383 Crate swap into my 72

[FairlyRandom]

Anyone have an opinion on how much rad cap holding PSI I should have with a 383? I've seen caps advertised with anywhere from 22 down to 6 PSI. I'm wondering if part of my issue is that the cap shouldve bled some pressure off allowing the thermostat to open...but maybe my cap holds too much pressure, holding the tstat closed, and lead to the heat issue?

Plus there are some cool billet caps with Chevy bowties on em with different pressure ratings...I'm happy for any chance to buy some new bling lol

Edited October 10, 2024 by FairlyRandom

[cny first gen 71]

I think original was around 16 pounds if memory serves me right. But I don't remember like I used to 😅

[jft69z]

15 psi was stock, according to the GM Heritage info specs, and AC Delco replacement parts listing.

[Scott S.]

I like the 19-21 psi cap. Also using a 165' thermostat. Stays a lot cooler in traffic. (160'-185')

Montelishi originally had the 16 psi/185' set up, but I'd get engine temps over 200' just sitting a the lights for a couple minutes. I was also refilling the system to often.

The cooling system is "circulatory"... The only reason your thermostat isn't opening is probably because it's gummed up. 

All the rad cap does is keep the pressure from building up and blowing hoses and seals,but if it opens at low pressures, it'll drain the cooling system on long drives. 

 

[FairlyRandom]

Thanks everyone for the details 

 

@Scott S. - I guess my concern is that the thermostat is brand new...less than 500 miles after the complete motor swap, so the chances it's gummed up are virtually zero. The rad hoses were rock hard, so there was a good bit of pressure in there. Once I let the engine cool enough that I could crack the cap and release the pressure, the tstat opened. My curiosity was as to whether that cap shouldve bled a bit of that pressure of and allowed the tstat to open 

I guess it's now possibly irrelevant as Blueprint has shipped me a new tstat and gasket, so that will go on. I will probably also drill a 1/16th inch hole in the tstat flange to act as a permanent pressure bypass.

But I appreciate all the advice!

[Scott S.]

If you're getting that kind of pressure on the hoses, my guess is that the thermostat isn't working...

My ex-brother in law went through 3 thermostats on his '63 Nova (with a re built 327) before he found one that worked.

I've had one or two brand new ones that failed as well. 

It's kind of hit or miss with the quality these days.

[420ponies]

A 16 lb cap is what I have on my new BBC setup. Just like the small block version. Do you have a temp gauge installed on this new motor? I'm hoping that it is installed in the cylinder head ( drivers side), and not next to the thermostat housing. Like I said before, 160 degree stat. And just 1  crossbar on the top of thermostat. You should have a firm hose at around 160-180 degrees. You should be able to run engine and see that this is happening thru the coolant cycle. I try to use a infrared gun to check temps( Harbor Freight), this way you can see when's happening. Start it cold , just ambient air is fine. Do you have good airflow from the fan blade or are you using a clutch fan. I hope you know how to check these if they are working properly. Just things to check out. You're new engine shouldn't be having problems with cooling, since it's been baked and cleaned prior to building. Hope this helps you out.😊😊

[Jason72]

The purpose of a pressure cap on a radiator is to pressurize the system. When you pressurize a liquid, you raise the boiling point of said fluid. 
 

I agree with the drilling a 1/16 hole in the thermostat. It will allow the air to pass through the thermostat as you fill the system 

if the thermostat did not have coolant at the underside of it, physically touching it, it will not open at its specified temperature. The steam isn’t saturated with heat like the liquid coolant is. If the temperature gauge is in the head it will definitely show hotter if air is under the thermostat. 
 

I always hook up all of the hoses, fill the engine through the thermostat opening to the top, install thermostat and then top off radiator. 

[FairlyRandom]

Thanks for the inputs guys!

@420ponies the gauge sensor is in the intake near the t-stat. I know that's not ideal, but the spot in the head is very close to the headers and would be difficult to shield from that heat. But I should invest in an infrared tool. Great suggestion! They did send me a new t-stat that I plan to get in maybe this weekend. Fingers crossed 

@Jason72 I did fill the system thru the t-stat hole initially, but had to add a good amount (more than a quart at least) after the first start and the system burped. When I have the system open to put in the new unit, I will top off at the opening for sure. I do plan to put the 1/16th hole in the flange as well.

[Scott S.]

On 10/14/2024 at 6:05 AM, Jason72 said:

The purpose of a pressure cap on a radiator is to pressurize the system. When you pressurize a liquid, you raise the boiling point of said fluid. 
 

I agree with the drilling a 1/16 hole in the thermostat. It will allow the air to pass through the thermostat as you fill the system 

if the thermostat did not have coolant at the underside of it, physically touching it, it will not open at its specified temperature. The steam isn’t saturated with heat like the liquid coolant is. If the temperature gauge is in the head it will definitely show hotter if air is under the thermostat. 
 

I always hook up all of the hoses, fill the engine through the thermostat opening to the top, install thermostat and then top off radiator. 

I found that having a "flushing tee" in the heater lines works well for releasing trapped air.

It's above the engine, so when filling through the radiator, I leave it open until the fluid reaches it. 

[DragCat]

8 hours ago, FairlyRandom said:

But I should invest in an infrared tool. Great suggestion!

Keep an eye out on the HF sales, they usually go to $20 

[FairlyRandom]

Frustration...

New torque converter is in, supposedly somewhere near 2200rpm stall. Definitely drives better, doesn't want to stall when idling at a stoplight.

The issue is that I'd raised the idle by turning the throttle stop screw on the carb to keep it from stalling while waiting for my appointment at the transmission shop. My assumption was that the stock TC was dragging the engine down at a stop, hence the need to raise the idle. With that idle raised up however, the engine would diesel when shutting it off in park.

So, with the new TC, I assumed that I could drop the idle back down. Well, it still wants to stall in gear at a stop with the idle brought back down. The new TC didn't fix that. If I raise the idle using the stop screw, I still have the dieseling issue.

Not sure where to turn. I am going to tune my idle mix using the vacuum gauge method. But in theory, the carb tune should be pretty sound considering Blueprint dynos their complete crates.

I guess I could have a vacuum leak too, this is probably less likely, but I will try to chase a potential leak using carn cleaner on my vac lines.

Many other suggestions I'm not thinking of?

[1970mcss]

Have you checked the advanced timing?? My motor is a stock original 454 but I had the same issue with idling and dieseling when I shut the car off and ran very rich. I set the mixture screws to the factory settings, set the advanced timing and then set the idle. The car has never run better for me. I hope this helps and good luck.

[Jason72]

The first 3.5 minutes of this video are extremely important on a performance engine 

 

[FairlyRandom]

Thanks @Jason72 and @1970mcss for the inputs. Looks like I have some work ahead of me!

I spoke with the techs at Blueprint, and they said that because they can't possibly predict all of the different setups their crate motors will drop into, they do shockingly little tuning before shipment. Essentially, they drop the distributor and carb onto the finished engine, make basic adjustments to ensure the engine runs, then do two to three dyno pulls to ensure the finished motor makes horsepower and torque numbers within a reasonable range to what is advertised. Luckily, mine made significantly more than advertised. 

With all that said, the tech also enlightened me about some advice they can't put in writing...due to international laws regarding efficiency and environmental standards, some of the installation guide provides direction that is not as practical in real life as it could be, but is necessary to meet those laws and requirements. They told me I should unplug the vacuum advance, and simply cap that port on the carb. It's possible to have detonation due to the vacuum advance on top of mechanical advance with the cam that's in there. Luckily, I haven't noticed any issues. The tech said that if I was experiencing detonation, I'd know it as it's pretty loud on a stroker and easily distinguishable compared to a healthy V8 sound. I only run 93 octane, never anything less, and he said that means I'm probably fine. 93 should be enough to hold off detonation at anything under 6k RPMs and WOT. I haven't gotten my foot that deep into the engine yet, so I'm probably good. If it weren't for those international laws, there would be no problems. Hopefully I've avoided that problem.

The tech ultimately suggested I recheck timing - both base and mechanically advanced, then set the idle mix for maximum vacuum. When I told them about my struggles keeping the car idling in gear, they weren't surprised at all, and suggested I go through that base timing and idle tune set up. Between setting the timing and idle, and unplugging the advance, I will likely overcome the stalling issue. I had assumed that both had already been established and set,  which had me leery of adjusting the idle mix myself.

Long story short, I purchased a timing light with tach, and already had a vacuum gauge. As soon as I have a few free hours, I will be getting that tune set properly. I will also be doing a vacuum check using carb cleaner on the lines and fittings to ensure that I'm not dealing with a vacuum leak on top of everything else.

I'm actually kind of looking forward to this because it's the kind of work that I haven't really been exposed to given that all of the cars I've owned before have all been fuel injected. This will be new knowledge, and I'm excited for that.

Wish me luck!

Edited October 28, 2024 by FairlyRandom

[1970mcss]

Good luck, and keep us posted on your findings. 

[DragCat]

Good news , especially anyone thinking about buying from blueprint. Ive heard good things about them 

[Jason72]

If I was in your shoes:

follow the video I posted earlier 

plug vacuum port like you mentioned 

Get engine to operation temp 

set idle speed as low as possible 

advance distributor 2 degrees at a time until idle stops increasing 

readjust carb mixture and speed to maximum vacuum 

repeat as many times as needed

Back off timing 2-4 degrees 

If timing makes it hard to start, put vacuum to advance can and reset timing to where it was in the previous step. Set timing curve with mechanical Advance.

check rotor phasing and adjust as necessary 

 

 

[FairlyRandom]

Jason, your advice was spot on. I did just as you mentioned, first I disconnected the vacuum advance from the distributor. I then connected a vacuum gauge and dropped curb idle till the gauge read juuuust off of zero, indicating the transfer slots were nearly covered.

I then attached my timing light which has a digital tach, and fine tuned curb idle to get to about 750 RPMs. The initial timing was spot on the factory spec, at about 12° BTDC, but total was low, only about 29° at 3500 RPMs, so I bumped timing up to 34°. Weirdly, idle RPMs didn't really fluxuate much, only came up about 25, so pulled it back down again with the curb idle screw.

I then reset the idle fuel mixture by bottoming the adjustment screws and brought them out 2 full turns. Vac gauge wasn't super steady, but from there I adjusted the mix to get about 13 inches, which was as much as I guess I could hope for with this cam.

All that work paid off though. After buttoning everything back up I went for a drive. The stalling issue is gone, and with the transfer slots covered, no more dieseling when shutting her off.

But the performance is what really blew me away. The new motor already packed a lot more punch compared to the 350 I pulled out, but tonight the thing really came to life. This car now moves way faster than a vehicle of this weight has any right to lol. The throttle response is great, and it pulls and pulls, even with the 2.73 gear in back. I suppose 5° more timing will do that lol, but disconnecting the vac advance I think also plays into it. The tech at Blueprint said I'd notice it, and he was sure right.

I have never been more convinced that I need to do a disc brake conversion in the rear as as am now...she moves quick, now she needs to stop quick too.

I will double check my initial timing again because in all my haste, I never checked to make sure that stayed put. Hoping it will, as the distributor is brand new.

But I guess I'm officially calling this swap complete. Thanks to all who helped me along the way!

[420ponies]

If you're going with disc brakes in the rear , Leed Brakes has a great bolt on kit. You will also need a new proportioning valve for the all disc brake set-up. They can help also with that. Sounds like you've made some good adjustments on that motor. Plus, it's under warranty.

[Michael Boyte]

They are not the cheapest route to go , however WILWOOD disc brakes is the manufacturer that we chose to go with, mainly due to the inhouse engineering and their long standing usage in the racing community. Most individuals are not going to push their vehicle to its limits, however I like the confidence in knowing that I can (we have nearly 800 horses without the nitrous and 4000 lbs to stop.) With WILWOOD, Their expertise relies on the development of custom engineered brake systems, utilizing a unique blend of off-the-shelf and custom-made components  They always go out of their way to make sure that you are  satisfied with their products. That being said, I'm sure there are other manufacturers that have nice setups, they just wasn't for me. 

Factory direct (805) 388-1188

Ask for Dave Brzozowski  

Wilwood Engineering
4700 Calle Bolero
Camarillo, CA 93012
USA

[Jason72]

12 hours ago, FairlyRandom said:

Jason, your advice was spot on. I did just as you mentioned, first I disconnected the vacuum advance from the distributor. I then connected a vacuum gauge and dropped curb idle till the gauge read juuuust off of zero, indicating the transfer slots were nearly covered.

I then attached my timing light which has a digital tach, and fine tuned curb idle to get to about 750 RPMs. The initial timing was spot on the factory spec, at about 12° BTDC, but total was low, only about 29° at 3500 RPMs, so I bumped timing up to 34°. Weirdly, idle RPMs didn't really fluxuate much, only came up about 25, so pulled it back down again with the curb idle screw.

I then reset the idle fuel mixture by bottoming the adjustment screws and brought them out 2 full turns. Vac gauge wasn't super steady, but from there I adjusted the mix to get about 13 inches, which was as much as I guess I could hope for with this cam.

All that work paid off though. After buttoning everything back up I went for a drive. The stalling issue is gone, and with the transfer slots covered, no more dieseling when shutting her off.

But the performance is what really blew me away. The new motor already packed a lot more punch compared to the 350 I pulled out, but tonight the thing really came to life. This car now moves way faster than a vehicle of this weight has any right to lol. The throttle response is great, and it pulls and pulls, even with the 2.73 gear in back. I suppose 5° more timing will do that lol, but disconnecting the vac advance I think also plays into it. The tech at Blueprint said I'd notice it, and he was sure right.

I have never been more convinced that I need to do a disc brake conversion in the rear as as am now...she moves quick, now she needs to stop quick too.

I will double check my initial timing again because in all my haste, I never checked to make sure that stayed put. Hoping it will, as the distributor is brand new.

But I guess I'm officially calling this swap complete. Thanks to all who helped me along the way!

Glad you got it sorted out!!