tfringo

Hi, I am putting together a 427 435hp. Goal is to build it as close to original configuration and run on pump gas. I will use original heads (106cc), intake and carburetors. It is a closed chambered configuration. Since I am sure there are others out there that have done this, can anyone tell me about there experiences, successes and failures. What should I shoot for regarding dynamic compression ratio vs static compression ratio. I would like to use a flat tappet camshaft. I want normal oil pressure. Anyways, I would really like to hear some ideas on how to achieve this. Thanks

Little Mouse

If your going to do a flat tappet on a BBC with its heavy 3/8 stem large valves the higher springs rates they require and a 1.7 rocker ratio putting more stress on the cam lobe and lifters. What i would do in this nice modern world is use a pro 55 cam core. Even back in the day with stock mild cams like your .520 lift BBC they were more likely to wipe a cam lobe then a SBC. So step up to the better grade iron cam core of a pro 55. Good insurance policy that costs little in extra cost. Chris Straub could sell you some quality lifters to use. Straub could sell you everything you need. Another upgrade i would do is go from the factory 3/8 size push rods to 7/16. BBC have extremely long push rods on the exhaust side and there pushing at a 4 degree angle off the lifter. The stiffer the push rod the better.

PcolaPaul

I would think hard about spending the extra bucks and go with a hydraulic roller set up ground to stock specs and never look back. As mentioned in the above post, big blocks have terrible valve train geometry and inadequate lifter face sizes. Well... They did work, but marginally. Nothing wrong with improving durability and reliability on a rebuild.

StraubTech

2 weeks ago I replace 3 flat BBC cams, 50 miles, 100 miles, and 160 miles. Roller is a good investment if you are going to keep the car.

Little Mouse

What sucks about the 396/375hp.....427/435hp cam is its 6500 rpm. If you had an oval port head that would work out fine but with your shall we say monster size rectangle port heads you can't get full use out of them with only 427 cubic inches at only 6500 rpm.


You do have a valued engine no one but you would have to know it has a roller cam in it.

tfringo

I am considering all options. Goal is to make it run right on pump gas without going too aggressive. Just wondering about dynamic VS static compression ratios. Factory vs up graded roller cam. Anyone that has built one and had good success running on pump gas. Thanks

StraubTech

Manipulation of the valve events is the key to running on pump gas. Rollers naturally have more area under the curve and will produce more average power when correctly cammed.

Little Mouse

Your goal is a good one aggressive cams require more aggressive springs and longevity can become a factor. Sometimes its better to give up a few ponies for longevity with say a more reasonable ramp rate of cam. What good is that extra 20 ponies you could have had if your not racing if you end up replacing parts early or failures because of it.

If you follow speed talk you will quickly learn both straub and mike jones. ( jones goes by cam king ) are cam grinders and do cams for about anything you can think up. It would be worth a call to straub and talk to him on what to do for your cam and your higher compression worries with todays gas.

But if i were you and you do decide to go flat tappet with that BBC use a PRO 55 cam core no matter what form it is. Make sure your lifter bores are in good shape helps. If the lifter does not stay rotating your done no matter what you do. 16 lifters only one does not rotate for whatever reason its good by lifter and cam.

68/70Vette

I would get a GM Performance Parts Catalog and start looking at their crate engines in the 427/454 cubic inch displacements. These engines are warrantied and use modern technology parts. I'd recommend that you duplicate the GM specifications and probably their parts. These are engineered engines. For the cam .....look at their cam shaft descriptions...also you can find the part numbers for these individual parts if you just want to order them for your engine.

I plan to build a 496/502 engine. I'll use the GM Performance Parts Catalog 496/502 crate engines as a baseline for parts for my engine. I have a Gem Performance Parts Catalog ZZ4 (350) in my 68 and I'm really pleased with it. The GM Performance Parts Catalog engines...both small block and big block....as far as I know, all have roller rocker cams. All the Corvettes, for many years now, have roller rockers...even the 600+hp 07 Z06. My recommendation..not an expert, is get rid of the tappets and go to rollers. ............If you are really fussy about the extra mass of a rocker, then buy rockers and titanium valve spring retainers..not expensive.

Super6

Many moons ago, I overhauled my 427/435 and re-used the factory heads with 10.5:1 SCR with 93 octane. Cam was Ultradyne hydraulic roller with 0.601" lift and 230/238 duration at 0.050" lift. Made about 475 HP per the builder. Used 3/8" pushrods with 0.080" wall...plenty good.

Big change was going to Edelbrock/GMPP 290CC oval port aluminum heads and then later an RPM Air Gap (L88 hood required). Different engine completely and much better. No waiting for rpm/power to build.

Flat tappet is not worth the worry, IMHO. Latest engine is 540 with Chris Straub hydraulic roller cam, 11:1, Morel lifters, titanium intake valves, titanium retainers, T&D shaft rocker system and 6000 plus rpm.

tfringo

Thank you for the sound advice. So far, all I can tell is that the block, crank and rods are original. The pistons appear to be TRW L2239, which appear to be 30 over and were intended for L88 engines. Not sure if they used the same piston in 435 set up. Maybe someone was trying for some extra ponies with the higher compression pistons. I will keep people informed on how this turns out. I will be going to the Portland swap meet to hunt some parts down.

I am thinking of using the factory crank, factory rods (if check out or rebuildable) and using either SpeedPro or Keith Black forged alloy pistons. This seems like it would improve bob weight and lesson the strain on the cylinder walls. They will be closed chambered pistons and I will aim for a static compression of 10:1. I will try to come close to a factory lift. Not sure about flat tappet or roller yet. I have no problem with either as long as the engine runs right. I don't want to be retarding the timing and stuff to make it sort of run, if you know what I mean.

I have NOS heavy duty timing chain and gears. Are these moronic to used compared to a full roller steel chain and gears?? Been told that for a street engine they be just fine.

Thanks in advance.

tfringo

Thanks for solid advice.