Hot Rod Forum banner

Looking for carb/spacer/ coolant temp and spring advice

1K views 7 replies 5 participants last post by  0trbo4myCHEVUICK 
#1 · (Edited)
Been running my 383 for about a month now, Changed the oil for the 3rd time last week and should be good to go for regular oil change intervals now. I decided to run Castrol magnatec synthetic blend 10W30 with my wix filter.

With penzoil 10W30 I was seeing very low oil pressure(under 10psi)while idling around 650 rpms.
Even the slightest touch of throttle would shoot it up to 60-70 psi so I wasn't TOO concerned.

Now with the magnatec and a added bottle of Lucas stabilizer I run 20-25 psi at idle and 60-70 with hard throttle. So I think i'm all good there.


While inspecting my carb I noticed my secondaries were dusty and haven't even been opening. My QFT has a single adjustment screw for the secondaries, I loosened the adjustment screw and now they are clean and working but I have no idea when they are actually kicking in?
Does someone know about how many turns out I should have the screw? I think i'm about 5-6 turns out right now...
It's not bogging or anything but I am just wondering if I am leaving power on the table.

I am running a 2" tapered carb spacer with a thick heat insulating gasket... I am thinking about taking the spacer off to see if I notice a change. What would you guys expect to happen? I am already suffering through traction problems so I am thinking the spacer is helping me with that by moving my power band up?

Currently my engine pulls to 6500 rpms. I shift there constantly because that's where it feels good.. I expected my engine to stop pulling around 5500 with my small vortec runners and mild cam...

I am curious if the spacer has anything to do with this and although I have been shifting at 6500 maybe if I remove the spacer my power band would be better suited for my heads and cam.

Currently I am running a 180* thermostat. The engine seems to run better and better the hotter it gets so I was thinking of running a 195... Maybe too much for Texas summers though?

When i first start my engine, my fuel psi is bumping 8-9 psi and after warm up it drops to 4-5, is this okay?

My last question is about valve springs, I know mine are on the weaker limit so what gains would I notice by switching to a stiffer spring?



Here are some specs

1982 chevy C10 silverado standard wheel base, Heavy, not sure how much but a lot.

383ci "880" roller block. 9.4:1 SCR

Morel 4602 roller lifters

Comp ultra pro mag XD 1.5 rockers

Comp hi tech 5/16 .080 pushrods

Mahle inverted dome 26cc

Scat H beam 6.0 rods

Scat 4340 3.750 crank

DUI street/strip HEI distributor with live wires and AC delco rapid fire plugs.

Melling select standard volume, high pressure oil pump

Carter Muscle Car Mechanical Fuel Pump M6626

Lunati voodoo 60121 roller cam (.515 In. .530 EX, 270/278)

906 Vortec heads milled to 59cc, screw in studs, guide plates.

Spring Specs 135 lbs. @ 1.750, 325 lbs @ 1.200

Springs are 1.250 diameter



Performer RPM vortec intake and QTF 750ss vacuum secondaries w/ annular boosters.


24-2600 rpm 9" stall converter with reverse shift pattern manual valve body TH400

Stock rear end, 33X12X15 tires in rear.
 
See less See more
#2 ·
This sounds like a very nice build, you gotta love it when all the pieces turn out to be a great engine.

The valve springs should take a set after several cycles which will lower the PSI a small amount then remain stable for a long time.

Spacers are very much a tuning item you just have to try with and without to see how the engine likes 'em.

Bogie
 
#3 ·
Currently my engine pulls to 6500 rpms. I shift there constantly because that's where it feels good.. I expected my engine to stop pulling around 5500 with my small vortec runners and mild cam...
That's what I would have expected also, I can't see the L31 heads and that cam pulling to 6500 in a 383. It might REV to 6500, but when is the power trailing off? Can't you feel it nosing over before 6500? Have you tried shifting earlier? I would expect all the power to behind you at 5500.

I am curious if the spacer has anything to do with this and although I have been shifting at 6500 maybe if I remove the spacer my power band would be better suited for my heads and cam.
Spacers are a strange lot, you never know how the motor will respond until you try different spacer heights and configurations, or none at all.

Currently I am running a 180* thermostat. The engine seems to run better and better the hotter it gets so I was thinking of running a 195... Maybe too much for Texas summers though?
The best advice I can offer you is to engineer a top-shelf cooling system and then run at least a 195 thermostat. The motor needs that much heat to help burn off acids in the oil that are formed from blow-by past the rings as a result of the combustion process. Look at the new cars, some of them run 220...hotter makes more power.
http://www.crankshaftcoalition.com/wiki/Bulletproof_cooling_system

When i first start my engine, my fuel psi is bumping 8-9 psi and after warm up it drops to 4-5, is this okay?
Most modern needle and seat valves in the carb bowl will tolerate 5 psi. More than that can overpower them, depending on design, and allow the fuel pump to blow raw fuel into the intake manifold, creating a tuning nightmare for you.

My last question is about valve springs, I know mine are on the weaker limit so what gains would I notice by switching to a stiffer spring?
If you're revving the motor to 6500 without it hiccuping, you don't need more spring.

.
 
#4 ·
I am going to have to do some more seat of the pants testing but it sure seems like it's still pulling strong at 6 to 6500 rpms...
Maybe it is just feeling good because I am keeping it in first for too long? I read somewhere once that with a RMVB 1st gear is only to like 15-20 MPH!!?

I can tell you that after my first oil change I come out of first gear going 60-70 mph at least twice a day to and from work.


I am going to try shifting out of first a lot sooner more like 4500. After that I will try to slowly progress through the rpm range in 2nd gear until it stops pulling hard..

Then I will probably take the spacer and thick gasket off to see how it runs.


Tech:

I haven't noticed any "hiccups" or anything like that, I'll take your advice and leave the springs alone for now.

I feel like my cooling system is up to par for a 190* thermo, I will order one and try it out.
I have an electric fan mounted that I haven't even wired up yet if need be, and my water pump is a stock autozone unit so I know where to look if I need an upgrade for cooling. ( Even though I could NOT find an aftermarket vortec water pump for a good price, Stewarts doesn't even seem to make one for this app)
I have a large fully aluminum champion radiator that has treated me very well even with 2 tranny coolers mounted to it.



Now maybe if I solved my traction problems I would stop losing races to mustangs and civics.



This engine adventure has taught me a lot of things, one being that I really want an actual race CAR.
A Monte Carlo SS would be cool.
 
#5 ·
Here is the spacer I am running. Notice it is actually divided for a dual plane intake, one of the few I could find this way as a tapered 2" unit.

I didn't see any use for the 4 hole gasket that came with it, I just used gaskets that were divided down the middle matching my intake. Like the one I posted. I cut the diamond shape out of the middle of the gasket though so its just a straight divider. The diamond would have been sticking out in the intake path and I couldn't see any good in that either.
 

Attachments

#7 ·
I run the quick fuel vacuum secondary pod on my holley carb and the screw stock setting is about 1 and a half turns out and I have recently taken it apart to see how it works and its pretty much the same thing as the holley quick change vacuum secondary pod but way better in function and more fine tuning but obviously you can't change out the spring with out taking the housing off but the holley pod has a brass restriction or a check ball in it and it controls the rate on how quickly the vacuum secondary responds to signal but you can't adjust it and the quick fuel pod allows you to adjust how quickly the vacuum secondary's will react to the flow going into it thus giving it more opening on the screw allows quicker response to the secondary's opening along with what ever spring you use. Back in the old days some people used to take out the check ball in the holley pod and it allowed the signal to be too sensitive and sometimes folks would drill out the brass restrictor a hair more.

Basically besides what spring you use for rpm rate that quick fuel pod allows adjustment to the sensitivity of the signal going in. I have tuned mine and at about 2 turns at the most it allows me good opening and going more does not make my secondary's perform any better so I just leave it at that. Sort of like the idle mixture screw but it either restricts or allows more air.

The quick fuel pod comes with a purple spring and I tried a yellow spring on my build and it regardless of adjustment caused me to have a very faint bog when my secondaries kicked in and I went back to the purple and it ran fine. Usually the purple or yellow spring and on the rare occasion the white spring give the best secondary opening rate. All the other good Generals here gave some awesome advice on everything else :)
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top