Okay, here's my plan: Engine one is in my circle track car. It's a 355 SBC solid cam full on race motor. It's got a .533/.525 cam with forged Eagle rotating assy. 0 deck height, flat tops, 6.2" rods ARP studs and Pro Topline Lightning heads. They're 50cc chambered with 200 cc runners and all the good springs/aluminum roller rockers, etc. My engine builder said it was around 12.5:1 compression. Engine two lives in my 87 Monte Carlo SS: Stock replacement 350 shortblock. I added a .488 lift hydraulic cam, and stock 76cc heads that had been hogged out to 2.02"/1.60". They've got Crane double springs and ss valves. The plan is to swap heads and put the 76cc stockers with the good springs/valves on the solid cam race motor and drop it in my 1931 Tudor. I think the bigger combustion chamber will lower my combustion ratio and tame this motor a bit, allowing me to run premium not race fuel. I also hope this will help it to run a little cooler. Those race heads are going back on that stock motor with slightly dished pistons and valve reliefs to help boost the comp. ratio on that motor. So what do you guys think? Any problems running a solid cam motor built to run 7000 rpm on the streets?
Your cam wont match the RPM range you will be in most of the time (on the street) I would change the cam also for the 31. Something that makes its power down low 1500-5000 rpms
Some other things to think about.. Excessive rod bearing clearance. and how much side clearance on the rods.. I installed one of my race motors in a corvette with mufflers and it frightened me with all the knocking from the large clearances. I drove it for about 5 thousand miles on the road before I sold the car and it never blew up.Also heavy oil on the street is another question.. Narrow width rings as a general rule dont last a long time on the street.But I say go for it.... Fast is fun... Bobby..
More street friendly cam, and maybe some thicker head gaskets to drop the compression a bit and I'd say run it. I heard about this one HAMBer who's got a nasty 406 in his 38 Ford coupe. Used to be even nastier, but he de tuned it for the street and hasn't had any real issues with it.now if only I could remember his name....
My brother and I put a 283 race motor in a 52 GMC truck. It was a lot of fun for about 5 days, and then we pulled-up along-side a 68 corvette with a big block, popped the clutch, and you'd thought a nuclear bomb went off. We ended up off the side of the road with the rear-end and driveshaft completely torn out of the truck. I'd say go for it, as it was the most exciting 5 days of street racing I ever had
While swapping heads sounds like a good idea the problems that it will raise outweigh any advantages. With the high compression that you will still have the quinch area of the combustion chamber must be minimized to help prevent detonation. There are 2 types of compression ratio, static and dynamic. Static is the compression ratio that the engine would produce if the valves did not open and the cylinders did not leak down. Dynamic compression is the real compession that the engine gets from the time that the valves close to the top of the piston movement. Rather than risk having excessive quinch area in your engine with thicker head gaskets and a larger combustion chamber your best bet would be to install a camshaft with a longer duration to bleed off some of the dynamic compression. Here is a link to an article about dynamic compression and there is a free downloadable program to calculate it. http://cochise.uia.net/pkelley2/DynamicCR.html
That sucks, it was an expensive cam. Oh well, it's in a $6,000 motor that never got to see the track. So longer durration will be better for street use? I'm not running power brakes and I think it's going to use mechanical advance so generating vacuum really isn't a concern. However I do plan on flogging the dog shit out of this motor, and I'm concerned about overheating. I planned on pulling the 66 Mustang radiator trick with an electrical fan. So thicker gaskets, bigger cc heads, and swapping the cam for one with more durration should do the trick? Do I want one with more durration than lift? Any suggestions on cams you fellas like? As far as the other motor goes, I just planned on installing those 50cc race heads and their steel shim gaskets on the old 350. It's getting the Turbo 350 (also out of the racecar) and a 3,000 stall. It's already got headers and a 2.5" exhaust system I built. I would guess that it's around 8.5:1 right now, what do you think it'll be with those small chamber heads on it?
You live in a state with a lot of e85 stations. Drop it in as is. Otherwise big cams need big compression so you need to swap heads and cam. Heads are about 3 points in compression from the www.kb-silvolite.com compression calculator.
Its a 424 from what I remember... but I've heard it called a 434 as well... the mph he makes, if he could hook up... I'd think that 38 would run 11.30s-11.40s.
I've heard conflicting reports as to the actual displacment. I think he did post the motor's specs somewhere, but I can't find it. I've seen teh guy run on his street tires. You're right, if he ever decided to go for speed over style....
That cam is quite livable. I have a 355 small block running in a 74 camaro for a friend J Vandervelde. It is a 10.5 to one and as he will tell you he has never driven it any distance without at least one 7000 RPM shift. The cam is 312 duration and 562 lift on intake (532 on exhaust if my memory serves me right.) It is a real fun car to drive and darned scary to ride in. How long you ask? Well thank you for asking. I built this motor for him in 87 and freshened it once since (about 94 or 95 I think. )He is redoing the car now and asked if I would mind slipping in a fresh set of rod bearings while he has it out. The suggestion to try E 85 is i think right on. Then you wouldnt even have to lower the compression . In reality Engine compression ratio we quote is a theoretical thing , then there is the actual compression ratio. For me I would do a actual compression test. Rule of the thumb I use is if it is under 170-175 it could be street driven providing you insist on Sunoco 94. If it is in the 180 to 225 range then not however I suspect and it is only an educated guess that E 85 would work fine on the street in such an engine. E 85 gets a bum rap because it really requires much higher compression ratio than gasoline , Running it in a low compresssion engine is about driving a diesel with insufficient compression. However you are in the wonderful position to try this right the way it is. Worst case is you might later decide to swap to the large chamber heads. I for one would be very interested in the results should you try the eE85 on the engine as is. Don
OK...I'll bite. Engine 1....to me is not a full on race motor if it was built for circle track racing. The cam lift is quite short for being full on but anyways....you put a stock port size head on this and it would probably do better with throttle response and low to mid range performance due to the 200cc heads that are on it are on the big size for it them work to thier full potential. What is the duration @.050 lift on this cam? What are the cam lobe centerlines? What is the cam installed on? The lift is not usually an amount to actually make power up to 7000 rpm so I'm curious as to what the grind specs are on it. All very important to know for sure what this will run like on street gas and street use. The pistons in this motor are my biggest concern when going on the street. If you are running a 6.2" long con rod, what are the thicknesses of the compression and oil rings? Is the wrist pin through the oil ring location? Are they floater pins or pressed? If floaters what type of retainer are you using on them? If they are pressed, fine(but not a full on race motor type) if they are floaters hopefully you will have spiral or snap style retainers and not plastic plugs as they will not live long on the street. What type of skirt do these pistons have? Usually pistons I'd use for a long rod full on race motor would have little to no skirt. If yours have short or basically no skirt then you will not have an engine with a long "mileage" life. They are not meant to be run for thousands of miles and will cause extreme amounts of cylinder wear and ultimatly failure. Another thought is why do you want it to run cooler? is this motor overheating as is? If your cam has enough overlap your "actual" compression will be lower than the 12.5-1 that your engine builder claims and I believe it should run just fine on mid to high octane pump gas. Earlier this summer I completed a 13.8-1 357ci. small block chevy with a solid lift cam, aluminum heads for a customer to put in his 70 nova. It is driven regularly on the street and runs awesome on premium pump fuel. It was dynoed on pump gas and pumped out 613hp@7100rpm and 568lbs/ft of torque@5100rpm. So depending on the specs of your cam and the types of skirts on your pistons, I'd say your shortblock will do fine....the heads from engine 2 that have hogged out to 2.02/1.60 valves, was there any port work done to the runners as well or was it all in the bowls/chambers when the valve seats were enlarged? If portwork was done, how much was done? Do you know the runner cc's for these heads? Even if they are not ported much you will probably be hapier on the street with these heads over the topline 200's, once again cam specs will be the deciding factor here. Now for engine 2, what do you plan on doing with it once you put those huge topline heads on it? It will be a very very lazy responding engine if you do not plan on any other changes for it. Let's have the cam specs on engine 1 and then we will see for sure....you just might be better off changing the cam in engine 1 and leaving the heads on it....and just leave engine 2 the way it is. I'll check back to see if you post the cam specs...or you could email me all the info and I'll go over it and get back to you. You can email the info to me at [email protected]
I dug up the spec sheet for the solid cam in my race engine. It's Comp Cams 12-651-5 Grind CS 278XO-8 Intake exhaust Gross Valve lift .531 .525 Duration @ .020 lift .278
WTF? I hit tab, and it posted before I was done. Duration @ .020 tappet lift was 278 intake and 284 exhaust. Valve timing @ .050: intake 16 BTOC 52 ABDC exhaust 53 BBDC 17 ATDC Cam was installed at 108 intake center line. Duration at .050 Intake 248 Exhaust 250 Lobe lift .3540 .3500 Lobe separation 108.0 So does this sound like a streetable cam? The motor in my Monte SS in kind of a dog. It takes a long time to wind up. It has a .488 lift cam and that's all I can remember. I attributed the sluggishness to the clapped out 200 4R tranny and stock convertor. But is this cam holding me back? Thatnks a lot fellas.
ok...been thinking this over and I'm not really sure what to tell ya....to me the cam that was used isn't the best choice by no means. Now please keep in mind this is MY opinion...and not neccessarily the only opinion there is and lots of guys will tell you it's probably wrong. By the specs you've listed, this cam is not really one that would be a choice for an engine built such as yours. With the installation and seperation 108 it is not going to be a cam with a lot of power range at all. It would be something that would be used on a short, highbanked very fast oval track. Probably 3/8th mille or shorter and should more than likely be used with much less compression or maybe it might work with compression and a restrictor plate. It might make good power, but it will more than likely be somthing that would need to be kept up high in the rpm range as it will struggle a lot down low. Will it run ok on the street...probably...will it be a great setup...probably not. If you really want to use your race motor, I'd say you should check the piston to valve clearance and if there is pleanty of room put on 1.6 ratio rocker arms this will net you .566 lift int, and .560 exh. and then you might even want to advance the cam by 2* at least I'd prefere 4*. This will breing the top rpm down some into a more useable street range. You have not stated, or I didn't see just what kind of gear ratio you will run, but you will more than likely want to be at least running a 4.11 or steeper gear. This thing will work best with a 3000-3500 rpm stall convertor at least. If you do not have or want to run that much gear and stall...you really need to swap out this cam. If you choose to swap the cam out, you should find one that will allow you to use the 355 as is just change cam and put it into your rod. The setup could be quite a nice one with just a cam change. Now for your 2 engine. What gear are you running in your monte? If you want to get me all your cam specs on this one too and also the gear ratio and what your plans for the monte are, I'd be more than happy to offer up another opinion and suggestion to what might help you get what you want out of it without to much $ and work. Once again, this is just my opinion, and I'm not an expert I just know what has been working for the engines I've built for race and street use for the past 20 years.
Thanks a lot Al, I really appreciate your input. I'd like to run the race engine as is with the exception of a cam change. If I use a more street friendly cam I won't have to switch to 1:6 rockers will I? It's going to be backed up by a turbo 350 and I haven't chosen a stall convertor or rear gear yet. I am more than open to suggestion. As far as the Monte, it's getting the turbo 350 out of my racecar with a 3,000 stall and the stock 3:73 rear gears. Right now, that thing is a bone and I'm sure it has something to do with the cam, and stock convertor/tranny. The cam (.488) is also out of a race engine from the same track that I was going to use my new race engine at. By the way, you nailed it, the track is a high banked 1/4 mile asphalt bull ring. So what kind of cam would you put into a 355, with an Eagle/SRP rotating assembly with 6.2" rods and flat top pistons. Topped off with those Pro Topline 200 cc runner, 50cc chamber heads. I also planned on running multiple carbs, maybe a tunnel ram or I would love to run a tri-power with 3 Rochester 2G's on it. If I had to guess I'd say it will have right around 3,000 stall and at least 3:73 gears, maybe 3:90 or a little higher. Again, thanks for your time and knowledge.
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