Engine and Horsepower combinations

[Bill Musarra]

Just came across an article in Muscle Mustangs & Fast Fords mag. on Recipies for success Part 1. It explores the carburated engine combinations with dyno numbers and parts. It doesn't show all the combinations, but it list combinations from 270 HP Ford Racing GT-40 Crate motor, Edelbrock Performer 302 (300 HP), 325HP, 350HP, 350HP(several possible combinations), 375HP,400HP, 425HP, 450HP

,and 475HP

302's and 306's. There are 2 475HP, 500HP, 525HP, 550HP, and 575HP 347's

, and one monster 600HP 351. They tell you which will work on the street and which are meant for the strip. There is also a great article on Comp Cams new "beehive" valve springs.tells the dynamics of springs and spring surge. Check it out.
Bill

 

[Gordon Levy]

90% of the articals that are written for magazines about engines are for drag racing. I haven't seen a good artical on building a good road race engine. A good drag race motor will explode in a road race car. They need to be built totally differently. For a good street/race engine, I would recommend a road race type of engine. It will have more longevity than a drag race engine.

 

[Guest]

On the GTD40 Car Club web site (www.gtd40club.co.uk) Paul is planning on posting a specification of my car. In it I detailed the engine components which give me a dyno'd 306 bhp at the rear wheels, say 350 at the flywheel. This is a proven combination that I have used successfully over the years.

Interestingly, when it was dyno'd, the person doing the test thought that the specification was an odd one. He didn't think that it would give as much power as it did. However clearly the combination of parts brought some good power out of the package as a whole.

Anyway this package works for me, so I am sticking with it for now.

Malcolm

 

[Bill Musarra]

I have for some time, from different places and people, heard the same thing that both Gordon and Malcolm M have said. What I haven't heard is the specifics in the differences. I have been around drag racing more years than I have track and Nascar racing. My interest changed the first time I came across the old CanAm series, and have been hooked ever since. What I haven't figured out is their true differences. I would suppose that cam profiles and torque curves are the real differences. Let me pose this question to Gordon, Malcolm and whomever, If you took one of the engines that was in the article I mentioned, any one, any horsepower, how would you build it differently for the track. I think most would be interested in the 302/347/351 combos. They didn't talk about clearances in the article, but most of these engines have been spec'd out in previous articles, or the manufacturers could furnish them. Since this is the technical part of the forum, give us some idea of your thinking. I'm not asking for trade secrets, but in these articles, the engine builders will tell you the numbers behind their dyno numbers, and why they chose the parts and type parts (forged, billet, etc.). I may be asking for a lot, but I know there are those of us out there who would like to know the differences. I think this type question is why we need a technical article section. Any takers???

Bill

 

[Gordon Levy]

The biggest differences in drag race vs. road race has to do with machine work and the parts that are used. I can make a stock block, cast crank, stock rod engine that is well built turn 8000 revs on the drag strip and live, at least for a while. That same engine on a road coarse will explode after 3 laps. The differences is in the amount of stress you are putting the engine under and for what period of time. If you want an engine to live on a road coarse as well as street, there are ways to make it live longer.
First is to lay out the perameters of the engine. How high do you want it to rev, how much hp. From there it is designing the package.
taking one of these engines you are talking about for the articals and trying to make it a road race engine would mostly have to do with machine work and cam profile. What we don't know is what were the internal parts used, (I didn't read any of the articals). What most people don't understand is that the writer isn't going to print anything bad. Example, A friend who advertizes in some of these magazines did an artical a while back about a 650hp blown 5.0 engine. They built a moderate short block, put good heads and intake on it, and a really big blower. They did 20 pulls on the dyno and got great numbers for the artical. What wasn't printed as on pull #21 the block exploded in half. This is very common for magazine articals.
I could write a book on how to build a proper engine, but I still don't want to give away trade secrets.
I don't know if this is the answer you are looking for. If you give me a specific question, I will answer it the best that I can.

 

I am interested in Gordans reply as to the difference in road engines and drag engines. I can see a different camshaft profile,not using light pistons and different manifolds. What else do you recommend?
Vic

 

[Mike Dozier]

A successful drag RACE engine is designed for
short bursts along a VERY narrow RPM band.
Depending upon what class of drag racing you
are discussing, these engines are designed
to run only a few 1/4 mile blasts
(Pro category) to a few HUNDRED runs
(bracket racing) before being torn down.

The confusion lies in the fact that many Cobra/GT40 replicas are built as dual purpose cars (street and track).
The engine builder needs to know what the percent of street vs track time will be,
as well as the type of track work expected
(drags vs road race vs hillclimb, etc).

Most important is what level of performance
the owner expects/wants. Speed = money...
especially reliable speed.
How fast do you want to go?

MikeDD

 

[Guest]

And I don't have any trade secrets to give away as I am not an engine builder and can't really answer the specific points made. My Cam is a CompCams 280. It is not modified or custom ground in any way. The heads were machined to help with flame spread and heat disappation ie to create no hot spots between valves. I relied upon my engine builder to give me a good engine. He did. Only engine I really built killed every mosquito in the county it smoked so much. It is a black art I don't have!

Malcolm

 

[Mike Dozier]

It seems to me that the main differences between a road race and drag engine are curve shape and reliability.

Unless I'm missing something, curve shape is determined 99% by cam and head selection.
Pretty simple concept...where on the RPM range do you want to make power and how much?
The trick is then to make it happen, and
that's what you pay an engine builder for...
his experience and intellectual property.

Reliability is always a compromise in an engine. Lightweight components rev quicker,
but generally have limited # of life cycles.
Lately there has been a flood of good
aftermarket parts for the SBF that economically increase the reliability.

An SVO or sportman block with aftermarket crank and rods goes a LONG way towards reliably holding big HP. Not as glamorous
as aluminum heads, trick intake, Weber carbs,
crossover headers, etc, but that's what it takes.

Drag racers (especially professionals) cheat a little on clearances, RPM limits, weight removal, etc since they tear down and inspect their engines regularly. They also
run higher compression and more timing
than you'd want to in a street/track car.

I doubt the above is news to anyone...
just stating what seems obvious to me.
Those that want to know the ACTUAL differences in cam profiling, internal clearances, head porting, etc between
road race and drag can obtain books on the
subject from reputable engine builders.

But as Malcolm says...reading about engine building and successfully doing it are two
different things!

MikeDD

 

[Julian West]

What's the general opinion on Maximum RPM & BHP for a stock 302 crank?

I understand the first weakpoint in a SB bottom end is the big-end bolts, followed by the rods, then pistons....

At what point is a steel crank necessary?