DP4B Installed - Impressions and a couple questions

[Kern Dog]

Hughes engines did some heads for me years ago. we got to talking and he said put the rpm performer on and you will pick up 3 tenths and I was thinking yea right when he said that. he was exactly right.

The man is sharp.
Not super friendly but he does know these engines.

 

[RemCharger]

I was just going by the old saying 100 lb equals 1/10 of a second in a quarter mile. So saving 25 lb on the intake manifold will be one quarter of a tenth. Going a 10th faster in a quarter mile equals one mile per hour faster. I thought that's what I remembered

Yes thats pretty much the rule. However, there's so many variables run-to-run, you have to be fairly damn competitive and everything set razor sharp to actually announce that you positively altered your performance by .25 of a mile per hour.
1 whole tenth or 1 whole mph, thats enough to say yes 1 way is better. But that could be the tail wind picked up, or the clouds rolled in, or the cars hot/cold etc

 

[BSB67]

I put 3 tenth and 3 mph going from a factory intake to the DP4B.

 

[Virg464]

Do you know what your static CR and cranking PSI is? A lot of years ago I found that low compression engines like more timing. The first time I ran into it was with a teen with 360 heads which made the static fall even more than factory advertised. That little sucker liked 50 total and 3 different timing lights confirmed that. That engine was in a 72 Demon that ended up running a 13.51 best @102 mph. The 60 foot really sucked though with a 2.2 and the other engine was a 440 in a 67 Coronet. It too ran in the 13's but don't remember the exact numbers anymore and didn't bother checking it with two more timing lights lol

This is my first venture into an actual performance build versus bolt on stuff, so i didn't build it. It was built by Petit Racing, my friend that's been racing for decades recommended them, and told me the CR target was 10.2:1. I checked cylinder pressure back when I first brought it home and it ran 150 to 155 PSI, that was after break-in (maybe 45 min run time) I do have open chamber (alum) heads with domed pistons, don't know if that would matter? So it's not really a high compression motor?

 

[MikeyM]

Hey everyone,

Thanks for all the input. GTX, I think you were on to something with one of your previous posts. So I've been doing testing all weekend and finally just decided to install a lighter secondary vacuum pod spring and bump the timing like 1 degree. That totally made a difference. I guess the higher flow of the DP4B liked the secondaries coming in earlier. I had it dialed in before with the OEM manifold but it seems it needed a bit more with the new configuration. I went from the brown spring, past the plain, to the purple and there was a very noticeable difference in highway acceleration from 65-70 on up. Also from about 30, dropping into 1st and punching it, manually shifting up through the gears, it pulled hard but very smooth.

I'll keep playing with it and maybe go back down to 67 primaries from 68s to see what that's like.

Thanks again,
Mikey

 

[RemCharger]

I put 3 tenth and 3 mph going from a factory intake to the DP4B.

The other half of the statement would be at what performance level ( hp/ et) were you at then. 14.90s, 12.90s,,
And which factory intake

 

[BSB67]

The other half of the statement would be at what performance level ( hp/ et) were you at then. 14.90s, 12.90s,,
And which factory intake

Low 13s. Street car with P235 tires. 2.1-2.2 sec 60ft. Trapping 103 to 107.

The 301 factory intake. 4779 carb.

 

[gtxrt]

Hey everyone,

Thanks for all the input. GTX, I think you were on to something with one of your previous posts. So I've been doing testing all weekend and finally just decided to install a lighter secondary vacuum pod spring and bump the timing like 1 degree. That totally made a difference. I guess the higher flow of the DP4B liked the secondaries coming in earlier. I had it dialed in before with the OEM manifold but it seems it needed a bit more with the new configuration. I went from the brown spring, past the plain, to the purple and there was a very noticeable difference in highway acceleration from 65-70 on up. Also from about 30, dropping into 1st and punching it, manually shifting up through the gears, it pulled hard but very smooth.

I'll keep playing with it and maybe go back down to 67 primaries from 68s to see what that's like.

Thanks again,
Mikey

all that your doing is because of the block heat crossover giving you a cooler and leaner mixture. if I block the crossover even without changing to any different intake I always needed to go up at least 1 size jets and rods.

 

[gtxrt]

I put 3 tenth and 3 mph going from a factory intake to the DP4B.

just think if you went with the rpm performer could have picked up 6 tenths and 6 mph.

 

[BSB67]

Only if the intake is limiting. In this application, maybe another tenth.

 

[MikeyM]

all that your doing is because of the block heat crossover giving you a cooler and leaner mixture. if I block the crossover even without changing to any different intake I always needed to go up at least 1 size jets and rods.

Interesting. Good to know, thanks. So earlier on in my post, I mentioned that I noticed the intake manifold vacuum running about 1 inch higher at cruise. Could that be because the addition in primary jet size from 67 to 68 is providing more fuel due to the denser mixture, more power, and a little bit more efficiency? That’s what I attributed it to, but I could be off base. Originally I was running 67’s and it felt like a dog down low so I went up to 70s and that was really no better… Felt sluggish. Backed down to 68 and that seems to be where the happy place is.

Thanks,
Mikey

 

[gtxrt]

So earlier on in my post, I mentioned that I noticed the intake manifold vacuum running about 1 inch higher at cruise. Could that be because the addition in primary jet size from 67 to 68 is providing more fuel due to the denser mixture,

I don't know. more timing I think helps vacuum?

 

[MikeyM]

It does, yes, but my cruise vac was up 1 inch before I bumped the timing a degree. After the manifold install and up-jet from 67 to 68. I'll check the plugs and see how they look. Currently running NGKs cuz the run very well in my Jeep but any suggestions on plugs that might be a little better?

Thanks,
Mikey

 

[RemCharger]

NGK is the top shelf plugs.

 

[MikeyM]

Cool, thanks. Thunk so. Maybe a couple others, as well, but they've always worked well for me.

So regarding the crossover blockoff, I'm wondering if I should unblock it with the dp4b. I've read in a couple older posts that blocking it gave a pretty good bang for the buck increase cuz of the cooler fuel charge. The only "negative" thing I'm noticing is that it takes a bit longer to warm up but once it is, it stays like that all day so I can live with that.

Mikey

 

[TorRed]

So for me, the Airgrabber hood rules out the Performer RPM, too tall, so it's either stock, DP4B, Mopar M1 or Holley Street Dominator. If I go the route of 'stock appearing' the Holley is ruled out leaving the others painted Hemi Orange. So height has to be a consideration for many wanting to run stock air cleaners, etc.

 

[MikeyM]

TorRed,

True. Same for me. I have the N96 hood and needed to stick to a certain height. With the dp4b and a 1/4" Edelbrock 9266 heat isolator, it fits just right. As I get it dialed in (again) I think I am noticing some small gains that would likely be amplified with a 750 and headers.

Mikey

 

[Virg464]

Cool, thanks. Thunk so. Maybe a couple others, as well, but they've always worked well for me.

So regarding the crossover blockoff, I'm wondering if I should unblock it with the dp4b. I've read in a couple older posts that blocking it gave a pretty good bang for the buck increase cuz of the cooler fuel charge. The only "negative" thing I'm noticing is that it takes a bit longer to warm up but once it is, it stays like that all day so I can live with that.

Mikey

My engine does that same thing, it doesn't like to idle until it gets up to 140F and that takes a couple of mins.

 

[MikeyM]

A little update on this - the midrange of this manifold is outstanding once it's FULLY warmed up, coupled with an adjustable VS spring pod. I would recommend both. Consistent tire chirp from 1-2, and especially 2-3.

My only complaint is the length of time it takes for the manifold to "heat up". I blocked off the crossover ports as an experiment and if I were racing only, I would keep it. However, I am not. I'm the old guy who drives mellow, has nothing to prove, but likes to show up high dollar cars from time to time, when taunted (sorry... gen x'r here.).

Anyway, I would like to unblock the heat crossover to see if that will give me better atomization and drivability when "not hot". Currently I'm running the valley pan with no gaskets (all stock engine) but did apply light sealer around the intake ports on both sides. Can I just remove the intake, punch the exhaust heat crossovers, and reseal with permatex? Or do I need a new valley pan "gasket"?

Thanks,
Mikey

 

[gtxrt]

I always make up some block off plates with a 1/4 hole to get a little heat.