweight roller rockers, and stud girdles will greatly help with avoiding this. Do not restrict oil to the top end, it is needed to help cool the valve springs. Your cam manufacturer will advise you on the proper spring and installed height. Follow this to the letter. There have been great improvements in valve spring technology in the past 10 years.
I've heard of a shop class 327 build at a small town tech school that lived at 12,000 on a test stand in the mid-60s. (my brother was one of the students that built it) Most all of the money/work was in the valve train. Granted this engine never saw racing action, but the valve train has to live in either case. As primerhotrod said, springs have come a long ways, especially since the 60s!
Most of what you need to know is covered, valve train and tune up at that rpm will need to be good to prevent major issues. Problem is at that rpm things go bad fast when they go bad. Is there a reason to spin it so fast. With cast heads will you be able to move enough air to make any power or do you want to tell people you spin it 8g? I have a small block ford with 2 bolt mains I shift at 7,400 but it has a heavily ported set of heads and intake on it, shaft rockers and a large billet core solid roller cam to do it. What cam, intake do you plan on and what do your heads flow?
Quality machine work will be the difference between an engine that lives or dies. The 2 bolt block is fine at the RPM and power level. Do not use the factory balancer, buy a ATI or Fluidamper.
ran several 2bolts in the 9,000 10,000 area, found some old cam specs from (1975sorrynot1965info) .660in .637ex 321*/329* 108 center roller cam HOT LASH .033+.033 has been done -- can be done--- titanium <---- everywhere (period) knifed-edged crank aluminum rods and the usual bla bla bla DRAG car (speak)
Id suggest good aftermarket main studs. Don't just go by the factory torque specs. The aftermarket studs will take more torque to reach the proper "stretch". This stretch is what gives you your proper clamping force. Ive witnessed a BBC with ARP studs where the mains were torqued to stock specs and upon teardown you could see where the caps had moved around quite a bit. In hindsight, staking the caps may have helped with this also.
Smokey'sbc book ---published in Hot Rod around 67, answers all your questions also read what Joe Sherman says about 2 bolt studs---don't think you need to worry...
I read an article done in the early 60's that 327 bottom ends ' were failing at about 7500 rpm , and the fix was a girdle.May have been in a Hot Rod Or Car Craft letters to the editor. I have a 327, studded, with ARP Studs and rod bolts. I have a scraper, and it is running K.B. Hypereutectics. In its first configuration, with ported 186 castings, we ran it to 7500 rpm multiple times daily. It is now running a factory z-28 solid cam, and ported 462's, being treated a little nicer, but still pulling strong.