Engine issues - advice needed

[Roscobbc]

Taking on board the comments about low compression and RV cams, should I also be considering the Xteme 4x4 range or have I misunderstood this.

I'd be inclined to pop 'em over an email explaining you have a 8.5 c/r 454 Vette - stock heads - stock exhaust - Holley DP 'xxx' CFM - LS6 inlet - 'xxx' rear end ratio - 'xxx' gear box (so M20 or M21) - expain your useage and see what they suggest.
If Comp can't come up with sensible answers try another cam maker......there are more than a few.......
fill-in 'xxx'.
Just remember that quoted/advertised HP isn't really as bad as it sounds on 70's engines.......if it was I could imagine a few 1975 350 Vette owners with a mere 165 hp committing group hari-kari!

 

[teamzr1]

Going to have to also consider 2 other points in choosing the CAM grind
If having a auto tranny, the grind you pick, does it require a different torque converter with matching RPM stall rate and at what RPM range ?

What the LSA of the CAM grind is as the more narrow you select, the less vacuum there is from startup to what the power band of that CAM grind is
That can highly affect poor or good idle quality and if the auto tranny has control from engine vacuum

Looking in cyberspace, seems these 3 grinds are liked for the 454 CI
They are n the 270 and 268 model families as I show below

 

[MilkyNoSugar]

Going to have to also consider 2 other points in choosing the CAM grind
If having a auto tranny, the grind you pick, does it require a different torque converter with matching RPM stall rate and at what RPM range ?

What the LSA of the CAM grind is as the more narrow you select, the less vacuum there is from startup to what the power band of that CAM grind is
That can highly affect poor or good idle quality and if the auto tranny has control from engine vacuum

Looking in cyberspace, seems these 3 grinds are liked for the 454 CI
They are n the 270 and 268 model families as I show below

TO answer the first question, this is a manual 4 speed car.


The 11-207-3 is in stock and looks like it might be viable option.

The 11-400-4 returns no result from a search on the comp cams website.

The 11-560-4 is out of stock and says it is for cars with a +125 nitrous kit anyway. Am I giving the suggested use too much credit??


I have emailed Performance Unlimited, who appear to be a UK seller of Comp Cams kit, and asked for their advice.

 

[Roscobbc]

I have emailed Performance Unlimited, who appear to be a UK seller of Comp Cams kit, and asked for their advice.

Bought my Brodix heads from Dave powell at Performance Unlimited (in York) about 15 years ago - good guy - didn't realise he was still trading.

 

[Ray Quayle]

Bought my Brodix heads from Mike at Performance Unlimited (in York) about 15 years ago - good guy - didn't realise he was still trading.

I agree, he did the machine work on my small block. Good guy.

 

[MilkyNoSugar]

Bought my Brodix heads from Mike at Performance Unlimited (in York) about 15 years ago - good guy - didn't realise he was still trading.

Not sure they are still in business to be honest as the website has nothing in the news page for 4 years. I hope they reply as nothing else comes up for a UK distributor.

 

[Forrest Gump]

TO answer the first question, this is a manual 4 speed car.


The 11-207-3 is in stock and looks like it might be viable option.

The 11-400-4 returns no result from a search on the comp cams website.

The 11-560-4 is out of stock and says it is for cars with a +125 nitrous kit anyway. Am I giving the suggested use too much credit??


I have emailed Performance Unlimited, who appear to be a UK seller of Comp Cams kit, and asked for their advice.

The 11-207-3 you mention is a Magnum 270, and what I selected for my modified 383 small block. It works really well in my engine but I followed a proven “recipe” ie heads, intake, compression etc etc to build a performance engine.
Not saying this cam wouldn’t work for you but for a start it is single pattern which favours good flowing performance heads. Split pattern are there for a reason.
I would be inclined to speak to someone with actual experience like Performance Unlimited (edit - if they still exist. Real Steel then might be another option) if you are considering anything that differs from stock specs. There are so many cams out there and it’s easy to get carried away with going bigger.

 

[Emc]

I have a water, pump and some gaskets

 

[MilkyNoSugar]

I have a water, pump and some gaskets

Thanks Gavin. I will call you later to discuss.

 

[MilkyNoSugar]

Good news - Performance Unlimited Engineering are still in business and are liaising with CompCams to get a recommendation from them for a suitable cam. It will be interesting to see how close we have got to based on the collective knowledge and research.

 

[Roscobbc]

There's a certain 'male' physcology often seen when selecting engine tuning components. For example one will peruse a list of camshafts available for a specific engine.....so (much the same as we have seen on some of the cam charts on this thread already) - the person buying will look at the recomended camshaft (or other component) and think to themselves "that looks good, I like that.......I think I'd like a lttle more of all that" and orders the next item up the list, which unfortunately when finally installed runs a risk of turning his engine into a bit of a 'dog'. The 'smart move' in fact would have been to have gone the 'opposite' direction, and choosing the next item 'down' the list - the part that may appear a little less in performance terms but actually improves drivabilty and even perhaps fuel economy........just saying.

 

[MilkyNoSugar]

Sound advice. I already know I need to stick to the milder end of the range. I neither need or want a drag car that will not happily idle in traffic.

 

[Roscobbc]

Why not see where this thread ends up going - kinda applicable to your potential build?

Lost Cam lobe off 1974 454 - CorvetteForum - Chevrolet Corvette Forum Discussion

C3 Tech/Performance - Lost Cam lobe off 1974 454 - Original 49k 454 lost lobe off cam… so complete tear down and rebuild…. Looking for suggestions on a mild upgrade Cam pistons valves tappets using original intake and heads since I have to tear apart engine anyways… I want a nice horsepower...

www.corvetteforum.com

 

[MilkyNoSugar]

Performance Unlimited have been very helpful and got a recommendation on a cam from the supplier.

Rather surprising choice given the name - they have recommended the XM270H-12 cam which is the Xtreme Marine range. Information below.
Xtreme Marine™
• Extremely wide powerband helps get boat on plane while
making maximum horsepower
• Work against exhaust systems with restrictive back pressure
• Power enhancement helps maintain top-end speed for longer
distances
• Intended for applications where low idle speeds are required


Just waiting on prices and availability from them.

I am probably going for the complete kit K11-236-4 and RPM1411-16 or RP1411-16

 

[teamzr1]

XM270H specs

 

[MilkyNoSugar]

The parts have started to arrive from the various suppliers and all being well I will begin the top-end strip down this weekend after removing the bonnet and radiator. I am recovering from knee surgery at the moment so have not been able to work on the car recently.

I will try to make lots of notes and take plenty of photos to add to this thread, and may even try to put something together for the magazine.

 

[Vetman]

The parts have started to arrive from the various suppliers and all being well I will begin the top-end strip down this weekend after removing the bonnet and radiator. I am recovering from knee surgery at the moment so have not been able to work on the car recently.

I will try to make lots of notes and take plenty of photos to add to this thread, and may even try to put something together for the magazine.

If you are removing the stock cylinder heads over the wing then be prepared for a heavy lift. Mine weighed about 50 lbs each. I set up a small block and tackle that I was grateful for in the event.

 

[MilkyNoSugar]

Thanks for the warning. I assume they would be heavy.

All parts here other than the cam kit, so just about ready to go and hopefully making a start on the full strip down this weekend.

 

[Roscobbc]

If you are removing the stock cylinder heads over the wing then be prepared for a heavy lift. Mine weighed about 50 lbs each. I set up a small block and tackle that I was grateful for in the event.

You can almost double the weight for iron big block heads with ancillery bits and pieces............

 

[MilkyNoSugar]

We might need to get the manitou telehandler fired up to help lift the heads out.