Thread: SBC mileage

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Well thanks for the added tip on the Streetmaster manifold, I am not familiar with that manifold but I recognize the need for high velocity intake at low rpm; is the Streetmaster available new? What got me thinking was finding the Crane cam with a GM part No. with an even shorter intake duration of 180 degrees, so the Elgin 5911 has longer duration than the Crane cam! I am glad you are not offended because you are a source of a lot of valuable knowledge. I checked with the Automotive Warehouse folks in Charlotte and they do already use the 0.035"-0.040" quench/squish in their 9:1 C.R. crate motor and they say I should be able to use 89 octane gas for sure and maybe even 87 octane with the quench effect. They seem to offer reasonable custom features in the engines they build so I will hold them to a 0.040" squish and then pick the Melling 22108 and if that is too tame I will add 1.6 ratio rockers for a little more lift at the valve. You are only slightly younger than me and I am pushing within my economic limit to get my roadster built while I can still enjoy it, but the price of gas may continue to go up while I build!

Best wishes,
Don Shillady/teen rodder

ok- Don,
Tech hit it on his next to last response. I think that you have forgotten about cam phasing at the higher rpms. You have to make this up with improved intake runners & a "balenced" exhaust porting.
Also kill the overlap & you will get it.

I am sorry that I don't understand the last concept about cam phasing at higher rpms. Please explain more, I am learning fast. I did wonder about valve clearance with 1.6 ratio rockers and flat top (eyebrow) pistons and close squish/quench. Regarding the manifold, I will try a Streetmaster if I can get one and I still have an original iron 4 bbl manifold. With relatively low prices for an Edelbrock Peformer that would be available if needed. To make my question clearer, I am using a 2.79:1 rear ratio and probably 15" rear tires so as far as I can tell I will be running at about 2100 rpm at 70 mph on the Interstate and on local country roads I expect to be limited to 50-55 mph, unless the 2100 pound '29 has exceptional handling, so again I will be running at less than 2000 rpm in high gear. The only worry is the performance in low and second gear with the TH350 and stock converter. I am hoping that there will be jack rabbit torque at the light or for downshifts leading to sportscar 0-60 mph times (6 seconds or better?). It would appear that with a low rpm cam and intake, 1/4 mile times will be terriblly slow. However, I must consider my age, reflexes at my age and the fact that I am still working off "points" on my Va License from previous "frisky behavior" and it takes a few years to work off those points. If I can occasionally smoke the tires in low and get 0-60 mph in 6 seconds as well as have passing torque at 70 mph along with 20 mpg, I'll stay with the low cam and small intake. If I need "more" I can upgrade to 1.6 ratio rockers and a Edelbrock Performer intake. In any case I will use short tubular headers for "looks" as well as some added torque.

Thanks for valuable Tech Advice,
Don Shillady
Retired Scientist/teen rodder

OK- now that I've read thru the whole thread I can see that you've got the fever.
Being from Va. for 30+ years I understand the need to behave on the road.....so- don't get caught up in all the hype. Your roadster at 2100 lbs. with a crate 327, and even with those gears will have GREAT low end pull. Get yourself an Allison torque converter ( the are used for R.V.'s ) for a couple of hundred bucks.
Maybe change those rear gears to at least 3:08's.
If you want to get a Sealed Power 262 cam for it and that will give you a little bump.....you won't need much more than that if you expect to keep it rubber side down anyway, and you should still be in the mid twenty's range on fuel.

Good Luck....Let us know how it comes out....Jim

P.S.
If it get's too confusing for ya call Luther the roofer at Roofing Supply on Hull St.....he can help you too. He's got one of everything down there.

Jim,
Thanks for the encouragement. To make things interesting I am only about a mile from a State Trooper HQ and here you can be sure to see at least one Trooper car anytime I venture out on Rt. 1 or I-95! I only know of one other roadster down in Smithfield, a Brookville steel body, but I have not visited him yet. On the other hand I am only one block from the Harley Davidson Agency on Rt. 1 so maybe they get all the Trooper attention? Originally I just wanted to add a "3/4 cam" like the MTC-1 (Performer) to a rebuilt engine and have a good street car, but that seems to lead to about 16 mpg and I hoped to get up to 20 mpg with prices being what they are. As you say maybe there is enough torque to have good performance even if I sacrifice the top end and the Streetmaster should be a beast up to 2500 rpm. I guess you mean that at higher rpm the open chamber single-plane intake will experience "pulse conflict" or something where the intake pulse demand starts to rob one cylinder from another. Well I don't know at what rpm that starts, but maybe the high rear gear and light vehicle weight will work with the short cam and low end intake, we will see. Looking over the sports cars 0-60 times, maybe I can hope for 4 sec and some day try the 1/8 mile drags. Does anyone out there have a copy or a reference to the 1974 Motor Trend article on the Streetmaster debut by Edelbrock? Years ago when I was working on a '40 Ford convertible I got to know a number of the Early Ford enthusiasts in central Va, but now with a Chevy drive line I have to start all over since they generally frown on Chevy-in-Ford combinations. All I can say is that I still have a good set of crank and rods from a '49-51" Merc but after I bought three flathead blocks and found them cracked I gave up on flatheads and a SBC has an easy 240 HP where you would have to do a lot of expensive work to get a flathead up to 240 HP, so I will have to cultivate some new friends.

Best Wishes,
Don Shillady
Retired Scientist/teen rooder

I used to live on Norfolk street there just across from the school, there are still a few of us around, but there are just as many carpetbaggers around there too.
Don't listen to what everybody wants you to run - it's your rod.
Old Luther down on Hull is the one that can really help you so that you don't get knocked in the head so much by all the scam artist's, and so called friends with "just what you need" in their garage.
Good Luck with your project, Let us know how it turns out.

Jim

TechInspector1/Richard:

I have left you alone for a while, but I have taken a Summer job to buy a low end crate motor and the time is approaching to make the deal final. The cam you recommended (Elgin 5911) appears to be identical to a GM/Crane cam and the same specs are available as a Melling cam which means it is available through the company that will build my engine. The Crane description describes the performance as "brute torque" between 500-3000 rpm. I have calculated car speed with my 2.79:1 rear ratio and the gears in the TH350 and all the speeds available up to 3000 rpm are acceptably high in all three gears with 14" or 15" tires. My question is whether the torque between 500-1000 rpm is useful with a standard torque converter? Because this cam has LESS LIFT than the stock cam as well as shorter duration I find it difficult to believe there would be a performance enhancement as well as mileage increase. If this is so then for speeds up to say 85 mph this would be/is (?) a "wonder cam" when used with a stiff rear gear. Can you cite any knowledge of actual use of this cam?

The engine specs. will be:

4.040" bore, block decked and thin gaskets used to give 0.035" squish.

76 cc heads with flat top eybrow pistons for 9:1 Comp. Ratio

Edelbrock Performer dual plane manifold

Rochester Quadrajet 4 bbl (initially)

1 5/8" tubular headers

Elgin 5911 cam

The compromise cam is the grind Elgin calls #5870 ????

Don Shillady
Retired Scientist/teen rodder

Well here is an update on this idea which maybe most of you don't want to think about. I have learned from this Forum that a number of the members are serious drag racers with impressive cars and I admit I am over my head there since I am only interested in a "resto-rod" '29 Ford roadster. After the 2/4-bolt debate I decided that the 2-bolt is plenty strong enough for my needs and I went ahead with rebuilding a 0.030" over 2-bolt 350 with "882" 76 cc heads (shaved) and flat top pistons for a compression ratio of about 8.7:1. I really debated the use of a 184/194 @0.050" cam as suggested by Tech1 but the torque range only goes to 3200 rpm using the Crane version of this cam (Crane No. 10008) and if I decide to change the rear gear from 2.79:1 later to say 3.55:1 that will not be enough rpm, so I chose instead the Crane cam No. 10010 which is a 194/204 @0.050" "torque cam with specs just slightly hotter (longer duration by a few degrees) than the 300 HP Corvette cam for 350 SBC and a torque range of 1000-4200 rpm. This should still give pretty good mileage (18 mpg?) with the 2.79:1 rear and if I get disgusted with low gear bog I can change the rear ratio later without changing the cam. With a simple 0.040" gasket and 0.025" deck I will not worry about octane and hope to run 87. My machinist (2-bolt Butler) will measure the deck for me after the pistons are in and maybe I will chose to use a thinner head gasket, but I really do not want to risk a leak and "hydraulicing". Thus at the end after using new rods and new valve guides with a 3-angle valve job I will just have a rebuilt 355 SBC with a torque cam with a torque range of 1000-4200 rpm, which should be good to about 90 mph in second gear with 15" tires and the 2.79:1 rear if there is enough torque to push the full fendered car through the air at that speed. Anyway that cam will allow me to upgrade the rear ratio later if needed/wanted and I will never know what mileage I might have gotten with the 184/194@0.050" cam. Maybe it doesn't matter anyway if I only drive the car on weekends! I will still use the Performer intake and the Quadrajet 4 bbl carb. Now here is a question. In the thread on H.P. versus Torque an article in Car Craft was cited and it says that for under 300 H.P. 1 1/2" diameter primary header tubes will help torque. Any opinions on header tubing diameter?
Now here is the CONTROVERSY! See the Washington Post Writers Group Syndicated column by Ellen Goodman entitled "Hybrid Owners Laugh All the Way to the Pump". I know you don't want to read it and neither do I but I have always enjoyed Ellen Goodman's columns until now as being politically sensible. She is bragging in that column about her new Prius which gets 60 mpg! I think when you cost it out you don't really save any money buying an expensive Hybrid even though the mileage is good. In addition, you and I are mainly interested in the rush of acceleraton from a big engine in a small car, BUT (!!!) there are a lot of people out there in the population who ARE interested in higher mileage and the price of gas! I have seen a few Prius two-door sedans on I-95 every day commuting and they usually stay in the right lane and I have not observed any burst of speed from them in passing so I am guessing they are quite slow, BUT (!) they are coming and we need to recognize this fact so I would rather hear a few encouraging words about how to get higher mileage AND TORQUE from a standard engine like the SBC OR (!!) maybe we ought to be talking about the Buick V6? This is a sobering thought to the little boy/girl inside of each of us who would just like to "go fast" but we ought not to talk down to engineering principles that will/can improve mileage. Well if you get a chance to read the Ellen Goodman column, I hope you will think about ways to build "torque/mileage" motors so maybe (?) we can have acceleration AND mileage???? Also I would like to know if I use 1 1/2" headers instead of 1 5/8" headers, will that help torque below 4300 rpm in a SBC? Allow me to say thanks for a LOT of good advice from a number of you in planning for my mild SBC and other helpful comments.

Don Shillady
Retired Scientist/teen rodder

Don,
I gave you the combo for that in our first thread of discussion- you didn't listen to it then, so why should I bother to repeat myself?
882 heads are garbage, throw them away and use a quality set of heads. Those have a factory flaw in the intake runner design and flow for crap. your performance, as well as mileage will suffer.
If your going to run those heads than there will be no differance if you run 11/2 or 1 5/8 or any at all. Your worried about exhaust flow from a set of heads that are worthless for flow.

Jim/Hambiskit,

I appreciate your interest and thanks for your comments. I recently had a surprise tax bill after we paid off our house and now there is no escrow withholding, so I had to pay a pretty large lump sum of property taxes and I had to scale down the engine rebuild. I am using an article "Low-Buck Small-Block Buildup" from HOT ROD magazine, December 1995. Although they used a PAW 280 cam, they got 303.3 H.P., corrected, at 5000 rpm on a dyno using rebuilt 882 heads so I am hoping that I will have about 240 H.P. at 4200 rpm (guestimate). Their engine had a torque peak at 3750 rpm of 362 ft. lb. with 9:1 C.R. With my slightly lower C.R. of about 8.7:1 (we may cc one cylinder chamber to get a better idea of my C.R.) I may get 330 ft. lb.?? Anyway, I know the 882 ports were deliberately restricted for mileage in 1976, but let me try them and maybe in the future I will opt to buy better heads. For now I will be content to try 240 H.P. in a light body for a while and gradually make improvements. Thanks for your interest.

Don Shillady
Retired Scientist/teen rodder

With a small block Don - the power IS IN THE HEADS , if you have to run them for now then they are better than nothing I guess. I don't think that your going to be happy with that combo your putting togather.
OK, here it is again, 350 bored 30 over block,
307, or 327 steel crank,
327pistons & rods @ 4030
262H cam from Crane
461 or 441 heads- full port & polish
Edelbrock Torker Intake - ported
Holley 750 cfm w/1" spacer
1 5/8 Hedman headers, or better
283 solid damper
Cloyes hex-adjust timing set w/button

If you shop around, and do the assy. yourself, total cost of this build is less than 1500.00, INCLUDING the machine work. This combo will produce around 450 hp, with about 480 ft. lbs. of torque. With stock compression @ 9.5: 1 you can still run pump gas, and if you keep your foot out of it, you will get around 28 mpg.
The differance is the stroke & crossover, this is a Can-Am set-up for the cafe racers in the 60's. It works really good.

LOL- you know you aren't right , don't ya?
Just a little to the left??

Well it's nice to know I have some friends out there who care! I am not going to tell you my tax bill and I would not be surprised if Streets' is larger. One thing the younger members may not know is that once you are off a payroll with deductions you have to pay the IRS Quarterly Estimated Taxes as well as local property taxes (it was an unwelcome surprise to me!). Although my tax is probably less that for Streets, it did make a dent in my engine plans. Today Joe Bultler cc'd one of my rebuilt heads and got 75 cc after a slight shave and the pistons are in and the deck turned out to be 0.016" so I could still use a thin head gasket to get higher compression as well as more quench. So far I have not figured out the volume of the double eyebrows in the cast pistons, one guy says 7 cc and another says 4 cc. That makes the final compression with a 0.040" gasket as either 8.8 or 9.0 to 1. For Richard/Tech1 I was hoping he would say some really great things about the performance of the 184/194 @0.050" cam but it looked to me that I might end up in second gear a lot more with the mileage cam and as I said if I ever upgrade the rear to a 3.55 that cam really would be a limiting factor. No I do not plan to do 90 mph in second gear, but with a 2.79:1 rear gear I might want to hold it in second for an on ramp. I am selling my 461 heads because of the lack of accessory bolt bosses and high compression and I think I will end up with something like the Goodwrench Universal 350 which is rated at 240 H.P. with headers and a Performer intake. At least Jim/Hambiskit partially answered my question about primary header diameter and I will go with the 1 5/8". I note that the 350 in the Dec. 1995 Hot Rod article "Low-Buck Small-Block Buildup" used 1 3/4" diameter headers and their cam was 280/290 adv. duration with 0.443"/0.465" lift at the valve from PAW compared to my Crane 10010 cam with 260/270 adv. duration and only 0.398"/0.420" valve lift, but as Hambiskit says and as confirmed by flow graphs I have seen for the 882 heads, most of the flow increase is over by about 0.400" valve lift anyway and so I will end up with about 240 H.P. but hopefully good torque to pull the 2.79:1 rear. Anyway you can see from just the few comments you have made how different a person's goals can be and I am content that I did as well as I can for the bucks required. If Streets got 18 mpg with a 383 SBC and a 2.79 rear gear (when the blower was off) and the Magoo '29 roadster got 18 mpg with a hi-po 327 and a 3.08 gear, I think I can hope for 18 mpg with a 2.79 gear and while that is still low compared to a hybrid Prius, it compares favorably to one young man I talked to with a 350 SBC driving a two-speed Power Glide who informed me he was geting about 12 mpg! I HAVE learned a lot from your comments, thanks.

Don Shillady
Retired Scientist/teen rodder

Don, What do you want for those heads? Have they been fluxed? Are they a matching set? Are they complete? If so then if the price is right I will buy them from you. Let me know - ok? Also- are you on Norfolk Street?

The 461 heads are in Butler's shop looking for a circle track buyer, but I have said before on this Forum that the first $150 takes them. They are matched and have been pressure checked recently and found to have no cracks. The intake seats have been cut for 2.02 intake valves and I have over $200 in them so far but if you are visiting Richmond or want to pay the freight I can send them for $150 plus shipping costs. I am just six miles south of Ashland along Route 1, but maybe shipping them is easier, although expensive?

Don Shillady
Retired Scientist/teen rodder