I'm really happy with the way the front end sits now that I re-did the crossmember. One side effect was that the shocks were now too long and would only give me about 3/4" of suspension travel.
I ordered new shorty shocks from Pete & Jakes in January, but they were backordered and didn't come in until February. So I guess April is a good time to install them.
Now I've got some suspension travel again.
Looks nice. Do you have a picture showing th new stance?
JoeyM said:Looks nice. Do you have a picture showing th new stance?
Just the ones on page 5. I'll take a couple dead-on from the sides and post them soon.
So I've been telling the whole story and the whole truth with this build, so I've got to tell you about the work it has taken to get it driveable. The first few test drives went okay, but I barely touched the throttle and pretty much babied the car. Now that the weather is better, I took a few more drives and tried to lean on it a bit more. Not good. Every time I went quick on the throttle, even a bit, it would backfire badly and often quit running. Backfiring with a blower is a creepy thing--a lot of gas comes out of the blowoff valve and Holley power valves don't like backfires. I've tuned probably over 1000 cars, but this is my first 4-71 equipped small block. I've also got a lot of friends who've tuned a lot of cars, but none that have tuned this combination, so it was up to me and the internet to sort this out. I did a lot of reading (mostly misinformation) and watched quite a few YouTubes about setting up a Holley for a blower (slightly less misinformation, still not very helpful), but of course there was no silver bullet.
I think many of you have had that moment in a project where you say, "why did I take a perfectly good setup and mess it up?" I was there, and I was thinking about the people I know who have had 6-71s and 8-71s on their cars and pulled them off because they were too much trouble. I figured I'd do better with the 4-71 and my mild power goals. Did I make an expensive and time consuming mistake here? Honestly, I get to that point in almost every cool build I've been a part of, so at least I knew to stick with it. I usually figure things out when I get down to the basics and take each step pretty carefully. So it was time to slow down.
In my haste to get the car running, I had set the timing to 34 degrees, all in, and went on to take those first few test dries. Small blocks usually like about 36 degrees, so I went a little conservative because, you know, boost. Now with any customer car I work on, I also check the timing at idle and map the advance curve. But of course, I've never done that with my own car. So you know where this is going: That backfire was making me think I had a lean spike and I richened the mains and especially played with the accelerator pumps until I remembered my own mantra that most carb problems are ignition.
I mapped the ignition. It was 34 degrees all in at about 4000 RPM (I hadn't checked the RPM when I set the timing, I just had checked that it wasn't advancing any more). It was 0 at idle! The car has always had a cool old Mallory dual-point distributor on it, but only now did I know that it had a terrible advance curve. It should have been more like 15-20 degrees at idle and 34 all in at around 3000 RPM. Timing that retarded will cause backfires all day long.
I bumped the idle timing to 15 degrees and went off on a drive, being careful to keep the revs low because that would have been about 50 degrees all-in. No more backfires and a much crisper ride. Duh.
I was hoping I could get parts to re-curve the Mallory, but it's a dinosaur and those parts are not available. I could have made something work with a generic re-curve kit, but I decided I'll just throw a little more money at it and put in a new distributor. I went with an Allstar Performance unit from Lane Automotive. Allstar is Lane's own brand and the stuff is usually a lot cheaper than other brands. Of course, the Lane salespeople push it pretty hard, but they also hint when they think a more known brand may be a better choice. My guy suggested the Allstar, so I bought it. I feel a little guilty buying Allstar sometimes because a lot of it seems to be a Chinese copy of name brand stuff. The Allstar distributor I bought sure looks like a MSD Pro-Billet, but it's half the price so I decided that the guilt was worth it.
Anyway, too many words, not enough pictures. Here is the Mallory (left) and the Allstar (right). Setting up a dual-point is a little bit of a pain, so I had installed an MSD 6A on the car in during the original build. The points triggered the 6A and I got way better spark. More importantly, since the points were only an input for the 6A and weren't the switch for the coil anymore, they lasted a lot longer. I've done that with a lot of cars over the years. Back to the point, the Allstar is setup to trigger the 6A with its two-wire plug. It's really easy to adjust the advance curve. All of the components are right under the oversized rotor, so you could probably even change the curve without pulling the distributor. I set it up for the shortest, fastest curve. You'll see the map below. Okay, too many words again...here are the pictures:
You'll see I ordered a vacuum advance version. I like vacuum advance on street cars. Driveability is just that much nicers.
I needed a new set of plug wires because the cap had different terminals, so I bought Allstars. That was a mistake. They came numbered, but #1 and #3 were mislabeled. That's why you're seeing green tape on two wires. Also, #7 had two right angle plug boots on it instead of a right angle plug boot and a right angle distributor cap boot. Lane will make this right, but it's annoying to be sure. I don't care for the logos everywhere, so I'll probably exchange them for something else.
Since the wires are coming off, I didn't spend much time making them neat. I just made sure they were secure enough not to melt on the headers. (And I promise the ugly fuel lines will go away after the dyno tune--it's so much easier to pull the float bowls to change jets with rubber lines.)
The ignition map may be a little aggressive, but it seems to be working well so far. I may have to tone it down a bit once I've driven the car on a hot day. Here's the map:
1000 RPM 18 degrees
1500 RPM 23 degrees
2000 RPM 32 degrees
2500 RPM 34 degrees
3000 RPM+ 34 degrees
And with the ignition in good shape, the backfire and driveability were good. My butt dyno wasn't feeling that the car was any faster, so my frustration was still there...
I ordered the 750 Holley on Gary Dyer's advice, but that was like 15 years ago and I've been using that carb as a "mule" carb on other project cars over the years. There are a few minor mods that are proven to help blower carbs and I hadn't done that with this carb yet. I was considering doing that, but then I'd lose my mule, so I decided to throw money at this project again and buy a Holley carb setup for a blower from the factory. Since this is a street car and won't see anything above 5000 RPM very often, I've been pretty fixated on something a little smaller, like 600-650 CFM. I called the Holley tech line and they confirmed that a 600 should be good unless I want to go above 5000. So I ordered the 600. I like electric chokes and you can't get the supercharger version with an electric choke (only manual), but you can order a conversion, so I got that too. I know purists will say I should have a manual choke (and a manual transmission), but this car is built for simple driveability.
Anyway, the carb:
I'd rather have had it in the traditional gold/zinc, but the supercharger versions only come in shiny aluminum.
The choke kit:
The choke installed on the carb (by the way, the generic installation instructions need to be updated):
A good surprise was that they fuel inlets are on the passenger side, same as the fuel pump, so the plumbing ends up a little cleaner. That surprise was followed by a couple of less good surprises.
The first was that the carb would not sit flat on the baseplate like the 750 would. The accelerator pumps were interfering. A little time in the mill took care of that.
I was expecting the carb swap to go fast, but messing with the choke install and incorrect instructions, coupled with the clearancing, had me into it for about three hours now.
The next surprise happened when I got the carb on the car and went to hook up the return spring, but there was no place to put it. Here's what the carb linkage arm looks like on most Holley's, including the 750 I had just taken off:
Here's what the linkage arm looks like on a supercharger carb:
At first I thought it was just a defect and had broken off. But I checked the Holley website and that's the way they come. The little tab for return spring wasn't a bit deal, but the tab and larger hole for the transmission kickdown are a bigger deal and I need that. I think the issue is that most people run two of these 600 Holleys on 6-71 and bigger blowers, and when they do, the linkage is different (I think a lot sit 90 degrees offset as well). So apparently Holley cuts the bottom of the linkage arm off.
The quick swap took a little longer as I made up a little extension and riveted it to the linkage arm.
Don't worry about the bad metal rod connecting to the carb--that's getting replaced next.
I also checked the jetting and power valve: 68 Main on the primary with a 6.5 PV, 73 on the secondary no PV.
With all that done, I set the float levels before the first start. Why does every Holley adjustment involve spilling raw gas?
I also put a "T" into the manifold vacuum port that I use for the boost gauge so the carb had its boost-referenced vacuum signal (sorry, no pictures).
I was now somewhere like 6 hours into what I thought would be an easy Saturday. Oh well. But the car started right up, so I got a little satisfaction. However, I discovered I still didn't have the electric choke installed quite right (I had the red cam on the wrong side of the linkage arm up to the choke plate--not even mentioned in the instructions), so I had a little more fussing to do. Another half hour gone.
The test drive made it all worthwhile. In the previous post, my butt dyno wasn't telling me the car was any faster. I'm sure I could have dialed the 750 Holley in, and because I'd been chasing the wrong things, it was too rich. With the 600 and a little leaner mixture, the car is pretty happy. It's not as fast as I'd like, but that's mainly because when I step on it, it just spins the back tire (note: time for a limited slip). I'm sure there's more power on the table. I'll work that out in future test drives and a chassis dyno session. I'm not seeing a lot of boost on the gauge yet, either, but that's mainly because I haven't had a place to drive it up above 3500 RPM or so. More on the boost situation soon.
(By the way, sorry if this is boring, but I figure the other 3-5 people in the world running Holley 600s on 4-71 blown small blocks would like this info so they their Saturdays go a little better. )
Not boring. Fun.
In reply to Carl Heideman :
Something I have seen on my blown car, now that is a twin carb 8-71, but I think the principle is the same. With only part throttle no matter the rpm you will not see boost, and most of the time vacuum instead of boost. Since the carb is a restriction of air to the blower, there is not enough air coming in to overcome the demands of the engine. You will only see boost when the blower can produce more air than the engine can consume.
In my situation I set up my carbs as a progressive linkage so the second carb did not open until about 3/4 throttle ( twin 650 edelbrock carbs buy the way). When testing I was not giving enough throttle to open the second carb fully so I thought I was not generating enough boost. so I kept putting on smaller pulleys to produce more boost, but it did not make a huge difference until I put the throttle to the floor and then there was way more boost than anticipated!
I would also recommend a msd timing retard that pulls timing under boost, you can select how many degrees per pound of boost. This lets you keep the aggressive timing you have for part throttle operation and good street manners, but not cause detonation when you start producing boost.
Great build, I really like cars that are designed to be driven, so the 4-71 single carb setup makes good sense to me.
In reply to Fladiver64 (Forum Supporter) :
Thanks for the tips about the boost. I haven't put my foot all the way into it for very long yet--mainly 0-35 pulls on streets near the shop. If I put my foot in it right away, it just lights up one tire forever. So it's gonna be fast. I will be putting a limited slip in it!
I've used the MSD timing retards on other builds. I'm not sure if I'll need to do that with this car since it's pretty mild. I'll know more after the dyno session and some hot summer days. I've also got a buddy who builds vacuum canisters that retard slightly under boost, so I may do that since I got the vacuum advance distributor.
You were smart to use a progressive linkage on your 8-71. I don't know how those things run below 3000 RPM if both carbs had idle circuits.
Okay, today I declared that I'm done with the build and setup phase and onto the sorting and punch list phase. As I just mentioned above, the car will now fry off one tire indefinitely at will and the driveability is about 90% there. Whenever I'm sorting out a car, I take it on a lot of short errands. More issues come out on short drives than long drives.
Sorting item #1 was making a new throttle arm (bottom one). The last one was now fowling on the plug wires and wasn't quite getting WOT. I'm not sure the new one will stay with the car long as it has quite a bit of compliance, but I won't make another one until I get the next set of plug wires. I hope to stay old school with an arm rather than go to a cable setup, but in the end I want an extremely smooth-like-butter throttle pedal feel, so a cable may be necessary due to the height change and other packaging issues.
Since I'm now in sorting/punch list mode, I thought I'd start getting ready for a future project. I like to put a few miles on a car before I start into a build so I get a good feel for the car and its issues. Since you guys don't seem to mind my old Ford junk, I thought I'd share another one.
This is my 1938 Ford Tudor that's going to get a quickie moonshiner treatment. It'll go a bunch lower in the front, get some big and little blackwalls, a blanket interior and a few hop up items on the flathead. I've already redone the brakes and put a gas tank in it. It'll need a wiring harness and some other maintenance too. My son Chris was going to drive this car to his last month of high school, but the pandemic took that option away. Maybe he'll drive it his first month of college.
Anyway, I need to go through the ignition since it keeps fowling a couple of plugs. That's a painful job, so I just pulled the plugs, bead blasted them, and put them back in. They'll be good for about 10-20 drives. While I had them out, I checked the compression. The cylinders were generally 75-90, so I'm pretty happy as those are decent numbers for a stock flathead.
JoeyM said:Looks nice. Do you have a picture showing th new stance?
Here's a side view. I'm really happy with it.
I wanted the 4-bars and the drag link to be parallel to the ground, and they're pretty darn close. The car rides much better now too since the last bit of bind is out of the front end.
I put the hood tops back on for the sorting phase. My plan is to run no sides for the initial sorting. Once I'm done messing under the hood very often, I think I'm going to leave the driver side open and put the passenger side back on. I like louvers, so I'll at least have them on one side.
In reply to Carl Heideman :
It's your car so do as you please, to me though that buffer is a major attraction.
Aren't those shocks upside down?
Carl Heideman said:Okay, today I declared that I'm done with the build and setup phase and onto the sorting and punch list phase. As I just mentioned above, the car will now fry off one tire indefinitely at will and the driveability is about 90% there. Whenever I'm sorting out a car, I take it on a lot of short errands. More issues come out on short drives than long drives.
Sorting item #1 was making a new throttle arm (bottom one). The last one was now fowling on the plug wires and wasn't quite getting WOT. I'm not sure the new one will stay with the car long as it has quite a bit of compliance, but I won't make another one until I get the next set of plug wires. I hope to stay old school with an arm rather than go to a cable setup, but in the end I want an extremely smooth-like-butter throttle pedal feel, so a cable may be necessary due to the height change and other packaging issues.
Have you thought about a bell crank arrangement? It solved my throttle issues which really were bad angles and flexible rods.
In reply to frenchyd :
That's a good idea. Given you're a Jaguar guy, makes sense that you're mentioning bell cranks on throttles...
Mr_Asa said:Aren't those shocks upside down?
Nope, that's how they're supposed to be.
Question about the blower. How does it work without an intercooler of some sort? My only experience is with the ones fitted to the ford mod engines and they all seem to require air to water intercooling. Does the fuel already mixed in come into play for this?
Pete
Carl Heideman said:In reply to frenchyd :
That's a good idea. Given you're a Jaguar guy, makes sense that you're mentioning bell cranks on throttles...
+1 to bell crank to make the transition from vertical to horizontal motion. Or convert to pull action and use a cable and pulleys.
In reply to NOHOME :
Generally speaking, draw-through setups (fuel added to air before pressurizing) will have all sorts of fuel drop-out as the wet mixture flows through an IC.
In reply to AngryCorvair :
I guess that is true. An intercooler on a wet system would just fill the heat exchanger with liquid fuel.
But the things DO generate a lot of heat as they compress the charge, so I am guessing that you just hot-box it and go for the best?
What level of boost does this set-up build?
Pete
The fuel changes phase and absorbs heat?
how/where would you plumb the BOV? that right there is a big reason not to IC a wet charge.
The math says I should see about 5psi, so heat won't be much of an issue. Most of my boost experience is with small bore cars, and it usually around 7-10psi that an intercooler becomes a necessity in those.
About the only people who run GMC-based blowers any more are drag racers, boaters, and poseurs. Guess which one I am? The drag racers don't seem to intercool, but many run the cars on some variation of alcohol. The boaters often do intercool as they've got lake water at their disposal. I suspect those boats don't idle very well.
boaters are cheating scabs. They always make more power than any of us. By far. And neglect to mention the fact they are floating on acres and acres of heat-sink. :-)
In reply to Carl Heideman :
A lot of the Rootes type blowers for the street underboost deliberately and start out with relatively low compression. 5-6 psi doesn't generate much heat when you are working with compressors of 250-350 cu in. On top of 350 inch engines.
Besides most street blowers sit up in the air stream drawing cooler air than an enclosed engine compartment with the heat off the radiator being drawn in.
Aside from that it's a lot easier with E85 as readily available as it is. One final thing, hot rodders love to use windshield washer fluid to supliment high boost.
not only is it made of up to 20% methanol ( alcohol) but all that water cools the intake change extremely well.
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