racprops

OK Here is what I am trying to build:

A Chevy 383 with an aftermarket Scat 383 crank, stock 400 5.565 rods with new bolts, my heads are cleaned up #14102193...Swirl port 64CC 87-up...305/350......1.94"/1.5" valves Chamber is 65CC Crank Is one piece rear seal.

My pistons are KB Piston Style with a D-shaped cup +18CC Piston Material: Hypereutectic aluminum: Block had been prepped for them.

With stock 400 Rods and a 3.75 stroke I am told with a standard 040 Felpro head gasket and the pistons .018 below deck I should have a 9.1 compression ratio.

I plan on running an 86 up TPI with MAF.

Everything is stock, no hot rod performance changes.

My aim is to make the highest torque at as lowest RPMs possible. I know this set up TPI and Heads will not run over 5000 RPMs.

My plan is to gear the van for 1500 to 2000 RPMs at cruse speed of 75/85MPH. I plan on doing that by adding a second Over Drive. Current transmission is a 4L60E and the stock 343 rear end. Stock gearing has fine power which should be better with the TPI 383, so one more gear gets me home.

Thanks to this site I have learned a ton of things.

So two major questions remain:

The cam?

At this point I have a Hurbert Cam custom regrind hyd Roller 208/214 440/440 114

Nearly no one make the kind of near factory Hyd. Roller cam I want that I can find.

And I have been told I need to check Rocker Geology, which may require new push rods.

Is that a real problem with a low RPM engine adjustable height Chevy roller rocker??

Thanks.

Rich

Schurkey

Not my first choice. The short rods are not known for their strength. But, for <5K rpm, they should be OK.

.058 quench is a long way from ideal. Compression seems lower than stock. Why accept the reduction in compression? Fixing the quench distance would also give you improved compression ratio (although not as much as I'd like to see.) Might want to find thinner head gaskets. .020 coated-steel-shim gaskets, plus the .018 piston below deck, would cut the quench distance to .038, quite reasonable indeed.

Why post in the TBI section?

racprops

OPPS Wrong section.

racprops

I started 350 so pistons are all ready fitted, and I don't want to buy custom 5.56 Rod.

My understanding is IF (best guess) Pistol is .018 down from deck, and a stardard gasket of .040 is used I will have a 9-1 compression, and I perfir not to by high test.

My goof, reposted in TPI section.

Sorry.

Rich

Schurkey

The original TBI engine in my '88 K1500 pickup had 9.25:1 compression and went 200,000+ miles.

I replaced it with a TBI crate engine from a '91 Caprice. 9.6:1 compression. That went 18 years before popping a head gasket.

I don't think the truck has ever gotten fuel with greater than 87 or 88 octane in the decades I've owned it.

9:1 compression is throwing away power, throttle response, and fuel economy. Doing 9:1 with huge quench distance makes it even worse.

morgsie

iTrader: (1)

i agree. tighter quench is better >.040" for power and detonation prevention.

racprops

Well I will have to revisit this compression ratio.

First I have to get the 400 rods, waiting on three people so supply them.

Then order the 383 Crank.

Once I have them I can mount one piston and check the piston to deck height.

And perhaps find away to figure out how much was also machined off the heads.

My basic order was to please clean them until straight and flat, both block and heads.

My understanding is gas today is not as good as it was 20 years, so with to days gas is a higher compression worth it??

How high can I go before it starts knocking??

I am considering doing very minor clean up of the chamber to try to get it smooth and polished, making sure I remove all angles and sharp points to stop any hot spots that might cause preingation.

I also was looking into thremo coatings, wonder if they MIGHT also cause knocking?

PS a lot of my driving will be in HOT AZ.

Rich

racprops

Here is a kind of off the wall question: I understand there is a way to use the TBI PCM to run a TPI system.

My understanding there is a program to flash a EPROM for that.

I also understand the output transistors have problems with the added load, has not someone worked out a set up using stronger transistors to handle it??

Rich

PS Heck I have a PCM fail with one of its transistors failed with the stock injectors on a TBI intake.