Intake choices for a mild, low-comp. 355

[nxtruck]

Guys,
I built a mild, low-buck 355 sbc a couple of years ago, using a pair of open chamber 993-casting heads, some Summit-brand flat top hyper. pistons, and an Elgin # 1065 hyd. flat tappet cam, which is a generic version of Comp's old 268 H.E. grind ( single pattern: 218 @ .050, .458", 110 lobe sep. ). I have a set of el cheapo 1 5/8" headers, a 2 1/4" set of pipes w/ 40-series Flowmasters, and on top of all this are a Edelbrock 2101 performer along with an older 3310 750 that I freshened recently. This engine lives in a 4000 lb. C-10 that will be getting a th350 along with a 12", 2300 stall converter. In the rear is a 12-bolt with some 3.73s. 28" tall rear tires, also.
Here's my question: given this info, what would you guys say to trying a different intake on this combo? I have a performer rpm sitting on the shelf right now that could be used, and I had thought about trying to get my hands on a performer eps, if I could find one at the right price. I know some guys will say to throw the rpm on there and not look back, but I'm concerned that, as mild as this combo is, along with the 8.6:1 compression ratio, the shorter intakes may be a better fit. I can tell you that the current combo falls flat at about 4700 or so, and that was my original reason for wanting to try the rpm.
Any thoughts or opinions are appreciated.

[GARY C]

Guys,
I built a mild, low-buck 355 sbc a couple of years ago, using a pair of open chamber 993-casting heads, some Summit-brand flat top hyper. pistons, and an Elgin # 1065 hyd. flat tappet cam, which is a generic version of Comp's old 268 H.E. grind ( single pattern: 218 @ .050, .458", 110 lobe sep. ). I have a set of el cheapo 1 5/8" headers, a 2 1/4" set of pipes w/ 40-series Flowmasters, and on top of all this are a Edelbrock 2101 performer along with an older 3310 750 that I freshened recently. This engine lives in a 4000 lb. C-10 that will be getting a th350 along with a 12", 2300 stall converter. In the rear is a 12-bolt with some 3.73s. 28" tall rear tires, also.
Here's my question: given this info, what would you guys say to trying a different intake on this combo? I have a performer rpm sitting on the shelf right now that could be used, and I had thought about trying to get my hands on a performer eps, if I could find one at the right price. I know some guys will say to throw the rpm on there and not look back, but I'm concerned that, as mild as this combo is, along with the 8.6:1 compression ratio, the shorter intakes may be a better fit. I can tell you that the current combo falls flat at about 4700 or so, and that was my original reason for wanting to try the rpm.
Any thoughts or opinions are appreciated.

I would say that if your not testing the intakes on an engine dyno don't waste the time and money for gaskets, sealer and coolant..
How would you conclude one is better than the other, what if it gains rpm but is actually down on power through out the rest of the curve, the butt dyno will lie to you everytime?

[nxtruck]

Gary,
Yeah, I agree with that. I had thought about taking it to the track and making some before and after passes with it, but I don’t know how consistent it would be on street tires and tight suspension. I guess I was mainly curious if others had tried those intakes on low-compression mild small blocks similar to mine and what the results were.
Thank you for the advise.

[MT Jeff]

Try playing with some carb spacers. Probably make about as much difference. If you have an open spacer try a fully divided one. Or make a hybrid one out of a four hole. Open up one side over the shallow side of the manifold to even out the plenum volume and make the transition better. And true cold air intake would help too if you have open filter.
Just my thoughts. Jeff.

[GARY C]

Gary,
Yeah, I agree with that. I had thought about taking it to the track and making some before and after passes with it, but I don’t know how consistent it would be on street tires and tight suspension. I guess I was mainly curious if others had tried those intakes on low-compression mild small blocks similar to mine and what the results were.
Thank you for the advise.

Track testing would be better than none but yes the car and conditions would have to be dead consistent, you are probably looking at a maybe 10 hp difference at the most between those intakes and thats not likely to show on the track. Back in the 90's I track tested every change I made to my cars on slicks with enough passes to know what the car did on a consistent bases, few things made a big difference and a lot of things that I thought were butt dyno proven better only showed to be no better or slower at the track.

You may find one responds much better off idle at the hit of the throttle and that would probably be the best one for your application.

Here are a cpl of tests that seem to be consistent with all the tests I have seen published as well as what people I know have seen in their testing, I have personally seen an open spacer kill 20+ hp on a 400 hp 9.1 331 sbc with a Performer intake and we all thought for sure this application could only benefit from a spacer... we was wrong. Had the engine not been on the dyno the guy probably would have been running a spacer assuming it was helping.

[enigma57]

My youngest son and I are building a mild 350 for his '92 Camaro. We just went through this drill. With the engine specs and gearing you quoted (very close to his)...... If your choices are Edelbrock Performer, EPS or RPM...... Go with the EPS. If you use a carb spacer of any kind, make it a 4-hole spacer. We are running a water heated / cooled mid-'60s 4-hole Ford spacer under his carb (same pattern as Holley). Helps atomization and drivability a lot. Keep the center divider intact and don't do anything to compromise it (don't shorten it and no open spacers). And stay away from anything 'air gap' like the plague.

As Gary noted, don't expect a huge power increase by changing out only the intake. 10 -12 HP tops with your best choices. The main thing you can do to make this engine perform better is to raise static compression ratio to between 9.25 and 9.50:1 with the cam specs you are running (mill heads and / or use head gaskets with less compressed thickness). And if you can get some quench whilst you are at it, so much the better (shoot for 0.045" if you can get it, but no more than 0.050"). With your best intake choice, good valve springs and a modest bump in compression ratio, you should see a noticeable increase in performance and drivability. Your 750 Holley is really a bit large. A 650 would do the job, but as your 750 is a vacuum secondary carb and will only open the secondaries as much as your engine requires, that shouldn't be a problem.

Hope this gives you some ideas,

Harry

[Geoff2]

Why would you use a 6500 rpm intake [ the RPM ] with an engine that will be lucky to peg 5500 rpm? And weighs a hefty 4000lb. The std Performer is the bet match for the combo.

[nxtruck]

Thank you guys, all, for the constructive input! I really appreciate it!

You all have confirmed what I have been thinking. I do have a divided spacer on it right now and have thought about making one as was described earlier { a 4-hole with one side open }. I don’t know that I want to go much higher with the compression, as this truck is my summer daily driver and I’d like it to run on 87 octane w/o any problems. For now, I’ll concentrate on getting the glide/2000 stall converter out of it and putting the th350/2300 stall converter in it.

Thanks again to you all!!

[enigma57]

Good luck!

HB

[nxtruck]

Thank you, sir!!

[RCJ]

I would switch the 3310 holley out for a quick fuel carb.We raced in a class that required a performer intake and a 650 made more power than a 750.

[travis]

That thing should pull to 5500 as is. I think something else is amiss. What valve springs are you using? Have you tried it without the carb spacer? What does your ignition curve look like?

A proper q-jet or a spread bore 650 Holley would be your best choice IMO with the performer intake.

Of course, the first thing I would do is get that powerglide out of there!!

[F-BIRD'88]

The performer RPM intake will make more power everywhere vs the performer.... As long as the plenum is divided. Any spacers should be divided too..
It is just a much better intake.

If qjet is used on the RPM intake be sure the adapter is divided.

[nxtruck]

I would switch the 3310 holley out for a quick fuel carb.We raced in a class that required a performer intake and a 650 made more power than a 750.

Thanks for the info!
I did start out with an older 1850 600 on this setup and, just from the seat-of-the-pants, the 750 responds and runs noticeably better, but, it hasn't been to the track or on a dyno as of yet. I'm curious about your combo, especially being limited to a 2101 intake. What type of racing where you doing with yours?

[nxtruck]

That thing should pull to 5500 as is. I think something else is amiss. What valve springs are you using? Have you tried it without the carb spacer? What does your ignition curve look like?

A proper q-jet or a spread bore 650 Holley would be your best choice IMO with the performer intake.

Of course, the first thing I would do is get that powerglide out of there!!

Thank you for the help!
The valve springs came in a kit with the cam from Competition Products. They were set up @ 110# seat and around 270-280 open, if I recall correctly. I have not ran it w/o the spacer that's on it now, but that's something else to try, for sure. Timing-wise, it has 14* initial @ 700, 20* mechanical, and 34* total all in by 3000. With the vacuum advance connected, it has around 50-52* at cruise ( 2800-3000 ). This was set when I first got it running and I haven't played with it since then. I do plan on trying a little more initial, 18* or so, and ending up around 38* or so total.
I do have a qjet sitting around that I plan on trying at some point, but it does seem to run quite well with the Holley.
Yes, swapping the glide for the th350 is first on the agenda.