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Another blower question

3K views 21 replies 7 participants last post by  1932bantam 
#1 ·
I'm planning a 400 sbc blown build, using eagle internal balance kit with je 36 dish piston all forged,
Using a dart shp block, carburated, haven't picked cam yet or heads, probably go with afr 220's with a 75cc chamber and a solid roller cam. Plan to run around 9 psi.
Question is, I've built many small blocks up to 450 hp but never built over that and never in a blown application. Are there any tricks for tolerance? Specs? Or any special details I should be watching for when building blown short block? I have a good speed shop here that can do all the machining. Also never done a 400, do I have to worry about steam holes with all these after market pieces?

And no I'm not interested in having my speed shop build it.

Thank guys
 
#2 · (Edited)
On a street engine you will need the steam holes drilled in heads you are using,you can get by on engines no turning Less than around 3000 rpm such as circle track ,we ran Late Model Modified on dirt with alumimum block and Brodix # 7 heads prepared by Race Engine Design .we drilled heads just to be sure,some did not,but some had problems in pack out and during caution,I am assuming you will need all the help you can get to cool blown engine, I have built hundred or so racing engines But Never a blown engine ,will be building BBC with 671 crager blower later this year ,Just my opinion someelse might help us both ,Good luck
 
#5 · (Edited)
I contacted BDS They recomend cutting a second keyway in crank snout to keep hub from stripping key and spinning crank hub and destroying crank snout,also Must run run forged cranh and forged 8.1 or less pistons for street with 7 lbs boost or less,Is this just a recomendation or a Must,anyone had any experiance wiyh this ,It is a 454 stroker=496 i have steel crank forged pistons ,but stock rods with arp bolts in rods and mains are arp studs ..671 blower i have a crager and a weiand ,which would be better.have already purchaced Comp Cam Blower Cam.roller rockers pushrods roller chain,115cc aluminum heads 225/188 valves do not want to change these
 
#8 ·
have already purchaced Comp Cam Blower Cam
I'll bet your Comp "blower cam" is cut on a 114 LSA. Read this from Blower Drive Service...110 works best for gasoline...114 works best for ALCOHOL...

"Choosing the proper camshaft would be the most important requirement for a blower motor. An improper cam will cause a variety of problems that can easily be avoided by following a few simple guidelines. Hydraulic cams are recommended if you intend to drive the vehicle frequently, requiring little or no maintenance, and the maximum engine RPM's are kept around 6500 or lower. Roller rocker arms are recommended. Flat tappet and roller cams are recommended for high performance applications especially where the engine will see high RPM's. Exact camshaft specifications vary depending on the performance level you wish to attain. BDS offers different types or stages of cam grinds specifically made for blower motors. Refer to camshaft specs listed in tech info for BDS' individual engine camshaft specifications and their intended uses.
If you wish to purchase your cam from one of the many fine camshaft manufacturers, we suggest using our camshaft specs as a guidline. Extremely high lift and long duration cams are recommended for high RPM, high performance racing only.
The lobe center of the cam will play an important role in determining the performance characteristics of an engine. Wide lobe centers (112 to 114 degrees etc.) will create higher cylinder pressure providing more horsepower with cooler burning fuel such as alcohol and methanol. We have found 110° lobe centers to produce the best overall power on gasoline.
Whatever cam you choose, make sure that it will operate and perform properly in the RPM range required for your application."

I don't know what it is that makes you guys jump up and buy the cam as one of the first items. Cam and torque converter should be the last 2 items bought, after you've finished the drivetrain and everything else.
 
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#19 · (Edited)
Normaly the crank is not the weak link, the bolts and caps usually give up and crank gets blamed ,i agree with F bird on 383 ,mine is a two bolt big block ,but i have arp studs not bolts also billett caps knife edged crank,lightned and balanced with mallory I dont anticapet any problems with 7.9 cr alum heads and pump gas, Streetdriver, if you see this on trailor report it stolen.
 
#20 ·
I do have a mid 70's block 4 bolt never been bored that I can use for this build, but just thought when buying a $2000 rotating assembly is another 1500 for a block to protect it all that much? Will a mid 70's 4 bolt take 650 hp? I would think so but always that hint of doubt. Also u mention 8-71 on sbc, is that not to big for sbc? This is all going in 87 monte ss 9" 3.89 spool, coilovers, 8 point cage, notched frame, 3" exhaust with 1 3/4 hooker headers. This car is mainly for show and street but does hit the track a few times a year. Only drive it 2 times a month if I'm lucky.
 
#21 ·
A Properly machined and preped 4 bolt with aftermarket caps or straps,ARP studs in mains ,arp cap screw in good prepared forged rods ,something like C&A bearings ,high quality pistons ,good solid roller cam with maching springs & kit will live at that level.when i say Live engine producing this much horsepower has a SHORTER life than say 400 hp Also i think a $1500 assembly will not cut it.
 
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