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 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

PS another question, will a TPI with a MAF system be able to handle the change from a 350 to a 383 without any reprogramming?

CKone

iTrader: (2)

For the goals you have in mind it sounds like you have a pretty sound build in the works. My only suggestion would be to loose the short 400 rod and go with a 5.7 rod minimum. Only reason being less side loading on the piston to cylinder wall and longer piston ring life easier on parts. It looks like you already have your pistons selected so in no way is it a deal breaker. Will still run fine.

Cam choice seems good for that as well, but perhaps could use slightly more duration with the increased cubic inch. Again, with wanting to focus on torque, you’re probably in the ballpark there. And if the cam is a regrind definitely worth checking rocker arm geometry. Not a major job and info can be found online, fairly simple to do with minimal investment. Your machine shop may be able to do this for you as well and even order the correct length pushrods if you need a longer length. Usually with reground cams/milled heads/decked blocks you have to increase the length to correct the geometry. Special length pushrods generally are inexpensive.

And in my experience with programming, years ago I swapped my 305 to 350 with dart heads, TPIS cam, headers, intake, etc. The car ran with the stock 305 chip, but not well. Had to drive with two feet to keep it running, would stall out if not. Power not where it should be. Had TPIS burn a custom chip and car ran considerably better but this was 20 years ago and I think a guy could do much better with some tuning knowledge or a friend who knows nowadays. With the relatively mild combo you have, the jump from from 350 to 383 may not be as noticeable, but in any case I would still recommend a correct tune for safety sake.

And last but not least, pay attention to your total quench/squish area with heads and deck height. Shoot for around .040” total especially if running the shorter rods as it could make you more prone to detonation. Other than that it sounds like you have a great build going on, good luck with it!

CKone

iTrader: (2)

Reading your info again one last thing I could suggest would be adding 1.6 ratio rockers, full roller or at least roller tips. Frees up a little power from reduced friction and will increase lift by about .030” and “add” a couple degrees of duration to the cam. Then I think you’re golden! 😬

racprops

Thanks for the feedback.

One of the things I have read is running MAF vs. MAP is the MAF is able to handle changes like mild new cams heads etc. I hoped it can handle 350 to 383.

And yes I am trapped with the 5.56 rods as the 5.7 rods will pop my pistons out of the block. I am considering a skirt coating to off set the side loading.

And doing some mild clean up of the chamber and polishing and perhaps of the exhaust port.

We work so had to get rid of the spent gasses only to put them right back in with EGR, and I have read that EGR can also add MPG buy both returning unburned gas vapor and heat, and displacing some of the incoming air and fuel. Odd an't it.

But with a clean exhaust under power I figure I want no EGR so want everything flowing cleanly and under cruse have more EGR, this way it can be controlled as needed.

I am also considering themo costing the heads and perhaps the pistons. Wonder if that will increase likelihood of knocking or or help it??

These coatings will add to the costs and I am wondering if they are worth it of not.

I forgot to list Magnum Roller tip rockers, but again only at 1:5 ratios. The cam will already have over .400+ lift and as I am sticking with stock springs they are limited to a MAX of .500, so I am again keeping that as close to factory as I can. Darn cam makers really like to add lift and duration, they hardly can make a near stock cam.This has been the hardest part of this project, finding a near stock cam. I almost would go with a stock cam but for the stories that the factory cams might be retarded during the years of early smog, so cannot be 100% sure how to set them up straight up or even a little advanced.

I have been told by a number of cam makers that with the 383 set up even mild as I am going for I DO need a little more cam. I would go for a stock 400 cam BUT it was never a roller, and I fear a little dated and hope a modern version of it would have a little wider power range.

Rich

CKone

iTrader: (2)

Well actually the 5.7 rod wouldn’t pop out of the block but rather smash itself Into your heads 😬 And yeah that suggestion was based on if you still had to purchase pistons, which you already have done. It’s just the original way guys were building these back in the day using the 400 rod. The one benefit with the short rod will be the piston will accelerate quicker and may lend itself to torque production, not a bad thing.

And tbh, if you’re looking for a stock type cam in a 383 I believe what you have is about as good as it gets. The duration is not crazy, lift is moderate, and with 114 lsa you should have a nice smooth running engine. Plus you already have it. I say go for it! 👍🏻

racprops

Good news about the short rods.

The cam is not in my hands it will have to ordered, and sadly either a costly custom grind with a new cam stock or a reground of a factory cam, with its slight lack of good hardening, but I feel this is a less concern with roller lifters and roller tip rockers.

The cam has been the main nightmare...ask any speed shop or cam maker how to get MORE HP and they have a a thousand answers.

Ask the same shops how do I keep the torque range near 2000 RPMs and how to make the max torque at that RPMs and they react like you need to be fitted for a straight jacket.

The shop that did all my machining kept saying "But that set up will not REV over 5000RPMs..." He reacted that way with my heads, cam wants and TPI intake.

I kept saying "Yes that is what I want..."

Rich